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diff --git a/old/60212-0.txt b/old/60212-0.txt deleted file mode 100644 index 074201e..0000000 --- a/old/60212-0.txt +++ /dev/null @@ -1,17742 +0,0 @@ -The Project Gutenberg EBook of Problems of Life and Mind. Second series: -The Physical Basis of Mind, by George Henry Lewes - -This eBook is for the use of anyone anywhere at no cost and with -almost no restrictions whatsoever. You may copy it, give it away or -re-use it under the terms of the Project Gutenberg License included -with this eBook or online at www.gutenberg.org/license - - -Title: Problems of Life and Mind. Second series: The Physical Basis of Mind - -Author: George Henry Lewes - -Release Date: September 1, 2019 [EBook #60212] - -Language: English - -Character set encoding: UTF-8 - -*** START OF THIS PROJECT GUTENBERG EBOOK PROBLEMS OF LIFE AND MIND. *** - - - - -Produced by MWS, Bryan Ness, Charlie Howard, and the Online -Distributed Proofreading Team at http://www.pgdp.net (This -file was produced from images generously made available -by The Internet Archive/American Libraries.) - - - - - - - - - -Transcriber’s Note - -In PROBLEM I, CHAPTER III, Section 45 (originally page 38), chemical -formulas represent the numbers of atoms in a molecule with patterns -like this: C_{114}. Throughout this eBook, pairs of underscores enclose -italicized text, Small-caps text appears as ALL-CAPS, and pairs of -equals signs enclose boldface text. - - - - -Works by the same Author. - - - =PROBLEMS OF LIFE AND MIND. The Foundations of a Creed.= Two - Volumes. Octavo. Per volume, $3.00. - - CONTENTS: The Method of Science and its Applications to - Metaphysics--The Rules of Philosophizing--Psychological - Principles--The Limitations of Knowledge--The Principles - of Certitude--From the Known to the Unknown--Matter and - Force--Force and Cause--The Absolute in the Correlations of - Feeling and Motion. - - =THE STORY OF GOETHE’S LIFE.= New Edition. One volume. 16mo. With - Portrait. $1.50. - -*.* _For sale by all Booksellers. Sent, post-paid, on receipt of price -by the Publishers,_ - - -HOUGHTON, MIFFLIN & CO., BOSTON. - - - - - THE - PHYSICAL BASIS OF MIND. - - With Illustrations. - - - _BEING THE SECOND SERIES_ - OF - PROBLEMS OF LIFE AND MIND. - - BY - GEORGE HENRY LEWES. - - [Illustration: The Riverside Press.] - - BOSTON AND NEW YORK: - HOUGHTON, MIFFLIN AND COMPANY. - The Riverside Press, Cambridge. - 1891. - - - - - AUTHOR’S EDITION. - - _From Advance Sheets._ - - - _The Riverside Press, Cambridge, Mass., U. S. A._ - Printed by H. O. Houghton & Company. - - - - -PREFACE. - - -The title indicates that this volume is restricted to the group of -material conditions which constitute the organism in relation to the -physical world--a group which furnishes the data for one half of the -psychologist’s quest; the other half being furnished by historical and -social conditions. - -The Human Mind, so far as it is accessible to scientific inquiry, has -a twofold root, man being not only an animal organism but an unit in -the social organism; and hence the complete theory of its functions and -faculties must be sought in this twofold direction. This conception -(which has been declared “to amount to a revolution in Psychology”), -although slowly prepared by the growing conviction that Man could not -be isolated from Humanity, was first expounded in the opening volume of -these _Problems of Life and Mind_; at least, I am not aware that any -predecessor had seen _how_ the specially human faculties of Intellect -and Conscience were products of social factors co-operating with the -animal factors. - -In considering the Physical Basis a large place must be assigned to -the mechanical and chemical relations which are involved in organic -functions; yet we have to recognize that this procedure of Analysis is -artificial and preparatory, that none of its results are final, none -represent the synthetic reality of _vital_ facts. Hence one leading -object of the following pages has been everywhere to substitute -the biological point of view for the metaphysical and mechanical -points of view which too often obstruct research--the one finding its -expression in spiritualist theories, the other in materialist theories; -both disregarding the plain principle that the first requisite in a -theory of biological phenomena must be to view them in the light of -biological conditions: in other words, to fix our gaze upon what passes -in the organism, and not on what may pass in the laboratory, where -the conditions are different. Analysis is a potent instrument, but -is too often relied on in forgetfulness of what constitutes its real -aid, and thus leads to a disregard of all those conditions which it -has artificially set aside. We see this in the tendency of anatomists -and physiologists to assign to _one_ element, in a complex cluster of -co-operants, the significance which properly belongs to that cluster: -as when the property of a tissue is placed exclusively in a single -element of that tissue, the function of an organ assigned to its chief -tissue, and a function of the organism to a single organ. - -Another object has been to furnish the reader uninstructed in -physiology with such a general outline of the structure and functions -of the organism, and such details respecting the sentient mechanism, -as may awaken an interest in the study, and enable him to understand -the application of Physiology to Psychology. If he comes upon details -which can only interest specially educated students, or perhaps -only by them be really understood, he can pass over these details, -for their omission will not seriously affect the bearing of the -general principles. I have given the best I had to give; and must -leave each reader to find in it whatever may interest him. The uses -of books are first to stimulate inquiry by awakening an interest; -secondly, to clarify and classify the knowledge already gained from -direct contemplation of the phenomena. They are stimuli and aids to -observation and thought. They should never be allowed to see for us, -nor to think for us. - -The volume contains four essays. The first, on the _Nature of Life_, -deals with the speciality of organic phenomena, as distinguished -from the inorganic. It sets forth the physiological principles which -Psychology must incessantly invoke. In the course of the exposition I -have incorporated several passages from four articles on Mr. Darwin’s -hypotheses, contributed to the _Fortnightly Review_ during the year -1868. I have also suggested a modification of the hypothesis of Natural -Selection, by extending to the _tissues and organs_ that principle of -competition which Mr. Darwin has so luminously applied to _organisms_. -Should this generalization of the “struggle for existence” be accepted, -it will answer many of the hitherto unanswerable objections. - -The second essay is on the _Nervous Mechanism_, setting forth what is -known and what is inferred respecting the structure and properties of -that all-important system. If the sceptical and revolutionary attitude, -in presence of opinions currently held to be established truths, -surprises or pains the reader unprepared for such doubts, I can only -ask him to submit my statements to a similar scepticism, and confront -them with the ascertained evidence. After many years of laborious -investigation and meditation, the conclusion has slowly forced -itself upon me, that on this subject there is a “false persuasion of -knowledge” very fatal in its influence, because unhesitatingly adopted -as the ground of speculation both in Pathology and Psychology. This -persuasion is sustained because few are aware how much of what passes -for observation is in reality sheer hypothesis. I have had to point out -the great extent to which Imaginary Anatomy has been unsuspectingly -accepted; and hope to have done something towards raising a rational -misgiving in the student’s mind respecting “the superstition of the -nerve-cell”--a superstition which I freely confess to have shared in -for many years. - -The third essay treats of _Animal Automatism_. Here the constant -insistance on the biological point of view, while it causes a rejection -of the mechanical theory, admits the fullest recognition of all the -mechanical relations involved in animal movements, and thus endeavors -to reconcile the contending schools. In this essay I have also -attempted a psychological solution of that much-debated question--the -relation between Body and Mind. This solution explains why physical -and mental phenomena must necessarily present to our apprehension -such profoundly diverse characters; and shows that Materialism, in -attempting to deduce the mental from the physical, puts into the -conclusion what the very terms have excluded from the premises; -whereas, on the hypothesis of a physical process being only the -objective aspect of a mental process, the attempt to interpret the one -by the other is as legitimate as the solution of a geometrical problem -by algebra. - -In the final essay the _Reflex Theory_ is discussed; and here once -more the biological point of view rectifies the error of an analysis -which has led to the denial of Sensibility in reflex actions, because -that analysis has overlooked the necessary presence of the conditions -which determine Sensibility. In these chapters are reproduced several -passages from the _Physiology of Common Life_. - -According to my original intention, this volume was to have included an -exposition of the part I conceive the brain to play in physiological -and psychological processes, but that must be postponed until it can be -accompanied by a survey of psychological processes which would render -the exposition more intelligible. - - THE PRIORY, March, 1877. - - - - -CONTENTS. - - - PROBLEM I. THE NATURE OF LIFE. - - - CHAPTER I. - PAGE - THE PROBLEM STATED 3 - (_The Position of Biology_) 4 - (_Organisms_) 8 - (_Vital Force_) 14 - (_Vital Force controlling Physical and Chemical Forces_) 16 - - - CHAPTER II. - - DEFINITIONS OF LIFE 24 - - - CHAPTER III. - - ORGANISM, ORGANIZATION, AND ORGANIC SUBSTANCE 37 - (_Organism and Medium_) 45 - (_The Hypothesis of Germinal Matter_) 57 - (_Organisms and Machines_) 67 - - - CHAPTER IV. - - THE PROPERTIES AND FUNCTIONS 70 - (_Does the Function determine the Organ?_) 78 - - - CHAPTER V. - - EVOLUTION 89 - (_Natural Selection and Organic Affinity_) 115 - (_Recapitulation_) 152 - - - PROBLEM II. THE NERVOUS MECHANISM. - - - CHAPTER I. - - SURVEY OF THE SYSTEM, 157 - (_The Early Forms of Nerve-Centres_), 168 - (_The Peripheral System_), 171 - (_Ganglia and Centres_), 172 - - - CHAPTER II. - - THE FUNCTIONAL RELATIONS OF THE NERVOUS SYSTEM, 176 - - - CHAPTER III. - - NEURILITY, 189 - (_Origins of Nerve-Force_), 201 - (_The Hypothesis of Specific Energies_), 207 - - - CHAPTER IV. - - SENSIBILITY, 211 - - - CHAPTER V. - - ACTION WITHOUT NERVE-CENTRES, 227 - - - CHAPTER VI. - - WHAT IS TAUGHT BY EMBRYOLOGY?, 237 - - - CHAPTER VII. - - THE ELEMENTARY STRUCTURE OF THE NERVOUS SYSTEM, 251 - (_Difficulties of the Investigation_), 252 - (_The Nerve-Cell_), 258 - (_The Nerves_), 270 - (_The Neuroglia_), 273 - (_The Relations of the Organites_), 278 - (_Recapitulation_), 299 - - CHAPTER VIII. - - THE LAWS OF NERVOUS ACTIVITY 310 - (_The Energy of Neurility_) 311 - (_The Propagation of Excitation_) 314 - (_Stimuli_) 321 - (_Stimulation_) 324 - (_The Law of Discharge_) 326 - (_The Law of Arrest_) 333 - (_The Hypothesis of Inhibitory Centres_) 336 - (_Anatomical Interpretations of the Laws_) 339 - - - PROBLEM III. ANIMAL AUTOMATISM. - - - CHAPTER I. - - THE COURSE OF MODERN THOUGHT 345 - - - CHAPTER II. - - THE VITAL MECHANISM 363 - - - CHAPTER III. - - THE RELATION OF BODY AND MIND 376 - - - CHAPTER IV. - - CONSCIOUSNESS AND UNCONSCIOUSNESS 399 - - - CHAPTER V. - - VOLUNTARY AND INVOLUNTARY ACTIONS 415 - - - CHAPTER VI. - - THE PROBLEM STATED 431 - - - CHAPTER VII. - - IS FEELING AN AGENT? 440 - - - PROBLEM IV. THE REFLEX THEORY. - - - CHAPTER I. - - THE PROBLEM STATED 467 - - - CHAPTER II. - - DEDUCTIONS FROM GENERAL LAWS 490 - - - CHAPTER III. - - INDUCTIONS FROM PARTICULAR OBSERVATIONS 509 - (_Cerebral Reflexes_) 511 - (_Discrimination_) 520 - (_Memory_) 522 - (_Instinct_) 522 - (_The Acquisition of Instinct_) 536 - (_Acquisition_) 546 - - - CHAPTER IV. - - NEGATIVE INDUCTIONS 550 - - - - -PROBLEM I. - -THE NATURE OF LIFE. - - “La Physiologie a pour but d’exposer les phénomènes de la vie - humaine et les conditions d’où ils dépendant. Pour y arriver - d’une manière sûre, il faut nécessairement avant tout déterminer - quels sont les phénomènes qu’on désigne sous le nom de vie en - général. C’est pourquoi la première chose à faire est d’étudier - les propriétés générales du corps qu’on appelle organiques ou - vivans.”--TIEDEMANN, _Traité de Physiologie de l’Homme_, I. 2. - - “Some weak and inexperienced persons vainly seek by dialectics and - far-fetched arguments either to upset or establish things that are - only to be founded on anatomical demonstration and believed on the - evidence of the senses. He who truly desires to be informed of the - question in hand must be held bound either to look for himself, or - to take on trust the conclusions to which they who have looked have - come.”--HARVEY, _Second Dissertation to Riolan_. - - - - -THE NATURE OF LIFE. - - - - -CHAPTER I. - -THE PROBLEM STATED. - - -1. Although for convenience we use the terms Life and Mind as -representing distinct orders of phenomena, the one objective and the -other subjective, and although for centuries they have designated -distinct entities, or forces having different substrata, we may now -consider it sufficiently acknowledged among scientific thinkers that -every problem of Mind is necessarily a problem of Life, referring to -one special group of vital activities. It is enough that Mind is never -manifested except in a living organism to make us seek in an analysis -of organic phenomena for the material conditions of every mental fact. -Mental phenomena when observed in others, although interpretable by our -consciousness of what is passing in ourselves, can only be objective -phenomena of the vital organism. - -2. On this ground, if on this alone, an acquaintance with the -general principles of structure and function is indispensable to -the psychologist; although only of late years has this been fully -recognized, so that men profoundly ignorant of the organism have had -no hesitation in theorizing on its highest functions. In saying that -such knowledge is indispensable, I do not mean that in the absence -of such knowledge a man is debarred from understanding much of the -results reached by investigators, nor that he may not himself make -useful observations and classifications of psychological facts. It is -possible to read books on Natural History with intelligence and profit, -and even to make good observations, without a scientific groundwork of -biological instruction; and it is possible to arrive at empirical facts -of hygiene and medical treatment without any physiological instruction. -But in all three cases the absence of a scientific basis will render -the knowledge fragmentary and incomplete; and this ought to deter -every one from offering an opinion on debatable questions which pass -beyond the limit of subjective observations. The psychologist who has -not prepared himself by a study of the organism has no more right to -be heard on the genesis of the psychical states, or of the relations -between body and mind, than one of the laity has a right to be heard on -a question of medical treatment. - - -THE POSITION OF BIOLOGY. - -3. Science is the systematic classification of Experience. It -postulates unity of Existence with great varieties in the Modes of -Existence; assuming that there is one Matter everywhere the same, -under great diversities in the complications of its elements. The -distinction of Modes is not less indispensable than the identification -of the elements. These Modes range themselves under three supreme -heads: Force, Life, Mind. Under the first, range the general properties -exhibited by _all_ substances; under the second, the general properties -exhibited by _organized_ substances; under the third, the general -properties exhibited by organized _animal_ substances. The first -class is subdivided into _Physics_, celestial and terrestrial, and -_Chemistry_. Physics treats of substances which move as masses, -or which vibrate and rotate as molecules, without undergoing any -appreciable change of structural integrity; they show changes of -_position_ and _state_, without corresponding changes in their -elements. Chemistry treats of substances which undergo molecular -changes of composition _destructive_ of their integrity. Thus the blow -which simply moves one body, or makes it vibrate, explodes another. The -friction which alters the temperature and electrical state of a bit of -glass, ignites a bit of phosphorus, and so destroys its integrity of -structure, converting phosphorus into phosphoric acid. - -4. The second class, while exhibiting both physical and chemical -properties, is markedly distinguished by the addition of properties -called vital. Their peculiarity consists in this: they undergo -molecular changes of composition and decomposition which are -simultaneous, and _by this simultaneity preserve their integrity of -structure_. They change their state, and their elements, yet preserve -their unity, and even when differentiating continue specific. Unlike -all other bodies, the organized are born, grow, develop, and decay, -through a prescribed series of graduated evolutions, each stage being -the indispensable condition of its successor, no stage ever appearing -except in its serial order. - -5. The third class, while exhibiting all the characteristics of the -two preceding classes, is specialized by the addition of a totally -new property, called Sensibility, which subjectively is Feeling. Here -organized substance has become animal substance, and Vegetality has -been developed into Animality by the addition of new factors,--new -complexities of the elementary forces. Many, if not most, philosophers -postulate an entirely new Existence, and not simply a new Mode, to -account for the manifestations of Mind; they refuse to acknowledge -it to be a vital manifestation, they demand that to Life be added a -separate substratum, the Soul. This is not a point to be discussed -here. We may be content with the assertion that however great the -phenomenal difference between Humanity and Animality (a difference we -shall hereafter see to be the expression of a new factor, namely, the -social factor), nevertheless the distinctive attribute of Sensibility, -out of which rise Emotion and Cognition, marks the inseparable -_kinship_ of mental with vital phenomena. - -Thus all the various Modes of Existence may, at least in their -objective aspect, be ranged under the two divisions of Inorganic and -Organic,--Non-living and Living,--and these are respectively the -objects of the cosmological and the biological sciences. - -6. The various sciences in their serial development develop the -whole art of Method. Mathematics develops abstraction, deduction, -and definition; Astronomy abstraction, deduction, and observation; -Physics adds experiment; Chemistry adds nomenclature; Biology adds -classification, and for the first time brings into prominence the -important notion of _conditions of existence_, and the variation -of phenomena under varying conditions: so that the relation of the -organism to its medium is one never to be left out of sight. In -Biology also clearly emerges for the first time what I regard as the -true notion of causality, namely, the _procession_ of causes,--the -combination of factors in the product, and not an _ab extra_ -determination of the product. In Vitality and Sensibility we are made -aware that the causes are _in_ and not _outside_ the organism; that -the organic effect is the organic cause in operation; that there is -autonomy but no autocracy; the effect issues as a resultant of the -co-operating conditions. In Sociology, finally, we see brought into -prominence the _historical conditions of existence_. From the due -appreciation of the conditions of existence, material and historical, -we seize the true significance of the principle of Relativity. - -7. Having thus indicated the series of the abstract sciences we have -now to consider more closely the character of Biology. The term was -proposed independently yet simultaneously in Germany and France, in -the year 1802, by Treviranus and Lamarck, to express “the study of the -forms and phenomena of Life, the conditions and laws by which these -exist, and the causes which produce them.” Yet only of late years has -it gained general acceptance in France and England. The term Cosmology, -for what are usually called the Physical Sciences, has not yet come -into general use, although its appropriateness must eventually secure -its recognition. - -Biology,--the abstract science of Life,--embracing the whole organic -world, includes Vegetality, Animality, and Humanity; the biological -sciences are Phytology, Zoölogy, and Anthropology. Each of the -sciences has its cardinal divisions, statical and dynamical, namely, -Morphology--the science of form,--and Physiology--the science of -function. - -Morphology embraces--1°, _Anatomy_, i. e. the description of the parts -then and there present in the organism; and these parts, or organs, are -further described by the enumeration of their constituent tissues and -elements; and of these again the proximate principles, so far as they -can be isolated without chemical decomposition. 2°, _Organogeny_, i. e. -the history of the evolution of organs and tissues. - -Physiology embraces the properties and functions of the tissues and -organs--the primary conditions of Growth and Development out of -which rise the higher functions bringing the organism into active -relation with the surrounding medium. The first group of properties -and functions are called those of vegetal, or organic life; the second -those of animal, or relative life. - - -ORGANISMS. - -8. It will be needful to fix with precision the terms, Organism, Life, -Property, and Function. - -An organism, although usually signifying a more or less complex unity -of organs, because the structures which first attracted scientific -attention were all thus markedly distinguished from inorganic -bodies, has by the gradual extensions of research been necessarily -generalized, till it now stands for any organized substance capable of -independent vitality: in other words, any substance having the specific -combination of elements which manifests the serial phenomena of growth, -development, and decay. There are organisms that have no differentiated -organs. Thus a microscopic formless lump of semifluid jelly-like -substance (Protoplasm) is called an organism, because it feeds itself, -and reproduces itself. There are advantages and disadvantages in such -extensions of terms. These are notable in the parallel extension of -the term Life, which originally expressing only the complex activities -of complex organisms, has come to express the simplest activities of -protoplasm. Thus a Monad is an organism; a Cell is an organism; a Plant -is an organism; a Man is an organism. And each of these organisms is -said to have its Life, because - - “Through all the mighty commonwealth of things - Up from the creeping worm to sovereign man”[1] - -there is one fundamental group of conditions, one organized substance, -one vitality. - -Obviously this unity is an abstraction. In reality, the life manifested -in the Man is _not_ the life manifested in the Monad: he has Functions -and Faculties which the Monad has no trace of; and if the two organisms -have certain vital characteristics in common, this unity is only -recognized in an _ideal construction_ which lets drop all concrete -differences. The Life is different when the organism is different. -Hence any definition of Life would be manifestly insufficient which -while it expressed the activities of the Monad left unexpressed the -conspicuous and important activities of higher organisms. A sundial -and a repeater will each record the successive positions of the sun -in the heavens; but although both are instruments for marking time, -the sundial will not do the work of the repeater; the complexity and -delicacy of the watch mechanism are necessary for its more varied and -delicate uses. A semifluid bit of protoplasm will feed itself; but it -will not feed and sustain a complex animal; nor will it feel and think. - -9. Neglect of this point has caused frequent confusion in the attempts -to give satisfactory definitions. Biologists ought to have been warned -by the fact that some of the most widely accepted definitions exclude -the most conspicuous phenomena of Life, and are only applicable to the -vegetable world, or to the vegetal processes in the animal world. A -definition, however abstract, should not exclude essential characters. -The general consent of mankind has made Life synonymous with Mode of -Existence. By the life of an animal is meant the existence of that -animal; when dead the _animal_ no longer exists; the substances of -which the organism was composed exist, but under another mode; their -connexus is altered, and the organism vanishes in the alteration. -It is a serious mistake to call the corpse an organism; for that -_special_ combination which constituted the organism is not present in -the corpse. This misconception misleads some speculative minds into -assigning life to the universe. The universe assuredly exists, but it -does not live; its existence can only be identified with life, such as -we observe in organisms, by a complete obliteration of the speciality -which the term Life is meant to designate. Yet many have not only -pleased themselves with such a conception, but have conceived the -universe to be an organism fashioned, directed, and sustained by a soul -like that of man--the _anima mundi_. This is to violate all scientific -canons. The life of a plant-organism is not the same as the life of an -animal-organism; the life of an animal-organism is not the same as the -life of a human-organism; nor can the life of a human-organism be the -same as the life of the world-organism. The unity of Existences does -not obliterate the variety of Modes; yet it is the speciality of each -Mode which Science investigates; to some of these Modes the term Life -is consistently applied, to others not; and if we merge them all in a -common term, we must then invent a new term to designate the Modes now -included under Life. - -10. In resisting this unwarrantable extension of the term I am not -only pointing to a speculative error, but also to a serious biological -error common in both spiritualist and materialist schools, namely -that of assigning Life to other than organic agencies. Instead of -recognizing the speciality of this Mode of Existence as dependent on -a speciality of the organic conditions, the spiritualist assigns Life -to some extra-organic Vital Principle, the materialist assigns it to -some inorganic agent--physical or chemical. Waiving for the present all -discussion of Vitalism, let us consider in what sense we must separate -organic from all inorganic phenomena. - -11. There is a distinction between inorganic and organic which may -fitly be called radical: it lies at the root of the phenomena, and must -be accepted as an ultimate fact, although the synthesis on which it -depends is analytically reducible to a complication of more primitive -conditions. It has been already indicated in § 5. All organisms above -the very simplest are syntheses Of three terms: Structure, Aliment, -and Instrument. Crystals, like all other anorganisms have structure, -and in a certain sense they may be said to grow (_Mineralia crescunt_), -though the growth is by _increase_ and not by _modification_:[2] -the motherlye, which is the food of the crystal, is never brought -to the crystal, nor prepared for it, by any instrumental agency of -the crystal. Organisms are exclusively instrumental; the organ is an -instrument. The structural integrity of an organism is thus preserved -through an alimentation which is effected through special instruments. -Nothing like this is visible in anorganisms. - -The increase of a crystal is further distinguishable from the growth -of an organism, in the fact Of its being simple accretion without -development; and the structure of the crystal is distinguishable from -that of an organism in the fact that its integrity is preserved by -the _exclusion_ of all molecular change, and not by the simultaneous -changes of molecular decomposition and recomposition. Inorganic -substances are sometimes as unstable as organic, sometimes even more -unstable; but their instability is the source of their structural -destruction--they change into other species; whereas the instability -of _organized_ substances (_not_ of organic) is the source of their -structural integrity: the tissue is renovated, and its renovation is a -consequence of its waste. - -12. But while the distinction is thus radical, when we view the -organism from the _real_--that is, from the synthetic point of view--we -must also urge the validity of the analytical point of view, which -seizes on the conditions here complicated in a special group, and -declares these conditions to be severally recognizable equally in -anorganisms and in organisms. All the fundamental properties of Matter -are recognizable in organized Matter. The elementary substances and -forces familiar to physicists and chemists are the materials of the -biologist; nor has there been found a single organic substance, however -special, that is not reducible to inorganic elements. We see, then, -that organized Matter is only a special combination of that which in -_other_ combinations presents chemical and physical phenomena; and we -are prepared to find Chemistry and Physics indispensable aids in our -analysis of organic phenomena. Aids, but only aids; indispensable, but -insufficient. - -13. There is therefore an ambiguity in the common statement that -organized matter is not _ordinary_ matter. Indisputable in one sense, -this is eminently disputable when it is interpreted as evidence of -a peculiar Vital Force “wholly unallied with the primary energy of -Motion.” If by “ordinary matter” be meant earths, crystals, gases, -vapors, then assuredly organized matter is not ordinary. “Between the -_living_ state of matter and its _non-living_ state,” says Dr. Beale, -“there is an absolute and irreconcilable difference; so far from our -being able to demonstrate that the non-living passes by gradations -into or gradually assumes the scale or condition of the _living_, the -transition is sudden and abrupt, and matter already in the living -state may pass into the non-living condition in the same sudden and -complete manner.”[3] The ambiguity here is sensible in the parallel -case of the difference between crystallizable and coagulable matter, or -between one crystal and another. If we can decompose the organic into -the inorganic, this shows that the elements of the one are elements -of the other; and if we are not yet able to recompose the inorganic -elements into organic matter (not at least in its more complex forms), -may this not be due to the fact that we are ignorant of the proximate -synthesis, ignorant of the precise way in which the elements are -combined? I may have every individual part of a machine before me, but -unless I know the proper position of each, I cannot with the parts -reconstruct the machine. Indeed the very common argument on which so -much stress is laid in favor of some mysterious Principle as the source -of organic phenomena, namely, that human skill is hopelessly baffled in -the attempt to make organic substances, still more a living cell, is -futile. Men can make machines, it is said, but not organisms, _ergo_ -organisms must have a spiritual origin. But the fact is that no man can -make a machine, _unless_ he take advantage of the immense traditions of -our race, and apply the skill of millions who have worked and thought -before him, slowly and tentatively discovering the necessary means -of mechanical effect. The greatest thinker, or the deepest scholar, -who did not place himself in the line of the tradition, and learn the -principles of mechanism, and the properties of the materials, would be -as incapable of making a watch, as the physiologist now is of making -a cell. But the skill of man has already succeeded in making many -organic substances, and will perhaps eventually succeed in making a -cell, certainly will, if ever the special synthesis which binds the -elements together should be discovered. Not that such a discovery would -alter the position of Biology in relation to Chemistry. The making of -albumen, nay, the construction of an organism in the laboratory, would -not in the least affect the foundation of Biology, would not obliterate -the radical difference between organisms and anorganisms. It is the -speciality of organic phenomena which gives them a special place, -although the speciality may only be due to a complication of general -agencies. - - -VITAL FORCE. - -14. A similar ambiguity to that of the phrase “ordinary matter” lies -in the equally common phrase “Vital Force,” which is used to designate -a special group of agencies, and is then made to designate an agent -which has no kinship with the general group; that is to say, instead of -being employed in its real signification--that which alone represents -our knowledge--as the abstract statical expression of the complex -conditions necessary to the manifestation of vital phenomena, or as -the abstract dynamical expression of the phenomena themselves, it -is employed as an expression of their unknown Cause, which, because -unknown, is dissociated from the known conditions, and erected into -a mysterious Principle, having no kinship with Matter. In the first -sense the term is a shorthand symbol of what is known and inferred. -The known conditions are the relations of an organism and its medium, -the organism being the union of various substances all of which have -their peculiar properties when isolated; properties that disappear -in the union, and are replaced by others, which result from the -combination--as the properties of chlorine and sodium all disappear in -the sea-salt which results from their union; or as the properties of -oxygen and the properties of hydrogen disappear and are replaced by the -properties of water. When therefore Vital Force is said to be exalted -or depressed, the phrase has rational interpretation in the alteration -which has taken place in one or more of the conditions, internal and -external: a change in the tissues, the plasma, or the environment, -exalts or depresses the energy of the vital manifestations; and to -suppose that this is effected through the agency of some extra-organic -Principle is a purely gratuitous fiction. - -15. That we are ignorant of one or more of the indispensable conditions -symbolized in the abstract term Vitality or Vital Force, is no reason -for quitting the secure though difficult path of Observation, and -rushing into the facile but delusive path of Fiction, which proposes -metempirical Agents (in the shape of Vital and Psychical Principles) -to solve the problems of Life and Mind. We may employ the term Vital -Force to label our observations, together with all that still remains -unobserved; and we are bound to recognize the line which separates -observation from inference, what is proved from what is inferred; -but while marking the limits of the known, we are not to displace -the known in favor of the unknown. It is said that because of our -ignorance we must assume these causes of Life and Mind to be _unallied_ -with known material causes, and belonging to a different order of -existences. This is to convert ignorance into a proof; and not only -so, but to allow what we do not know to displace what we do know. The -organicist is ready to admit that much has still to be discovered; the -vitalist, taking his stand upon this unknown, denies that what has been -discovered is really important, and declares that the real agent is -wholly unallied to it. How _can_ he know this? - -He does not know it; he assumes it; and the chief evidence he adduces -is that the ordinary laws of inorganic matter are incapable of -explaining the phenomena of organized matter; and that physical and -chemical forces are controlled by vital force. I accept both these -positions, stripping them, however, of their ambiguities. The laws of -ordinary matter are clearly incompetent in the case of matter which is -not ordinary, but _specialized_ in organisms; and when we come to treat -of Materialism we shall see how unscientific have been the hypotheses -which disregard the distinction. The question of control is too -interesting and important to be passed over here. - - -VITAL FORCE CONTROLLING PHYSICAL AND CHEMICAL FORCES. - -16. The facts relied on by the vitalists are facts which every -organicist will emphasize, though he will interpret them differently. -When, for example, it is said that “Life resists the effect of -mechanical friction,” and the proof adduced is the fact that the -friction which will thin and wear away a dead body is actually the -cause of the thickening of a living--the skin of a laborer’s hand -being thickened by his labor; the explanation is not that Life, an -extra-organic agent, “resists mechanical friction”--for the mechanical -effect is _not_ resisted (the skin is rubbed off the rower’s hand -sooner than the wood is rubbed off the oar)--but that Life, i. e. -organic activity repairs the waste of tissue. - -17. Again, although many of the physical and chemical processes which -invariably take place under the influences to which the substances -are subjected out of the organism, will not take place at all, or -will take place in different degrees, when the substances are in the -organism, this is important as an argument against the notion of vital -_phenomena_ being deducible from physical and chemical _laws_, but is -valueless as evidence in favor of an extra-organic agent. Let us glance -at one or two striking examples. - -18. No experimental inquirer can have failed to observe the often -contradictory results which seemingly unimportant variations in the -conditions bring about; no one can have failed to observe what are -called chemical affinities wholly frustrated by vital conditions. Even -the ordinary laws of Diffusion are not always followed in the organism. -The Amœba, though semifluid, resists diffusion when alive; but when it -dies it swells and bursts by osmosis. The exchange of gases does not -take place in the tissues, precisely as in our retorts. The _living_ -muscle respires, that is, takes up oxygen and gives out carbonic -acid, not on the principle of simple diffusion, but by two separable -physiological processes. The carbonic acid is given out, even when -there is no oxygen whatever present in the atmosphere, and its place -may then be supplied by hydrogen; and this physiological process is so -different from the physical process which goes on in the dead muscle -(the result of putrefaction), that it has been proved by Ranke to go -on when the temperature is so low that all putrefaction is arrested. -The same experimenter finds[4] that whereas living nerve will take up, -by imbibition, 10 per cent of potash salts, it will not take up 1 per -cent of soda salts, presented in equal concentration; and he points -to the general fact that the absorption of inorganic substances does -_not_ take place according to the simple laws of diffusion, but that -living tissues have special laws, the nerve, for instance, having -a greater affinity for neutral potash salts than for neutral soda -salts. Let me add, by way of anticipating the probable argument that -may urge this in favor of Vital Principle which is lightly credited -with the prescience of final causes, that so far from this “elective -affinity” of the tissues being intelligent and always favorable, -Ranke’s experiments unequivocally show that it is more active towards -destructive, poisonous substances, than towards the reparative, -alimentary substances; which is indeed consistent with the familiar -experience that poisons are more readily absorbed than foods, when both -are brought to the tissues. Thus it is well known that of all the salts -the sulphate of copper is that which plants most readily absorb--and -it kills them. The special affinities disappear as the vitality -disappears, and dying plants absorb all salts equally. - -19. The more the organism is studied, the more evident it will become -that the simple laws of diffusion, as presented in anorganisms rarely -if ever take effect in tissues; in other words, what is called -Imbibition in Physics is the somewhat different process of Absorption -in Physiology.[5] The difference is notable in this capital fact, that -whereas the physical diffusion of liquids and gases is determined -by differences of density, the physiological absorption of liquids -and gases is determined by the molecular organization of the tissue, -which is perfectly indifferent to, and resists the entrance of, all -substances incapable of entering into organic combination, either as -aliment or poison. A curious example of the indifference of organized -substances to some external influences and their reaction upon others, -is the impossibility of provoking ciliary movement in an epithelial -cell, during repose, by any electrical, mechanical, or chemical stimuli -except potash and soda. Virchow discovered that a minute quantity of -either of these, added to the water in which the cell floated, at once -called forth the ciliary movements. - -20. The true meaning of the resistance of Vitality to ordinary chemical -affinity is, that the conditions involved in the phenomena of Vitality -are not the conditions involved in the phenomena of Chemistry; in other -words, that in the living organism the substances are placed under -conditions different from those in which we observe these substances -when their chemical affinities are displayed in anorganisms. But we -need not go beyond the laboratory to see abundant examples of this -so-called resistance to chemical affinity, when the conditions are -altered. The decomposition of carbonates by tartaric acid is a chemical -process which is wholly resisted if alcohol instead of water be the -solvent employed. The union of sulphur with lead is said to be due -to the affinity of the one for the other; but no one supposes this -affinity to be irrespective of conditions, or that the union will take -place when any one of these conditions is absent. If we fuse a compound -of lead and iron in a crucible containing sulphur, we find it is the -iron, and not the lead, which unites with the sulphur; yet we do not -conclude that there is a Crucible Principle which frustrates chemical -affinity and resists the union of sulphur and lead; we simply conclude -that the presence of the iron is a condition which prevents the -combination of the sulphur with the lead: not until all the iron has -taken up its definite proportion of sulphur will the affinity of the -lead come into play. This is but another illustration of the law that -_effects are processions of their causes_, summations of the conditions -of their existence. If the fire burns no hole in the teakettle so long -as there is water to conduct the heat away, this is not due to any -principle more mysterious than the presence of a readily conducting -water.[6] - -21. In accordance with the law of Causation just mentioned, which -has been expounded in detail in our First Series (Vol. II. p. 335), -the special combinations of Matter in organisms must present special -phenomena. Therefore since the province of Biology is that of -explaining organic phenomena by means of their organic conditions, -it must be radically distinguished from the provinces of Physics and -Chemistry, which treat not of organized but of inorganic matter. It -is idle, it is worse, for it is misleading, to personify the organic -conditions, known and inferred, in a Vital Principle; idle, because we -might with equal propriety personify the conditions of crystallization -in a Crystal Principle; misleading, because the artifice is quickly -dropped out of sight, and the abstract term then becomes accepted as -an entity, supposed to create or rule the phenomena it was invented to -express. - -22. Inquirers are but too apt to misconceive the value of Analysis, -which is an artifice of Method indispensable to research, though -needing the complementary rectification by Synthesis before a real -explanation can be reached. Analysis decomposes the actual fact into -ideal factors, separates the group into its components, and considers -each of these, not as it exists in the group, in the reality, but as -it exists when theoretically detached from the others. The oxygen -and hydrogen into which water is decomposed did not exist as these -gases in the water; the albumen and phosphate we extract from a nerve -did not exist _as_ isolated albumen and phosphate in the nerve, they -were molecularly combined. In like manner the physical and chemical -processes which may analytically be inferred in vital processes do -not really take place in the same way as out of the organism. The -real process is always a vital process, and must be explained by the -synthesis of all the co-operant conditions. The laws of Physics and -Chemistry formulate abstract expressions of phenomena, wherever and -whenever these appear, without reference to the _modes of production_; -and in _this_ sense the movement of a limb is no less a case of -Dynamics than the movement of a pulley--the decomposition of a tissue -is a case of Chemistry no less than the decomposition of a carbonate; -the electromotor phenomena observed in muscle are as purely physical -as those observed in a telegraph. But when a biologist has to explain -the movements of the limbs, or the decompositions of tissues, he has -to deal with the phenomena and their modes of production, he has -a particular group before him, and must leave out nothing that is -characteristic of it. The movements of the pulley do not depend on -Contractility and Sensibility, which in turn depend on Nutrition. The -decomposition of the carbonate does not depend on conditions resembling -those of a living tissue. Vaucanson’s duck was surprisingly like a -living duck in many of its movements; but in none of its actions was -there any real similarity to the actions of a bird, because the machine -was unlike an organism in action. The antithesis of mechanism and -organism will be treated of in § 78. - -23. We conclude, then, that defining physical phenomena as the -movements which take place _without_ change of structure, and chemical -phenomena as the movements _with_ change of structure, although -both classes may be said to take place in the organism, and to be -the primary conditions on which organic phenomena depend, they do -not embrace the whole of the conditions, nor are the sciences which -formulate them capable of formulating either the special phenomena -characteristic of organisms or their special modes of production. The -biologist will employ chemical and physical analysis as an essential -part of his method; but he will always rectify what is artificial in -this procedure, by subordinating the laws of Physics and Chemistry -to the laws of Biology revealed in the synthetic observation of -the organism as a whole. The rectification, here insisted on, will -be recognized as peculiarly urgent in Psychology, which has greatly -suffered from the misdirection of Analysis. - -24. No one will misunderstand this specialization of Biology to mean -a separation of Life from the series of objective phenomena, and -the introduction of a new entity; the specialization points to a -Mode of Existence. All classifications are artifices, but they have -their objective grounds; the ground of difference on which Biology -is separated from Chemistry and Physics, though all three may be -merged in a common identity, is such as to justify the term radical. -A vital process is no more to be considered physico-chemical, because -physico-chemical conditions are presupposed in it, than a feeling is -to be considered a nutritive process, because Nutrition is presupposed -in all Feeling. Organic substances have been made by chemists, and -inorganic “cells” have also been made; but these substances were not -organized, these “cells” would not live. The germ-cell is the workshop -of generation, the secreting-cell the workshop of secretion, the -muscle-cell the workshop of contraction. What is required over and -above organic substances and cell-forms, is that special state called -_organization_. See § 49. - -Those who contemplate the manifestations without also taking into -account their modes of production may see nothing but physico-chemical -facts in vital facts. It is by a similar limitation of the point of -view that Vitality is often confounded with Movement, and portions -of organic matter are said to live, simply on the evidence of their -movements.[7] - - - - -CHAPTER II. - -DEFINITIONS OF LIFE. - - -25. Biology, the science of Life, being thus assigned its place in the -hierarchy of objective laws, we now proceed to consider what the term -Life symbolizes. - -By a large preliminary simplification, Life may be defined as _the -mode of existence of an organism in relation to its medium_. To render -this of any value, however, a clear conception of the organism is -first indispensable; and this must be preceded by an examination of -the various attempts to define life in anticipation of such a clear -conception. - -26. Every phenomenon, or group of phenomena, may be viewed under -two aspects--the _statical_, which considers the conditions of -existence; and the _dynamical_, which considers these conditions in -their resultant,--in their _action_. The statical definition of Life -will express the connexus of the properties of organized substance, -all those conditions, of matter, form, and texture, and of relation -to external forces, on which the organism depends. These various -conditions, condensed into a single symbol, constitute Vitality or -Vital Force, and are hence taken as the Cause of vital phenomena. -The dynamical definition will express the connexus of Functions and -Faculties of the organism, which are the statical properties of -organized substance in action, under definite relations. - -It is obvious that the term Life must vary with the varying -significates it condenses,--every variation in the complexity of the -organism will bring a corresponding fulness in the signification of -the term. The life of a plant is less significant than the life of -an animal; and the life of a mollusc less than that of a fish. But -not only is the term one of varying significance, it is always an -abstract term which drops out of sight particular concrete differences, -registering only the universal resemblances. - - * * * * * - -27. It would be a profitless labor to search out, and a wearisome -infliction to set down, the various definitions which have been -proposed and accepted; but certain characteristic examples may be -selected. All that I am acquainted with belong to two classes: 1°, the -_meta_-physiological hypothesis of an _extra_-organic agent, animating -lifeless matter by unknown powers; 2°, the physiological hypothesis -which seeks the cause of the phenomena (i. e. the conditions) _within_ -the organism itself,--a group of conditions akin to those manifested -elsewhere, but differently combined. The first hypotheses are known -under the names of Animism and Vitalism,--more commonly the latter. The -second are known as Organicism and Materialism,--but the latter term -only applies to some of the definitions. - -28. Under Vitalism are included all the hypotheses of a soul, a spirit, -an archæus, a vital principle, a vital force, a _nisus formativus_, -a plan or divine idea, which have from time to time represented the -metaphysical stage of Biology. The characteristic of that stage is -the personification of a mystery, accompanied by the persuasion that -to name a mystery is to explain it. In all sciences when processes -are imperfectly observed, the _theory_ of the processes (which is a -systematic survey of the available evidence marshalled in the order -of causal dependence) is supplemented by _hypothesis_, which fills up -with a guess the gap left by observation. The difference between the -metaphysical and the positive stages of a science lies in the kind of -guess thus introduced to supplement theory, and the degree of reliance -accorded to it. I have more than once insisted on the scientific -canon that “to be valid, an explanation must be expressed in terms of -phenomena already observed”; now it is quite clear that most of the -extra-organic hypotheses do not fulfil this condition; no one having -ever _observed_ a spirit, an archæus, or a vital principle; but only -_imagined_ these agents to explain the facts observed. As an example of -the difference, and a proof that the value of an hypothesis does not -rest on the facility with which it connects observations, and seems -to explain them, take the three hypotheses of animal spirits, nervous -fluid, and electricity, by which neural processes have been explained. -The animal spirits are imaginary; the nervous fluid is without a basis -in observation, no evidence of such a fluid having been detected; -but electricity (or, speaking rigorously, the movements classed as -electrical), although not proved to be _the_ agent in nerve-action, -is proved to exist in nerves as elsewhere, and its modes of operation -are verifiable. It, therefore, and it alone of the three hypotheses, -is in conformity with the scientific canon. It may not, on full -investigation, meet all requirements; it may be rejected as imperfect; -but it is the kind of guess which scientific theory demands. - -The second difference noticeable between the metaphysical and the -positive stages is the degree of reliance accorded to hypothesis; -which is very much the same as that noticeable in the uncritical and -critical attitudes of untrained and trained intellects. The one accepts -a guess as if it were a proof; is fascinated by the facility of linking -together isolated observations, and, relying on the guess as truth, -proceeds to deduce conclusions from it; the other accepts a guess as -an aid in research, trying by its aid to come upon some observation -which will reveal the hidden process; but careful never to allow the -guess to _supersede observation_, or to form a basis of deductions not -immediately verified. - -29. A glance at the metaphysiological definitions will detect both the -kind of guess and the kind of reliance which prevailed. The mystery -was not simply recognized, it was personified as an entity: Will and -Intelligence were liberally accorded to it, for it was supposed to -shape matter, and direct force into predestined paths by prescience of -a distant end. The observed facts of the egg passing through successive -changes into a complex organism were so marvellous, so unlike any -facts observable in the inorganic world, that they seemed to demand a -cause drawn from higher sources. The mystery of life obtruded itself -at every turn. It was named, and men fancied it explained. But in -truth no mystery is got rid of by explanation, however valid; it is -only shifted farther back. Explanation is the resolution of a complex -phenomenon into its conditions of existence--the product is reduced to -its factors; the explanation is final when this resolution has been -so complete that a reconstruction of the product is possible from -the factors. The vast majority of explanations--especially in the -organic region--are no more than what mathematicians call “a first -approximation.” It is through successive approximations that science -advances; but even when the final stage is reached a mystery remains. -We may know that certain elements combine in certain proportions -to produce certain substances; but why they produce these, and not -different substances, is no clearer than why muscles contract or -organisms die. This Why is, however, an idle question. That alone which -truly concerns us is the How, and not the Why. - -30. Biology is still a long way off the How. But it can boast of -many approximations; and its theories are to be tested by the degree -of approximation they effect. In this light the physiological, -_intra_-organic, hypotheses manifestly have the advantage. Many of them -are indeed very unacceptable; they are guided by a mistaken conception -of the truths reached by Analysis. For when men first began to discard -the extra-organic hypotheses, and to look into the organism itself, -they were so much impressed by the mechanical facts observed, that they -endeavored to reduce all the phenomena to Mechanics. The circulation -became simply a question of hydraulics. Digestion was explained as -trituration. The chemists then appeared, and their shibboleths were -“affinities” and “oxidations.” With Bichat arose the anatomical school, -which decomposing the organism into organs, the organs into tissues, -and these tissues into their elements, sought the analytical conditions -of existence of the organism in the properties of these tissues, and -the functions of these organs. The extra-organic agent was thus finally -shown to be not only a fiction, but a needless fiction. - -Every student of the history of the science will note how from the very -necessities of the case the metaphysiologists, without relinquishing -their Vital Principle, have been led more and more to enter on the -track of the physiologists, pursuing their researches more and more -into the processes going on in the organism, and assigning more and -more causal efficiency to these, with a corresponding restriction -of the province of their extra-organic cause. Hence in the ranks of -the vitalists have been found some of the very best observers and -theorists; but they were such in despite of, and not in consequence -of, their hypothesis, which was only invoked by them when evidence -was at fault. Nor, unscientific as vitalism is, can we deny that it -has been so far serviceable to the science, that it has corrected the -materialist error of endeavoring to explain organic phenomena by -physico-chemical laws; and has persistently kept in view the radical -difference between organic and inorganic. - -31. These remarks may justify a selection of definitions, classified -under the two heads. The selection is fitly opened by the Aristotelian -definition which prevailed for centuries. - -Aristotle distinguishes Life, which he says means “the faculties of -self-nourishment, self-development, and self-decay,” from the Vital -Principle. Every natural body manifesting life may be regarded as an -essential existence (οὐσία); but _then it is an existence only as a -synthesis_ (ὡς συθέτη); and since an organism is such a synthesis, -being possessed of Life, it cannot be the Vital Principle (ψυχή). -Therefore it follows that the Vital Principle must be an essence, as -being the Form of a natural body holding life in _potentiality_. The -Vital Principle is the primary reality of an organism. “It is therefore -as idle to ask whether the Vital Principle and Organism are one, as -whether the wax and the impress on it are one.... Thus if an eye -were an animal, Vision would be its Vital Principle: for Vision is, -abstractedly considered, the essence of the eye; but the eye is the -body of Vision, and if Vision be wanting, then, save in name, it is no -longer an eye.” - -Apart from certain metaphysical implications, inevitable at that -period, there is profound insight in this passage. His adversary -Telesio quite misconceives the meaning here assigned to the Vital -Principle.[8] - -32. Let us pass over all the intermediate forms of the hypothesis, and -descend to Kant, who defines Life “an internal principle of action” -(this does not distinguish it from fermentation); an organism he says -is “that in which every part is at once means and end.” “Each part -of the living body has its cause of existence in the whole organism; -whereas in non-living bodies each part has its cause in itself.” -Johannes Müller adopts a similar view: “The harmonious action of the -essential parts of the individual subsist only by the influence of a -force, the operation of which is extended to all parts of the body, -and does not depend on any single parts; this _force must exist before -the parts_, which are in fact formed by it during the development of -the embryo.... The vital force inherent in them generates from the -organic matter the essential organs which constitute the whole being. -This _rational creative force_ is exerted in every animal strictly in -accordance with what the nature of each requires.” - -33. This is decidedly inferior to Aristotle, who did not confound -the vegetative with the rational principle. It rests on the old -metaphysical error of a _vis medicatrix_, an error which cannot -sustain itself against the striking facts which constantly point to -a _vis destructrix_, a destructive tendency quite as inexorable as -the curative tendency. And the experimental biologist soon becomes -impressed with the fact that the tissues have indeed a _selective_ -action, by which from out the nutrient material only these substances -are assimilated which will enter into combination with them; but this -selective action is fatal, no less than reparative: substances which -poison the tissue are taken up as readily as those which nourish -it. The idea of prescience, therefore, cannot be sustained; it is -indeed seldom met with now in the writings of any but the Montpellier -school, who continue the traditions of Stahl’s teaching. It has been -so long exploded elsewhere that one is surprised to find an English -physiologist clinging to a modification of it--I mean Dr. Lionel Beale, -who repeatedly insists on Life as “a peculiar Force, _temporarily -associated_ with matter,” a “power capable of controlling and directing -both matter and force,” an “_undiscovered_ form of force _having no -connection with primary energy or motion_.” “The higher phenomena of -the nervous system are probably due primarily to the movements of the -germinal matter due to vital power, which vital power of this the -highest form of germinal matter is in fact the living _I_.” - -34. Apart from the primary objection to all these definitions, -namely, that they seek to express organic phenomena in terms of an -extra-organic principle, to formulate the facts _observed_ in terms -of a cause _inferred_, there is the fatal objection that they speak -confidently on what is avowedly unknown. If the force be, as Dr. Beale -says, “undiscovered,” on what grounds can he assert that it has _no_ -connection with the forces which are known? All that the observed facts -warrant is the assertion that organic phenomena are special (which -no one denies), and must therefore depend on special combinations of -matter and force. But on this ground we might assume a crystallizing -Force, and a coagulating Force, having no connection with the molecular -forces manifested elsewhere: these also are special phenomena, not to -be confounded with each other. - -35. Schelling defines Life as “a principle of individuation” and a -“cycle of successive changes determined and fixed by this internal -principle.” Which is so vague that it may be applied in very different -senses. Bichat’s celebrated definition (which is only a paraphrase of -a sentence in Stahl), “the sum of the functions which resist Death,” -although an endeavor to express the facts from the Intra-organic point -of view, is not only vague, but misrepresents one of the cardinal -conditions, by treating the External Medium as antagonistic to Life, -whereas Life is only possible in the relation to a Medium. - -36. Were it not so vague, the definition proposed by Dugès and Béclard -would be unexceptionable: the former says it is “the special activity -of organized beings”; the latter, “the sum of the phenomena proper to -organized bodies.” When supplemented by a description of organized -bodies, these formulæ are compendious and exact. The same remark -applies to the definition of Lamarck: “that state of things which -permits organic movements; and these movements, which constitute active -life, result from a stimulus which excites them.” - -37. De Blainville, and after him Comte and Charles Robin, define -it thus: “Life is the twofold internal movement of composition and -decomposition at once general and continuous.” This, excellent as -regards what is called vegetal life, is very properly objected to by -Mr. Herbert Spencer in that it excludes those nervous and muscular -functions which are the most conspicuous and distinctive of vital -phenomena. The same objection must be urged against Professor Owen’s -definition: “Life is a centre of intussusceptive assimilative force -capable of reproduction by spontaneous fission.” - -38. In 1853, after reviewing the various attempts to express in a -sentence what a volume could only approximately expound, I proposed the -following: “Life is a series of definite and successive changes, both -of structure and composition, which take place within an individual -without destroying its identity.” This has been criticised by Mr. -Herbert Spencer and by Dr. Lionel Beale, and if I had not withdrawn -it before their criticisms appeared, I should certainly have modified -and enlarged it afterwards. I mention it, however, because it is an -approach to a more satisfactory formula in so far as it specifies two -cardinal characteristics distinguishing organisms from all anorganisms, -namely, the incessant evolution through definite stages, and the -preservation of specific integrity throughout the changes; not only -the organism as a whole is preserved amidst incessant molecular -change, but each tissue lives only so long as the reciprocal molecular -composition and decomposition persist. On both of these points I shall -have to speak hereafter. The definition, however, is not only defective -in its restriction to the molecular changes of Nutrition, taking no -account of the Properties and Functions of the organism; but defective -also in giving no expression to equally important relations of the -organism to the medium. - -39. This last point is distinctly expressed in Mr. Spencer’s -definition: “Life is the continuous adjustment of internal relations -to external relations.” Considered as a formula of the most general -significance, embracing therefore what is common to all orders of vital -phenomena, this is the best yet proposed.[9] If I propose another it -will not be to displace but to run alongside with Mr. Spencer’s; and -this only for more ready convenience. Before doing so I must say a few -words by way of clearing the ground. - -40. What does the term Life stand for? What are the concrete -significates of this abstract symbol? As before stated, it is sometimes -a compendious shorthand for the special phenomena distinguishing living -from non-living bodies; and sometimes it expresses not these observed -phenomena, but their conditions of existence, which are by one school -personified in an abstract and extra-organic cause. Thus the life of -an animal, a man, or a nation, means--1°, the special manifestations -of these organisms, and groups of organisms; or 2°, the causes which -produce these manifestations. We are often misunderstood by others, and -sometimes vague to ourselves, when we do not bear these two different -meanings in view. It was probably some sense of this which made -Aristotle distinguish Vitality from Life, as that of the one uniform -cause separated from its multiple effects; it was certainly the motive -of Fletcher, who thus expressly limits the meanings: “_Vitality_ or -_Irritability_, the property which characterizes organized beings -of being acted on by certain powers otherwise than either strictly -mechanically or strictly chemically; _Life_, the sum of the actions -of organized beings resulting directly from their vitality so acted -on.”[10] - -Vitality and Life being thus discriminated as the statical and -the dynamical aspects of the organism, we find in relation to the -former two radically opposed conceptions: the metaphysiological or -extra-organic, and the physiological or intra-organic. The first -conceives Vitality to be a Vital Principle, or extra-organic agent, -sometimes a soul, spirit, archæus, idea, and sometimes a force, which -easily becomes translated into a property. - -The conception of an entity must be rejected, because it is -metempirical and unverifiable, § 34. The conception of a force must -be rejected, because it is irreconcilable with any definite idea we -have of force. What the term Force signifies in Physics and Chemistry, -namely, mass animated by velocity, or _directed pressure_, which is -the activity of the agent,--is precisely that which these vitalists -pertinaciously exclude. They assume a force which has nothing in -common with mass and velocity; which is _not a resultant, but a -principle_; which instead of being a _directed quantity_, is itself -autonomous and _directive_, shaping matter into organization, and -endowing it with powers not assignable to matter. If this vital force -has any mass at its back, it is a spiritual mass; if it is directed, -the direction issues from a “Mind somewhere.” Now this conception is -purely metempirical. Not only is it inexact to speak of Vitality as -a force, it is almost equally inexact to speak of it as a property; -since it is a term which includes a variety of properties; and when -Fletcher assigns the synonym of Irritability, this at once reveals the -inexactness; for beside this property, we must place Assimilation, -Evolution, Disintegration, Reproduction, Contractility, and -Sensibility,--all characteristic properties included in Vitality. - -41. Having thus rejected the conceptions of entity, force, and -property, we are left in presence of--1°, the organic conditions as the -elements, and 2°, of their synthesis (in the state called organization) -as the personified principle. Vital forces, or the vital force, if -we adopt the term for brevity’s sake, is a _symbol of the conditions -of existence of organized matter_; and since organisms are specially -distinguishable from anorganisms by this speciality of their synthesis, -and not by any difference in the nature of the elements combined, this -state of organization is the “force” or “principle” of which we are in -quest. To determine what Life means, we must observe and classify the -phenomena presented by living beings. To determine what Vitality--or -organization--means, we must observe and classify the processes which -go on in organized substances. These will occupy us in the succeeding -chapters; here I may so far anticipate as to propose the following -definitions:-- - -42. Life is the functional activity of an organism in relation to -its medium, as a synthesis of three terms: Structure, Aliment, and -Instrument; it is the sum of functions which are the resultants of -Vitality; Vitality being the sum of the properties of matter in the -state of organization. - -43. Vital phenomena are the phenomena manifested _in_ organisms when -external agencies disturb their molecular equilibrium; and _by_ -organisms when they react on external objects. Thus everything done in -an organism, or by an organism, is a vital act, although physical and -chemical agencies may form essential components of the act. If I shrink -when struck, or if I whip a horse, the blow is in each case physical, -but the shrinking and the striking are vital. - -Every part of a living organism is therefore vital, as _pertaining_ -to Life; but no part has this Life when isolated; for Life is the -synthesis of all the parts: a federation of the organs when the -organism is complex, a federation of the organic substances when the -organism is a simple cell. - -44. All definitions, although didactically placed at the introduction -of a treatise, are properly the final expression of the facts which -the treatise has established, and they cannot therefore be fully -apprehended until the mind is familiarized with the details they -express. Much, therefore, which to the reader may seem unintelligible -or questionable in the foregoing definition, must be allowed to pass -until he has gone through the chapters which follow. - - - - -CHAPTER III. - -ORGANISM, ORGANIZATION, AND ORGANIC SUBSTANCE. - - -45. There is a marked difference between organ_ic_ and organ_ised_ -substances. The organic are non-living, though capable of living -when incorporated in organized tissue (albumen is such a substance); -or they may be incapable of living because they have lived, and are -products of waste, e. g. urea. The organized substance is a specific -combination of organic substances of various kinds, a combination -which is organization. Any organized substance is therefore either an -independent organism, or part of a more complex organism. Protoplasm, -either as a separate organism or as a constituent of a tissue, is -organized substance. - -Organic substances are numerous and specific. They are various -combinations of proximate principles familiar to the chemist, which may -conveniently be ranged under three classes: The first class of organic -substances comprises those composed of principles having what is called -a mineral origin; these generally quit the organism unchanged as they -entered it. The second class comprises those which are crystallizable, -and are formed _in_ the organism, and generally quit it in this state -as excretions. The third class comprises the colloids, i. e. substances -which are coagulable and not crystallizable, and are formed in and -decomposed in the organism, thus furnishing the principles of the -second class. All the principles are in a state of solution. Water is -the chief vehicle of the materials which enter and the materials which -quit the organism; and bodies in solution are solvents of others, so -that the water thus acquires new solvent properties. - -45_a_. Two points must be noted respecting organic substances: they are -mostly combinations of _higher multiples_ of the elements; and their -combinations are not _definite_ in quantity. Albumen, for example, -has (according to one of the many formulas which have been given) an -elementary composition of 216 atoms of Carbon, 169 of Hydrogen, 27 of -Nitrogen, 3 of Sulphur, and 68 of Oxygen; whereas in its final state, -in which it quits the organism as Urea, it is composed of 2 atoms -of Carbon, 4 of Hydrogen, 2 of Nitrogen, and 2 of Oxygen, all the -Sulphur having disappeared in other combinations. In like manner in -the organism Stearin falls from C_{114}, H_{110}, O_{12}, to Oxalic -Acid, which is C_{4}, H_{2}, O_{8}. It is obvious that the necessary -modifiability of organic substance is due to this multiplicity of its -elementary parts and the variety of its molecular structure. - -45_b_. Nor is the indefiniteness of the quantitative composition less -important, though seldom adequately appreciated, or even suspected. -Robin and Verdeil[11] are the only writers I can remember who have -distinctly brought the fact into prominence. That all inorganic -substances are definite in composition, every one knows. Quicklime, -for example, may be got from marble, limestone, oyster-shells, or -chalk; but however produced, it always contains exactly 250 ounces -of calcium to 100 ounces of oxygen; just as water is always OH_{2}. -Not so the pre-eminently vital substances, those which are coagulable -and not crystallizable: no precise formula will express one of these; -for the same specific substance is found to vary from time to time, -and elementary analyses do not give uniform results. Thus, if after -causing an acid to combine with one of these substances, we remove -the acid, we are not certain of finding the substance as it was -before--as we are, for example, after urea is combined with nitric -acid and then decomposed. The same want of definiteness is of course -even more apparent in the _combinations_ of these proximate principles -into organized substance. Protoplasm differs greatly in different -places. Epithelial cells differ. Muscular and nervous fibres are never -absolutely the same in different regions. A striped and unstriped -muscular fibre, the muscular fibre of a sphincter or of a limb, a -nerve-fibre in a centre, in a trunk, or in a gland, will present -variations of composition. The elastic fibres of the ligaments are -larger in the horse than in man; and in other animals they are smaller. -These differences are sometimes due to the constituents, and sometimes -to the arrangement of the constituents; the conversion of Albumen into -Fibrine without elementary loss or addition, is a good example of the -latter. That the tissues of one man are not absolutely the same as -the tissues of another, in the sense in which it is true to say that -the chalk of one hill is the same as that of another, or as gold in -Australia is the same as gold in Mexico, is apparent in their very -different reactions under similar external conditions: the substance -which poisons the one leaves the other unaffected. The man who has once -had the small-pox, or scarlet fever, is never the same afterwards, -since his organism has now become insusceptible of these poisons. And -Sir James Paget has called attention to the striking fact revealed in -disease, namely, that in the same tissue--say the bone or the skin--a -morbid substance fastens only on certain small portions leaving all -the rest unaltered, but fastens on exactly corresponding spots of the -opposite sides of the body; so that on both arms, or both legs, only -the corresponding bits of tissue will be diseased. “Manifestly when -two substances display different relations to a third their composition -cannot be identical; so that though we may speak of all bone or -of all skin as if it were all alike, yet there are differences of -intimate composition. No power of artificial chemistry can detect the -difference; but a morbid material can.”[12] It is to this variability -of composition that we must refer individual peculiarities, and those -striking forms of variety known as idiosyncrasies, which cause some -organisms to be affected by what seem inexplicable influences--physical -and moral. - -In spite of all these variations, however, there are certain specific -resemblances dependent of course on similarity of composition and -structure, so that the muscle of a crustacean is classed beside the -muscle of a vertebrate, although the elementary analysis of the two -yields different results. Nerve-tissue, according to my experience, -is the most variable of all, except the blood; variable not only from -individual to individual, and from genus to genus, but even in the same -individual it never contains the same quantities of water, phosphates, -etc. Hence it is that different nerves manifest different degrees of -excitability, and the same nerve differs at different times. Thus the -fifth pair, in a poisoned animal, retains its excitability long after -the others are paralyzed; and the patient under chloroform feels a -prick on the brow or at the temples, when insensible at any other spot. -The pneumogastric which is excitable during digestion is--in dogs at -least--inexcitable when the animal is fasting. - -46. The organic substances are what analysis discovers in organized -substances, but none of them, not even the highest, is living, except -as organized. Albumen alone, or Stearin alone, is as incapable of -Vitality, as Plumbago, or Soda; but all organic substances are -capable of playing a part in vital actions; and this part is the -more important in proportion to their greater molecular variety. -Organization is a special synthesis of substances belonging to all -three classes; and the organized substance, thus formed, alone merits -the epithet living. We see how organized substances, being constituted -by principles derived from the inorganic world, and principles derived -from the organic world, have at once a dependence on the external -Medium, and an independence of it, which is peculiar to living beings. -An analogous dependence and independence is noticeable with respect to -the parts; and this is a character not found in inorganic compounds. -The organism, even in its simplest forms, is a structure of different -substances, each of which is complex. While one part of a crystal is -atomically and morphologically identical with every other, and is the -whole crystal “writ small,” one part of an organism is unlike another, -and _no part_ is like the whole. Hence the dependence of one organ and -one tissue on another, and each on all. Yet, while every part is, so to -speak, a condition of existence of every other, and the unity of the -organism is but the expression of this solidarity,--wherever organized -substance has been differentiated into morphological elements (cells, -etc.), each of these has its own course of evolution independently of -the others,--is born, nourished, developed, and dies. - -47. The interdependence of nerve and muscle is seen in this, that the -more the muscle is excited the feebler its contractions become; this -decrease in contractility is compensated by an increased excitability -in its nerve; so that while the muscle demands a more powerful -stimulus, the nerve acquires a more energetic activity. Ranke’s curious -and careful experiments seem to prove that this depends on the wearied -muscle absorbing more water, owing to the acids developed by its -activity, and on the nerve losing this water--a nerve being always -more irritable when its quantity of water diminishes. - -48. Herein we see illustrated the great law of organized activity, -that it is a simultaneity of opposite tendencies, as organized matter -is a synthesis of compositions and decompositions, always tending -towards equilibrium and disturbance, storing up energy and liberating -it. Unlike what is observed in unorganized matter, the conditions of -waste bring with them conditions of repair, and thus--within certain -limits--every loss in one direction is compensated by gain in another. -There is a greater flow of nutrient material, or, more properly -speaking, a greater assimilation of it by the tissue, where there has -been made a greater opening for it by previous disintegration. The -alkaline state of the nutrient material, and the acid state of the -material that has been used,--the alkaline state which characterizes -repose and assimilation, and the acid state which characterizes -activity and deassimilation, are but cases of this general law; on the -synthesis of these opposite tendencies depends the restless change, -together with the continued specific integrity, of organized matter. - -49. The state of organization may therefore be defined as the -_molecular union of the proximate principles of the three classes -in reciprocal dissolution_. An organism is formed of matter thus -organized, which exists in two states--the _amorphous_ and the -_figured_. The amorphous substances are liquid, semi-liquid, and solid; -the figured are the cells, fibres, and tubes, called “anatomical -elements.” For these I prefer the term suggested, I believe, by Milne -Edwards, namely, _organites_, because they are the individual elements -which mainly constitute the organs, and are indeed by many biologists -considered as elementary organisms. These organites, which go to form -the tissues, and by the tissues the organs, have their specific form, -volume, structure, and chemical reactions. They exist in textures -or tissues, or separately (e. g. blood corpuscles), and are in many -respects like the simplest organisms known, such as Monads, Vibrios, -Amœbæ, etc. - -50. The simplest form of life is not--as commonly stated--a cell, but -a microscopic lump of jelly-like substance, or protoplasm, which has -been named _sarcode_ by Dujardin, _cytode_ by Haeckel, and _germinal -matter_ by Lionel Beale. This protoplasm, although entirely destitute -of texture, and consequently destitute of organs, is nevertheless -considered to be living, because it manifests the cardinal phenomena -of Life: Assimilation, Evolution, Reproduction, Mobility, and -Decay. Examples of this simplest organism are Monads, Protamœbæ, -and Polythalamia.[13] Few things are more surprising than the vital -activity of these organites, which puzzle naturalists as to whether -they should be called plants or animals. All microscopists are familiar -with the spectacle of a formless lump of albuminous matter (a Rhizopod) -putting forth a process of its body as a temporary arm or leg, or else -slowly wrapping itself round a microscopic plant, or morsel of animal -substance, thus converting its whole body into a mouth and a stomach; -but these phenomena are surpassed by those described by Cienkowski,[14] -who narrates how one Monad fastens on to a plant and sucks the -chlorophyll first from one cell and then from another; another Monad, -unable to make a hole in the cell-wall, thrusts long processes of its -body into the opening already made, and drags out the remains of the -chlorophyll left there by its predecessor; while a third Monad leads a -predatory life, falling upon other Monads that have filled themselves -with food. Here, as he says, we stand on the threshold of that dark -region where Animal Will begins; and yet there is here only the -simplest form of organization.[15] - -51. Now let our glance pass on to the second stage--the Cell. Here we -have a recognized differentiation in the appearance of a nucleus amid -the protoplasm. The nucleus is chemically different from the substance -which surrounds it; and although perhaps exaggerated importance has -been attributed to this nucleus, and mysterious powers have been -ascribed to it, yet as an essential constituent of the cell it commands -attention. Indeed, according to the most recent investigations, the -definition of a cell is “a nucleus with surrounding protoplasm.” The -cell-wall, or delicate investing membrane--that which makes the cell a -closed sac--is no longer to be regarded as a necessary constituent, but -only as an accessory.[16] - -52. The cell may be either an organism or an organite. It may lead an -isolated life as plant or animal, or it may be united with others and -lead a more or less corporate existence; but always, even as an element -of a higher organism, it preserves its own individuality. At first we -see that the corporate union is very slight, merely the contact of one -cell with another of its own kind, as in the filament of a Conferva. -Rising higher, we see the cell united with others different from -it; plants and animals appear, having structures composed of masses -of various cells. Rising still higher, we see animal forms of which -the web is woven out of myriads upon myriads of cells, with various -cell-products, processes, fibres, tubes. - - -ORGANISM AND MEDIUM. - -53. But we have only one half of the great problem of life, when we -have the organism; and it is to this half that the chief researches -have been devoted, the other falling into neglect. What is that -other? The Medium in which the organism lives. Every individual -object, organic or inorganic, is the product of two factors:--first, -the relation of its constituent molecules to each other; secondly, -the relation of its substance to all surrounding objects. Its -properties, as an object or an organism, are the results of its -constituent molecules, and of its relation to external conditions. -Organisms are the results of a peculiar group of forces, exhibiting -a peculiar group of phenomena. Viewing these in the abstract, we -may say that there are three regulative laws of life:--(1) The _Lex -Formationis_--the so-called _nisus formativus_, or “organizing force”; -(2) the _Lex Adaptationis_, or adaptive tendency; (3) the _Lex -Hereditatis_, or tendency to reproduce both the original form and its -acquired modifications. We have always to consider the organizing -force in relation to all surrounding forces--a relation succinctly -expressed in the word Adaptation. Just as water is water only under a -certain relation of its constituent molecules to the temperature and -atmospheric pressure--just as it passes into other forms (ice or steam) -in adapting itself to other conditions; so, likewise, the organism only -preserves its individuality by the adjustment of its forces with the -forces which environ it. - -54. This relation of Organism and Medium, the most fundamental of -biological data, has had a peculiar fortune: never wholly unrecognized, -for it obtrudes itself incessantly in the facts of daily experience, -it was very late in gaining recognition as a principle of supreme -importance; and is even now often so imperfectly apprehended that one -school of philosophers indignantly rejects the idea of the Organism and -Medium being the two factors of which Life is the product. Not only -is there a school of vitalists maintaining the doctrine of Life as an -entity independent both of Organism and Medium, and using these as its -instruments; but there is also a majority among other biologists, who -betray by their arguments that they fail to keep steadily before them -the fundamental nature of the relation. Something of this is doubtless -due to the imperfect conception they have formed of what constitutes -the Medium; instead of recognizing in it the sum of external conditions -affecting the organism--i. e. the sum of the relations which the -organism maintains with external agencies,--they restrict, or enlarge -it, so as to misapprehend its significance--restrict it to only a few -of the conditions, such as climate, soil, temperature, etc., or enlarge -it to embrace a vast array of conditions which stand in no directly -appreciable relation to the organism. Every one understands that an -organism is dependent on proper food, on oxygen, etc., and will perish -if these are withheld, or be affected by every variation in such -conditions. Every one understands that an animal which can devour or be -devoured by another, will flourish or perish according to the presence -of its prey or its enemy. But it is often forgotten that among external -existences, all those which stand in no appreciable relation to the -organism are not properly to be included in its Medium. In consequence -of this oversight we frequently hear it urged as an objection to the -Evolution Hypothesis, that manifold organisms exist under the _same_ -external conditions, and that organisms persist unchanged amid a -great variety of conditions. The objection is beside the question. In -the general sum of external forces there are certain items which are -nearly related to particular organisms, and constitute their Medium; -those items which are so distantly related to these organisms as to -cause no reactions in them, are, for them, as if non-existent.[17] Of -the manifold vibrations which the ether is supposed to be incessantly -undergoing, only certain vibrations affect the eye as light; these -constitute the Medium of Sight; the others are as if they were not. -Only certain vibrations of the air affect the ear as Sound; to all -other vibrations we are deaf; though ears of finer sensibility may -detect them and be deaf to those which affect us. - -55. “The external conditions of existence” is therefore the correct -definition of the Medium. An animal may be surrounded with various -foods and poisons, but if its organism is not directly affected by them -they cannot be food or poison to it. An animal may be surrounded with -carnivorous rivals, but if it is not adapted to serve them as food, or -is too powerful to be attacked by them, they only indirectly enter into -its Medium, by eating the food it would eat. The analogy is similar -with anorganisms and their relation to their media. Every physical or -chemical phenomenon depends on the concurrence of definite conditions: -namely, the substance which manifests the change, and the medium in -which the change is manifested. Alter the medium, solid, liquid, or -gaseous, change its thermal or electrical state, and the phenomenon is -altered. But although similar alterations in the medium notoriously -influence the organism, yet, because a great many variations in -external conditions are unaccompanied by appreciable changes in the -organism, there are biologists who regard this as a proof of Life being -independent of physical and chemical laws; an error arising from their -not recognizing the precise nature of organic conditions. - -56. To give greater precision to the conception of a Medium it will -be desirable to adopt the distinction much insisted on by Claude -Bernard, namely, 1°, an External or Cosmical Medium, embracing the -whole of the circumstances outside the organism, capable of directly -affecting it, and 2°, an Internal or Physiological Medium, embracing -the conditions inside the organism, and in direct relation with -it--that is to say, the plasma in which its tissues are bathed, by -which they are nourished. To these add its temperature and electrical -conditions. Bernard only includes the nutritive fluid; but inasmuch as -each organism possesses a temperature and electrical state of its own, -and these are only indirectly dependent on the external temperature -and electricity, and as it is with these internal conditions that -the organism is in direct relation, I include them with the plasma -among the constituents of the Physiological Medium. Any change in the -External Medium, whether of temperature or electricity, of food or -light, which does not disturb the Internal Medium, will of course leave -the organism undisturbed; and for the most part all the changes in -the External Medium which do affect the organism, affect it by first -changing the Internal Medium. External heat or cold raises or depresses -the internal temperature _indirectly_ by affecting the organic -processes on which the internal temperature depends. We see here the -rationale of acclimatization. Unless the organism can adapt itself to -the new External Medium by the readjustment of its Internal Medium, it -perishes. - -57. We are now enabled to furnish an answer to the very common -objection respecting the apparent absence of any direct influence of -external conditions. Let the objection first be stated in the words -of a celebrated naturalist, Agassiz: “It is a fact which seems to be -entirely overlooked by those who assume an extensive influence of -physical causes upon the very existence of organized beings, that the -most diversified types of animals and plants are everywhere found under -identical circumstances. The smallest sheet of fresh water, every -point of the sea-shore, every acre of dry land, teems with a variety -of animals and plants. The narrower the boundaries which are assigned -as the primitive home of all these beings, the more uniform must be -the conditions under which they must be assumed to have originated; so -uniform indeed that in the end the inference would be that the same -physical causes can produce the most diversified effects.” - -Obviously there is a complete misstatement of the argument here; and -the excess of the misstatement appears in the following passage: “The -action of physical agents upon organized beings presupposes the very -existence of those beings.” Who ever doubted it? “The simple fact that -there has been a period in the history of our earth when none of these -organized beings as yet existed, and when, nevertheless, the material -constitution of our globe and the physical forces acting upon it were -essentially the same as they are now, shows that these influences are -insufficient to call into existence any living being.”[18] Although -most readers will demur to the statement that because the material -constitution of our globe was “essentially the same” before and after -animal life appeared, therefore there could have been no special -conditions determining the appearance of Life, the hypothesis of -Evolution entirely rejects the notion of organic forms having been -diversified by diversities in the few physical conditions commonly -understood as representing the Medium. Mr. Darwin has the incomparable -merit of having enlarged our conception of the conditions of existence -so as to embrace _all_ the factors which conduce to the result. In -his luminous principle of the Struggle for Existence, and the Natural -Selection which such a struggle determines, we have the key to most of -the problems presented by the diversities of organisms; and the Law of -Adaptation, rightly conceived, furnishes the key to all organic change. - -58. In consequence of the defective precision with which the phrase -“Medium,” or its usual equivalent “physical conditions,” is employed, -several biological errors pass undetected. Haeckel[19] calls attention -to the common mistake of supposing the organism to be passive under the -influence of external conditions, whereas every action, be it of light -or heat, of water or food, necessarily calls forth a corresponding -reaction, which manifests itself in a modification of the nutritive -process. He points out the obverse of this error in the current notion -that Habit is solely due to the spontaneous action of the organism, -in opposition to the influence of external agency,--as if every -action were not the response to a stimulus. Corresponding with the -fluctuations in the Medium there must necessarily be fluctuations of -Adaptation, and I think we may safely assume that it is only when these -fluctuations cease that the Adaptation becomes Habit. This is the -interpretation of the phrase “Habit is _second_ Nature,” and is very -different from the common interpretation which attributes it to the use -or disuse of organs; as if use or disuse were a spontaneous uncaused -activity. - -59. The organism, simple or complex, is, we have already seen, built -up from materials originally derived from the External Medium, but -proximately from the Internal Medium. This statement, however, requires -some qualification, especially in view of the hypothesis that organized -substance was originally created such as we now find it, and not -evolved from inorganic materials. Whether this hypothesis be adopted, -or rejected, we have the fact that the immense majority of organisms -_now_ existing--if not all--are products of pre-existing organisms; -and therefore organized matter is now mainly, if not solely, formed by -organized matter. - -We take, therefore, as our point of departure, the protoplasm; this -is the first of the three terms of the vital synthesis: Structure, -Aliment, and Instrument. The evolution of this is proximately -dependent on the _pabulum_ afforded it in the Internal Medium, which -is the true nutrient material, and to which what is usually called -_food_ stands in an external relation: for between the reception of -food and its assimilation by the organite, there is an indispensable -intermediary stage, through which matter passes from the unorganized -to the organized state. This intermediate is now recognized in plants -as in animals. The old belief that plants were nourished _directly_ -from the soil and atmosphere can no longer be sustained. The process -of Nutrition is alike in both: in both the materials drawn from the -External Medium are formed into proximate principles and organic -substances. It is daily becoming more and more probable that the -inorganic materials, water and oxygen, so freely entering into the -organism, never pass directly from the External Medium to the tissues, -but have to pass through the Internal Medium where they are changed, -so that the water is no longer free, but exists in a fixed state -which has no analogue out of the living substance. Only a part of -the water can be pressed out mechanically; the rest--that which is -already incorporated with the other elements--can only be got rid -of in a vacuum and at a high temperature. Oxygen, also, comports -itself differently in the tissue; as is proved by the fact that its -physiological absorption is markedly different from any chemical -oxidation in a dead or decomposing tissue.[20] Be this as it may, we -know that organic substances have to be unbuilt and rebuilt in the -organism; that the albumen of our food never passes directly into -the albumen of our tissues; any more than the milk drunk by a nursing -mother will pass into her breasts, and increase her supply, except by -nourishing her. - -60. In the First Series of these Problems the term Bioplasm was -employed to designate this organized part of the Internal Medium. I -was led to adopt it as a corresponding term to that of Psychoplasm, -by which I wished to designate the _sentient_ material of the -psychological medium. There can be little doubt that the term Bioplasm -was an unconscious reproduction of the title of Dr. Beale’s work, -which I must have seen advertised. I withdraw it now that I have read -Dr. Beale’s work, and see that the signification he attaches to the -term is almost identical with Protoplasm. In lieu thereof, the term -Plasmode (from _plasma_, anything formed, and _odos_, a pathway) may -be substituted: it represents the _nutrient_ material on its way to -form Protoplasm, which is _formative_ material; while the materials -_formed_ may be termed Organites and Products: the organite being -the cell or cell-derivative (fibre, tube); the products being the -gaseous liquid and solid derivatives of vital processes, which are -_secretions_ when they form intercellular substance or return into the -plasmode and re-enter the vital circle; _excretions_ when they are -rejected, as incapable of further assimilation. The liver-cell will -furnish an example of each kind of product. The bile, though containing -principles serviceable in the chemical transformations, is for the -most part excreted; but besides bile, the liver-cell produces starchy -and saccharine principles which are true secretions, and re-enter the -plasmode. - -61. The organite is thus composed of sap, substance, and product; -the organism, of plasmode, tissue, and product. A glance at the -vegetable-cell shows it to be constituted by the primordial utricle, -or protoplasm, the outermost layer of which is condensed into a -membrane, or cell-wall, and the cavity thus enclosed is filled with -sap. The cell-wall grows as the protoplasm grows, and the protoplasm -draws its material from the plasmode. A glance at the blood, the great -reservoir of the river of life, shows us plasmode in the serum, and -organites in the corpuscles; the one distinguished by sodic salts, -the other by potassic salts. The plasmode, or serum, is in a constant -change of composition and decomposition, giving up to the various -tissue-organites and intercellular plasmodes the requisite materials, -and receiving from organites and plasmodes the products of their -changes. The serum is fed from the food _and_ the tissues; and it feeds -the several plasmodes which bathe the several tissues. Passing into the -capillaries, it becomes transformed as it passes through their walls -into the intercellular spaces, saturating the acid products of the -cell-activities with its alkalies, and furnishing the protoplasms with -their needed materials. - -62. It will be understood that, although in appearance these stages -are sharply defined, in reality they are insensible. But from the -analytical point of view we may regard Nutrition as the office -of the plasmode, and Evolution as the office of the protoplasm. -Although evolution or genesis of form depends on assimilation, it is -not a necessary consequence: the plasmode or the protoplasm might -preserve such perfect equality in the waste and repair, such complete -equilibrium, as not to undergo any development. The ova, for example, -which exist in the ovaries at birth are not all subsequently developed; -and if with modern embryologists we conclude that there is no -replacement of these by proliferation we shall in them have examples of -organites remaining unchanged through a period of fifty years.[21] But -such an equilibrium is perhaps only possible in complete inactivity. - -63. Again, although the office of the plasmode is primarily that of -forming protoplasm, I think there is evidence to suggest that it not -only does this, but that some of it is used in the direct development -of energy, especially heat and electricity. The various forms of starch -and sugar taken in with the food or formed in the liver, certainly do -not as such enter into protoplasm. The same with alcohol. - -64. It is perhaps in forgetfulness of the artificial nature of -analytical distinctions that controversies rage respecting what are -called intercellular substances and cell-walls. Now that the wall -is no longer regarded as an essential constituent of the cell, but -as a secondary formation, two opinions are maintained: first, that -it is merely a concentration of the external layer of protoplasm; -secondly, that it is a product of secretion from the protoplasm. -Both positions may be correct. Certainly in some cases there is no -other appreciable difference between wall and protoplasm than that -of a greater consistence; whereas in many other cases there exists a -decided difference in their chemical reactions, showing a difference -of composition. Taking both orders of fact, we may conclude that the -cell-wall is sometimes part of the organite, and sometimes product: a -blood-cell and a cartilage-cell may be cited as examples of each. And -this argument applies to the intercellular substance also. - -65. The terms plasmode and protoplasm are general, and include many -species. There are different plasmodes for the different tissues, -so that we find phosphates of soda in the blood-serum, phosphates -of potash in the nerve-plasma, phosphates of magnesia in the -muscle-plasma, and phosphates of lime in the bone-plasma; having -severally to form the specifically different protoplasms of these -tissues. Observe, moreover, the gradations of these in respect of their -physical state: the blood being the most liquid, the nerve a degree -more solid, the muscle still more solid, and the bone almost entirely -solid; and since solubility of material is a necessary condition of -the chemical changes, we can understand how the blood, the nerve, the -muscle, and the bone represent degrees of vital activity: the greater -the instability of organized substance, the more active its molecular -renovation. Many serious errors result from overlooking the specific -differences of protoplasms; among them may be mentioned that very -common one of asserting that the ovum of a man is not distinguishable -from the ovum of any other mammal, nor the ovum of a mammal from that -of a reptile; nay, we sometimes see it stated that the protoplasm from -which a mammal may be developed is the same as that which is the germ -of an oak. So long as this simply asserts that we have at present no -means of distinguishing them by any chemical or physical tests, there -can be no objection raised; but it is a serious misconception, which -any embryological investigation ought to rectify, to suppose that the -ovum is not specific from the first. - -66. Between the organites and their plasmodes there is the necessary -relation, which corresponds with the relation between organisms and -their mediums. Once formed, the organites are arranged side by side, -or end on end, into textures or tissues, and these are grouped into -organs, every organ being constituted by a collection of tissues, as -every apparatus is by a collection of organs, and the organism by the -federation of all the parts. We have more than once insisted on the -necessity of synthetic interpretation to complete the indications of -analysis: which means that no account of vital phenomena is _real_ -unless it takes in all the co-operant factors, both those of the -organism and the medium. Neglect of this canon vitiates Dr. Beale’s -otherwise remarkable labors. - - -THE HYPOTHESIS OF GERMINAL MATTER. - -67. It may help to elucidate certain important points if I here examine -the hypothesis which Dr. Beale has worked out with such patient skill, -but with what seem to me such unphysiological results. He deserves, I -think, more applause than has been awarded to him, not only for the -admirable patience with which he has pursued the idea, but also for -the striking definiteness of the idea itself--always a great advantage -in an hypothesis, since it gives precision to research. If biologists -have paid but little attention to it, this is no doubt due to the -theoretical, still more than to the observational contradictions it -presents. Histologists dispute his facts, or his interpretations; -while other biologists do not see their way in the application of -his hypothesis. Respecting all disputed points of observation I -shall be silent, for I have myself made no systematic researches in -this direction, such as would entitle me to form an estimate of the -evidence. But my dissent from the hypothesis is founded on biological -principles so fundamental that I should be willing to take my stand -entirely on the facts he himself puts forward.[22] - -68. The hypothesis is that nothing in the organism has any claim -to vitality except the minute masses of protoplasm (by him called -bioplasm), which in the egg represent, he thinks, about the -one-thousandth part of the whole mass, the rest being lifeless matter, -namely, pabulum, and formed material. This bioplasm is the _germinal -matter_ out of which, by a _process of dying_, arise the tissues and -humors constituting the _formed material_--these, with the pabulum -which feeds the germinal matter, being all dead material. The germinal -matter itself, though living, only lives because there is temporarily -associated with it that Vital Force of which we have already spoken (§ -14). In virtue of this association, a particle of matter not exceeding -the one hundred-thousandth of an inch in diameter is said to be alive; -and, presumably, to contain within it all those manifold powers which -the term Life condenses. The pabulum brought under the influence of -this Vital Force is transformed into germinal matter which, escaping -from this mysterious influence, _dies into tissue_. Muscle-fibres and -nerve-fibres are thus not living parts, nor are their actions vital. So -that, to be consistent, we must not speak of the organism as living, -but as a dead structure _produced_ by the Vital Force, and _set in -action_ by the aid of scattered bits of germinal matter. He has not, I -think, stated whether each of these bioplasms has its own Vital Force, -so that the organism is the theatre of millions of Vital Forces; or -whether it is one Vital Force which animates the whole organic world of -plants and animals. But nothing can be less equivocal than his position -respecting the lifelessness of every part of the organism except the -germinal matter. - -69. The germinal matter may be selected as the primary stage of the -formed material, the initial point of growth, and thus stand for the -pre-eminently distinctive centre of Nutrition; but were we to limit all -Nutrition to the germinal matter, as defined by Dr. Beale, and deny -the co-operation of all the formed material, we should still not be -justified in restricting Life to simple Nutrition. We cannot exclude -such phenomena as those of Sensation and Motion, nor can we assign -these to the germinal matter.[23] To suppose this, would be equivalent -to saying that the steam which issues from a teakettle is capable of -the actions of a locomotive engine. The steam from the kettle is like -the steam from the boiler, it has molecular energy, and by this will -co-operate in the production of mechanical work, if the mechanism be -adjusted to it. The molecular energy of the protoplasm in muscular -fibre may be indispensable to the movements of the muscles, but these, -and not the protoplasmic movements alone, are muscular contractions. An -hypothesis, therefore, which is obliged to declare that muscle-fibre -and nerve-fibre are not living, even when active in the organism, -seems to me defective at its base. If we view these apart from the -organism, they may, like all the other formed materials, be regarded -as dead; and no one doubts that epidermis, nail, horn, hair, and bone -are dead in this sense, that they cannot live independently, and do not -reproduce themselves. But so long as even these form constituents of -the living organism, they also are _living_ (§ 42).[24] It is only by a -misconception of the analytical artifice that so simple a truth could -have been missed. - -70. But this misconception meets us at many a turn. The Vitalist -hypothesis of an extra-organic agent of course refuses to regard Life -as the expression of all the co-operant conditions; and even opponents -of that hypothesis often fall into the same error of principle, when -they attempt to explain Life by localizing it in the cells; which is -simply a morphological substitution for the once popular doctrine that -only the vascular parts were organized, and every part destitute of -blood-vessels was dead. This idea seemed supported by the facts of the -most highly vascular parts being the most vital, and of a parallelism -existing between the vital activity of those organs which when injected -seemed almost entirely composed of blood-vessels, as the liver and -brain, and those which showed scarcely a trace of vessels, as cartilage -and bone; it seemed supported also by the appearance of blood-vessels -in all new formations, and by the idea of the blood as the nutrient -fluid. Then came the cell-doctrine, and the belief that the cell was -the really ultimate morphological element--which may be true--and that -“here alone there is any manifestation of life to be found, so that -we must not transfer the seat of vital action anywhere beyond the -cell,”[25]--which is very questionable. - -71. We have already seen that the cell is an anatomical element, or -organite; the organism is but an aggregate of organites _and_ their -plasmodes. But Biology, which deals with the organism as a whole, and -with functions which are the resultants of all the vital properties, -must not be restricted to any single factor, however important. -It would assuredly be deemed absurd to say that diamond rings and -lead-pencils were the same, because the diamond and the plumbago, -which are the specific elements of each, are both the same chemical -element,--carbon. The substance is really different in diamond and -plumbago, is different in properties, and is, in rings and pencils, -united with different substances into objects having very different -properties. Whatever analysis may discover as to the identities of -organic structures, we cannot explain a single vital phenomenon -without taking into account the three terms, Structure, Aliment, -and Instrument; and whenever a cell is said to be the seat of vital -action, these three terms must be implied. In Dr. Beale’s hypothesis -the restriction is carried to its extreme; not content with the cell, -he withdraws vital action from the cell as a whole, assigning it to -the protoplasm and nucleus--cell-contents and cell-wall being, in his -view, dead. If it be true that the protoplasm is alone concerned in -Nutrition, yet Nutrition is not Life. Occupied mainly with formative -processes, it leaves other indispensable processes to other parts. He -instances the removal of all the tissues during the metamorphoses of -insects:--“new organs and textures are laid down afresh and developed -_ab initio_, instead of being built up upon those first formed.” But to -show how he restricts the idea of Life, he adds: “Such complete change, -however, necessitates a state of existence during which _action_ or -_function remains in complete abeyance_.”[26] - -The muscles and nerves which are instrumental in this functional life -are said to be dead. It is true that the muscle-fibre does not develop -fresh fibres. But it is equally true that the protoplasm of muscle does -not alone execute _muscular_ contraction. Each has its special office. -Hence I reject the idea that formed material is dead. He further says -“formed material may _be_ changed, it cannot _change_ itself.” The -antithesis is doubly inexact: 1°, nothing changes itself, but only -yields to pressure, or reacts on being stimulated; and 2°, all the -evidence at hand is against the notion that the formed material is -not the seat of incessant molecular change; it is wasted and repaired -molecule by molecule. Kölliker properly protests against the growing -tendency of histologists to deify protoplasm, and to make it the sole -seat of vital changes, the cell-wall and cell-products having also, he -says, their physiological importance. It is manifestly erroneous to -deny vital changes to the red blood-corpuscles on the ground of their -no longer containing germinal matter.[27] - -72. The analytical view may separate certain parts as active, and -other parts as passive, and thus regard the cells as the seats of -vital activity, the intercellular substance as merely accessory and -instrumental; but the real or synthetical view must recognize both -parts as equally indispensable, equally vital. Take cartilage, for -instance, with its enormous preponderance of intercellular substance -(formed material), and consider how absolutely impossible any of its -uses would be were it reduced to the germinal matter of its corpuscles! -And so of all the tissues. - -73. If formed material is not to be excluded from the living parts of -the organism, neither is the plasmode, out of which the germinal matter -arises, since here we have the nutritive changes in their highest -activity; and because the property of Nutrition is here most active, -the other property of Development is in abeyance. Dr. Beale holds that -pabulum necessarily becomes germinal matter; but when we come to treat -of Nutrition it will appear that this is not more true than that Food -necessarily becomes Tissue: some of it does; but much of it is used up -for heat and other purposes. - -74. What is true and important in the distinction between germinal -matter and formed material is, that from the former onwards there is a -gradual process of devitalization, the older parts of every organite -and tissue approaching more and more to the state of inorganic matter. -But to show how vain is the attempt to restrict Vitality to any one -out of a complex of co-operant factors, we might set up a chemical -hypothesis to the effect that Vitality depends on phosphates, and -with it explain the phenomena quite as well as with the hypothesis of -germinal matter. For not only is it found that the productive quality -of a soil depends on its richness in phosphates, but, as Lehmann has -shown, wherever cells and fibres make their appearance phosphates -are found, even in the lowest organisms, which, however, contain but -little. Phosphates abound in seeds and ova, in muscles and ganglia, -and are deficient in the woody parts of plants and the elastic fibres -of animals. The infant absorbs phosphates in large quantities and -excretes them in small quantities. Nervous activity is accompanied -by the consumption of a third more phosphorus than accompanies -muscular activity. Phosphates are among the most energetic of organic -stimulants. But who would endow the phosphates with Vitality, on the -ground of their indispensable presence in all vital processes? - -75. Life, as we saw, is the expression of the whole organism. Many of -the parts are incapable of manifesting any vital phenomena except in -connection with all the rest; and of those parts which may be separated -from the organism and continue to manifest some vital phenomena, none -are capable of manifesting all. When the connexus of the parts is -destroyed the organism is dead. Long after that cessation which we call -Death, there are still evidences of Vitality in some of the parts: -the heart will continue to beat, the glands will secrete, the hair -will grow, the temperature will still be above that of the surrounding -medium, the muscles will be excitable; these vital properties are -the activities of organized substances, and so long as the state of -organization is preserved they are preserved; but the Life, which -is the synthesis of all the vital properties, vanishes with the -destruction of that synthesis. - -76. May we not generalize this, and say that every special form of -existence, organic or inorganic, is determined by the synthesis of its -elements? Atoms are grouped into molecules, molecules into masses, -masses into systems. Out of the textureless germinal membrane and -the yolk, with no additions from without except oxygen and heat, -are developed all the textures and organs of the chick; and this -chick weighs no more than the egg out of which it was evolved. The -development has been a succession of syntheses--epigenesis upon -epigenesis. We may, if we please, regard each organite, as it appears, -living its separate life, and each tissue its separate life; but we -must not confound under the same symbol modes of existence so widely -different as the activities of an organite, and the activities of an -organism constituted by millions of organites. - -77. If therefore we cannot restrict Life to the processes of Nutrition, -Dr. Beale’s hypothesis, whatever value it may have as explaining -histogenesis, is quite unacceptable. Neither Vital Force nor Bioplasm -covers the whole ground. For the former there is no better evidence -than our ignorance of the real synthesis; for the latter the evidence -is positive in its nature, but its interpretation is questionable. Dr. -Beale selects as the germinal matter those portions of tissue which -are susceptible of being deeply stained by the carmine solution, the -formed material being only stained in a faint degree; the nucleus -and nucleolus are the portions of germinal matter which are most -deeply stained; and hence he concludes that the older the matter the -fainter will be its coloration. There is no dispute as to the value -of the staining process, invented by Gerlach, for the discrimination -of chemically different parts of a tissue; and Dr. Beale has made -excellent use of it in his researches.[28] But I altogether dispute -the conclusion that the staining process reveals the parts which are -exclusively vital; and for this reason: it depends solely on the acid -reaction of those parts; and we cannot divorce the acid from the -alkaline agencies, both being indispensable. Nay, it has been proved -that in the _living animal_ no organized substance can be stained. Lord -Godolphin Osborne first discovered, in 1856, that the protoplasm of -growing wheat was susceptible of coloration;[29] but Gerlach, in 1858, -found that this never took place in the _animal_ during life. He kept -tadpoles and intestinal worms for weeks in colored fluids, without a -single spot becoming stained; although no sooner did these animals die -than the staining began. Nor even when he injected the colored fluids -under the skin and into the stomach, was the slightest coloration -produced.[30] - -To Gerlach’s testimony may be added that of Stein, who, in his -magnificent work on _Infusoria_, says that not only has no foreign -substance ever been found in the protoplasm of the _Opalina_, but -in the _Acineta_, and all the embryos of the higher Infusoria known -to him, he has been unable to color the living substance.[31] This -resistance of the living protoplasm is surely a serious objection -to the hypothesis that only those parts of the dead organism which -are stained were the truly vital parts. Ranke sums up the results -of his experiments thus: “They all show that the living cell resists -the imbibition of every substance which it cannot assimilate. It is -precisely the impossibility of staining the cell that proves this -conclusively, since every particle of carmine absorbed would have -revealed its presence.” - -It is not to be supposed that Dr. Beale was unacquainted with Gerlach’s -experiments. He has at any rate so far qualified the statement of his -hypothesis as to admit that it is only after death that the germinal -matter is stained. “The living matter” (he says, _How to Work with the -Microscope_, p. 107) “possesses an acid reaction, or to speak more -correctly, an acid reaction is always developed immediately after its -death.” Now, since this acid reaction only presents itself after death, -and it is this which is revealed by the carmine, we have no right to -conclude that the carmine singles out the vital parts. Every one knows -that the living muscle and nerve, when in repose, present an alkaline -or faintly neutral reaction, and after excitation this is changed into -an acid reaction, which increases with the exhaustion of the tissue. In -strict logic, therefore--if we could logically apply such a test--it -is the unstained parts that ought to be called vital. But, in truth, -alkalinity and acidity are equally indispensable. - -78. The main object of my bringing this question forward was to -illustrate the danger of being misled by analysis: a danger we shall -see to be very serious in psychological inquiries. The aid derived from -analysis need never be undervalued; all that we have to bear in mind is -that it is only a logical artifice, and that our real explanation must -always be synthetic. Because of the tendency to rely on analysis there -has been an imperfect discrimination of the profound difference between - - -ORGANISMS AND MACHINES; - -and while on the one hand the legitimate striving of the biologist -to display the mechanism of organic actions has been denounced by a -certain school as Materialism and a hateful attempt to “rob Life of -its mystery,” there has been on the other hand a misconception of this -mechanism, as if its dependent actions were of the nature of machines, -that is to say, as if organized mechanisms were strictly comparable -with machines constructed of inorganic parts. No doubt the laws of -Mechanics are the same in both, for these are abstract laws which take -no account of concrete differences. But when elaborate parallels are -drawn up between steam-engines and animal organisms, the coal consumed -in the one likened to the food in the other, and the force evolved in -the combustion in both being the same, there is a complete obliteration -of all that specially distinguishes vital activity. - -79. Between an organism and a machine there is the superficial -resemblance that both have a complex structure, and are constructed of -different and dependent parts. But underneath this resemblance there -is a radical diversity.[32] The arrangement of parts in the organism -is more than a _juxtaposition_, it is a _solidarity_, arising from -the fact of their being all differentiations from a common substance -which is a special combination of the three classes of proximate -principles. Thus they are not parts which have been _put together_, but -which have been _evolved_, each out of a pre-existing part, and each -co-operating in the very existence of the other. The machine is made -of independent and primarily unrelated parts; its integrity depends -on the continued preservation of the substance of each part; waste -is here destruction. The organism is constituted by interdependent -and primarily related parts; its integrity depends on the continued -destruction and renovation of their substance; waste is a condition of -vitality. The actions of the machine are _sub_ordinated; the actions -of an organism are _co_-ordinated. The lever moves a wheel, and the -wheel in moving liberates a spring, each transmitting a communicated -impulse, but otherwise each acts independently--no slight modification -in the structure or movement of the wheel will modify the structure or -the movements of the lever, no alteration in the tension of the spring -will affect the structure of the wheel. But in the organism all are -parts of one sympathetic whole; each reacts on each; each is altered -by the other. Not a nerve is stimulated, nor a muscle moved, but the -entire organism is affected. A condensation here is the cause of a -greater imbibition there. The injection of salt or sugar under the skin -of the frog’s leg will produce cataract in its eye. The activity of -a secreting cell in the ovary, or liver, alters the condition of the -brain; the activity of the brain will check the secretion of a gland, -or relax the sphincters of the bladder. When we observe the growth of -horns, or the appearance of the beard, concomitant with the secretion -of spermatic cells--and especially when we observe with these a -surprising change in the physical and moral capabilities and tendencies -of the organism--we understand how the remotest parts of this mechanism -are bound together by one subtle yet all-powerful tie. Nothing of -this is visible in a machine. In a machine the material is so far of -secondary importance that it may be replaced by materials of various -kinds: a pulley may be worked with a hempen cord, a silken cord, or an -iron chain; a wheel may be wood, iron, copper, brass, or steel; the -actions will in each case be similar. Not so the organic mechanism: -the slightest variation, either in composition or intimate structure, -will affect, and may frustrate the organic activity. It is only in the -skeleton that the specific character of the materials may be changed; -and here only in the substitution of one phosphate for another in the -solid masonry.[33] - -80. Another marked characteristic of the organism is that it has a -connexus of actions, the simultaneous effect of a continuous evolution, -appearing in stages and ages. And in the animal organism there is a -_consensus_ as well as a _connexus_, through which there is evolution -of Mind; and in the Social Organism an evolution of Civilization. -This consensus forms an intermediate stage through which the animal -actions are sensitive as well as nutritive, and the nutritive are -regulated by the sensitive. It is obvious that nothing like this is to -be found in a machine; and we conclude, therefore, that any view of the -organism which regards its mechanism without taking in these cardinal -characteristics must be radically defective. We no more deny the -existence of mechanical phenomena in denying that the organism is like -a machine, than we deny the existence of chemical phenomena in denying -that Vitality is chemical. - - - - -CHAPTER IV. - -THE PROPERTIES AND FUNCTIONS. - - -81. The terms Property and Function are not always used with desirable -precision. There is, however, a marked distinction between the property -which characterizes a tissue in whatever organ the tissue may be found, -and the function which is exhibited by an organ composed of several -tissues. We ought never to speak of a function unless we imply the -existence of a correlative organ; and it is therefore incorrect to -speak of the function of Nutrition, since _all_ the tissues nourish -themselves; but we may speak of certain organs as special instruments -in facilitating Nutrition. Thus also with respiration, usually, but not -accurately, spoken of as the function of the lungs; the lungs being -simply the most effective of the instruments by which the interchange -of gases (which also takes place in every tissue) is facilitated. If -by Respiration we mean Breathing, then, indeed, Respiration is the -function of the lungs; if we mean the absorption of oxygen and the -exhalation of carbonic acid, Respiration is a general property of -vital tissue. A fragment of muscle removed from the body respires, so -long as its organization is intact; but it does not _breathe_--it has -no accessory instruments, nor does it need them. The co-operation of -nerve centres, diaphragm, ribs, circulating system, etc., necessary -in the complex organism to bring the due amount of oxygen to the -tissues, and convey away the carbonic acid, is here needless. In -the ascending animal series we find this necessity growing with the -complexity of the organism. The whole skin respires in the amphibia, -and to some extent in man also: a frog will live for ten or fourteen -days after extirpation of its lungs, the skin respiring sufficiently -to keep up a feeble vitality. But the skin does not suffice; and, very -early, certain portions are specialized into organs (at first in the -shape of external gills, and finally as internal lungs), for the more -energetic, because more specialized, performance of this office. In the -simpler organisms the blood is easily reached by the air; therefore no -instrument is needed. In primitive societies the transport of goods is -effected by men and women carrying them; in civilized societies by the -aid of horses and camels, and wagons drawn by oxen; till finally these -are insufficient, and railways are created, whose power of transport -transcends the earlier methods, as the breathing of a mammal transcends -the respiration of a mollusc. Breathing is the special function of an -organ--the lungs (or more strictly, the thoracic apparatus)--as Railway -Transport is a special social function. Although each of the tissues -forming this organ can, and does, exhale carbonic acid and absorb -oxygen--and each of the railway servants can, and does, transport -objects to and from the locomotive--yet the main work is thrown upon -the special apparatus. - -82. What is meant by properties of tissue and functions of organs -may be thus illustrated. Let us suppose ourselves investigating the -structure of a ship. We find it composed of various _materials_--wood, -iron, copper, hemp, canvas, etc.; and these under various -_configurations_ are formed into particular parts serving particular -purposes, such as deck, masts, anchor, windlass, chains, ropes, sails, -etc. In all these parts the materials preserve their properties; and -wherever wood or iron may be placed, whatever purpose the part may -serve, the properties of wood and iron are unaffected; and it is -through a combination of these properties that the part is effective; -while through the connection of one part with another the purpose -becomes realized. The purposes to which masts, ropes, or sails are -subservient may be called their functions; and these of course only -exist, _as such_, in the ship. It is the same with the organism. We -find it composed of various Tissues, and these are combined into -various Organs or Instruments.[34] The properties of Tissues remain -the same, no matter into what Organs they may be combined; they -preserve and exert their physical, chemical, and vital properties, -as wood and iron preserve their properties. Each Tissue has its -characteristic quality; and the Organ which is constructed out of a -combination of several Tissues, more or less modified, is effective -solely in virtue of these properties,[35] while the Function of that -organ comes into play through its combination with other organs. For -example, muscular tissue has a vital property which is characteristic -of it, Contractility; and muscles are organs constituted by this -tissue and several others;[36] such organs have the general function -of Contraction, but whether this shall be specially manifested in -the beating of the heart, the winking of the eyelid, the movement -of the chest, or the varied movements of the limbs, will depend on -the _anatomical connections_. The reader unfamiliar with Biology is -requested to pay very particular attention to this point; he will find -many obscurities dissipated if he once lays hold of the “principal -connections.” - -82_a_. Although Bichat’s conception was of great value, it was -not sufficiently disengaged from the metaphysical mode of viewing -biological phenomena. Both he and his disciples will be found treating -Properties as entities, and invoking them as _causes_ of the phenomena -instead of recognizing them simply as abstract _expressions_ of the -phenomena. Readers of my First Series will remember how often I have -had occasion to point out this common error: men having baptized -observed facts with a comprehensive name, forget the process of -baptism, and suppose the name to represent a mysterious agency. The -fact that gases combine is expressed in the term affinity; and then -Affinity is understood to be the cause of the combinations. The fact -that bodies tend towards each other is called their gravitation, and -Gravitation is then said to cause the tendency. The doctrine of vital -properties has been thus misunderstood. While no one imagines that -he can operate on affinity otherwise than by operating on the known -conditions under which gases combine, many a biologist and physician -speaks as if he could operate on the Irritability of a tissue, or the -Co-ordination of muscles, by direct action on these abstractions. - -Let it be therefore once for all expressly stated that by the property -of a tissue is simply meant the _constant mode of reaction of that -tissue under definite conditions_. The property is not a cause, -otherwise than the conditions it expresses are a cause. And these -conditions are first those of the organized structure itself, and -secondly those of the medium in which it lives. Oxygen unites with -Hydrogen to form water, but only under certain pressures; so likewise -muscles manifest Contractility on being stimulated (that is their mode -of reaction), but only under certain degrees of temperature, humidity, -and a certain chemical composition of the plasmode. The property is -so truly an expression of the co-operant conditions, that it is found -to vary with those conditions, and to vanish when they vary beyond a -certain limit. - -An attempt has been made to restrict the notion of a property to an -ultimate fact. Whatever is not reducible to known conditions is to -be accepted as a property. Combustion, for example, is reducible to -the molecular combination of oxygen and some other gas; but this -combination itself is not reducible, and it is therefore christened -affinity. I cannot accept this view. Admitting our inability to say -_why_ gases combine under certain conditions (and in this sense all -facts are inexplicable and ultimate, unless we take the _how_ as -ample explanation of the _why_), I must still say that since affinity -itself depends on the co-operation of known conditions, it is not less -explicable than combustion. But the point is unimportant: what we have -here to settle is the meaning of a property of tissue,--and that is the -mode of reaction which that tissue manifests under constant conditions, -internal and external. - -83. The evolution of Life is the evolution of special properties and -functions from general properties and functions. The organism rises in -power as it ramifies into variety. Out of a seemingly structureless -germinal membrane, by successive differentiations certain portions -are set apart for the dominant, or exclusive, performance of certain -processes; just as in the social organism there is a setting apart -of certain classes of men for the dominant or exclusive performance -of offices, which by their co-operation constitute Society. The -soldier fights, but ceases to build or reap, weave or teach; the -mason builds; the agriculturist sows and reaps; the priest and -thinker teach; the statesman governs. In simple societies each -does all, or nearly all; but the social life thus manifested is -markedly inferior to the energetic life of a complex society. So with -organisms. An amœba manifests the general properties of Nutrition, -Reproduction, Sensibility, and Movement. But it has no special organs, -consequently no special functions. The polype has a certain rudimentary -specialization of parts: it has a simple alimentary cavity, and -prehensile tentacles; and although by these it can seize and digest its -prey, it can only do so in a limited way--all the manifold varieties -and power of prehension and digestion observed in more complex -organisms are impossible with such organs as the polype possesses. - -84. Differences of structure and connection necessarily bring about -corresponding differences in Function, since Function is the _directed -energy_ of the Properties of tissues. One organ will differ from -another in structure, as the liver from the pancreas, or the kidney -from the spleen; or one organ may closely resemble another but differ -from it only in _connections_, as a sensory and a motor nerve, or an -extensor and a flexor muscle. We must therefore always bear both points -in mind. Every modification, structural or connectional, is translated -by a corresponding modification in the office. The hand and the foot -show this well. The tissues are the same in both, the properties are -the same, and both have the same general function of Prehension; but -their morphological differences carry corresponding differences in -their uses. - -Suppose we have a galvanic battery, we know that its electric force -may be variously applied. Two pieces of charcoal fixed to the ends of -its conducting wires give us the electric light; replacing the charcoal -by a telegraphic apparatus we can transmit a message from one continent -to the other; the wires dipped in a solution effect a chemical -decomposition, dipped into a mixture of gases they effect a chemical -composition. In these, and many other applications, the property of the -battery is constant; but the functions it subserves have varied with -the varying co-operants. So with the properties of tissue.[37] Not only -have we to bear in mind the organic connections of the tissues, but -also the relation of the organs to their media. Swimming and Walking, -for example, are both functions of the locomotive apparatus, but they -are specially differenced by the media in which the animal moves. - -85. The properties of tissues are their peculiar modes of reaction, and -each tissue has its dominant characteristic, such as the Contractility -of the muscle, and the Neurility of the nerve. But there has of late -years sprung up a misleading conception, partly a consequence of the -cell-theory, and partly of the almost inevitable tendency of analysis -to disregard whatever elements it provisionally sets aside; this -conception is the removal of the property from its _tissue_, and the -localization of it in one of the _organites_--cell or fibre. This has -been conspicuously mischievous in the case of the nerve-cell, which has -been endowed with mysterious powers, and may be said to have usurped -the place of nerve-tissue. I shall have to speak of this in the next -problem. Here I only warn the student against the common error. The -properties of a tissue depend on the structure and composition of -that tissue, together with its plasmode and products; they vary as -these vary. To select any one element in this complex, and ascribe the -reaction of the tissue to that, is only permissible as a shorthand -expression. - -86. What has just been expounded may be condensed in the following -biological law:-- - - _Identity of tissue everywhere implies identity of property; and - similarity of tissue corresponding similarity of property. Identity - of organic connection everywhere implies identity of function; and - similarity of organic connection similarity of function._ - -87. This law, first formulated by me in 1859, and then applied to the -interpretation of nervous functions, was so little understood that for -the most part it met with either decided denial or silent neglect; -no doubt because of the general disinclination to admit that the -properties and functions of the spinal cord could be _similar_ to those -of the brain, in correspondence with the similarity of their tissues -and organic connections. Even Professor Vulpian, who adopted it, as -well as my principal interpretations, hesitated, and relapsed into the -orthodox view in assigning three different properties to one and the -same tissue in cord, medulla oblongata, and cerebrum.[38] In the course -of our inquiries we shall so frequently have to invoke this law that I -earnestly beg the reader to meditate upon it, and ask himself upon what -other grounds, save those of structure and connection, the properties -and functions can possibly rest? If on no other, then similarity in -structure and connection by logical necessity involves similarity in -property and function. - - -DOES THE FUNCTION DETERMINE THE ORGAN? - -88. Closely connected with this law, which simply formulates the -self-evident principle that _every action is rigorously determined by -the nature of the agent, and the conditions under which the act takes -place_, is the surprising question whether functions are dependent -upon organs, or organs dependent on functions?--a question which -sometimes takes this shape: Is Life the result of organization, or is -organization the result of Life? - -The vitalist, who holds that Life is an extra-organic agent, is logical -in declaring organization to be the consequence of Life;[39] but there -are many organicists who conclude from certain facts that organs are -developed by functions, and that organization is a result of Life. -There seems, however, to be some equivoque here. I cannot otherwise -understand how Mr. Spencer should have written: “There is one fact -implying that Function must be regarded as taking the precedence of -Structure. Of the lowest rhizopods which present no distinctions -of parts, and nevertheless feed and grow and move about, Professor -Huxley has remarked that they exhibit Life without Organization.”[40] -The equivoque here arises from the practice of calling all living -bodies “organisms,” even those destitute of the differentiations -called organs; but if we substitute the term “living body” in lieu of -“organism,” the equivoque will disappear, and Function no longer seem -to precede Structure. Neither Mr. Spencer nor Mr. Huxley would affirm -that Life can be manifested without a living body; and every living -body must have a structure of some sort--unless by structure be meant -a special configuration of parts. The properties of a body, whether it -be simple or complex in structure, result from the properties of its -components; and the vital phenomena vary with these varying components. -The substance of a Rhizopod is indeed simple as compared with that of -higher organisms, but is complex as compared with anorganisms; and -corresponding with this simplicity of structure there is simplicity of -vital function.[41] - -89. The _properties_ of steam are exhibited by the kettle on the fire, -no less than by the gigantic engine which animates a manufactory; -but the _uses_ of steam (the functions of the engine) vary with the -varying structure, and the applications of that structure to other -structures. Precisely analogous is the case of the organ and its -function, in relation to the living substance of which it is a peculiar -modification. Vital actions are manifested by a lump of protoplasm; but -these actions are as sharply demarcated from the actions of more highly -organized animals, as the phenomena of a steam-engine are from those of -a teakettle. - -90. Mr. Spencer has nowhere defined what he means by Structure, nor -given a definition of Organ, and this neglect makes it difficult -rightly to appreciate his view. But whether we take structure to -signify the _substance_ of the living body, or the _differentiations_ -of that substance into separate tissues and organs, in either case -the actions (functions) of which this structure is the agent must be -rigorously determined by it. Mr. Spencer has avowed this in declaring -that the “general physiologist may consider functions in their widest -sense as the correlatives of tissue.” Is this true in the widest sense -and not true in the narrowest? I am puzzled to find him insisting that -“function from beginning to end is the determining cause of structure. -Not only is this manifestly true where the modification of structure -arises by reaction from modification of function; but it is also -true where a modification of structure otherwise produced apparently -initiates a modification of function.” Such language would be -consistent were he a vitalist who believed in a Principle independent -of Matter which shapes matter into organic forms; but as a positive -thinker he can scarcely escape the admission that since Function is the -activity of the Agent (Function in the widest sense being the action -of the whole Organism, and in its narrowest sense the action of the -special Organ) there cannot be an _activity preceding the agent_. I -suspect that he does not always bear in mind the distinction between -Property and Function, and consequently is led into statements at -variance with the principles he professes. As far as I understand the -course of his thought, it runs somewhat thus: With the increased use -of an organ its volume may be increased, its structure altered; this -alteration will, by reaction, cause alterations in other organs, and -thus the result of a change in the habitual activities of an animal -will be an alteration in the arrangement of its parts. - -91. We speak loosely of an organ being developed by increased activity; -but this is loose speech, and investigation shows that the organ is not -developed _by_, but accompanies the increased activity, every increment -of activity being necessarily preceded by a corresponding increment -of structure. This is evident _à priori_: the force manifested is -inherent in the structure manifesting it. Thus we ought not to say -“the vascular system furnishes good instances of the increased growth -that _follows_ increased function”; we ought to say, “that _permits_ -increased function.” The muscle having a contractile power represented -by 10, expends, we will suppose, 7 units of force in its normal -activity, and these are replaced by its normal nutrition. If from an -extra demand upon it 9 units are expended, the muscle becomes fatigued, -if 10, exhausted, and it will no longer contract, the whole disposable -sum of its contractility being dissipated. During all these stages the -structure of the muscle--or to prevent all equivoque, let us say the -substance of the muscle--has been changing, not indeed in any degree -appreciable to the eye, but appreciable by the more decisive tests of -chemical and physiological reactions. Yet inasmuch as in the ordinary -course of things the waste is quickly repaired, the muscle in repose -once more regains its original state, once more represents 10 units of -contractility. Now let us consider what takes place when extra labor -is thrown upon the muscle, when exercise causes growth. At the outset -of a walking tour we may not be able to compass more than twenty miles -a day, at its close we manage thirty. Is it the increased activity -of the function which has caused this increase of structure? In one -sense, yes; but let us understand it. Had the increase of activity -been temporary, there would have been only a temporary increase of -structure. But when the ordinary expenditure of 7 units rises to 9, -on several successive days, this extra expenditure of tissue has had -to be met by an extra nutrition--i. e. more plasmode has been formed -and more protoplasm. It is a physiological law, easily explained, -that, within due limits, extra waste brings about extra repair: as the -channels are widened and multiplied, the _derived_ currents become -stronger, and the increased flow of nutrition which was temporary -becomes permanent, because this increase is no longer dependent on an -extra stimulus, but on an enlarged channel.[42] When the channels have -not become multiplied or enlarged, which must be the case whenever the -extra stimulus is fluctuating and temporary, the extra expenditure is -not followed by increased size of the muscle: the currents resume their -old directions, no longer being diverted. - -92. Let the social organism furnish us with an illustration. At the -present moment there is a movement against the retail shopkeepers of -London in favor of Co-operative Stores. The stimulus of getting better -goods and cheaper, attracts the flow of custom from its old channels; -and if this continue a certain time the new arrangements will be so -thoroughly organized, and will work so easily, that Co-operative Stores -will to a great extent supplant the retail shops. But if from any -causes the stimulus slackens before this reorganization has passed from -the oscillating into the permanent stage--if the goods are not found -to be superior, or the cheapness not worth the extra trouble--the old -influences (aiding our indolence) which have been long and continuously -at work, will cause the social organism to resume its old aspect, -and the co-operative “varieties” will disappear, or exist beside the -ancient “species.” - -In the one case as in the other a glance at the process is enough -to detect that the increase in the activity has been preceded by -a corresponding increase in the structure. The muscle has not been -enlarged _by_ extra activity, but _with_ it. The co-operative action -has grown with each additional co-operator. Looking at the cases from -afar we may justly say that development has been due to function; but -looking to the process we see that each increment of activity was -necessarily dependent on an increment of substance. When changes of -habit or adaptation are said to produce modifications in structures, -this is true in as far as one modification of structure necessarily -brings with it correlative modifications, the growth of one part -affecting the growth of all more or less; but we must remember that -to render the structure capable of new adaptations corresponding -modifications must have been going on. The retail shopkeepers might -securely laugh at the co-operative movement if the respectable families -would not or could not become co-operant. When Mr. Spencer urges that -“not only may leaf-stalks assume to a great degree the character of -stems when they have to discharge the functions of stems by supporting -many leaves, and very large leaves, but they may assume the characters -of leaves when they have to undertake the functions of leaves,” I would -ask if he is not reversing the actual process? The stem cannot assume -the functions of a leaf until it has first assumed the character of a -leaf. The assumptions of both must be gradual, and _pari passu_. - -93. The hand is an organ, its function is prehension. The performance -of this function in any of its numerous applications is rigorously -limited by the structure of the hand--the bones, muscles, nerves, -circulating and absorbent vessels, connective tissue, fat, etc. Fatigue -the nerve, and the function will be feebly performed; exhaust it, -and the function ceases; diminish the action of the heart, tie an -artery, or vitiate the structure of the blood, and the function will -be correspondingly affected; stiffen the tendons, soften the bones, -diminish the synovial fluid, or increase the fat--in short, make _any_ -alteration whatever in the structure of the hand, and an alteration -is necessarily produced in its function. So rigorously is function -dependent upon structure, that the hand of one man will execute -actions which are impossible to another. The hand of a baby is said to -be the same in structure as the hand of a man; and since the powers -(functions) of the two are notoriously different, we might rashly -conclude that here function was dissociated from structure. The case is -illustrative. In baby and man the structure is similar, not the same; -the resemblance is of kind, not of degree; and the function likewise -varies with the degree. The penny cannon which delights the child is -similar in structure to the ten-pounder which batters down walls; and -though, speaking generally, we may say that the function of both is to -fire gunpowder for human ends, no one expects the penny cannon to be -employed in warfare. In physiology, as in mechanics, the effect varies -with the forces involved. - -There can be no doubt that an exaggerated activity will produce a -modification in the active organ, for this is only the familiar case of -increased growth with increased exercise, and this is the biological -meaning in which Function can be said not, indeed, to _create_, but to -_modify_ an existing Organ. Preceding the activity there must be the -agent. Every organ although having its special function has also the -properties of all the tissues which constitute it. The function is only -the synthesis of these properties to which a dominant tissue gives a -special character. The eye, for example, though specially characterized -by its retinal sensibility to light, is largely endowed with muscles, -and its movements are essential to Vision. The intestinal canal, again, -though specially characterized by its secretions for the decomposition -of food, has muscles which are essential to Digestion. In many animals, -especially vegetable-feeders, there is an exaggeration of the muscular -activity in certain parts of the intestinal canal which is only -possible through a corresponding development of the muscular tissue, so -that in some birds, crustaceans, and molluscs we find a gizzard, which -is wholly without a mucous membrane to secrete fluids, and which aids -Digestion solely by trituration. - -94. Mr. Spencer, as I have already suggested, seems to have been -led into his view by not keeping distinctly present to his mind the -differences between Properties of tissue and Function, the activity -of an organ. “That function takes precedence of structure,” he says, -“seems implied in the definition of Life. If Life consist of inner -actions so adjusted as to balance outer actions--if the actions are -the _substance_ of Life, while the adjustment constitutes its _form_; -then may we not say that the actions formed must come before that which -forms them--that the continuous change which is the basis of function -must come before the structure which brings the function into shape?” -The separation of “actions formed” from “that which forms them” is -inadmissible. An action cannot come _before_ the agent: it is the -agent in act. The continuous change, which is the basis of Vitality, -is a change of molecular arrangements; and the organ which gives a -special _direction_ to the vital activity, e. g. which shapes the -property of Contractility into the function of Prehension, this organ -must itself be formed before it can manifest this function. It is true -that in one sense the organs are formed by, or are differentiated in, -a pre-existent organism; true that the general activity of living -substance must precede the special activity of any organ, as the -expansions of steam must precede any steam-engine action; but the -general activity depends on the general structure; and the special -actions on the special structures. If by Organization we are to -understand not simply organized substance, but a more or less complex -arrangement of that substance into separate organs, the question is -tantamount to asking whether the simplest animals and plants have life? -And to ask the question, whether Life precedes organic substance? is -tantamount to asking whether the convex aspect of a curve precedes -the concave! or whether the motions of a body precede the body! To -disengage ourselves from the complicated suggestions of such a word as -Life, let us consider one of the vital phenomena, Contraction. This -is a phenomenon manifested by simple protoplasm, and by the highly -differentiated form of protoplasm known as muscle. In one sense it -would be correct to say that Contractility as a general property of -tissue precedes Contraction, which is specialized in muscle. But -it would be absurd to say that _muscular_ contraction preceded the -existence of muscle, and formed it. The contractions of the protoplasm -are not the same as muscular contractions any more than the hand of -a baby is the same as a man’s; the general property which both have -in common depends on the substance both have in common; the special -property which belongs to the muscle depends on its special structure. -An infinite activity of the contractile protoplasm would be incompetent -to form a muscle, unless it were accompanied by that peculiar change in -structure which constitutes muscle. The teakettle might boil forever -without producing a steam-engine or the actions of a steam-engine. That -which is true of one function is true of all functions, and true of -Life, which is the sum of vital activities. - -95. It is this haziness which made Agassiz “regret to observe that -it has almost become an axiom that identical functions presuppose -identical organs. There never was a more incorrect principle leading -to more injurious consequences.”[43] And elsewhere he argues that -organs can exist without functions. But this is obviously to pervert -the fundamental idea of an organ. “The teeth of the whale which never -eat through the gums, and the breasts of the males of all classes -of mammalia,” are cited by him as examples of such organs without -functions; but in the physiological significance of the term these are -not organs at all. It is no more to be expected that the breasts of -the male should act in lactation, than that the slackened string of a -violin should yield musical tones; but the breasts of the male may be -easily stimulated into yielding milk, and the slackened string of the -violin may be tightened so as to yield tone. Even the breasts of the -female do not yield milk except under certain conditions, and in the -absence of these are on a par with those of the male. - -96. Organized substance has the general properties of Assimilation, -Evolution, Sensibility, and Contractility; each of the special -tissues into which organized substance is differentiated manifests a -predominance of one of these properties. Thus although the embryo-cells -all manifest contractility, it is only the specialized muscle-cell -which continues throughout its existence to manifest this property, -and in a dominant form; the muscle-cell also assimilates and develops, -but besides having these properties in common with all other cells, it -has the special property of contracting with an energy not found in -the others. All cells respire; but the blood-cells have this property -of absorbing oxygen to a degree so far surpassing that of any other -cell that physiologists have been led to speak of their containing a -peculiar respiratory substance. In like manner all, or nearly all, -the tissues contain _myeline_--which indeed is one of the chief -constituents of the yolk of eggs--but only in the white sheath of the -nerves is it detached and specialized as a tissue. - -97. But while Sensibility and Contractility are general properties -of organized substance, specialized in special tissues; Sensation -and Contraction are functions of the organs formed by such tissues; -and these organs are only found in animal organisms. It is a serious -error, which we shall hereafter have to insist on, to suppose that -Sensation can be the property of ganglionic cells, or, as it is more -often stated, the property of the central gray matter. Sensation is -the function of the organism; it varies with the varying organ; the -sensation of Touch not being the same as the sensation of Sight, or of -Sound. - -98. We may consider the organism under two aspects--that of Structure -and that of Function. The latter has two broad divisions corresponding -with the vegetal and animal lives; the one is Nutrient, the other -Efficient. The one prepares and distributes Food, the other distributes -Motion. Of course this separation is analytical. In reality the two are -interblended; and although the neuro-muscular system is developed out -of the nutritive system, it is no sooner developed than it plays its -part as Instrument in the preparation and distribution of Aliment. - -This not being a treatise on Physiology, there can be no necessity for -our here considering the properties and functions in detail. What is -necessary to be said on Sensibility and Contractility will find its -place in the course of future chapters; for the present we will confine -ourselves to Evolution on account of its psychological, no less than -its physiological, interest. - - - - -CHAPTER V. - -EVOLUTION. - - -99. That organized substance has the property of nourishing itself -by assimilating from its internal medium substances there present in -an unorganized state, and that this is followed by a development or -differentiation of structure, is familiar to every inquirer. - -Every one who has pursued embryological researches, and in a lesser -degree every one who has merely read about them, must have been -impressed by this marvel of marvels: an exceedingly minute portion -of living matter, so simple in aspect that a line will define it, -passes by successive modifications into an organism so complex that a -treatise is needed to describe it; not only do the cells in which the -ovum and the spermatozoon originate, pass into a complex organism, -reproducing the forms and features of the parents, and with these -the constitutional peculiarities of the parents (their longevity, -their diseases, their mental dispositions, nay, their very tricks and -habits), but they may reproduce the form and features, the dispositions -and diseases, of a grandfather or great-grandfather, which had lain -dormant in the father or mother. Consider for an instant what this -implies. A microscopic cell of albuminous compounds, wholly without -trace of organs, not appreciably distinguishable from millions of other -cells, does nevertheless contain within it the “possibilities” of an -organism so complex and so special as that of a Newton or a Napoleon. -If ever there was a case when the famous Aristotelian notion of a -“potential existence” seemed justified, assuredly it is this. And -although we can only by a fallacy maintain the oak to be _contained_ -in the acorn, or the animal contained in the ovum, the fallacy is so -natural, and indeed so difficult of escape, that there is no ground -for surprise when physiologists, on first learning something of -development, were found maintaining that the perfect organism existed -already in the ovum, having all its lineaments in miniature, and only -growing into visible dimensions through the successive stages of -evolution.[44] The preformation of the organism seemed an inevitable -deduction from the opinions once universal. It led to many strange, -and some absurd conclusions; among them, to the assertion that the -original germ of every species contained within it all the countless -individuals which in process of time might issue from it; and this in -no metaphysical “potential” guise, but as actual boxed-up existences -(_emboîtés_); so that Adam and Eve were in the most literal sense -progenitors of the whole human race, and contained their progeny -already shaped within them, awaiting the great accoucheur, time. - -100. This was the celebrated “emboîtement” theory. In spite of obvious -objections it gained scientific acceptance, because physiologists could -not bring themselves to believe that so marvellous a structure as that -of a human organism arose by a series of successive modifications, or -because they could not comprehend how it was built up, part by part, -into forms so closely resembling the parent-forms. That many and -plausible reasons pleaded in favor of this opinion is evident in the -fact that illustrious men like Haller, Bonnet, Vallisneri, Swammerdamm, -Réaumur, and Cuvier, were its advocates; and if there is not a sigle -physiologist of our day who accepts it, or who finds any peculiar -difficulty in following the demonstrations of embryologists, how from -the common starting-point of a self-multiplying epithelial cell parts -so diverse as hairs, nails, hoofs, scales, feathers, crystalline lens, -and secreting glands may be evolved, or how from the homogeneous -germinal membrane the complex organism will arise, there are very -few among the scorners of the dead hypothesis who seem capable of -generalizing the principles which have destroyed it, or can conceive -that the laws of Evolution apply as rigorously to the animal and -vegetable _kingdoms_ as to the individual _organisms_. The illustrious -names of those who advocated the preformation hypothesis may serve to -check our servile submission to the authorities so loudly proclaimed as -advocates of the fixity of species. The more because the two doctrines -have a common parentage. The one falls with the other, and no array of -authorities can arrest the fall. That the manifold differentiations -noticeable in a complex organism should have been evolved from a -membrane wholly destitute of differences is a marvel, but a marvel -which Science has made intelligible. Yet the majority of those to -whom this has been made intelligible still find an impossibility in -admitting that the manifold forms of plant and animal were successively -evolved from equally simple origins. They relinquish the hypothesis of -preformation in the one case, and cling to it in the other. Evolution, -demonstrable in the individual history, seems preposterous in the -history of the class. And thus is presented the instructive spectacle -of philosophers laughing at the absurdities of “preformation,” and -yet exerting all their logic and rhetoric in defence of “creative -fiats”--which is simply the preformation hypothesis “writ large.” - -101. It would not be difficult to show that the doctrine of -Epigenesis, with which Wolff forever displaced the doctrine of -Preformation, leads by an inevitable logic to the doctrine of universal -Evolution; and that we can no more understand the appearance of a -new organism which is not the modification of some already existing -organism, than we can understand the sudden appearance of a new organ -which is not the modification of some existing structure. In the one -case as in the other we may disguise the process under such terms as -creative fiat and preformation; but these terms are no explanations; -they re-state the results, they do not describe the process; whereas -Epigenesis describes the process as it passes under the eye of science. - -102. If any reader of these pages who, from theological or zoölogical -suspicion of the Development Hypothesis, clings to the hypothesis -of a creative Plan which once for all arranged the organic world in -Types that could not change, will ask what rational interpretation can -be given to the succession of phases each embryo is forced to pass -through, it may help to give him pause. He will observe that _none_ of -these phases have any adaptation to the future state of the animal, but -are in positive contradiction to it, or are simply purposeless; whereas -all show stamped on them the unmistakable characters of _ancestral_ -adaptations and the progressions of Organic Evolution. What does the -fact imply? There is not a single known example of a complex organism -which is not developed out of simpler forms. Before it can attain the -complex structure which distinguishes it, there must be an evolution of -forms similar to those which distinguish the structures of organisms -lower in the series. On the hypothesis of a Plan which prearranged -the organic world, nothing could be more unworthy of a supreme -intelligence than this inability to construct an organism at once, -without previously making several tentative efforts, undoing to-day -what was so carefully done yesterday, and _repeating for centuries the -same tentatives, and the same corrections, in the same succession_. Do -not let us blink this consideration. There is a traditional phrase much -in vogue among the anthropomorphists, which arose naturally enough from -the tendency to take human methods as an explanation of the divine--a -phrase which becomes a sort of argument--“The Great Architect.” But -if we are to admit the human point of view, a glance at the facts of -embryology must produce very uncomfortable reflections. For what should -we say to an architect who was unable, or being able was obstinately -unwilling, to erect a palace except by first using his materials in the -shape of a hut, then pulling it down and rebuilding them as a cottage, -then adding story to story and room to room, _not_ with any reference -to the ultimate purposes of the palace, but wholly with reference to -the way in which houses were constructed in ancient times? What should -we say to the architect who could not form a museum out of bricks -and mortar, but was forced to begin as if going to build a mansion: -and after proceeding some way in this direction, altered his plan -into a palace, and that again into a museum? Yet this is the sort of -succession on which organisms are constructed. The fact has long been -familiar; how has it been reconciled with Infinite Wisdom? Let the -following passage answer for a thousand:--“The embryo is nothing like -the miniature of the adult. For a long while the body in its entirety -and its details presents the strangest of spectacles. Day by day and -hour by hour the aspect of the scene changes, and this instability is -exhibited by the most essential parts no less than by the accessory -parts. One would say that Nature feels her way, and only reaches the -goal after many times missing the path,--on dirait que la nature -tâtonne et ne conduit son œuvre à bon fin qu’après s’être souvent -trompée.”[45] Writers have no compunction in speaking of Nature feeling -her way and blundering; but if in lieu of Nature, which may mean -anything, the Great Architect be substituted, it is probable that the -repugnance to using such language of evasion may cause men to revise -their conceptions altogether; they dare not attribute ignorance and -incompetence to the Creator. - -103. Obviously the architectural hypothesis is incompetent to explain -the phenomena of organic development. Evolution is the universal -process; not creation of a direct kind. Von Baer, who very properly -corrected the exaggerations which had been put forth respecting the -identity of the embryonic forms with adult forms lower in the scale, -who showed that the mammalian embryo never was a bird, a reptile, -or a fish, nevertheless emphasized the fact that the mammalian -embryo passes through all the lower typical forms; so much so that, -except by their size, it is impossible to distinguish the embryos of -mammal, bird, lizard, or snake. “In my collection,” he says, “there -are two little embryos which I have omitted to label, so that I am -now quite incompetent to say to what class they belong. They may be -lizards, they may be small birds, or very young mammals; so complete -is the similarity in the mode of formation of the head and trunk. -The extremities have not yet made their appearance. But even if they -existed in the earliest stage we should learn nothing from them, for -the feet of lizards, mammals, and the wings of birds, all arise from -the same common form.” He sums up with his formula: “The special type -is always evolved from a more general type.”[46] - -Such reminiscences of earlier forms are intelligible on the supposition -that originally the later form was a modification of the earlier form, -and that this modification is repeated; or on the supposition that -there was a similarity in the organic conditions, which similarity -ceased at the point where the new form emerged. But on no hypothesis -of creative Plan are they intelligible. They are useless structures, -failing even to subserve a temporary purpose. Sometimes, as Mr. Darwin -remarks, a trace of the embryonic resemblance lasts till a late age: -“Thus birds of the same genus, and of closely allied genera, often -resemble each other in their first and second plumage: as we see in -the spotted feathers in the thrush group. In the cat tribe most of the -species are striped and spotted in lines; and stripes or spots can -plainly be distinguished in the whelp of the lion and the puma. We -occasionally, though rarely, see something of this kind in plants.... -The points of structure in which the embryos of widely different -animals of the same class resemble each other often have no direct -relation to their conditions of existence. We cannot, for instance, -suppose that in the embryos of the vertebrata the peculiar loop-like -courses of the arteries near the bronchial slits are related to similar -conditions in the young mammal which is nourished in the womb of its -mother, in the egg of a bird which is hatched in a nest, and in the -spawn of a frog under water.” - -104. It would be easy to multiply examples, but I will content myself -with three. The tadpole of the Salamander has gills, and passes his -existence in the water; but the _Salamandra atra_, which lives high -up among the mountains, brings forth its young full-formed. This -animal never lives in the water. Yet if we open a gravid female, we -find tadpoles inside her with exquisitely feathered gills, and (as I -have witnessed) these tadpoles “when from the mother’s womb untimely -ripped,” if placed in water, swim about like the tadpoles of water -newts. Obviously this aquatic organization has no reference to the -future life of the animal, nor has it any adaptation to its embryonic -condition; it has solely reference to ancestral forms, it repeats a -phase in the development of its progenitors. Again, in the embryo of -the naked Nudibranch, we always observe a shell, although the animal -is without a shell, and there can be no purpose served by the shell in -embryonic life.[47] Finally, the human embryo has a tail, which is of -course utterly purposeless, and which, although to be explained as a -result of organic laws, is on the creative hypothesis only explained as -an adherence to the general plan of structure--a specimen of pedantic -trifling “worthy of no intellect above the pongo’s.”[48] - -105. Humanly appreciated, not only is it difficult to justify the -successive stages of development, the incessant building up of -structures immediately to be taken down, but also to explain why -development was necessary at all. Why are not plants and animals -formed at once, as Eve was mythically affirmed to be taken from Adam’s -rib, and Minerva from Jupiter’s head? The theory of Evolution answers -this question very simply; the theory of Creation can only answer -it by affirming that such was the ordained plan. But the theory of -Evolution not only gives the simpler and more intelligible answer to -this question, it gives an answer to the further question which leaves -the theory of Creation no loophole except a sophism--namely, why the -formation of organisms is constantly being frustrated or perverted? -And, further, it gives an explanation of the law noticed by Milne -Edwards, that Nature is as economical in her means as she is prodigal -in her variation of them: “On dirait qu’avant de recourir à des -ressources nouvelles elle a voulu épuiser, en quelque sorte, chacun -des procédés qu’elle avait mis en jeu.”[49] The applause bestowed on -Nature for being economical is a curious transference to Nature of -human necessities. Why, with a whole universe at her disposal, should -Nature be economical? Why must she always be working in the same -groove, and using but a few out of the many substances at her command? -Economy is a virtue only in the poor. If Nature, in organic evolutions, -is restricted to a very few substances, and a very few modes of -combination, always creating new forms by modification of the old, and -apparently incapable of creating an organism at once, this must imply -an inherent necessity which is very unlike the free choice that can -render economy a merit. - -106. There may indeed be raised an objection to the Development -Hypothesis on the ground that if the complex forms were all developed -from the simpler forms, we ought to trace the identities through all -their stages. If the fish developed into the reptile, the reptile -into the bird, and the bird into the mammal (which I, for one, think -questionable), we ought to find, it is urged, evidence of this passage. -And at one time it was asserted that the evidence existed; but this -has been disproved, and on the disproof the opponents of Evolution -take their stand. Although I cannot feel much confidence in the idea -of such a passage from Type to Type, and although the passage, if ever -it occurred, must have occurred at so remote a period as to leave -no evidence more positive than inference, I cannot but think the -teaching of Embryology far more favorable to it than to our opponents. -Supposing, for the sake of argument, that the passage did take place, -ought we to find the embryonic stages accurately reproducing the -permanent forms of lower types? Von Baer thinks we ought; and lesser -men may follow him without reproach. But it seems to me that he starts -from an inadmissible assumption, namely, that the development must -necessarily be in a straight line rather than in a multiplicity of -divergent lines. “When we find the embryonic condition,” he says, -“differing from the adult, we ought to find a corresponding condition -somewhere in the lower animals.”[50] Not necessarily. We know that -the mental development of a civilized man passes through the stages -which the race passed through in the course of its long history, and -the psychology of the child reproduces the psychology of the savage. -But as this development takes place under conditions in many respects -different, and as certain phases are hurried over, we do not expect -to find a complete parallel. It is enough if we can trace general -resemblances. Von Baer adds, “That certain correspondences should occur -between the embryonic states of some animals and the adult states of -others seems inevitable and of no significance(?). They could not fail, -since the embryos lie within the animal sphere, and the variations -of which the animal body is capable are determined for each type by -the internal connection and mutual reaction of its organs, so that -particular repetitions are inevitable.” A profound remark, to which I -shall hereafter have occasion to return, but its bearing on the present -question is inconclusive. The fact that the embryonic stages of the -higher animals resemble in general characters the permanent stages -of the lower animals, and very closely resemble the embryonic stages -of those animals, is all that the Development Hypothesis requires. -Nor is its value lessened by the fact that many of the details and -intermediate stages seem passed over in the development of the higher -forms, for the recapitulation can only be of outlines, not of details; -since there are differences in the forms, there must be differences in -their histories. - -107. In the preceding observations the object has simply been to show -that the phenomena to be explained can be rationally conceived as -resulting from gradual Evolution, whereas they cannot be so rationally -interpreted on any other hypothesis. And here it may be needful to say -a word respecting Epigenesis. - -The Preformation hypothesis, which regarded every organism as a simple -educt and not the product of a germ, was called by its advocates an -evolution hypothesis--meaning that the adult form was an outgrowth of -the germ, the miniature magnified. Wolff, who replaced that conception -by a truer one, called his, by contrast, Epigenesis, meaning that -there was not simply _out_-growth but _new_ growth. “The various -parts,” he says, “arise one _after_ the other, so that always one is -secreted from (_excernirt_), or deposited (_deponirt_) on the other; -and then it is either a free and independent part, or is only fixed -to that which gave it existence, or else is contained within it. So -that _every part is the effect of a pre-existing part, and in turn -the cause of a succeeding part_.”[51] The last sentence expresses -the conception of Epigenesis which embryologists now adopt; and -having said this, we may admit that Wolff, in combating the error -of preformation, replacing it with the truer notion of gradual and -successive formation, was occasionally open to the criticism made -by Von Baer, that he missed the true sense of Evolution, since the -new parts are not _added on_ to the old parts as new formations, -but _evolved from_ them as transformations. “The word Evolution, -therefore, seems to me more descriptive of the process than Epigenesis. -It is true that the organism is not preformed, but the course of its -development is precisely the course which its parents formerly passed -through. Thus it is the Invisible--the course of development--which is -predetermined.”[52] When the word Epigenesis is used, therefore, the -reader will understand it to signify that necessary succession which -determines the existence of new forms. Just as the formation of chalk -is not the indifferent product of any combination of its elements, -carbon, oxygen, and calcium, but is the product of only one series of -combinations, an evolution through necessary successions, the carbon -uniting with oxygen to form carbonic acid, and this combining with the -oxide of calcium to form chalk, so likewise the formation of a muscle, -a bone, a limb, or a joint has its successive stages, each of which -is necessary, none of which can be transposed. The formation of bone -is peculiarly instructive, because the large proportion of inorganic -matter in its substance, and seemingly deposited in the organic tissue, -would lead one to suppose that it was almost an accidental formation, -which might take place anywhere; yet although what is called -connective tissue will ossify under certain conditions, true bone is -the product of a very peculiar modification, which almost always needs -to be preceded by cartilage. That the formation of bone has its special -history may be seen in the fact that it is the last to appear in the -animal series, many highly organized fishes being without it, and all -the other systems appearing before it in the development of the embryo. -Thus although the mother’s blood furnishes all the requisite material, -the fœtus is incapable of assimilating this material and of forming -bone, until its own development has reached a certain stage. Moreover, -when ossification does begin, it generally begins in the skull (in -man in the clavicle); and the only approach to an internal skeleton -in the Invertebrates is the so-called skull of the Cephalopoda. -Not only is bone a late development, but cartilage is also; and -although it is an error to maintain that the Invertebrates are wholly -destitute of cartilage, its occasional presence having been fully -proved by Claparède and Gegenbaur, the rarity of its presence is very -significant. The animals which can form shells of chalk and chitine are -yet incapable of forming even an approach to bone. - -108. Epigenesis depends on the laws of succession, which may be likened -to the laws of crystallization, if we bear in mind the essential -differences between a crystal and an organism, the latter retaining -its individuality through an incessant molecular change, the former -only by the exclusion of all change. When a crystalline solution -takes shape, it will always take a definite shape, which represents -what may be called the _direction_ of its forces, the polarity of -its constituent molecules. In like manner, when an organic plasmode -takes shape--crystallizes, so to speak--it always assumes a specific -shape dependent on the polarity of its molecules. Crystallographers -have determined the several forms possible to crystals; histologists -have recorded the several forms of Organites, Tissues, and Organs. -Owing to the greater variety in elementary composition, there is in -organic substance a more various polar distribution than in crystals; -nevertheless, there are sharply defined limits never overstepped, and -these constitute what may be called the specific forms of Organites, -Tissues, Organs, Organisms. An epithelial cell, for example, may be -ciliated or columnar, a muscle-fibre striated or non-striated, a -nerve-fibre naked or enveloped in a sheath, but the kind is always -sharply defined. An intestinal tube may be a uniform canal, or a canal -differentiated into several unlike compartments, with several unlike -glandular appendages. A spinal column may be a uniform solid axis, or -a highly diversified segmented axis. A limb may be an arm, or a leg, a -wing, or a paddle. In every case the anatomist recognizes a specific -type. He assigns the uniformities to the uniformity of the substance -thus variously shaped, under a history which has been similar; the -diversities he assigns to the various conditions under which the -processes of growth have been determined. He never expects a muscular -tissue to develop into a skeleton, a nervous tissue into a gland, -an osseous tissue into a sensory organ. He never expects a tail to -become a hand or a foot, though he sees it in monkeys and marsupials -serving the offices of prehension and locomotion. He never expects -to find fingers growing anywhere except from metacarpal bones, or an -arm developed from a skull. The well-known generalization of Geoffroy -St. Hilaire that an organ is more easily annihilated than transposed, -points to the fundamental law of Epigenesis. In the same direction -point all the facts of growth. Out of a formless germinal membrane we -see an immense variety of forms evolved; and out of a common nutritive -fluid this variety of organs is sustained, repaired, replaced; and -this not indifferently, not casually, but according to rigorous laws -of succession; that which precedes determining that which succeeds -as inevitably as youth precedes maturity, and maturity decay. The -nourishment of various organs from plasmodes derived from a common -fluid, each selecting from that fluid only those molecules that are -like its own, rejecting all the rest, is very similar to the formation -of various crystals in a solution of different salts, each salt -separating from the solution only those molecules that are like itself. -Reil long ago called attention to this analogy. He observed that if -in a solution of nitre and sulphate of soda a crystal of nitre be -dropped, all the dissolved nitre crystallizes, the sulphate remaining -in solution; whereas on reversing the experiment, a crystal of sulphate -of soda is found to crystallize all the dissolved sulphate, leaving the -nitre undisturbed. In like manner muscle selects from the blood its own -materials which are there in solution, rejecting those which the nerve -will select. - -109. Nay, so definite is the course of growth, that when a limb or part -of a limb is cut off from a crab or salamander, a new limb or new part -is reproduced in the old spot, exactly like the one removed. Bonnet -startled the world by the announcement that the _Naïs_, a worm common -in ponds, spontaneously divided itself into two worms; and that when he -cut it into several pieces, each piece reproduced head and tail, and -grew into a perfect worm. This had been accepted by all naturalists -without demur, until Dr. Williams, in his “Report on British Annelida, -1851,” declared it to be a fable. In 1858, under the impulse of Dr. -Williams’s very emphatic denial, I repeated experiments similar to -those of Bonnet, with similar results. I cut two worms in half, and -threw away the head-bearing segments, placing the others in two -separate vessels, with nothing but water and a little mud, which was -first carefully inspected to see that no worm lay concealed therein. In -a few days the heads were completely reformed, and I had the pleasure -of watching them during their reconstruction. When the worms were quite -perfect, I again cut away their heads, and again saw these reformed. -This was repeated, till I had seen four heads reproduced; after which -the worms succumbed. - -110. The question naturally arises, Why does the nutritive fluid -furnish only material which is formed into a part like the old one, -instead of reproducing another part, or one having a somewhat different -structure? The answer to this question is the key to the chief problem -of organic life. That a limb _in situ_ should replace its molecular -waste by molecules derived from the blood, seems intelligible enough -(because we are familiar with it), and may be likened to the formation -of crystals in a solution; but how is it that the limb _which is not -in existence_ can assimilate materials from the blood? How is it that -the blood, which elsewhere in the organism will form other parts, -here will only form this particular part? There is, probably, no one -who has turned his attention to these subjects who has not paused to -consider this mystery. The most accredited answer at present before the -world is one so metaphysiological that I should pass it by, were it -not intimately allied with that conception of Species, which it is the -object of these pages to root out. It is this: - -111. The organism is determined by its Type, or, as the Germans say, -its Idea. All its parts take shape according to this ruling plan; -consequently, when any part is removed, it is reproduced according to -the Idea of the whole of which it forms a part. Milne Edwards, in a -very interesting and suggestive work, concludes his survey of organic -phenomena in these words: “Dans l’organisme tout semble calculé en -vue d’un résultat déterminé, et l’harmonie des parties ne résulte -pas de l’influence qu’elles peuvent exercer les unes sur les autres, -mais de leur co-ordination sous l’empire d’une puissance commune, -d’un plan préconçu, d’une force pré-existante.”[53] This is eminently -metaphysiological. It refuses to acknowledge the operation of immanent -properties, refuses to admit that the harmony of a complex structure -results from the mutual relations of its parts, and seeks _outside_ -the organism for some mysterious force, some plan, not otherwise -specified, which regulates and shapes the parts. Von Baer, in his great -work, has a section entitled, “The nature of the animal determines -its development”; and he thus explains himself: “Although every stage -in development is only made possible by the pre-existing condition -[which is another mode of expressing Epigenesis], nevertheless the -entire development is ruled and guided by the Nature of the animal -which is about to be (von der gesammten Wesenheit des Thieres welches -werden soll), and it is not the momentary condition which alone -and absolutely determines the future, but more general and higher -relations.”[54] One must always be slow in rejecting the thoughts -of a master, and feel sure that one sees the source of the error -before regarding it as an error; but in the present case I think the -positive biologist will be at no loss to assign Von Baer’s error to -its metaphysical origin. Without pausing here to accumulate examples -both of anomalies and slighter deviations which are demonstrably due -to the “momentary conditions” that preceded them, let us simply note -the logical inconsistency of a position which, while assuming that -_every separate stage_ in development is the necessary sequence of its -predecessor, declares the _whole of the stages_ independent of such -relations! Such a position is indeed reconcilable on the assumption -that animal forms are moulded “like clay in the hands of the potter.” -But this is a theological dogma, which leads to very preposterous and -impious conclusions; and whether it leads to these conclusions or to -others, positive Biology declines theological explanations altogether. -Von Baer, although he held the doctrine of Epigenesis, coupled it, -as many others have done, with metaphysical doctrines to which it is -radically opposed. He believed in Types as realities; he was therefore -consistent in saying, “It is not the Matter and its arrangements which -determine the product, but the nature of the parent form--the Idea, -according to the new school.” How are we to understand this Idea? If -it mean an independent Entity, an agency external to the organism, we -refuse to acknowledge its existence. If it mean only an _a posteriori_ -abstraction expressing the totality of the conditions, then, indeed, -we acknowledge that it determines the animal form; but this is only an -abbreviated way of expressing the law of Evolution, by which each stage -determines its successor. The Type does not _dominate_ the conditions, -it _emerges_ from them; the animal organism is not cast in a mould, but -the imaginary mould is the form which the polarities of the organic -substance assume. It would seem very absurd to suppose that crystals -assumed their definite shapes (when the liquid which held their -molecules in solution is evaporated) under the determining impulse -of phantom-crystals, or Ideas; yet it has not been thought absurd to -assume phantom forms of organisms. - -112. The conception of Type as a determining influence arises from -that fallacy of taking a resultant for a principle, which has played -so conspicuous a part in the history of philosophy. Like many others -of its class it exhibits an interesting evolution from the crude -metaphysical to the subtle metaphysical point of view, which at last -insensibly blends into the positive point of view. At first the Type or -Idea was regarded as an objective reality, external to the organism it -was supposed to rule. Then this notion was replaced by an approach to -the more rational interpretation, the idea was made an internal not an -external force, and was incorporated with the material elements of the -organism, which were said to “endeavor” to arrange themselves according -to the Type. Thus Treviranus declares that the seed “dreams of the -future flower”; and “Henle, when he affirms that hair and nails grow in -virtue of the Idea, is forced to add that the parts endeavor to arrange -themselves according to this Idea.”[55] Even Lotze, who has argued -so victoriously against the vitalists, and has made it clear that an -organism is a vital mechanism, cannot relinquish this conception of -legislative Ideas, though he significantly adds, “these have no power -in themselves, but only in as far as they are grounded in mechanical -conditions.” Why then superfluously add them to the conditions? If -every part of a watch, in virtue of the properties inherent in its -substance, and of the mutual reactions of these and other parts, -has a mechanical value, and if the sum of all these parts is the -time-indicating mechanism, do we add to our knowledge of the watch, and -our means of repairing or improving it, by assuming that the parts have -over and above their physical properties the metaphysical “tendency” -or “desire” to arrange themselves into this specific form? When we -see that an organism is constructed of various parts, each of which -has its own properties inalienable from its structure, and its uses -dependent on its relation to other parts, do we gain any larger insight -by crediting these parts with desires or “dreams” of a future result -which their union will effect? That which is true in this conception of -legislative Ideas is that when the parts come together there is mutual -reaction, and the resultant of the whole is something very unlike -the mere addition of the items, just as water is very unlike oxygen -or hydrogen; further, the connexus of the whole impresses a peculiar -direction on the development of the parts, and the law of Epigenesis -necessitates a serial development, which may easily be interpreted as -due to a preordained plan. - -113. In a word, this conception of Type only adds a new name to the -old difficulty, adding mist to darkness. The law of Epigenesis, -which is simply the expression of the material process determined by -the polarity of molecules, explains as much of the phenomena as is -explicable. A lost limb is replaced by the very processes, and through -the same progressive stages as those which originally produced it. We -have a demonstration of its not being reformed according to any Idea -or Type which exists apart from the immanent properties of the organic -molecules, in the fact that it is not reformed at once, but by gradual -evolution; the mass of cells at the stump are cells of embryonic -character, cells such as those which originally “crystallized” into -muscles, nerves, vessels, and integument, and each cell passes through -all its ordinary stages of development. It is to be remembered that so -intimately dependent is the result on the determining conditions, that -any external influence which disturbs the normal course of development -will either produce an anomaly, or frustrate the formation of a new -limb altogether. One of my tritons bit off the leg of his female;[56] -the leg which replaced it was much malformed, and curled over the back -so as to be useless; was this according to the Idea? I cut it off, and -examined it; all the bones were present, but the humerus was twisted, -and of small size. In a few weeks a new leg was developed, and this -leg was normal. If the Idea, as a ruling power, determined the growth -of this third leg, what determined the second, which was malformed? -Are we to suppose that in normal growth the Idea prevails, in abnormal -the conditions? That it is the polarity of the molecules which at -each moment determines the group those molecules will assume, is well -seen in the experiment of Lavalle mentioned by Bronn.[57] He showed -that if when an octohedral crystal is forming, an angle be cut away, -so as to produce an artificial surface, a similar surface is produced -spontaneously on the corresponding angle, whereas all the other angles -are sharply defined. “Valentin,” says Mr. Darwin, “injured the caudal -extremity of an embryo, and three days afterwards it produced rudiments -of a double pelvis, and of double hind limbs. Hunter and others have -observed lizards with their tails reproduced and doubled. When Bonnet -divided longitudinally the foot of the salamander, several additional -digits were occasionally formed.”[58] Where is the evidence of the Idea -in these cases? - -114. I repeat, the reproduction of lost limbs is due to a process which -is in all essential respects the same as that which originally produced -them; the genesis of one group of cells is the necessary condition -for the genesis of its successor, nor can this order be transposed. -But--and the point is very important--it is not every part that can be -reproduced, nor is it every animal that has reproductive powers. The -worm, or the mollusk, seems capable of reproducing every part; the crab -will reproduce its claws, but not its head or tail; the perfect insect -of the higher orders will reproduce no part (indeed the amputation of -its antennae only is fatal), the salamander will reproduce its leg, -the frog not. In human beings a muscle is said never to be reproduced; -but this is not the case in the rare examples of supplementary fingers -and toes, which have been known to grow again after amputation. -The explanation of this difference in the reproductive powers of -different animals is usually assigned to the degree in which their -organisms retain the embryonic condition; and this explanation is made -plausible by the fact that the animals which when adult have no power -of replacing lost limbs, have the power when in the larval state. But -although this may in some cases be the true explanation, there are -many in which it fails, as will be acknowledged after a survey of the -extremely various organisms at widely different parts of the animal -series which possess the reproductive power. Even animals in the same -class, and at the same stage of development, differ in this respect. -I do not attach much importance to the fact that all my experiments -on marine annelids failed to furnish evidence of their power of -reproducing lost segments; because it is difficult to keep them under -conditions similar to those in which they live. But it is significant -that, among the hundreds which have passed under my observation, not -one should have been found with a head-segment in the process of -development, replacing one that had been destroyed; and this is all the -more remarkable from the great tenacity of life which the mutilated -segments manifest. Quatrefages had observed portions of a worm, after -gangrene had destroyed its head and several segments, move about in the -water and avoid the light![59] - -115. A final argument to show that the reproduction is not determined -by any ruling Idea, but by the organic conditions and the necessary -stages of evolution, is seen in the reappearance of a tumor or cancer -after it has been removed. We find the new tissue appear with all the -characters of the normal tissue of the gland, then rapidly assume one -by one the characters of the diseased tissue which had been removed; -and there as on is, that the regeneration of the tissue is accompanied -by the same abnormal conditions which formerly gave rise to the tumor: -the directions of “crystallization” are similar because the conditions -are similar. In every case of growth or regrowth the conditions being -the same, the result must be the same. - -116. It seems a truism to insist that similarity in the results must be -due to similarity in the conditions; yet it is one which many theorists -disregard; and especially do we need to bear it in mind when arguing -about Species. I will here only touch on the suggestive topic of the -analogies observed not simply among animals at the extreme ends of the -scale, but also between animals and plants where the idea of a direct -kinship is out of the question. - -My very imperfect zoölogical knowledge will not allow me to adduce a -long array of instances, but such an array will assuredly occur to -every well-stored mind. It is enough to point to the many analogies -of Function, more especially in the reproductive processes--to the -existence of burrowers, waders, flyers, swimmers in various classes--to -the existence of predatory mammals, predatory birds, predatory -reptiles, predatory insects by the side of herbivorous congeners,--to -the nest-building and incubating fishes; and in the matter of Structure -the analogies are even more illustrative when we consider the widely -diffused spicula, setæ, spines, hooks, tentacles, beaks, feathery -forms, nettling-organs, poison-sacs, luminous organs, etc.; because -these have the obvious impress of being due to a community of substance -under similar conditions rather than to a community of kinship. The -beak of the tadpole, the cephalopod, the male salmon, and the bird, -are no doubt in many respects unlike; but there is a significant -likeness among them, which constitutes a true analogy. I think there -is such an analogy between the air-bladder of fishes and the tracheal -rudiment which is found in the gnat-larva (_Corethra plumicornis_).[60] -Very remarkable also is the resemblance of the _avicularium_, or -“bird’s-head process,” on the polyzoon known popularly as the Corkscrew -Coralline (_Bugula avicularia_), which presents us in miniature -with a vulture’s head--two mandibles, one fixed, the other moved by -muscles visible within the head. No one can watch this organ snapping -incessantly, without being reminded of a vulture, yet no one would -suppose for a moment that the resemblance has anything to do with -kinship. - -117. Such cases are commonly robbed of their due significance by being -dismissed as coincidences. But what determines the coincidence? If we -assume, as we are justified in assuming, that the _possible directions_ -of Organic Combination, and the resultant forms, are limited, there -must inevitably occur such coincident lines: the hooks on a Climbing -Plant will resemble the hooks on a Crustacean or the claws of a Bird, -as the one form in which under similar external forces the more solid -but not massive portions of the integument tend to develop. I am too -ill acquainted with the anatomy of plants to say how the hooks so -common among them arise; but from examination of the Blackberry, and -comparison of its thorns with the hooks and spines of the Crustacea, -I am led to infer that in each case the mode of development is -identical--namely, the secretion of chitine from the cellular matrix of -the integument. - -Another mode of evading the real significance of such resemblances -is to call them analogies, not homologies. There is an advantage in -having two such terms, but we ought to be very clear as to their -meaning and their point of separation. Analogy is used to designate -similarity in Function with dissimilarity in Structure. The wing -of an insect, the wing of a bird, and the wing of a bat are called -analogous, but not homologous, because their anatomical structure is -different: they are not constructed out of similar anatomical parts. -The fore-leg of a mammal, the wing of a bird, or the paddle of a -whale, are called homologous, because in spite of their diverse uses -they are constructed out of corresponding anatomical parts. To the -anatomist such distinctions are eminently serviceable. But they have -led to some misconceptions, because they are connected with a profound -misconception of the relation between Function and Organ. Embryology -teaches that the wing of the bird and the paddle of the whale are -developed out of corresponding parts, and that these are not like the -parts from which the wing of an insect or the flying-fish will be -developed; nevertheless, the most cursory inspection reveals that the -wing of a bird and the paddle of a whale are very unlike in structure -no less than in function, and that their diversities in function -correspond with their diversities in structure; whereas the wing of the -insect, of the bird, and of the bat, are in certain characters very -similar, and correspondingly there are similarities in their function. -It is, however, obvious that the resemblance in function is strictly -limited to the resemblance in anatomical structure; only in loose -ordinary speech can the flight of an insect, a bird, or a bat be said -to be “the same”: it is different in each--the weight to be moved, the -rapidity of the movement, the precision of the movements, and their -endurance, all differ. - - -NATURAL SELECTION AND ORGANIC AFFINITY. - -118. It is impossible to treat of Evolution without taking notice -of that luminous hypothesis by which Mr. Darwin has revolutionized -Zoölogy. There are two points needful to be clearly apprehended before -the question is entered upon. The first point relates to the lax use -of the phrase “conditions,” sometimes more instructively replaced by -“conditions of existence.” Inasmuch as Life is only possible under -definite relations of the organism and its medium, the “conditions of -existence” will be those physical, chemical, and physiological changes, -which _in_ the organism, and _out_ of it, _co-operate_ to produce the -result. There are myriads of changes in the external medium which have -no corresponding changes in the organism, not being in any direct -relation to it (see § 54). These, not being co-operant conditions, -must be left out of the account; they are not conditions of existence -for the organism, and therefore the organism does not vary with their -variations. On the other hand, what seem very slight changes in the -medium are often responded to by important changes in the vital -chemistry, and consequently in the structure of the organism. Now the -nature of the organism at the time being, that is to say, its structure -and the physico-chemical state of its tissues and plasmodes, is the -main _condition_ of this response; the same external agent will be -powerful, or powerless, over slightly different organisms, or over the -same organism at different times. Usually, and for convenience, when -biologists speak of conditions, they only refer to external changes. -This usage has been the source of no little confusion in discussing -the Development Hypothesis. Mr. Darwin, however, while following the -established usage, is careful in several places to declare that of the -two factors in Variation--the nature of the organism and the nature of -the conditions--the former is by far the more important. - -118_a_. A still greater modification of terms must now be made. Instead -of confining the “struggle for existence” to the competition of rivals -and the antagonism of foes, we must extend it to the competition and -antagonism of tissues and organs. The existence of an organism is not -only dependent on the external existence of others, and is the outcome -of a struggle; but also on the internal conditions which co-operate in -the formation of its structure, this structure being the outcome of a -struggle. The organism is this _particular_ organism, differing from -others, because of the particular conditions which have co-operated. -The primary and fundamental struggle must be that of the organic -forces at work in creating a structure capable of pushing its way -amid external forces. The organism must find a footing in the world, -before it can compete with rivals, and defend itself against foes. -Owing to the power of reproduction, every organism has a potential -indefiniteness of multiplication; that potential indefiniteness is, -however, in reality restricted by the supply of food, and by the -competition of rivals for that supply. The multiplication of any one -species is thus kept down by the presence of rivals and foes: a balance -is reached, which permits of the restricted quantities of various -species. This balance is the result of a struggle. - -Now let me call attention to a similar process in the formation of the -organism itself. Every organite, and every tissue, has a potential -growth of indefinite extent, but its real growth is rigorously limited -by the competition and antagonism of the others, each of which has -its potential indefiniteness, and its real limits. Something, in the -food assimilated, slightly alters the part which assimilates it. This -change may be the origin of other changes in the part itself, or in -neighboring parts, stimulating or arresting the vital processes. A -modification of structure results. Or there may be no new substance -assimilated, but external forces may call a part into increased -activity--which means increased waste and repair; and this increase -here is the cause of a corresponding decrease somewhere else. Whatever -the nature of the change, it finds its place amid a complex of changes, -and its results are compounded with theirs. When organites and tissues -are said to have a potential indefiniteness of growth, there is -assumed a potential indefiniteness in the pabulum supplied: _if_ the -pabulum were supplied, and _if_ there were no antagonism thwarting its -assimilation, growth would of course continue without pause, or end; -but in reality this cannot be so. For, take the blood as the vehicle -of the pabulum--not only is its quantity limited, and partly limited -by the very action of the tissues it feeds, but even in any given -quantity there is a limit to its composition--it will only take up a -limited quantity of salts, iron, albumen, etc.; no matter how abundant -these may be in the food. So again with the plasmodes of the various -tissues--they have each their definite capacities of assimilation. What -has already been stated respecting chemical affinity (§ 20) is equally -applicable to organic affinity; as the presence of fused iron in the -crucible partially obstructs the combination of sulphur and lead, so -the presence of connective tissue partially obstructs the combination -of muscle protoplasm with its pabulum. - -118 _b_. Owing to the action and reaction of blood and plasmode, of -tissues on tissues, and organs on organs, and their mutual limitations, -the growth of each organism has a limit, and the growth of each organ -has a limit. Beyond this limit, no extra supply of food will increase -the size of the organism; no increase of activity will increase the -organ. “Man cannot add a cubit to his stature.” The blacksmith’s arm -will not grow larger by twenty years of daily exercise, after it has -once attained a certain size. Increase of activity caused it to enlarge -up to this limit; but no increase of activity will cause it to pass -this limit. Why? Because here a balance of the co-operating formative -forces has been reached. Larger muscles, or more muscle-fibres, demand -arteries of larger calibre, and these a heart of larger size; with -the increase of muscle would come increase of connective tissue; and -this tissue would not only compete with the muscle for pabulum, but -by mechanical pressure would diminish the flow of that pabulum. And -why would connective tissue increase? Because, in the first place, -there is a formative association between the two, so that owing to a -law, not yet understood, the one always accompanies the other; and, -in the second place, there is a functional association between the -two, a muscle-fibre being _inoperative_ unless it be attached to a -tendon, or connective tissue; it will contract _out_ of the body -although separated from its tendon or other attachment; but _in_ the -body its contraction would be useless without this attachment. We must -bear in mind that muscle-fibres are very much shorter than ordinary -muscles; according to the measurements of W. Krause they never exceed -4 _cm_ in length, and usually range between 2 and 3 _cm_; their fine -points being fixed to the interstitial connective tissue, as the whole -muscle is fixed to its tendon. The function of the muscle is thus -dependent on a due balance of its component tissues; if that balance -is disturbed the function is disturbed. Should, from any cause, an -excess of muscle-fibre arise, the balance would be disturbed; should an -encroachment of connective tissue, or of fat, take place, there would -be also a defect of function. - -Here we have the co-operation and limitation of the tissues -illustrated; let us extend our glance, and we shall see how the -co-operation and limitation of the organs come into play, so that -the resulting function depends on the balance of their forces. The -contractile power of each individual muscle is always limited by the -resistance of antagonists, which prevent the muscle being contracted -more than about a third of its _possible_ extent, i. e. possible when -there are no resistances to be overcome. Not only the increasing -tension of antagonist muscles, but the resistance of tendons, bones, -and softer parts must be taken into account. Thus, the increase of -the blacksmith’s muscular power would involve a considerable increase -in all the tissues of the arm; but such an increase would involve a -reconstruction of his whole organism. - -Whenever there is an encroachment of one tissue on another, there -is a disturbance of the normal balance, which readily passes into a -pathological state. If the brain is overrun with connective tissue, or -the heart with fatty tissue, we know the consequences. If connective -tissue is deficient, epithelial runs to excess, no longer limited by -its normal antagonist, and pus, or cancer, result. - -118_c_. It is unnecessary here to enlarge on this point. I have -adduced it to show that we must extend our conception of the struggle -for existence beyond that of the competition and antagonism of -organisms--the external struggle; and include under it the competition -and antagonism of tissues and organs--the internal struggle. -Variability is inherent in organic substances, as the result of -their indefiniteness of composition (§ 45_b_). This variability is -indefinite, and is rendered definite by the competition and antagonism, -so that every particular variation is the resultant of a composition -of forces. The forces in operation are the internal and external -conditions of existence--i. e. the nature of the organism, and its -response to the actions of its medium. A change may take place in -the medium without a corresponding response from the organism; or the -change may find a response and the organism become modified. Every -modification is a selection, determined by laws of growth; it is the -resultant of a struggle between what, for want of a better term, may -be called the _organic affinities_--which represent in organized -substances what chemical affinities are in the anorganized. Just as -an organism which has been modified and thereby gained a superiority -over others, has by this modification been _selected_ for survival--the -selection being only another aspect of this modification--so one -tissue, or one organ, which has surpassed another in the struggle -of growth, will thereby have become selected. Natural Selection, -or survival of the fittest, therefore, is simply the metaphorical -expression of the fact that any balance of the forces which is best -adapted for survival will survive. Unless we interpret it as a -shorthand expression of _all_ the internal and external conditions of -existence, it is not acceptable as the origin of species. - -118_d_. Mr. Darwin has so patiently and profoundly meditated on the -whole subject, that we must be very slow in presuming him to have -overlooked any important point. I know that he has not altogether -overlooked this which we are now considering; but he is so preoccupied -with the tracing out of his splendid discovery in all its bearings, -that he has thrown the emphasis mainly on the external struggle, -neglecting the internal struggle; and has thus in many passages -employed language which implies a radical distinction where--as I -conceive--no such distinction can be recognized. “Natural Selection,” -he says, “depends on the survival under various and complex -circumstances of the best-fitted individuals, but has no relation -whatever to the primary cause of any modification of structure.”[61] -On this we may remark, first, that selection does not _depend_ on -the survival, but _is_ that survival; secondly, that the best-fitted -individual survives because of that modification of its structure -which has given it the superiority; therefore if the primary cause -of this modification is not due to selection, then selection cannot -be the cause of species. He separates Natural Selection from all the -primary causes of variation, either internal or external--either as -results of the laws of growth, of the correlations of variation, of -use and disuse, etc., and limits it to the slow accumulations of such -variations as are profitable in the struggle with competitors. And for -his purpose this separation is necessary. But biological philosophy -must, I think, regard the distinction as artificial, referring only -to one of the great factors in the production of species. And for -this reason: Selection only comes into existence in the modifications -produced either by external or internal changes; and the selected -change cannot be developed further by mere inheritance, unless the -successive progeny have such a disposition of the organic affinities -as will repeat the primary change. Inherited superiority will not by -mere transmission become greater. The facts which are relied on in -support of the idea of “fixity of species” show at any rate that a -given superiority will remain stationary for thousands of years; and -no one supposes that the progeny of an organism will vary unless some -external or internal cause of variation accompanies the inheritance. -Mr. Darwin agrees with Mr. Spencer in admitting the difficulty of -distinguishing between the effects of some definite action of external -conditions, and the accumulation through natural selection of inherited -variations serviceable to the organism. But even in cases where the -distinction could be clearly established, I think we should only see an -_historical_ distinction, that is to say, one between effects produced -by particular causes now in operation, and effects produced by very -complex and obscure causes in operation during ancestral development. - -118_e_. The reader will understand that my criticism does not pretend -to invalidate Mr. Darwin’s discovery, but rather to enlarge its -terms, so as to make it include all the biological conditions, and -thus explain many of the variations which Natural Selection--in the -restricted acceptation--leaves out of account. Mr. Darwin draws a broad -line of distinction between Variation and Selection, regarding only -those variations that are favorable as selected. I conceive that all -variations which survive are by that fact of survival, _selections_, -whether favorable or indifferent. A variety is a species in formation; -now Selection itself is not a cause, or condition, of variation, it is -the _expression_ of variation. Mr. Darwin is at times explicit enough -on this head: “It may metaphorically be said that Natural Selection -is daily and hourly scrutinizing throughout the world the slightest -variations; rejecting those that are bad, preserving and adding up -all that are good; silently and insensibly working, whenever and -wherever opportunity offers, at the improvement of each organic being -in relation to its organic and inorganic conditions of life.”[62] But -the metaphorical nature of the term is not always borne in mind, so -that elsewhere Natural Selection is said to “act on and modify organic -beings,” as if it were a positive condition and not the expression -of the modifying processes. Because grouse are largely destroyed by -birds of prey, any change in their color which would render them less -conspicuous would enable more birds to escape; but it is obvious that -this change of color will be due to Organic Affinity; and only when -the change is _effected_ will there have been that selection which -_expresses_ it. Mr. Darwin’s language, however, is misleading. He -says: “Hence Natural Selection might be most effective in _giving_ the -proper color to each kind of grouse, and in _keeping_ that color when -once acquired.” This is to make Selection an agent, a condition of -the development of color; which may be accepted if we extend the term -so as to include the organic changes themselves. Again: “Some writers -have imagined that Natural Selection _induces variability_, whereas it -only implies the _preservation_ of such variations as are beneficial to -the being under its conditions of life.” It, however, is made to imply -more than this, namely, the accumulation and further modification of -such variations. “The mere existence of individual variability and of -some well-marked varieties, though necessary as the foundation, helps -us but little in understanding how species arise in nature. How have -all those exquisite adaptations of one part of the organization to -another part, and to the conditions of life, and of one organic being -to another being, been perfected?” My answer to this question would -be: By Organic Affinity, and the resulting struggle of the tissues and -organs, the consequences of which are that very _adaptation_ of the -organism to external conditions, which is expressed as the _selection_ -of the structures best adapted. The selections are the results of the -struggle, according to my proposed extension of the term “struggle.” -Mr. Darwin defines the struggle: “The dependence of one being on -another, and including (what is more important) not only the life of -the individual but success in leaving progeny.” This definition seems -defective, since it omits the primary and more important struggle -which takes place between the organic affinities in operation. To -succeed in the struggle with competitors, the organism must have first -acquired--by selection--a superiority in one or more of its organs. - -118_f_. A little reflection will disclose the importance of keeping -our eyes fixed on the internal causes of variation, as well as on the -external conditions of the struggle. Mr. Darwin seems to imply that the -external conditions which cause a variation are to be distinguished -from the conditions which accumulate and perfect such variation, that -is to say, he implies a radical difference between the process of -variation and the process of selection. This, I have already said, does -not seem to me acceptable; the selection, I conceive, to be simply the -variation which has survived.[63] - -If it be true that a Variety is an incipient Species and shows -us Species in formation, it is in the same sense true that a -variation is an incipient organ. A species is the result of a slowly -accumulating divergence of structure; an organ is the result of a -slowly accumulating differentiation. At each stage of differentiation -there has been a selection, but we cannot by any means say that this -selection was determined by the fact of its giving the organism a -superiority over rivals, inasmuch as during all the early stages, -while the organ was still in formation, there could be no advantage -accruing from it. One animal having teeth and claws developed will -have a decided superiority in the struggle over another animal that -has no teeth and claws; but so long as the teeth and claws are in an -undeveloped state of mere preparation they confer no superiority. - -118_g_. Natural Selection is only the expression of the results of -obscure physiological processes; and for a satisfactory theory of such -results we must understand the nature of the processes. In other words, -to understand Natural Selection we must recognize not only the facts -thus expressed, but the factors of these facts,--we must analyze the -“conditions of existence.” As a preliminary analysis we find _external -conditions_, among which are included not only the dependence of the -organism on the inorganic medium, but also the dependence of one -organism on another,--the competition and antagonism of the whole -organic world; and _internal conditions_, among which are included not -only the dependence of the organism on the laws of composition and -decomposition whereby each organite and each tissue is formed, but also -the dependence of one organite and one tissue on all the others--the -competition and antagonism of all the elements. - -The changes wrought in an organism by these two kinds of conditions -determine Varieties and Species. Although many of the changes are due -to the process of natural selection brought about in the struggle -with competitors and foes, many other changes have no such relation -to the external struggle, but are simply the results of the organic -affinities. They may or they may not give the organism a greater -stability, or a greater advantage over rivals; it is enough that they -are no disadvantage to the organism, they will then survive by virtue -of the forces which produced them. - -119. The position thus reached will be important in our examination -of the Theory of Descent by which Mr. Darwin tentatively, and his -followers boldly, explain the observed resemblances in structure and -function as due to blood-relationship. The doctrine of Evolution -affirms that all complex organisms are evolved by differentiation from -simpler organisms, as we see the complex organ evolved from simpler -forms. But it does not necessarily affirm that the vast variety of -organisms had one starting-point--one ancestor; on the contrary, I -conceive that the principles of Evolution are adverse to such a view, -and insist rather on the necessity of innumerable starting-points. Let -us consider the question. - -That the Theory of Descent explains many of the facts must be admitted; -but there are many which it leaves obscure; and Mr. Darwin, with -that noble calmness which distinguishes him, admits the numerous -difficulties. Whether these will hereafter be cleared away by an -improvement in the Geological Record, now confessedly imperfect, or -by more exhaustive exploration of distant countries, none can say; -but, to my mind, the probability is, that we shall have to seek our -explanation by enlarging the idea of Natural Selection, subordinating -it to the laws of Organic Affinity. It does not seem to me, at present, -warrantable to assume Descent as the sole principle of morphological -uniformities; there are other grounds of resemblance beyond those of -blood-relationship; and these have been too much overlooked; yet a -brief consideration will disclose that similarity in the physiological -laws and the conditions of Organic Affinity must produce similarity -in organisms, independently of relationship; just as similarity in -the laws and conditions of inorganic affinity will produce identity -in chemical species. We do not suppose the carbonates and phosphates -found in various parts of the globe, or the families of alkaloids and -salts, to have any nearer kinship than that which consists in the -similarity of their elements and the conditions of their combination. -Hence, in organisms, as in salts, morphological identity may be due -to a community of conditions, rather than community of descent. Mr. -Darwin justly holds it to be “incredible that individuals identically -the same should have been produced through Natural Selection from -parents _specifically distinct_,” but he, since he admits analogous -variations, will not deny that identical forms might issue from parents -having widely different origins, provided that these parent forms -and the conditions of their reproduction were identical, as in the -case of vegetable and animal resemblances. To deny this would be to -deny the law of causation. And that which is true of identical forms -under identical conditions is true of similar forms under similar -conditions. When History and Ethnology reveal a striking uniformity in -the progression of social phases, we do not thence conclude that the -nations are directly related, or that the social forms have a common -parentage; we conclude that the social phases are alike because they -have had common causes. When chemists point out the uniformity of type -which exists in compounds so diverse in many of their properties as -water and sulphuretted or selenetted hydrogen, and when they declare -phosphoretted hydrogen to be the congener of ammonia, they do not mean -that the one is descended from the other, or that any closer link -connects them than that of resemblance in their elements. - -In the case of vegetal and animal organisms, we observe such a -community of elementary substance as of itself to imply a community in -their laws of combination; and under similar conditions the evolved -forms must be similar. With this community of elementary substance, -there are also diversities of substance and of co-operant conditions; -corresponding with these diversities there must be differences of -form. Thus, although observation reveals that the bond of kinship does -really unite many widely divergent forms, and the principle of Descent -with Natural Selection will account for many of the resemblances and -differences, there is at present no warrant for assuming that all -resemblances and differences are due to this one cause, but, on the -contrary, we are justified in assuming a deeper principle which may be -thus formulated: All the complex organisms are evolved from organisms -less complex, as these were evolved from simpler forms; the link which -unites all organisms is not always the common bond of heritage, but the -uniformity of organized substance acting under similar conditions. - -It is therefore consistent with the hypothesis of Evolution to admit a -variety of origins or starting-points, though not consistent to admit -the sudden appearance of complex Types, such as is implied in the -hypothesis of specific creations. - -119 _a_. The analogies of organic forms and functions demand a more -exhaustive scrutiny than has yet been given them. Why is it that -vessels, nerves, and bones _ramify_ like branches, and why do these -branches take on the aspect of many crystalline forms? Why is it that -cavities are constantly prolonged in ducts, e. g. the mouth succeeded -by the œsophagus, the stomach by the intestines, the bladder by the -urethra, the heart by the aorta, the ovary by the oviduct, and so -on? Why are there never more than four limbs attached to a vertebral -column, and these always attached to particular vertebræ? Why is -there a tendency in certain tissues to form tubes, and in these tubes -commonly to assume a muscular coat?[64] To some of these queries an -answer might be suggested which would bring them under known physical -laws. I merely notice them here for the sake of emphasizing the fact -that such analogies lie deeply imbedded in the laws of evolution, and -that what has been metaphorically called organic crystallization will -account for many similarities in form, without forcing us to have -recourse to kinship. To take a very simple case. No one will maintain -that the crystalline forms of snow have any kinship with the plants -which they often resemble. Mr. Spencer has noticed the development -of a wing-bearing branch from a wing of the _Ptilota plumosa_, when -its nutrition is in excess. “This form, so strikingly like that of the -feathery crystallizations of many inorganic substances, proves to us -that in such crystallizations the simplicity or complexity of structure -at any place depends on the quantity of matter that has to be polarized -at that place in a given time. How the element of time modifies the -result, is shown by the familiar fact that crystals rapidly formed -are small, and that they become larger when they are formed more -slowly.”[65] - -It may be objected, and justly, that in the resemblance between -crystals and organisms the analogy is purely that of form, and usually -confined to one element, whereas between organisms there is resemblance -of substance no less than of form, and usually the organisms are alike -in several respects. The answer to this objection is, that wherever -there is a similarity in the causal conditions (substance and history) -there must be a corresponding similarity in the results; if this -similarity extends to only a few of the conditions, the analogy will -be slight; if to several, deep. But whether slight or deep we are not -justified, simply on the ground of resemblance, in assuming, short of -evidence, that because they are alike, two organisms are related by -descent from a common ancestor. - -120. Let us glance at a few illustrations. It has been urged as a -serious objection to Mr. Darwin’s hypothesis,[66] that it fails to -explain the existence of phosphorescent organs in a few insects; and -certainly, when one considers the widely different orders in which -these organs appear, and their absence in nearly related forms, it -is a difficulty. In noctilucæ, earthworms, molluscs, scolopendra, -and fireflies, we may easily suppose the presence of similar organic -conditions producing the luminosity; but it requires a strong faith to -assign Descent as the cause.[67] We may say the same of the electric -organs possessed by seven species of fish, belonging to five widely -separated genera. Although each species appears to have a limited -geographical range, one or the other is found in almost every part -of the globe. These organs occupy different positions, being now on -each side of the head, now along the body, and now along the tail; -and in different species they are innervated from different sources. -Their intimate structure also varies; as appears from the remarkable -investigations of Max Schultze.[68] They cannot, therefore, be -homologous. How could they have arisen? Not by the slow accumulations -of Natural Selection, because, until the organs were fully formed, they -could be of no advantage in the struggle; hence the slow growth of -the organ must have proceeded without the aid of an advantage in the -struggle--in each case from some analogous conditions which produced -a differentiation in certain muscles. The fundamental resemblance to -muscles was pointed out by Carus long ago. It has been insisted on by -Leydig:[69] and Owen says, “The row of compressed cells constituting -the electric prism of the Torpedo offers some analogy to the row of -microscopic discs of which the elementary muscle fibre appears to -consist.”[70] We must not, however, forget that these resemblances are -merely such as suggest that the electric organ is a _differentiation_ -of the substance which elsewhere becomes muscular, and that Dr. -Davy was justified in denying the organ to be muscular.[71] That it -is substituted for muscle cannot be doubted. Now, although we are -entirely ignorant of the conditions which cause this differentiation of -substance which elsewhere becomes muscular, but here becomes electric -organs, we can understand that, when once such a development had -taken place, if it in any way profited the fish in its struggle for -existence, Natural Selection would _tend_ to its further increase and -propagation. So far Mr. Darwin carries us with him; but we decline -proceeding further. The development of these organs in fishes so widely -removed, does not imply an ancestral community. It is interpretable as -mere growth on a basis once laid; and therefore would occur with or -without any advantage in the struggle with rivals. The similarity in -concurrent conditions is quite enough to account for the resemblance -in structure. This, with his accustomed candor, Mr. Darwin admits. “If -the electric organs,” he says, “had been inherited from one ancient -progenitor thus provided, we might have expected that all electric -fishes would be specially related to each other. Nor does Geology at -all lead to the belief that formerly most fishes had electric organs -which most of their modified descendants have lost.” - -121. It may seem strange that he should urge a difficulty against -his hypothesis when it could be avoided by the simple admission that -even among nearly allied animals great differences in development -are observable, and the electric organs might be ranged under such -diversities. But Mr. Darwin has so thoroughly wrought out his scheme, -that he foresees most objections, and rightly suspects that if this -principle of divergent development be admitted, it will cut the ground -from under a vast array of facts which his hypothesis of Descent -requires. - -The sudden appearance of new organs, not a trace of which is -discernible in the embryo or adult form of organisms lower in the -scale,--for instance, the phosphorescent and electric organs,--is -like the sudden appearance of new instruments in the social organism, -such as the printing-press and the railway, wholly inexplicable -on the theory of Descent,[72] but is explicable on the theory of -Organic Affinity. For observe: if we admit that differentiations -of structure, and the sudden appearance of organs, can have arisen -spontaneously--i. e. not hereditarily--as the outcome of certain -changed physical conditions, we can hardly refuse to extend to the -whole organism what we admit of a particular organ. If, again, we -admit that organs very similar in structure and function spontaneously -appear in organisms of widely different kinds--e. g. the phosphorescent -and electric organs--we must also admit that similar resemblances may -present themselves in organisms having a widely different parentage; -and thus the admission of the spontaneous evolution of closely -resembling organs carries with it the admission of the spontaneous -evolution of closely resembling organisms: that the protoplasm of -muscular tissue should, under certain changed conditions, develop -into the tissue of electric organs, is but one case of the law that -organized substance will develop into organisms closely resembling each -other when the conditions have been similar. - -122. It is to be remarked that Mr. Darwin fixes his attention somewhat -too exclusively on the adaptations which arise during the external -struggle for existence, and to that extent neglects the laws of organic -affinity; just as Lamarck too exclusively fixed his attention on the -influence of external conditions and of wants. Not that Mr. Darwin can -be said to overlook the organic laws; he simply underestimates the part -they play. Occasionally he seems arrested by them, as when instancing -the “trailing palm in the Malay Archipelago, which climbs the loftiest -trees by the aid of exquisitely constructed hooks, clustered around -the ends of the branches, and this contrivance no doubt is of the -highest service to the plant; but as there are nearly similar hooks -on many trees which are not climbers, the hooks on the palm may have -arisen from unknown laws of growth, and have been subsequently taken -advantage of by the plant undergoing further modification and becoming -a climber.” - -123. I come round to the position from which I started, that the -resemblances traceable among animals are no proof of kinship; even a -resemblance so close as to defy discrimination would not, in itself, -be such a proof. The absolute identity of chalk in Australia and in -Europe is a proof that there was absolute identity in the formative -conditions and the constituent elements, but no proof whatever that the -two substances were originally connected by genesis. In like manner -the similarity of a plant or animal in Africa and Europe may be due -to a common kinship, but it may also be due to a _common history_. It -is indeed barely conceivable that the history, from first to last, -would ever be so rigorously identical in two parts of the globe as -to produce complex identical forms in both; because _any_ diversity, -either in structure or external conditions, may be the starting-point -of a wide diversity in subsequent development; and the case of organic -combinations is so far unlike the inorganic, that while only one form -is possible to the latter (chalk is either formed or not formed), many -forms are possible to organic elements owing to the complexity and -indefiniteness of organic composition. But although forms so allied as -those of Species are not readily assignable to an identical history -in different quarters of the globe, it is not only conceivable, but -is eminently probable, that Orders and Classes have no nearer link of -relationship than is implied in their community of organized substance -and their common history. The fact that there is not a single mammal -common to Europe and Australia is explicable, as Mr. Darwin explains -it, on the ground that migration has been impossible to them; but it -is also explicable on the laws of Evolution--to have had mammals of -the same species and genera would imply a minute coincidence in their -history, which is against the probabilities. Again, in the Oceanic -Islands there are no Batrachians; but there are Reptiles, and these -conform to the reptilian type. Mr. Darwin suggests that the absence of -Batrachia is due to the impossibility of migration, their ova being -destroyed by salt water. But may it not be due to the divergence -from the reptilian type, which was effected elsewhere, not having -taken place in these regions? When we find the metal Tin in Prussia -and Cornwall, and nowhere else in Europe, must we not conclude that -in these two countries, and nowhere else, a peculiar conjunction of -conditions caused this peculiar evolution? - -124. The question at issue is, Are the resemblances observable -among organic forms due to remote kinship, and their diversities -to the divergences caused by adaptation to new conditions? or -are the resemblances due to similarities, and the diversities to -dissimilarities in the _substance and history_ of organic beings? -Are we to assume one starting-point and one centre of creation, or -many similar starting-points at many centres? So far from believing -that all plants and animals had their origin in one primordial cell, -at one particular spot, from which descendants migrated and became -diversified under the diverse conditions of their migration, it seems -to me more consistent with the principle of Evolution to admit a vast -variety of origins more or less resembling each other; and this initial -resemblance will account for the similarities still traceable under -the various forms; while the _early differences_, becoming intensified -by development under different conditions, will yield the diversities. -The evolution of organisms, like the evolution of crystals, or the -evolution of islands and continents, is determined, 1st, by laws -_inherent in the substances evolved_, and, 2d, by relations to the -medium in which the evolution takes place. This being so, we may -_à priori_ affirm that the resultant forms will have a community -strictly corresponding with the resemblance of the substances and -their conditions of evolution, together with a diversity corresponding -with their differences in substance and conditions. It is usually -supposed that the admission of separate “centres of creation” is -tantamount to an admission of “successive creations” as interpreted by -the majority of those who invoke “creative fiats.” But the doctrine -of Evolution, which regards Life as making its appearance _consequent -upon a concurrence of definite conditions_, and regards the specific -forms of Life as the necessary consequences of special circumstances, -must also accept the probability of similar conditions occurring at -different times and in different places. Upon what grounds, cosmical -or biological, are we to assume that on only _one_ microscopic spot of -this developing planet such a group of conditions was found--on only -one spot a particle of protein substance was formed out of the abundant -elements, and under conditions which caused it to grow and multiply, -till in time its descendants overran the globe? The hypothesis that -all organic forms are the descendants of a single germ, or of even -a few germs, and are therefore united by links of kinship more or -less remote, is not more acceptable than the hypothesis that all -the carbonates and phosphates, all the crystals, and all the strata -found in different parts of the globe, are the _descendants of a -single molecule_, or a few molecules; or,--since this may seem too -extravagant,--than that the various maladies which afflict organic -beings are, in a literal sense, members of _families_ having a nearer -relationship than that of being the phenomena manifested by similar -organs under similar conditions--a conception which might have been -accepted by those metaphysical pathologists who regarded Disease as -an entity. Few philosophers have any hesitation in supposing that -other planets besides our own are peopled with organic forms, though, -from the great differences in the conditions, these forms must be -extremely unlike those of our own planet. If separate worlds, why not -separate centres? The conclusion seems inevitable that wherever and -whenever the state of things permitted that peculiar combination of -elements known as organized substance, there and then a centre was -established--Life had a root. From roots closely resembling each other -in all essential characters, but all more or less different, there have -been developed the various stems of the great tree. Myriads of roots -have probably perished without issue; myriads have developed into forms -so ill-adapted to sustain the fluctuations of the medium, so ill-fitted -for the struggle of existence, that they became extinct before even our -organic record begins; myriads have become extinct since then; and the -descendants of those which now survive are like the shattered regiments -and companies after some terrific battle. - -125. There seems to me only one alternative logically permissible to -the Evolution Hypothesis, namely, that all organic forms have had -either a single origin, or else numerous origins; in other words, that -a primordial cell was the starting-point from which all organisms -have been successively developed; or that the development issued -from many independent starting-points, more or less varied. This is -apparently not the aspect presented by the hypothesis to many of its -advocates; they seem to consider that if all organic forms are not the -lineal descendants of one progenitor, they must at any rate be the -descendants of not more than four or five. The common belief inclines -to one. Mr. Darwin, whose caution is as remarkable as his courage, and -whose candor is delightful, hesitates as to which conclusion should -be adopted: “I cannot doubt,” he says, “that the theory of descent, -with modifications, embraces all the members of the same class. I -believe that animals have descended from, at most, only four or five -progenitors, and plants from an equal or lesser number. Analogy would -lead me one step further, namely, to the belief that all animals and -plants have descended from some one prototype. But analogy may be a -deceitful guide.” - -126. I cannot see the evidence which would warrant the belief that Life -originated solely in one microscopic lump of protoplasm on one single -point of our earth’s surface; on the contrary, it is more probable that -from innumerable and separate points of this teeming earth, myriads -of protoplast sprang into existence, _whenever_ and _wherever_ the -conditions of the formation of organized substance were present. It is -probable that this has been incessantly going on, and that every day -new protoplasts appear, struggle for existence, and serve as food for -more highly organized rivals; but whether an evolution of the lower -forms is, or is not, still going on, there can be no reluctance on -the part of every believer in Evolution to admit that when organized -substance was first evolved, it was evolved at many points. If this be -so, the community observable in organized substance, wherever found, -may as often be due to the fact of a common elementary composition as -to the fact of inheritance. If this be so, we have a simple explanation -both of the fundamental resemblances which link all organisms together, -and of the characteristic diversities which separate them into -kingdoms, classes, and orders. The resemblances are many, and close, -because the forms evolved had a similar elementary composition, and -their stages of evolution were determined by similar conditions. -The diversities are many, because the forms evolved had from the -first some diversities in elementary composition, and their stages of -evolution were determined under conditions which, though similar in -general, have varied in particulars. Indeed, there is no other ground -for the resemblances and differences among organic beings than the -similarities and dissimilarities in their Substance and History; and, -whether the similarities are due to blood-relationship, or to other -causes, the results are the same. There is something seductive in the -supposition that Life radiated from a single centre in ever-increasing -circles, its forms becoming more and more various as they came under -more various conditions, until at last the whole earth was crowded -with diversified existences. “From one cell to myriads of complex -organisms, through countless æons of development,” is a formula of -speculative grandeur, but I cannot bring myself to accept it; and I -think that a lingering influence of the tradition of a “creative fiat” -may be traced in its conception. May we not rather assume that the -earth at the dawn of Life was a vast germinal membrane, every slightly -diversified point producing its own vital form; and these myriads upon -myriads of forms--all alike and all unlike--urged by the indwelling -tendencies of development, struggled with each other for existence, -many failing, many victorious, the victors carrying their tents into -the camping ground of the vanquished. The point raised is the immense -improbability of organized substance having been evolved only in one -microscopic spot; if it were evolved at more than one spot, and under -slightly varying conditions, there would necessarily have arisen in -these earliest formations the _initial_ diversities which afterwards -determined the essential independence and difference of organisms. - -129. Let us for a moment glance at the resemblances and diversities -observable in all organisms. All have a _common basis_, all being -constructed out of the same fundamental elements: carbon, hydrogen, -nitrogen, and oxygen; these (the organogens, as they are named), -with varying additions of some other elements, make up what we know -as Organic Substance, vegetal and animal. Another peculiarity all -organisms have in common, namely, that their matter is neither solid -nor liquid, but viscid. Beside this community of _Substance_ we must -now place a community of _History_. All organisms grow and multiply by -the same process; all pass through metamorphic stages ending in death; -all, except the very simplest, differentiate parts of their substance -for special uses, and these parts (cilia, membranes, tubes, glands, -muscles, nerves) have similar characters in whatever organism they -appear, and their development is always similar, so that the muscles or -nerves of an intestinal worm, a lobster, or a man, are in structure and -history fundamentally alike. When, therefore, we see that there is no -biological character of fundamental importance which is not universal -throughout the organic world, when we see that in Structure and History -all organisms have a community pervading every variety, it is difficult -not to draw the conclusion that some hidden link connects all organisms -into one; and when, further, it is seen that the most divergent forms -may be so arranged by the help of intermediate forms only slightly -varying one from the other, that the extreme ends--the monad and the -man--may be connected, and a genealogical tree constructed, which -will group all forms as modified descendants from a single form, the -hypothesis that kinship is the bidden link of which we are in search -becomes more and more cogent. - -130. But now let the other aspect be considered. If there is -an unmistakable uniformity, there is also a diversity no less -unmistakable. The chemical composition of organic substances is -various. Unlike inorganic substances, the composition of which is -rigorously definite, organic substances are, within narrow limits, -variable in composition (§ 45). - -I pass over the resemblances and differences observed in the earliest -stages of development, marked as they are, and direct attention to the -fact, that down at what must be considered the very lowest organic -region, we meet with differences not less striking than those met with -in the highest, we find structures (if structures they may be called), -which cannot be affiliated, so widely divergent is their composition. -The structureless vibrio, for example, is not only capable of living -in a medium destitute of Oxygen, but is, according to M. Pasteur, -actually killed by oxygen; whereas the equally simple bacteria can -no more dispense with Oxygen than other animals can. Consider for a -moment the differences implied in the fact that one organism cannot -even form an enveloping membrane to contain its protoplasm, whereas -another contrives to secrete an exquisite shell; yet between the -naked Rhizopod and the shelled Rhizopod our lenses and reagents fail -to detect a difference. One Monad can assimilate food of only one -kind, another Monad assimilates various kinds.[73] What a revelation -of chemical differences appears in the observations of M. Pasteur -respecting the vibrio and bacteria, in a fermentescible liquid--the -former beginning the putrid fermentation which the latter completes! -We cannot doubt that some marked difference must exist between the -single-celled organism which produces alcoholic fermentation, and that -which produces acetic fermentation, and that again which produces -butyric fermentation; and if we find distinctions thus established -at the lowest region of the organic series, we need not marvel if -the distinctions become wider and more numerous as the series becomes -more diversified. The structure and development of an organism are -dependent on the affinities of its constituent molecules, and it is -a biological principle of great importance which Sir James Paget -insists on, when he shows how “the existence of certain materials -in the blood may determine the formation of structures in which -they may be incorporated.”[74] _Any_ initial diversity may thus -become the starting-point of a considerable variation in subsequent -evolution.[75] Thus, supposing that on a given spot there are a dozen -protoplasts closely resembling each other, yet each in some one detail -slightly varying; if this variation is one which, by its relations to -the external medium, admits of a difference in the assimilation of -materials present in the medium, it may be the origin of some _new -direction_ in development, and the ultimate consequence may be the -formation of a shell, an internal skeleton, a muscle, or a nerve. -Were this not so, it would be impossible to explain such facts as -that chitine is peculiar to the Articulata, cellulose to Molluscoida, -carbonates of lime to Mollusca and Crustacea, and phosphates to -Vertebrata--all assimilated from the same external medium. But we -see that from this medium one organism selects the materials which -another rejects; and this selection is determined by the nature of the -structure: which assimilates only those materials it is _fitted_ to -assimilate. We hear a great deal of Adaptation determining changes of -structure and function, and are too apt to regard this process as if it -were not intimately dependent on a corresponding structural change. By -no amount of external influence which left the elementary composition -of the structure unchanged, could an organism with only two tissues -be developed into an organism with three or four. By no supply or -stimulus, could an animal incapable of assimilating peroxide of iron -acquire red blood corpuscles, although it might have the iron without -the corpuscles; nor could an oyster form its shell unless capable of -assimilating carbonate of lime. For myriads of years, in seas and -ponds, under endless varieties of external conditions, the amœbæ have -lived and died without forming a solid envelope, although the materials -were abundant, and other organisms equally simple have formed envelopes -of infinite variety. In all the seas, and from the earliest ages, -zoophytes have lived, and assumed a marvellous variety of shapes and -specialization of functions; but although some of them have acquired -muscles, none have acquired true nerves, none bone. Ages upon ages -rolled on before fishes were capable of forming bone; and thousands are -still incapable of forming it, though living in the same waters as the -osseous fishes. - -131. “Looking to the dawn of life,” says Mr. Darwin (repeating an -objection urged against his hypothesis), “when all organic beings, as -we imagine, presented the simplest structure, how could the first steps -in advancement, or in the differentiation and specialization of parts -have arisen? I can make no sufficient answer; and can only say that, -as we have no facts to guide us, all speculation would be baseless and -useless.” - -Where Mr. Darwin hesitates, lesser men need extra caution; but I -must risk the danger of presumption, at least so far as to suggest -that while an answer to this question is difficult on that dynamical -view of Evolution which regards Function as determining Structure, -it is less difficult on the statico-dynamical view propounded in -these pages; the difficulty which besets the explanation when all the -manifold varieties of organic forms are conceived as the successive -divergences from an original starting-point, is lessened when a variety -of different starting-points is assumed, in each of which some initial -diversity prepared the way for subsequent differentiations; just as -we know that between the ovum of a vertebrate and the ovum of an -invertebrate, similar as they are, there is a diversity which manifests -itself in their subsequent evolution. If Function is determined by -Structure, and Evolution is the product of the two, it is clear that -the different directions in the lines of development will have their -origin in structural differences, and not in the action of external -circumstances, unless these previously bring about a structural change. -The action of the medium on the organism is assuredly a potent factor -which Biology cannot ignore: but the organism itself is a factor, and -according to its nature the influence of the medium is defined. (§ 118.) - -132. Quitting for a moment the track of this argument, let us glance -at the resemblances and differences observable in Plants and Animals, -because most people admit that these have separate origins. The -resemblances are scarcely less significant than those existing among -animals. Both have a similar basis of elementary composition; not only -are both formed out of protoplasts with similar properties, but in both -the first step from the protoplasm to definite structure is the Cell. -And the life of this Cell is remarkably alike in both, its phases of -development being in many respects identical; nay, even such variations -as obtain in the cell-membranes are curiously linked together by a -community in the formative process.[76] In both Plants and Animals -we find individuals constituted--1st, by single cells; 2d, by groups -of cells undistinguishable among each other; and 3d, by groups of -differentiated cells. In both we find colonies of individuals leading -a common life. In both the processes of Nutrition and Reproduction -are essentially similar; both propagate sexually and asexually; both -exhibit the surprising phenomena of parthenogenesis and alternate -generations. In both there are examples of a free-roving embryo which -in maturity becomes fixed to one spot, losing its locomotive organs -and developing its reproductive organs. In both the development of the -reproductive organs is the climax which carries Death. So close is the -analogy between plant-life and animal-life, that it even reaches the -properties usually held to be exclusively animal; I mean that even -should we hesitate to accept Cohn’s discovery of the muscles in certain -plants,[77] we cannot deny that plants exhibit Contractility; and -should we refuse to interpret as Sensibility the phenomena exhibited by -the Sensitive Plants, we cannot deny that they present a very striking -analogy to the phenomena of Sensibility exhibited by animals. - -133. It is unnecessary to continue this enumeration, which might easily -be carried into minute detail. A chapter of such resemblances would -only burden the reader’s mind, without adding force to the conclusion -that a surprising community in Substance and Life-history must be -admitted between Plants and Animals. This granted, we turn to the -differences, and find them no less fundamental and detailed. Chemistry -tells us nothing of the differences in the protoplasms from which -animals and plants arise; but that initial differences must exist is -proved by the divergence of the products. The vegetable cell is not -the animal cell; and although both plants and animals have albumen, -fibrine, and caseine, the _derivatives_ of these are unlike. Horny -substance, connective tissue, nerve tissue, chitine, biliverdine, -creatine, urea, hippuric acid, and a variety of other products of -evolution or of waste, never appear in plants; while the hydrocarbons -so abundant in plants are, with two or three exceptions, absent from -animals. Such facts imply differences in elementary composition; and -this result is further enforced by the fact that where the two seem -to resemble, they are still different: the plant protoplasm forms -various cells, but never forms a cartilage-cell or nerve-cell; fibres, -but never a fibre of elastic tissue; tubes, but never a nerve tube; -vessels, but never a vessel with muscular coatings; solid “skeletons,” -but always from an organic substance (_cellulose_), not from phosphates -and carbonates. In no one character can we say that the plant and the -animal are identical; we can only point throughout the two kingdoms to -a great similarity accompanying a radical diversity. - -134. Having brought together the manifold resemblances, and the no -less marked diversities, we must ask what is their significance? Do -the resemblances imply a community of origin, an universal kinship? -If so, the diversities will be nothing more than the divergences -which have been produced by variations in the Life-history of the -several groups. Or--taking the alternative view--do the diversities -imply radical differences of origin? If so, the resemblances will be -nothing more than the inevitable analogies resulting from Organized -Substance being everywhere somewhat similar in composition, and similar -in certain phases of evolution. To state the former position in the -simplest way, we may assume that of two masses of protoplasm having -a common parentage, one, by the accident of assimilating a certain -element not brought within the range of the other, thereby becomes so -differentiated as to form the starting-point of a series of evolutions -widely divergent from those possible to its congener; and at each stage -of evolution the introduction of a new element (made possible by that -stage) will form the origin of a new variation. It is thus feasible to -reduce all organic forms to a primordial protoplasm, in the evolutions -of which successive differentiations have been established. On the -other hand, it is equally feasible to assume that the existence of -radical differences must be invoked to account for the possibility of -the successive differentiations. - -135. The hunt after resemblances has led to much mistaken speculation; -and with reference to the topic now before us, it may be urged, -that although by attaching ourselves to the points of community, in -disregard of the diversities, we may make it appear that all animals -have a common parentage, and that plants and animals are merely -divergent groups of the same prototype, a rigorous logic will force us -onwards, and compel us to admit that a kinship no less real unites -the organic with the inorganic world. For upon what principle are we -to pause at the cell or protoplasm? If by a successive elimination -of differences we reduce all organisms to the cell, we must go on -and reduce the cell itself to the chemical elements out of which it -is constructed; and inasmuch as these elements are all common to the -inorganic world, the only difference being one of synthesis, we reach a -result which is the stultification of all classification, namely, the -assertion of a kinship which is universal. We must bear in mind that -all things may be reduced to a common root by simply disregarding their -differences. All things are alike when we set aside their unlikeness. - -136. Suppose, for the sake of illustration, we regard an Orchestra -in the light of the Development Hypothesis. The various instruments -of which it is composed have general resemblances and particular -differences, not unlike those observable in various organisms; and -as we proceed in the work of classification we quickly discover that -they may be arranged in groups analogous to the Sub-kingdoms, Classes, -Orders, Genera, and Species of the organic world. Each group has its -cardinal distinction, its initial point of divergence. All musical -instruments resemble each other in the fundamental character of -producing Tone by the vibrations of their substance. This may be called -their organic basis. The first marked difference which determines the -character of two sub-kingdoms (namely, instruments of Percussion and -Wind instruments) arises from a difference in the method of impressing -the vibrations; and the grand divisions of these sub-kingdoms arise -from the nature of the vibrating substances. Each type admits of many -modifications, but the primary distinction is ineffaceable. We can -conceive the Pipe modified into a Flute, a Flageolet, a Clarionet, -a Hautbois, a Bassoon, or a Fife, by simple accessory changes; to -modify the Pipe into a Trumpet, and thus produce the peculiar _timbre_ -of the trumpet, would be impossible except by the _substitution_ -of a new material; by replacing the wood with metal we may adhere -to the old Type, but we have created a new Class. (Attention is -requested to this point, because the current views respecting the -transmutation of tissues, which seem to lend a decisive support to the -hypothesis of the transmutation of species are very commonly vitiated -by the confusion of transformation with substitution. No anatomical -element is _transformed_ into another specifically different--an -epithelial-cell into a nerve-cell, for instance--but one anatomical -element is frequently _substituted_ for another.) To convert the Pipe -or the Trumpet into a Violin or a Drum would be impossible. We can -follow the modifications of a Tambourine into a Drum or Kettle-drum, -but no modifications of these will yield the Cymbals. That is to say, -the vibrating materials--wood, metal, parchment, and the combination -of wood and strings--have peculiar properties, and the instruments -formed of such materials must necessarily from the very first belong -to different groups, each subdivision of the groups being dependent on -some characteristic difference in methods of impressing the vibrations, -or in the materials. Although all musical instruments have a common -property and a common purpose, we do not regard them as transformations -of one primitive instrument; their kindred nature is a subjective -conception; the analogies are numerous and close, but we know their -origin. It is obvious that men being pleased by musical tones, have -been led by their delight to construct instruments whenever they have -discovered substances capable of musical vibrations, or methods of -impressing such vibrations. By substituting the bow for the plectrum or -the fingers, they may have changed the Lyre into the Violin, Viola, -Violoncello, and Bass. (It seems historically probable that the real -origin of the Violin class was an instrument with one string played on -by a bow.) By grouping together Pipes of various sizes they got the -Panpipes; by substituting metal and enlarging the blowing apparatus -they got the Organ. By beating on stretched parchment with the finger, -they got the Tambourine and Tom-Tom; by doubling this and using a stick -they got the Drum. By beating metal with metal they got the Cymbals; by -beating wood they got the Castanets. - -137. The application of this illustration is plain. Just as a -wind-instrument is incapable of becoming a stringed instrument, so -a Mollusc, with all its muscles unstriped, and its nervous system -unsymmetrical, is incapable of becoming a Crustacean, with all its -muscles striped and its nervous system symmetrical. Indeed there -are probably few biologists of the present day who imagine the -transmutation of one kind into the other to be possible; but many -biologists assume that both may have been evolved from a common root. -The point is beyond proof; yet I think there is a greater probability -in the assumption that both were evolved from different roots. At any -rate, one thing is certain; a divergence could only have been effected -by a series of _substitutions_; and the question when and how these -substitutions took place is unanswerable: one school believes them to -have been creative fiats, the other school believes them to have been -transmutations. - -138. When we see an annelid and a vertebrate resembling each other in -some special point which is not common either to their classes or to -any intermediate classes--as when we see the wood-louse (_Oniscus_) -and the hedgehog defend themselves in the same strange way by rolling -up into a ball--we cannot interpret this as a trace of distant -kinship. When we see a breed of pigeons and a breed of canaries -turning somersaults, and one of the Bear family (_Ratel_) given to the -same singular habit, we can hardly suppose that this is in each case -inherited from a common progenitor. When we see one savage race tipping -arrows with iron, and another, ignorant of iron, using poison, there is -a community of object effected by diversity of means; but the analogy -does not necessarily imply any closer connection between the two races -than the fact that men with similar faculties and similar wants find -out similar methods of supplying their wants. Even those who admit that -the human race is one family, and that the various peoples carried with -them a common fund of knowledge when they separated from the parent -stock, may still point to a variety of new inventions and new social -developments which occurred quite independently of each other, yet are -strikingly alike. Their resemblance will be due to resemblance in the -conditions. The existence, for example, of a religious worship, or a -social institution, in two nations widely separated both in time and -space, and under great historical diversities, is no absolute proof -that these two nations are from the same stock, and that the ideas have -the same parentage. It may be so; it may be otherwise. It may be an -analogy no more implying kinship than the fact of ants making slaves -of other ants (and these the black ants!) implies a kinship with men. -Given an organization which in the two nations is alike, and a history -which is in certain characteristics analogous, there must inevitably -result religious and social institutions having a corresponding -resemblance. I do not wish to imply that the researches of philologists -and ethnologists are misdirected, or that their conclusions -respecting the kinship of mankind are to be rejected; I only urge the -consideration that perhaps too much stress is laid on community of -blood, and not enough on community of conditions. - - -RECAPITULATION. - -139. The various lines of argument may here be recapitulated. The -organic world presents a spectacle of endless diversity, accompanied by -a pervading uniformity. The general resemblances in forms and functions -are more or less masked by particular differences. The resemblances, it -is said, may be all due to kinship, all the living individuals having -descended from a primordial cell; and at each stage of the descent the -adaptations to new conditions may have issued in deviations from the -ancestral form, while the process of Natural Selection giving stability -to those variations which best fitted the organism in the struggle of -existence, has made greater and greater gaps, and produced more marked -diversities among the descendants. This is the Darwinian Theory: “On my -theory unity of Type is explained by unity of Descent.” - -140. By the general consent of biologists, this theory is held to -explain many if not all the observed facts. It is a very luminous -suggestion; but it requires an enlargement so as to include Organic -Affinity; and when once this fundamental principle is admitted, it -brings with it very serious doubts as to the theory of Descent. -We are then entitled to assume that many of the most striking -resemblances, instead of being due to kinship, are due simply to the -general principle that similar causes must have similar effects, and -that organic substances having a very close resemblance, organized -substances must have similar stages of evolution under similar -conditions; and thus organs will necessarily take on very similar forms -in very different organisms (for example, the eye of the cephalopod -and the eye of the vertebrate), and organisms having widely different -parentage may closely resemble each other. If we are entitled to -assume that protoplasm appeared not in one microscopic spot alone, but -in many places and in vast quantities--and this is surely the more -justifiable assumption--then we must also admit that these germinal -starting-points were from the first, or very shortly afterwards, -differentiated by variations in their elementary composition. Now we -know that a very minute change in composition may lead to immense -differences in evolution. Thus the descendants of two slightly -different progenitors may, by continual differentiation, become very -markedly unlike; yet, because of the original resemblance of their -substances, they will reveal a pervading similarity. - -While it is thus conceivable that all organisms may resemble each -other, and all differ, owing to the similarities and diversities in the -“conditions of existence” (and among those conditions that of descent -is of wide range), it is not very readily conceivable how advantage -in the external struggle could have determined the varieties of form -and function, because many differentiations give no superiority in the -struggle. As Mr. St. George Mivart urges, “Natural Selection utterly -fails to account for the conservation and development of the minute and -rudimentary beginnings, the slight and infinitesimal commencements of -structures, however useful those structures may afterwards become.”[78] -And this is undeniable on the supposition that Natural Selection is an -agency not identical with the variations of growth, but exclusively -confined to the accumulation of favorable variations. - -141. In estimating the two hypotheses--First, of Descent from one -primordial germ, and the modifications _due_ to Natural Selection, or, -as I should say, _expressed_ in Selection; and Secondly, of Descent -from innumerable germs having initial differences, which differences -radiated into the marked modifications, there is this superiority to -be claimed for the first, that it is more easily handled as an aid to -research, and is therefore more decidedly useful. The laws of Organic -Affinity are at present too obscure for any successful application. -I only wish to point out that the theory of Descent is an imaginary -construction of what _may have been_ the process of species-formation, -not a transcription of the process observed. It constructs an imaginary -Type as progenitor of a long line of widely different descendants. The -annelid which is taken as the ancestor of the vertebrates is not any -annelid known either to zoölogists or geologists, but a generalized -and imaginary type. So daringly liberal is the imagination in endowing -the ancestor with whatever may be required for the descendants, that -Mr. Darwin thinks it _probable_, from what we know of the embryos -of vertebrates, that these animals “are the modified descendants -of some ancient progenitor which was furnished in its adult state -with branchiæ, a swim-bladder, four simple limbs, and a long tail, -all fitted for an organic life,” (p. 533); and Dr. Dohrn conceives -the original type to have contained within itself all that has been -subsequently evolved in the highest vertebrate, the other and less -elaborate organisms being mere degradations from this type.[79] This -use of the imagination, although not without advantages, is also not -without dangers. It may direct research, it must not be suffered to -replace research. - - - - -PROBLEM II. - -THE NERVOUS MECHANISM. - - “All the functions of the nervous system are as dependent upon its - structure and nature, as the accurate indication of time upon the - construction of the chronometer.”--PROCHASKA. - - “Unser Wissen wird nie vollendet, ist und bleibt Stückwerk; dessen - Ergänzung das Streben und Hoffen der forschenden Denker bleiben - wird für alle Zeit.”--RADENHAUSEN, _Osiris_. - - “Our nimble souls - Can spin an insubstantial universe - Suiting our mood, and call it possible, - Sooner than see one grain with eye exact, - And give strict record of it.” - GEORGE ELIOT, _The Spanish Gypsy_. - - “If we compare the teachings of our books with what Nature is - constantly showing, we find there is no agreement between those two - sources of learning.”--BROWN SÉQUARD. - - - - -THE NERVOUS MECHANISM. - - - - -CHAPTER I. - -SURVEY OF THE SYSTEM. - - -1. Our knowledge of mental processes is derived from reflection on our -personal experiences, combined with inferences from our observation -of other men and animals, under similar conditions. The processes -are complex and variable; so complex and variable, that knowledge of -their component factors can only be gained through long tentative -study, aided by fortunate circumstances which present these factors -separately, or at any rate in such marked predominance as to fix -attention. This subjective analysis of the _processes_ has to be -supplemented by, and confirmed by an objective analysis of, the -_conditions_, external and internal: the facts of Feeling have to be -traced to facts of Physiology, which will exhibit that Physical Basis -of Mind so earnestly sought by the inquirer. - -Both the subjective and the objective analysis are at present in a -very imperfect state. Although there is much confident assertion and -“false persuasion of knowledge” in both regions, there is, unhappily, -little that can be seriously accepted as demonstrated. In the present -volume we shall concern ourselves almost exclusively with the objective -analysis, and do our utmost to mark what is mere inference from what -is verified observation. It is only by Observation that facts can be -_settled_; however Analogy and Inference may suggest where the truth -may lie, they are finger-posts, not goals. At the best they only tell -us what Observation _would_ reveal could the processes be submitted to -Sense. - -In a loose and general way every one knows that the Nervous System is -a dominant agent in all sentient processes; although not by any means -the only agent, yet, because of its predominance, it is artificially -accepted as the only one. With the greater complexity of this system, -there is observed a corresponding increase in the variety of sentient -phenomena. The labors of anatomists have secured a tolerably exact plan -of the topographical distribution of this system; a somewhat chaotic -mass of observation and inference passes as a description of its -elementary structure. The labors of physiologists have succeeded to a -small extent in localizing certain functions in certain organs of this -system. But imperfect as our knowledge of the elementary structures is, -our knowledge of the functions is still more so. I wish I could say -otherwise, and that I could ask my readers to accept with confidence -what teachers confidently propound. The attitude of scepticism is -always repulsive; the sceptic is seldom received without disfavor, -because he throws on us the labor of investigation there where we wish -for the confidence of knowledge. Yet it is only by facing the facts -that we can hope one day to solve the great questions. - -2. The nervous system has, in our artificial view of it, two divisions: -the Peripheral, which connects the organism with the external world; -and the Central, which connects each part of the organism with all -the other parts. Although the system is constituted by various -tissues--neural, connective, vascular, and elastic--it receives its -characteristic designation from nerve-fibrils, nerve-fibres, and -nerve-cells; just as the muscular system receives its designation -from contractile cells and fibres. This neural tissue assumes three -well-marked forms: 1°, _nerves_, which are bundles of fibres and -fibrils, enclosed in a membranous sheath; 2°, _ganglia_, which are -clusters of cells, fibres, and fibrils, sometimes enclosed in a sheath, -sometimes not; 3°, _centres_, which are artificial divisions of the -neural axis, serving as points of union for different organs. - -In the Invertebrata the neural axis is the chain of ganglionic masses -running along the ventral side, and giving off the nerves to organs of -sense, and to the muscles. It may be seen represented in Fig. 1. - -[Illustration: Fig. 1.--_Nervous system of a beetle._ The small round -masses, or _ganglia_, are seen to be connected by longitudinal fibres, -and from the ganglia issue fibres to the limbs, organs of sense, and -viscera.] - -In the Vertebrata the axis is dorsal, and is called the _cerebro-spinal -axis_, including brain and spinal cord. When we look at this structure -superficially we see various nerves radiating _from_ it to skin, -glands, and muscles; but a closer examination, enlightened by knowledge -of function, shows that some of these nerves pass _into_ it from the -various surfaces and sense-organs, and are therefore called _afferent_ -or _sensory_; whereas another set passes out of it to glands and -muscles, and these nerves are therefore called _efferent_ or _motory_. -There are also fibres which, passing from one part of the great centre -to another, are called _commissural_. - -To this brief account of the cerebro-spinal system may be added a word -on the connected chain of ganglia and nerves known as the Sympathetic, -because it was formerly supposed to be the organ through which the -various “sympathies” were effected. It is now held to be the system -devoted to the viscera and blood-vessels; but there is still great want -of agreement among physiologists as to whether it is an independent -system, having a special structure somewhat different from that of the -cerebro-spinal, or whether it is simply a great plexus of nerves and -ganglia, only topographically distinguishable from the rest of the -nervous system. Into this point it is unnecessary for me to enter here. -Enough to say, that I entirely agree with Sigmund Mayer in adopting -the second view.[80] In no histological character, yet specified, are -the sympathetic nerves and ganglia demarcated from the others. There -are, indeed, _more_ non-medullary fibres (the gray fibres of Remak) -in the sympathetic; but the same fibres are also abundant in the -cerebro-spinal system; and the sympathetic has also its large medullary -fibres. - -3. The Centres are composed of two substances: the gray and the white. -The gray substance is often called the vesicular because of its -abundant cells; but it has even more fibres than cells, and the white -substance has also a few cells.[81] The gray substance is distributed -over the surface of the brain--in the convolutions; and in various -other parts of the encephalon. It surrounds the central canal which -forms the ventricles of the brain and is continued as a very small -cavity all down the spinal cord. Besides entering into the important -and conspicuous masses known as the cerebral ganglia--(the _optic -thalami_, and _corpora striata_)--the gray substance is massed in the -_corpora quadrigemina_, _crura cerebri pons varolii_, and _medulla -oblongata_. We shall have occasion to refer to each of those parts. -Until modern times all the masses included in the skull under the -familiar term Brain (or the technical term Encephalon) were regarded -as the only centre, and also as the origin of all the nerves. Nor has -this notion even yet entirely disappeared, although the spinal cord -is known not to be a large nerve trunk, but a centre or connected -chain of centres, structurally and functionally similar to the cranial -centres. The shadow of the ancient error still obscures interpretation -of the part this spinal cord plays in the sentient mechanism; and thus -although the cord is universally admitted to be a centre for “sensitive -impressions,” it is usually excluded from Sensation. This widespread -and misleading notion will be critically examined in a future problem. - -4. Beginning our survey of the cerebro-spinal axis with the Spinal -Cord, we observe it to consist: 1°, of _central gray substance_ -surrounding the scarcely visible canal, which is all that remains of -the primitive groove in the germinal membrane (§ 9); 2°, irregular -gray masses, called the _anterior and posterior horns_,[82] connected -with the anterior and posterior _roots_ of the spinal nerves; and 3°, -strands of white fibres enclosing this central substance, and called -the _anterior lateral and posterior columns_. - -Like the Cerebrum, it is a double organ formed by two symmetrical -halves, as the cerebrum is of two hemispheres. Each half innervates -the corresponding half of the body. The cord is unlike the cerebrum -in external form, though very like it in internal structure. The gray -structure is mainly external in the cerebrum, and is internal in the -cord. - -From the anterior side of the cord (that which in animals is the under -side) the motor nerves issue; from the posterior (in animals the -upper) side, issue the sensory nerves. On each of the sensory nerves -there is a ganglion. The _roots_ of each nerve, formed of several -rootlets issuing from the anterior and posterior columns, subsequently -unite together, and proceed in a single sheath to muscles and skin, -separating again, however, before they reach muscles and skin. Fig. 2 -represents this arrangement. - -[Illustration: Fig. 2.--_A portion of the spinal cord with its nerves_ -(after Bernard). The left-hand figure shows the anterior side; the -right-hand the posterior. A the anterior, and P, the posterior root, -they meet at _g_, the ganglion; _c_ and _d_ are filaments connecting -two posterior roots.] - -5. There are thirty-one pairs (sometimes thirty-two) of such -nerves--namely, eight cervical, twelve thoracic, five lumbar, five -sacral, and one (or two) coccygeal. Figs. 3 to 6 represent transverse -sections, which display the entrance of the roots of the nerves into -the anterior and posterior horns. - -6. Similar masses of gray substance in the _Medulla Oblongata_ (which -is the name given to the cord when it passes into the skull)[83] are -supposed to be the origins of some other nerves (the cranial). - -[Illustration: Fig. 3.--_Transverse section of one half of the -spinal cord in the lumbar region_ (after Kölliker). _a_, anterior -root entering the anterior gray horns, _m_ and _l_, where cells are -clustered; _c_, central canal; _d_ and _e_, the anterior and posterior -commissures uniting the two halves of the cord; _b_, posterior root -entering the posterior gray horn.] - -[Illustration: Fig. 4.--_Transverse section of both halves of the cord, -cervical region._ _a_, Fissure separating the anterior columns; _b_, -fissure of the posterior.] - -[Illustration: Fig. 5.--_Transverse section of the cord in the dorsal -region._] - -[Illustration: Fig. 6.--_Transverse section in the lumbar region._] - -Although the Medulla Spinalis is unquestionably continued as the -Medulla Oblongata, the arrangement of its tissues here becomes -gradually changed, and so complicated that it baffles the scalpel. -Anatomists are, however, agreed on the one point of fundamental -importance to us here--namely, that there is only a rearrangement, not -a new tissue. Accepting the artificial division into two organs, we may -say that their functions are different, inasmuch as they are different -in their anatomical connections--they innervate different parts; but as -nerve-centres they have one and the same property. - -On its posterior surface the Medulla Oblongata opens as the _fourth -ventricle_. It is then no longer a closed canal, but an expansion of -the spinal canal, which is covered by the Cerebellum. On its anterior -surface projects the _pons varolii_. Figs. 7 and 8 represent these. - -[Illustration: - - Fig. 7.--_Back, or upper view of the Medulla Oblongata as it - continues the Med. Spinalis._ 1, Section of the thalami; 2, corpora - quadrigemina (the two lower bodies are imperfectly represented in - the engraving); 3, section of the crura cerebelli; 4, the fourth - ventricle; 5, the restiform bodies; 6, the calamus scriptorius. -] - -[Illustration: - - Fig. 8.--_Front, or under view of the Med. Oblong._ 1, Optic nerves - cut off at the chiasma; 2, crura cerebri; 3, pons varolii; 4, - olivary bodies; 5, anterior pyramids; 6, spinal columns. -] - -While thus on the one hand continuing the Medulla Spinalis, the -Medulla Oblongata is seen on the other hand to be continuous with the -Brain--its white columns passing upwards in the _crura cerebri_, its -cavity repeated in the other ventricles. Above it lie the ganglionic -masses, the _corpora quadrigemina_, _optic thalami_, and _corpora -striata_. Crowning these are the big and little brains, Cerebrum and -Cerebellum. Figs. 9 and 10 represent this relation of Medulla Spinalis, -Medulla Oblongata, and Brain. Fig. 11 is a purely artificial diagram -which will give the reader some idea of the disposition of the white -and gray substances. - -[Illustration: - - Fig. 9.--_Human Brain in Profile._ 1, Cerebrum; 2, cerebellum; 3, - pons varolii and medulla oblongata. -] - -[Illustration: - - Fig. 10.--_One half of the Brain in Profile, from the inside._ - 1, Convolutions of the cerebrum; 2, corpus callosum or great - commissure uniting the two hemispheres; 3, arbor vitæ or branching - arrangement of gray and white matter in the cerebellum; 4, pons - varolii and medulla. -] - -[Illustration: - - Fig. 11.--_Diagram of a vertical section of the Brain_ (after - Dalton). 1, Olfactory ganglion; 2, cerebral hemisphere; 3, corpus - striatum; 4, thalamus; 5, corpora quadrigemina; 6, cerebellum; 7, - ganglion of the pons varolii; 8, olivary body. -] - -7. In man the Cerebrum is to the Cerebellum as 9 to 1. In the lower -vertebrates the preponderance is still greater. The cerebrum is in our -artificial systems commonly divided into three lobes. The frontal lobe -is that portion which lies in front of the deep fissure named after -Rolando; between that fissure and the “internal perpendicular fissure” -lies the parietal lobe; behind this we have the occipital lobe; and, -below the fissure of Sylvius, the tempero-sphenoidal lobe. Each lobe is -again subdivided according to its convolutions. - -The disposition of the fibres in the brain is far too complex to be -accurately followed. All that we can say is, that there are strands -which connect one convolution with another, strands which connect -one hemisphere with another, strands which connect cerebrum with -cerebellum, and strands which connect the cerebrum with the lower -ganglia. It is important to conceive this distinctly; for we shall -hereafter see that the function of the Brain (by brain is here meant -both Cerebrum and Cerebellum) is not that of _innervation_, but of -_incitation and regulation_. To speak metaphorically, it is the -coachman who holds in his hands the reins, and guides the team. One -cardinal fact should arrest attention, namely, that not a single nerve -in the body has its origin or centre of innervation in the cerebrum and -cerebellum. The olfactory and optic nerves do indeed _seem_ to issue -from the cerebrum; and are commonly described as cerebral nerves. But -the facts of Development, minute Anatomy, and Experiment prove this to -be inexact. Although I shall continue to speak of the olfactory and -optic nerves in accordance with universal usage, not wishing to burden -the reader with unnecessary innovations, I must at the outset express -my opinion that these nerves cannot be brought under the same general -type as the other sensory nerves. Embryology and Anatomy suggest that -they have no more claim to the title than the _crura cerebri_. Of this -hereafter. Setting these aside, no one now refuses to acknowledge -that Cerebrum and Cerebellum, although centres of Incitation and -Association, are not the centres of direct Innervation: the organic -mechanism in all its _physiological_ processes will act independently -of them (so far as such artificial distinctions are admissible at all). -This does not throw a doubt on their _physiological_ functions, nor on -their participation in the normal execution of physiological processes. - -8. From this rapid survey two important points may be selected for -special attention. First, the continuity of the neural axis throughout; -secondly, the fundamental similarity of its _structure_, underlying -great variations in its form and connections. This, which is the -anatomical expression of the Unity of the nervous system, will become -more evident after we have expounded what Embryology and Microscopic -Anatomy teach. We may therefore digress here awhile to consider - - -THE EARLY FORMS OF NERVE CENTRES. - -9. In the outermost layer of the germinal membrane of the embryo a -groove appears, which deepens as its sides grow upwards, and finally -close over and form a canal. This canal is composed of cells all alike. -Its foremost extremity soon bulges into three well-marked enlargements, -which are then called the _primitive cerebral vesicles_. The cavities -of these vesicles are continuous. Except in position and size, there -are no discernible differences in these vesicles, which are known as -the Fore-brain, Middle-brain, and Hind-brain. - -10. The _Fore-brain_ soon buds off from each side a small vesicle. This -is the optic vesicle, the first rudiment of what subsequently becomes -optic nerve and retina. At this period it is simply a vesicle with -a hollow stem, the cavity being continuous with the cavity of the -cerebral vesicle, and the walls continuous with the cerebral wall. - -It thus appears that the retina and optic “nerve” are primitive -portions of the brain--a detached segment of the general centre, -identical in structure with the cerebral vesicle, and not unlike in -form. A cup-like depression quickly forms the optic vesicle into an -inner and an outer fold. The inner or concave fold becomes the retina, -and the outer or convex fold (that nearest to the brain) becomes its -choroid membrane. On the fourth day of incubation the retina of the -chick is composed of spindle-shaped cells, all alike. On the seventh -day there is a differentiation into layers, one of which on the eighth -day is granular; on the tenth two are granular; and on the thirteenth -ganglionic cells appear. Some of the cells have elongated into radial -fibres (known as Müller’s fibres); and with the appearance of rods and -cones the normal retinal elements are complete. - -11. The researches of Foster and Balfour[84] confirm the statement that -all the different parts of the retina (whether nervous or connective) -are derived from one and the same layer of embryonic cells, which -originally formed a portion of the first cerebral vesicle. - -12. Meanwhile the hollow stem of this optic vesicle begins to develop -fibres amidst the nuclei of its walls. The “optic nerve” arises: it -is still hollow; and in birds remains so through life. The fibres as -they are developed _grow forwards towards the retina_, and spread over -its internal surface. _They also grow forwards towards the brain_, -and spread over its substance; but it is _not_, as might be supposed, -and is generally believed, with the cerebral hemispheres (or that -portion of the Fore-brain from which these are derived), but with the -Middle-brain (which becomes the _corpora quadrigemina_), that the optic -fibres are in connection.[85] - -13. This will be understood when the further development is traced. -The Fore-brain, after budding off the optic vesicles, buds off two -larger vesicles--the future cerebral hemispheres. This is noticeable -on the second day of incubation, and by the third day each vesicle is -as large as the whole of the original Fore-brain. Their development is -essentially like that of the optic vesicles; both as to the cellular -and the fibrous elements. - -The _convolutions_, _corpus callosum_, _nucleus lentiformis_, -and _corpora striata_ are then indicated. Meanwhile, that which -originally was the Fore-brain has lapsed into the secondary rank as -Intermediate-brain (_Zwischenhirn_), and becomes the parts surrounding -the third ventricle, namely, the _thalami_, _corpora candicantia_, -_infundibulum_, and what is called the “posterior perforated substance.” - -14. The _Middle-brain_, or Second Vesicle, develops the _corpora -quadrigemina_ from the roof of its cavity, and the _crura cerebri_ from -its floor. - -The _Hind-brain_, or Third Vesicle, divides into two, like the First -Vesicle; it buds off the hemispheres of the cerebellum; its cavity -forms the fourth ventricle; its walls the _medulla oblongata_. - -15. It thus appears that the primitive membrane forms into a canal, -which enlarges at one part into three vesicles, and from these are -developed the encephalic structures. The continuity of the walls -and cavities of these vesicles is never obliterated throughout the -subsequent changes. It is also traceable throughout the medulla -spinalis. And microscopic investigation reveals that underneath all the -morphological changes the walls of the whole cerebro-spinal axis are -composed of similar elements on a similar plan.[86] - -16. Two conclusions directly follow from this exposition:--first, that -_since the structure of the great axis is everywhere similar, the -properties must be similar_; secondly, that _since there is structural -continuity, no one part can be called into activity without at the same -time more or less exciting that of all the rest_. - - -THE PERIPHERAL SYSTEM. - -17. Following the analytical division, we now come to the Peripheral -System of nerves and ganglia. The separation, I must often repeat, -is purely artificial; but the artifice has conveniences. We separate -in the same way the heart from veins and arteries, and the capillary -circulation from the arterial. - -Each nerve has its direct connection with a particular centre, and -indirectly with the whole system. It has its circumscribed territory, -and individual office. Except in a few cases of anastomosis, the action -of one nerve does not involve that of another: only one muscle or one -group of muscles is moved, without exciting motion in a neighbor. It is -through the centres that these individual territories are united; and -a wave of excitation always passes throughout the central substance. -Thus the centres are not simply organs of association, consequently of -regulation, but are the nexus whereby the diversity of the actions is -integrated into the unity of consensus. - -18. Nothing further need at present be stated respecting the nerves; -but it is needful to give precision to the ideas of - - -GANGLIA AND CENTRES, - -usually spoken of as if they were convertible terms. That this is -inexact may be readily shown, and that it is misleading appears in its -causing physiologists to credit every ganglion, wherever found, with -central functions; and, by an almost inevitable extension of the error, -has led to the assignment of central functions to a single ganglionic -cell! This is but part of that “superstition of the cell” against -which I shall have to protest. I will not here raise the doubt which -presses from various sides respecting the central functions of the -ganglia in the heart and intestines, because the reader perhaps shares -the general opinion on that point; but let me simply ask what central -function can possibly be assigned to the ganglia on each of the spinal -sensory nerves? above all to those grouped and scattered ganglionic -cells which are found at the peripheral termination of some nerves, and -in the very trunks of others? There may, indeed, be imagined a central -function for the ganglia in the mesentery, and even in the choroid coat -of the retina, on the hypothesis (quite gratuitous, I think) of their -regulating the circulation; but even this explanation cannot be adopted -with respect to the ganglionic cells which appear in the course of the -nerve.[87] - -The meaning of a physiological centre is, that it is a point _to_ which -stimulations proceed, and _from_ which they are reflected. The meaning -of a ganglion is, that it is a group of nerve cells dispersed among, or -in continuation with, nerve fibres: it may be a centre of reflection, -or it may not; and in the latter case its physiological office is at -present undetermined. A ganglion is no more a centre in virtue of its -cell-group than a muscle is a limb. All function depends on connection, -and central function demands a connection of afferent and efferent -parts. - -19. The ganglia found in the ventral cord of the Invertebrate (see -Fig. 1) are centres, each of which has considerable independence, -each regulating a single segment of the body, or a group of similar -segments. As the scale of animal complexity ascends, these separated -centres tend more and more to coalesce, and with this coalescence -comes an increasing _combination_ of movements.[88] Observe the -caterpillar slowly crawling over a leaf; each segment of its body moves -in succession; but when this caterpillar becomes a butterfly the body -moves rapidly, and all at once. Open the caterpillar, and you find its -nervous centres are thirteen separate ganglia, each presiding over a -distinct part of the body, and each capable of independent action. -Open the butterfly, and you find the thirteen ganglia greatly changed: -the second and third are fused into one; the fourth, fifth, and sixth -into another; the eleventh and twelfth into another; the only trace of -the original separation is in a slight constriction of the surface. The -movements of the caterpillar were few, simple, slow, and those of the -butterfly are many, varied, and rapid. - -20. In the Vertebrates the coalescence of ganglia is such that the -spinal axis is one great centre. We do indeed anatomically and -physiologically subdivide it into several centres, because several -portions directly innervate separate organs; but its importance lies in -the intimate blending of all parts, so that _fluctuating combinations_ -of its elements may arise, and varied movements result. Each centre -combines various muscles; the axis is a combination of centres. The -brainless frog, for instance, has still the spinal cord, and therefore -the power not only of moving either of his limbs, but also of combining -their separate movements: if grasped, he struggles and escapes; if -pricked, he hops away. But these actions, although complex, are much -less complex and varied than the actions of the normal frog. - -There is not only a coalescence of ganglia, but a greater and greater -concentration of the substance in the upper portions of the axis. In -the inferior vertebrates, and in the mammalian embryo, the spinal -cord occupies the whole length of the vertebral canal from the head -to the tip of the tail; and here the centres of reflexion correspond -with the several segments. But as the cranial mass develops there is a -withdrawal of neural substance from the lower parts, and the centres of -reflexion are then some way removed from the segments they innervate. -In the animal development there is even a greater and greater -predominance of the upper portions, so that the brain and medulla -oblongata are of infinitely more importance than the spinal cord. - -21. Besides the central group of elements which belong to fixed and -definite actions, we must conceive these elements capable of variable -combinations, like the pieces of colored glass in a kaleidoscope, which -fall into new groups, each group having its definite though temporary -form. The elements constitute really a continuous network of variable -forms. It is to such combinations, and not to fixed circumscribed -ganglia, that we must refer the subordinate centres of the axis. We -speak of a centre for Respiration, a centre for Laughing, a centre for -Crying, a centre for Coughing, and so on, with as much propriety as -we speak of a centre for Swallowing or for Walking. Not that in these -cases there is a circumscribed mass of central substance set apart for -the innervation of the several muscles employed in these actions, and -for no other purpose. Each action demands a definite group of neural -elements, as each geometric form in the kaleidoscope demands a definite -group of pieces of glass; but these same pieces of glass will readily -enter into other combinations; and in like manner the muscles active -in Respiration are also active in Laughing, Coughing, etc., though -differently innervated and co-ordinated. - -22. The physiological rank of a centre is therefore the expression of -its power of fluctuating combination. The medulla oblongata is higher -than the medulla spinalis, because of its more varied combinations; -the cerebrum is higher than all, because it has no fixed and limited -combinations. It is the centre of centres, and as such the supreme -organ. - - - - -CHAPTER II. - -THE FUNCTIONAL RELATIONS OF THE NERVOUS SYSTEM. - - -23. The distinguishable parts of this system are the central axis, the -cranial nerves, and the spinal nerves, with the chain of ganglia and -nerves composing the Sympathetic. Let us briefly set down what is known -of their special offices. - -Men very early discovered that the nerves were in some way ministrant -to Sensation and Movement; a divided nerve always being accompanied -by insensibility and immobility in the limb. Galen, observing that -paralysis of movement sometimes occurred without insensibility, -suggested that there were two kinds of nerve; but no one was able to -furnish satisfactory evidence in support of this suggestion until early -in the present century, when the experiments of Charles Bell, perfected -by those of Majendie and Müller, placed the suggestion beyond dispute. - -[Illustration: Fig. 12.--_Transverse sections of spinal cord (dorsal -region)._] - -24. Fig. 12 is a _diagram_ (not a drawing of the actual aspect, which -would be hardly intelligible to readers unversed in such matters) -representing two transverse sections of the spinal cord just where the -nerve-roots issue. The gray substance is somewhat in the form of a -rude H, in the dorsal region, and of the expanded wings of a butterfly -in the lumbar enlargements (Figs. 4–6); the extremities of this gray -substance are the _anterior and posterior horns_. We have already said -that from the anterior horns of each half issue the roots of the motor -nerves, which pass to the muscles. From the posterior horns issue the -sensory nerves, which, soon after leaving the cord, enter the ganglia -before joining the motor nerves, and then pass to the skin, in the -same sheath with their companions, separating again as they reach the -muscles and surfaces where they are to be distributed. When this mixed -nerve is cut through, or tied, all sensation and movement disappear -from the parts innervated. But if only one of the roots be cut through, -above the ganglion, there will then be only a loss of movement or a -loss of sensation. Thus suppose the section be made at _a_, _b_, A: -we have then divided a sensory nerve, and no pinching or pricking of -the part innervated by that nerve will be felt; but movement will take -place if the under nerve be irritated, or if a sensation _elsewhere_ be -excited. Now reverse the experiment, as at B, _c_, _d_. Then, pricking -of the skin will be felt, but no movement will respond. The nerve which -enters the cord at the upper (posterior) part is therefore a sensory -nerve; that which enters at the under (anterior) part is motor. The -direction is in each case indicated by the arrow. The central end _b_, -if irritated, will produce sensation; whereas the peripheral end _a_ -produces neither sensation nor movement. The central end _d_ produces -neither sensation nor movement; the peripheral end _c_ produces -movement. - -25. Two facts are proved by these experiments. First, that the -co-operation of the centre is necessary for Sensation, but not for -Movement. Although normally all the muscles of the trunk are moved only -when their centre has been excited, yet any irritation applied directly -to the muscle nerve, even when separated from its centre, produces a -movement. And to this we may add that a slighter stimulus will move the -muscle by direct irritation of the nerve, than by indirect irritation -through the centre; a slighter stimulus also will suffice when applied -to the nerve than when applied to the muscle itself. - -26. The second fact proved is known as _Bell’s Law_, that the sensory -and motor channels are respectively the posterior and anterior nerves. -The fact is indisputable, but its theoretic interpretation can no -longer be accepted in its original form. Bell supposed the two nerves -to be different in kind, endowed with different specific energies, the -one sensitive, the other motor. The majority of writers still express -themselves as if they adopted this view. We shall, however, presently -see reason for replacing it by the more consistent interpretation -which assigns one and the same property to both nerves, marking their -distinction by the terms afferent and efferent; the one set being -anatomically so disposed that it conveys stimuli from the surfaces to -the centre, and the other set conveying stimuli from the centre to the -muscles, glands, and other cells.[89] - -27. Bell’s discovery was rapidly generalized. The principle of -localization was extended to all nerves, and of course to the posterior -and anterior columns of the spinal cord, which indeed were assumed to -be continuations of the nerves. Bell, who was greater as an anatomist -than as a philosopher, always maintained that anatomical deduction was -superior to experiment. But this was to misunderstand the reach of -deduction, which is only valid to the extent of its premises.[90] In -the present case, the premises assumed that the posterior columns were -continuations of the posterior roots, and carried impressions to the -brain, the anterior columns carrying back from the brain the “mandates -of the will.” Experiment has, however, decisively shown that it is -_not_ through the posterior columns that sensory impressions travel to -the brain, but through the central gray substance. - -28. The spinal cord with its central gray substance is at each point -a centre of reflexion. Connected as it is with different organs, we -artificially consider it as a chain of different centres, and try to -detect the functional relations of its parts. The inquiry is important, -but we must bear in mind the cardinal principle that diversity of -Function depends on the organs innervated, and not on a diversity of -Property in the nervous tissue. Although all nerves have a common -structure and common property, yet we distinguish them as sensory and -motor; and the sensory we subdivide into those of Special Sensation -and those of Systemic Sensation. The motor we divide into muscular, -vasomotor, and glandular. The hypothesis of specific energies must be -relinquished (§ 63). - -In like manner all centres have a common structure and a common -property, with a great diversity of functional relations. Here also the -hypothesis of specific energies has been generally adopted, owing to -a mistaken conception of the biological principle just mentioned. The -cerebral hemispheres are credited with the properties of sensation, -thought, and volition; the cerebellum with the property of muscular -co-ordination; the spinal cord with the property of reflexion. - -29. No attempt to assign the true functional relations of the centres -will be made at the present stage of our exposition. We must learn more -of the processes in Sensation, Thought, and Volition, before we can -unravel the complex physiological web on which they depend. But here, -provisionally, may be set down what observation and experiment have -disclosed respecting the part played by certain centres. We know, for -example, that when the cerebral hemispheres are carefully removed from -a reptile or a bird, all the essentially _vital_ functions go on pretty -much as before, but a great disturbance in some of the _psychical_ -functions is observed. The brainless bird eats, drinks, sleeps, moves -its limbs separately and in combination, manifests sensibility to -light, sound, and touch, performs such instinctive actions as preening -its feathers, or thrusting the head under the wing while roosting. -Throw it into the air and it will fly. In its flight it will avoid -obstacles, and will alight upon a ledge, or your shoulder. But it will -not fly unless thrown into the air; it will not escape through the -open door or window; it will avoid objects, but will show no fear of -them,--alighting on your head, for example, without hesitation. It is -sensitive to light, and may in a certain sense be said to _see_; but -it fails to _perceive_ what is _seen_. It will eat and drink, if food -and water be administered, but it will starve near a heap of grain and -never peck it, not even if the beak be thrust into the heap. A grain, -or strip of meat, may be thrust inside the beak; there it will remain -unswallowed, unless it touches the back of the mouth, then swallowing -at once follows the stimulus. The bird _with_ its brain will fly away -if you turn the finger, or stick, on which it is perching; _without_ -its brain, it makes no attempt to fly, but flutters its wings, and -balances itself. If you open the mouth of a cat, or rabbit, and drop -in some bitter fluid, the animal closes its mouth firmly, and resists -your efforts to repeat the act; without its brain, the animal shows the -same disgust at the taste, but never resists the preliminaries of the -repetition. - -30. These, and analogous facts, have been noted by various -experimenters. They are very far from proving what is usually -concluded; but they prove the important negative position that the -cerebrum is not the centre of innervation for any of the organs on -which the observed actions depend. Thus, the cerebrum is not necessary -to sight: _ergo_ it does not innervate the eye. It is not necessary to -hearing: _ergo_ it does not innervate the ear.[91] It is not necessary -to breathing, swallowing, flying, etc.: _ergo_ it does not innervate -the organs of these functions. - -What then is lost? We have only to remember that the cerebrum is -continuous with the thalami and corpora striata, and, through its -crura, with the medulla oblongata and medulla spinalis, to foresee -that its removal must more or less affect the whole neural axis, -and consequently disturb the actions of the whole organism; this -disturbance will often have the appearances which would be due to the -removal of a central apparatus, so that we shall be apt to attribute -the cessation of a function to the loss of its organ, when in fact the -cessation is due simply to an arrest of the organ by irritation. Thus -the cessation of consciousness, or of any particular movements, when -the cerebrum is removed, is no decisive proof that the cerebrum is the -organ of consciousness, or of the movement in question. This point will -be duly considered hereafter. What we have now to consider is the facts -observed after removal of the cerebrum. - -First, we observe a loss of that power of combining present states -with past states, present feelings with feelings formerly excited in -conjunction with them, the power which enables the animal to adjust -its actions to certain sensations _now unfelt_ but which _will be_ -felt in consequence of the adjustment. Secondly, we observe a loss of -Spontaneity: the bird, naturally mobile and alert, now sits moveless -for hours in a sort of stupor, occasionally preening its feathers, but -rarely quitting its resting-place. All the most conspicuous phenomena -which we assign to Intelligence and Will seem absent. The sensations -are altered and diminished. Many Instincts have disappeared, but some -remain. The sexual feeling is preserved, although the bird has lost -all power of directing its actions so as to gratify the desire. But -these effects are only observed when the whole of both hemispheres have -been removed. If a small portion remain the bird retains most of its -faculties, though with less energy. In frogs and fishes there is little -discernible effect observed when a large portion of the cerebrum is -removed. - -31. Now take away from this mutilated bird its cerebellum: all the -functions continue as before except that _some_ combined movements can -no longer be effected; flight is impossible; walking is a mere stagger. -Remove only the lateral lobes, and though flight is still possible -great _incoherence_ of the wings is observed, whereas walking is not -much affected. If only the cerebellum be removed, the cerebrum being -intact, the phenomena are very different. All the perceptions and -almost all the emotions, all the spontaneity and vivacity are retained; -but the sexual instinct, which was manifested when the cerebrum was -removed, is now quite gone. What we call Intelligence seems unaffected. -The bird hears, and understands the meaning of the sounds, sees and -perceives, sees and fears, sees and adjusts its movements with a mental -vision of unseen consequences.[92] - -32. Are we from these facts to conclude that the cerebrum is the “organ -of the mind”; that it is “the seat” of sensation, thought, emotion, -volition; and that the cerebellum is the “seat” of the sexual instinct, -and muscular co-ordination? Such conclusions have found acceptance, -even from physiologists who would have been startled had any one -ventured to affirm that the medulla oblongata was the “organ” of -Respiration, because Respiration ceases when this centre is destroyed. -I shall have to combat this notion at various stages of my exposition. -Here let me simply say that it is irreconcilable with any clear -conception of organ and function; and is plainly irreconcilable with -any survey of psychical phenomena in animals in whom the cerebrum does -not exist, and in animals from whom it has been removed. - -What the facts indisputably prove is that the cerebrum has an important -part in the mechanism by which the most complex psychical combinations -are effected, and that the cerebellum has an important part in the -mechanism by which the most complex muscular combinations are -effected. The supreme importance of the cerebrum may be inferred from -its dominating all the other centres, and from its preponderance in -size. In man it stands to all the other cranial centres together in -the relation of 11 to 3. It is about five times as heavy as the spinal -cord--that is to say from 1,100 to 1,400 grammes, compared with 27 to -30 grammes. The quantity of blood circulating through it is immense. -Haller estimated the cranial circulation as one fifth of the whole -circulation. If, therefore, the Nervous Centres are agents in the -production of Sensation and Intelligence, by far the largest share must -be allotted to the cranial centres, and of these the largest to the -Cerebrum. - -33. It is, however, one thing to recognize the Cerebrum as having -an important part in the production of psychical phenomena, another -thing to localize all the phenomena in it as their organ and seat--a -localization which soon becomes even more absurd, when of all the -cerebral structure the multipolar cells alone are admitted as the -active agents! - -As was said just now, we recognize in the Medulla Oblongata the nervous -centre of Respiration, but we do not suppose that Respiration has its -_seat_ there, nor that this centre is absolutely indispensable for -the essential part of the process. We respire by our skin, as well as -by our lungs; many animals respire who have nothing like a medulla -oblongata; as many animals feel, and manifest will, who have nothing -like a cerebrum. The destruction of centres is of course a disturbance -of the mechanisms which they regulate. But even the observed results -of a destruction require very close examination, and are liable to -erroneous interpretations. The disappearance of a function following -the destruction, or disease of a particular part, is not to be accepted -as a proof that this part is the organ of the lost function; because -precisely the same phenomena may often be observed following the -destruction of a totally different part.[93] But one result may always -be relied on, and that is the _persistence_ of a function after removal -of a particular part. Thus there is a certain spot of the cerebral -convolutions from which movements of the limbs are excited when the -electrodes are applied to it; removal of the substance is immediately -followed by paralysis of the limbs. Are we to conclude that this spot -is the organ of the function? It is true that the function is called -into action by a stimulus applied to this spot: true that the function -suddenly vanishes when the substance of this spot is destroyed. -Nevertheless, what seems a loss of function is only a disturbance. In -two or three days the paralysis begins to disappear, and at the end -of a week the limbs are moved nearly in the normal manner. And the -same is true when the spot in question is destroyed on both sides. The -recovery of the function shows that the absent part was not its organ. -There is a paradoxical experiment recorded by M. Paul Bert which may be -cited here. He removed the right cerebral hemisphere from a chameleon, -and found that the limbs on the left side were paralyzed; but on his -then removing the left cerebral hemisphere the limbs of the left side -recovered their activity. A similar result was obtained by Lussana and -Lemoigne by extirpation of the thalami. When we find combined movements -persisting after the cerebellum has been destroyed, we may be sure that -the cerebellum is not the organ by which such combinations take place; -and when we find sensation and volition manifested after the cerebrum -has been removed, we may be sure that the cerebrum is not the organ for -these sensations and volitions. - -34. And this we do find. Physiologists, indeed, for the most part, -deny it; or rather, while they admit the observed facts, they refuse -to admit the only consistent interpretation, biassed as they are by -the traditional conception of the brain. After having for many years -persistently denied Sensibility to any centre except the cerebrum, they -are now generally agreed in including the medulla oblongata within the -privileged region; but they still exclude the medulla spinalis. - -35. If all the cranial centres as far as the medulla oblongata are -removed from young rabbits, dogs, or cats, there are unmistakable -evidences of Sensibility in their _cries_ when their tails are pinched, -their _moving jaws_ (as in mastication) when bitters are placed in -their mouths, and their _raised paws rubbing their noses_, when -irritating vapors are applied. It is said indeed that the cries are no -signs of _pain_; and this is probable; but they are assuredly signs of -Sensibility. - -35. The frog thus mutilated has lost indeed all its special senses, -except Touch, but it still breathes, struggles when grasped, thrusts -aside the pincers which irritate it, or wipes away acid dropped on its -skin. If the eye be lightly touched, the eyelid closes; if the touch -be repeated three or four times, the foreleg is raised to push the -irritant away; if still repeated, the head is turned aside; but however -prolonged the irritation, the frog neither hops, nor crawls away, as he -does when the cerebellum remains. Place the brainless frog on his back, -and if the medulla oblongata remains he will at once regain the normal -position; but if that part is absent he will lie helpless on his back. -The power of preserving equilibrium in difficult positions--which -of course implies a nice co-ordination of muscles--resides in the -so-called _optic lobes_ of the frog (what in mammals are called the -_corpora quadrigemina_). - -37. With the destruction of each part of the central mass there will -necessarily be some disturbance of the mechanism; but difficult as -may be the task of detecting by experiment what is the normal action -of any one part, there ought to be no hesitation in recognizing the -persistence of functions after certain parts are destroyed. The -spinal cord is anatomically known to be the centre from which the -limbs, trunk, and genito-urinary organs are innervated. So long as -the mechanism of the actions involving such organs is intact, no -removal of other parts will prevent this mechanism from exhibiting its -normal action. There may indeed arise, and there has arisen, the doubt -whether Sensibility is involved in the action of any nerve centre below -the medulla oblongata. But this doubt is founded on the traditional -hypothesis respecting the seat of Sensation, and is flagrantly at -variance with the logical conclusions of Anatomy and Experiment. - -38. Anatomy shows that the structure of the spinal cord is in all -essential characters the same as that of the medulla oblongata; and -indeed that the whole central axis has one continuous tissue, somewhat -variously arranged, and in relation with various organs. - -Abundant Experiment has shown that the spinal cord, apart from the -encephalon, is capable of acting as a sensorial and volitional centre. -The striking facts advanced by Pflüger, Auerbach, and myself, have -not been impugned;[94] but their interpretation has been generally -rejected. We showed that a brainless frog responded to stimulation in -actions which bore so close a resemblance to actions admitted to be -sensorial and volitional--showed the frog _adapting_ itself to new -conditions, and _acquiring_ dexterity in executing actions which at -first were impossible or difficult, _devising_ combinations to effect -a purpose which never by any possibility could have formed part of its -habits--manifesting, in a word, such signs of Sensibility, that no one -witnessing the experiments could hesitate as to the interpretation, had -he not been biassed by the traditions of the schools. - -39. Our opponents argued that in spite of all appearances there -were profound differences between the actions of the normal and the -brainless animal, and that the latter were due simply to Reflex Action. -I also insist on profound differences; but underlying these there -are fundamental identities. As to the Reflex Action, two points will -hereafter be brought forward: 1°, that _all_ central action is reflex, -the cerebral no less than the spinal; 2°, that the hypothesis of Reflex -Action being purely _mechanical_, and distinguished from Voluntary -Action in not involving Sensibility, is an hypothesis which must be -relinquished. - -40. Postponing, however, all discussion of these points, let me here -say that the doctrine maintained in these pages is that the whole -cerebro-spinal axis is a centre of Reflexion, its various segments -taking part in the performance of different kinds of combined action. -It has one common property, Sensibility; and different parts of it -minister to different functions--the optic centre being different from -the auditory, the cerebral from the spinal; and so on. To make this -intelligible, however, we must first learn what is known respecting the -properties of nerve-tissue. - - - - -CHAPTER III. - -NEURILITY. - - -41. Observation having found that the activity of a nerve was always -followed by a sensation when the nerve ended in a centre, and by a -movement when the nerve ended in a muscle, Theory was called upon -to disclose the nature of this peculiar property of nerves. That a -peculiar and mysterious power did act in the nerves no one doubted; -the only doubt was as to its nature. The ancient hypothesis of Animal -Spirits seemed all that was needed. The spirits coursed along the -nerves, and obeyed the mandates of the Soul. When this hypothesis fell -into discredit, its place was successively taken by the hypotheses of -Nervous Fluid, Electricity, and Nerve Force. The Fluid, though never -manifested to Sense, was firmly believed in, even so late as the days -of Cuvier;[95] but when the so-called electrical currents were detected -in nerves, and the nervous phenomena were shown to resemble electrical -phenomena, there was a general agreement in adopting the electrical -hypothesis. The brain then took the place of a galvanic battery; the -nerves were its electrodes. - -42. Closer comparison of the phenomena detected various irreconcilable -differences, which, if they proved nothing else, proved that -nerve-action took place under conditions so special as to demand a -special designation. Electricity itself is so little understood, that -until its nature is more precisely known, we cannot confidently say -more than that nerve-action resembles electrical-action; meanwhile the -speciality of neural conditions renders all deduction illusory which -is based on electrical-action as observed under _other_ conditions. -In presence of these difficulties, cautious physiologists content -themselves with assigning the observed phenomena to the observed -and inferred conditions, condensing these in the convenient symbol -“nerve-force,” without pretending to any specification of the nature -of that force. It may be a wave of molecular movement dependent on -isometric change or on metamorphic change. It may be the liberation of -molecular tension resembling electricity; it may be electricity itself. -But whatever the nature of the change, it is an activity of the tissue, -and as such comes under the general dynamic conception of Force or -Energy. - -43. In this sense the term has nothing equivocal or obscure. -It is a shorthand expression symbolizing certain well-defined -observations. Nevertheless, it is a term which we shall do well to -avoid when possible, and to replace by another having less danger of -misinterpretation; the reason being that Force has become a sort of -shibboleth, and a will-o’-wisp to speculative minds. All that we _know_ -of Force is Motion. But this is too meagre for metempirical thinkers, -who disdain the familiar experiences expressed in the term Motion, -and demand a transcendent cause “to account” for what is observed. -They seek an entity to account for the fact. Motion is a very definite -conception, expressing precise experiences; we know what it means, and -know that the laws of moving bodies admit of the nicest calculation. -A similar precision belongs to Force when understood as “mass -acceleration,” or M V². But this does not content those metaphysicians -who understand by Force “the unknown reality behind the phenomena”--the -_cause_ of Motion. This cause they refuse to recognize in some -antecedent motion (what I have termed a “differential pressure”), but -demand for it a physical or metaphysical _agent_: the physical agent -being a subtle fluid of the nature of Ether, or a nerve atmosphere -surrounding the molecules; the metaphysical agent being a Spirit or -aggregate of Soul-atoms. The second alternative we may decline here -to discuss. The first alternative is not only a pure fiction, but one -which is inconsistent with the demonstrable velocity of the neural -process, which is not greater than the pace of a greyhound, whereas -the velocities of light and electricity are enormously beyond this. It -is inconsistent also with the observation that a much feebler current -of electricity is requisite for the stimulation of a muscle through -its nerve than when directly applied to the muscle: a proof that the -nerve does not act solely by transmission of electricity--unless we -gratuitously assume that the nerve is a multiplicator. - -When it is said that the living nerve is incessantly liberating Force -which can be communicated to other tissues, the statement is acceptable -only if we reject the metaphysical conceptions it will too generally -suggest--the conceptions of Force as an entity, and of its being -passed from one object to another like an arrow shot from a bow. The -physical interpretation simply says that the molecules of the nerve are -incessantly vibrating, and with varying sweep; these vibrations, when -of a certain energy, will set going vibrations in another substance by -disturbing the tension of its molecules, as the vibrations of heat will -disturb the tension of the gunpowder molecules, and set them sweeping -with greater energy: this is the _communication_ of the force. Just as -we say that a magnet communicates magnetic force to a bit of iron, -though all we mean is that the magnet has so altered the molecular -condition of the iron as to have given it the movements called -magnetism--in short, has excited in the iron the dormant property of -becoming magnetic--so we say the nerve communicates its force to the -muscle, exciting in the muscle its dormant property of contraction. -But in truth nothing has passed from magnet to iron, or from nerve to -muscle. - -44. Do what we will, however, there is always, in the present condition -of philosophical chaos, the danger of being misunderstood when we -employ the term Nerve-force; and I have proposed the term Neurility as -an escape from the misleading suggestions. It is a symbol expressing -the general property of nerve-tissue. For reasons presently to be -stated, I restrict Neurility to the peripheral system, employing -Sensibility for the central system. The excited muscle manifests its -special property of Contractility; the excited nerve manifests its -special property of Neurility; the excited centre manifests its special -property of Sensibility.[96] The terms are simply descriptive, and -carry with them no hypothesis as to _what_ Neurility is in its hidden -process, nor _how_ Sensibility arises in a nerve-centre, and not -elsewhere. We know that a stimulated muscle contracts, and we express -the fact by assigning to muscular tissue the property of Contractility. -We know that a stimulated nerve translates an impulse from one point to -another, and excites the muscle to contract; and we express the fact -by assigning to nerve-tissue the property of transmitting stimulation, -which is further specified, as unlike other transmissions, by the term -Neurility. - -45. What is the meaning attached to the term Property, and how it is -distinguished from Function, has been already expounded in Problem -1, §§ 81–6. There also was laid down the principle of _identity of -structure implying identity of property_. Inasmuch as observation -reveals a fundamental similarity in the structure of the nervous tissue -throughout the animal kingdom, we must conclude the existence of a -fundamental similarity in the property of that tissue: a conclusion -confirmed by observation. There is a corresponding agreement in the -organs and functions; so that, within certain limits, the experiments -performed on an insect may be verified on a mammal. Everywhere -nerve-tissue has certain characters in common, accompanied by -variations in the degree and mode of manifestation corresponding with -variations in structure and connection. Obvious as the fact is, we -must emphasize the great variety which accompanies the underlying -uniformity, for this is recognizable both in the individual organism -and in the animal kingdom at large. Even such seemingly individual -terms as nerve-cell and nerve-fibre are in truth generic; and the -description which accurately represents one cell or fibre needs -modifying for others. - -Properties are generalized expressions; they result from the -_composition_, the _structure_, and the _texture_ of a substance. Thus -one bar of iron may differ from another of equal bulk in being more or -less crystalline in structure, though having the same composition and -the same texture. This difference will modify the mode of manifestation -of the iron-properties. Cast-iron pillars, for example, will support, -as a roof, a weight which would break them if suspended; wrought-iron -pillars of similar bulk will bear a weight suspended which would crush -them as a roof. Yet both cast and wrought iron pillars have the same -properties, because they have the _same_ composition and _similar_ -structure; the variation of structure only producing a difference in -the modes. Texture may also vary. The bar of iron may be beaten into -a plate, rolled into a cylinder, or split into wire-work, without any -change in its properties, but with marked differences in its modes of -manifestation, and in the _uses_ to which it may be applied. These uses -are of course dependent on the connections established between the iron -and other things. In Physiology, _uses_ are called _functions_. - -46. Nerve-tissue must be understood as having everywhere the same -general Property. In one animal and in another, in one part and in -another, Neurility is the same in kind, but not everywhere manifesting -the same degree, nor applied to the same Function. The _composition_ -of nerve-tissue varies, but not more than the composition of all other -organized substances; the _structure_ is variable, but only within -a small range; the _texture_ also; while the _connections_ are very -various. Hence, whatever the variations in composition or structure, -the nerve-fibre has everywhere one fundamental property, which in -connection with a muscle has the functional activity of exciting -contraction; in connection with a gland of exciting secretion; and in -connection with a centre of exciting reflexion.[97] - -47. Had a clear idea of Function as dependent on connexion been present -to their minds certain physiologists would hardly have raised the -mirage of “Nerve-force,” a mysterious entity endowed with “specific -energies,” and capable of producing vital and psychical phenomena by -an occult process; nor would others have been led to the monstrous -hypothesis of particular nerve-cells being endowed with thought, -instinct, and volition. They would have sought an explanation of -functions in the combined properties of the co-operant organs and -tissues. They would not have endowed one nerve with Sensibility, and -another nerve of identical structure with Motility;[98] one nerve with -a motor property, and another with the opposite property of inhibition. -They would have seen that all nerves have the same _property_, but -different _uses_ when in different connexions. - -48. Throughout the animal kingdom we see movement following on -stimulation. Stimulation may be defined the change of molecular -equilibrium. The stimulation of a muscle is produced indirectly through -a change in the nerve, or directly through a change in the muscle -itself. In the simplest organisms there is no trace of nerve-tissue; -but their substance manifests Irritability (or as it is often called -Sensibility); and a stimulus to one part is propagated throughout--the -whole body moves when touched. Even in Polypes, where there is the -beginning of a differentiation, the motion is slowly propagated from -one part to the rest. A single tentacle retracts when touched; but the -movement rarely ends there; it is slowly communicated from one tentacle -to the other, and from them to the whole mass. Touching the body, -however, will not, if the touch be slight, cause the tentacles to move; -so that we see here a beginning of that principle of specialization -which is so manifest in the higher organisms: the tentacles have -become the specially sensitive parts. Ascending higher in the scale of -organisms we find those which habitually move particular parts without -at the same time necessarily moving the rest; and this independence -of parts, accompanying a more perfect consensus, we find to be -developed _pari passu_ with a nervous system. An immense variety of -part-movements, with varying combinations of such movements, is the -physiological expression of the more complex nervous system. - -48 _a_. Deferring what has to be said of Sensibility till the next -chapter, we may here touch on its relation to Irritability, which is -often used as its synonym. _Objectively_ it cannot be distinguished -from Irritability, nor indeed from the most general phenomenon of -reaction under stimulation; in this it is an universal property. But -_subjectively_ it is distinguishable as a peculiar mode of reaction, -only known in nerve-tissues. While all tissues are irritable, and react -on being stimulated, each tissue has its special mode of reaction. The -secreting-cell reacts differently from the muscle-cell. The reaction -of the nerve is the innervation of a centre or a muscle; the reaction -of an innervated centre is sensation; of a muscle, contraction. There -are three aspects of neural reaction: excitation, propagation of the -disturbance, and innervation. The first is expressed by irritability, -the second by conductibility, the third by sensibility; but these are -only artificial distinctions in the general phenomenon of transmitted -excitation. The nerve substance is specially distinguished by its -instability of molecular equilibrium; it undergoes chemical change -with a readiness comparable to that of explosive substances. Hence -its facility of propagation of disturbance. There is irritability and -propagation of disturbance in muscular tissue, notably evident in -the continuous tissue of the heart, intestines, and ureter; but the -propagation is slow and diffusive; whereas in the nerve it is rapid, -and restricted along a definite path. By this rapidity and restriction -the force of the impact is increased; and thus a slight stimulus -applied to the nerve is capable of disturbing the state of the muscle. - -49. Thus while molecular movement is a fundamental condition of -Vitality, and is incessant throughout organized substance, the massive -movements of the organism, and the movements of particular parts, are -the _directed quantities_ of this molecular agitation. They are due -to stimulation. We distinguish this from mechanical impulsion. It -is a vital process involving molecular change; it is not simply the -_communication_ of motion from without, but the _excitation_ of motion -within. It is not like the blow which merely displaces an object, but -like the blow which disturbs its molecular equilibrium. The effect, -therefore, depends on this molecular condition: the blow which scatters -a heap of gunpowder will explode a fulminating salt, and this, in -exploding, will excite the gunpowder to explode. The stimulus which -is too feeble to excite contraction in a muscle will be powerful -enough to excite the neurility of a nerve, and _that_ will excite the -contractility of the muscle. The nerve-force is simply neural stimulus. -It acts upon the other tissues as the nitrogenous salt upon the -gunpowder. - -Although it is now common to speak of nerves as transmitting waves of -molecular motion, and to regard nerves as the passive medium for the -“transference of force,” whereby the force is thus made an abstract -entity, we must always remember that such phrases are metaphors, and -that the truer expression will be not “transference of force,” but the -“propagation of excitation.” I mean that it is not the _force_ of the -impact nor its _energy_ which a nerve transmits, it is the vibratory -change produced in the nerve by the impact, which excites another -change in the organ to which the nerve goes. We know by accurate -measurements that the excitation of a nerve lasts much longer than the -_stimulus_, a momentary impact producing an enduring agitation. We know -also that the excitation of a centre lasts longer than the muscular -contraction it has initiated. We know, moreover, that a nerve may be -totally incapable of conducting an external stimulus, yet quite capable -of conducting a central stimulus; were it a passive conductor like a -wire this would not be so.[99] - -50. The nerve is essentially an exciter of change, and thereby a -regulator. A muscle in action does not appreciably determine action -in any other (except in the comparatively rare cases of anastomosing -muscles); a secreting cell does not propagate its excitation to others. -The nerve, on the contrary, not only propagates its excitation, and -awakens the activity of the muscle or gland with which it is connected, -but through the centre affects the whole organism-- - - “Ein Schlag tausend Verbindungen schlägt.” - -Thus it is that stimulation which in the simpler organisms was diffused -throughout the protoplasm, has in the complex organisms become the -specialized property of a particular tissue. - -51. Two general facts of supreme importance must now be stated: One is -the law of stimulation--_every excitation pursues the path of least -resistance_. The second is the condition of stimulation--_unlike -mechanical impulsion, it acts only at insensible distances_. - -52. This means that although a nerve may be excited by any stimulus -external to it which changes its molecular condition, no propagation of -that change (i. e. no stimulation through the nerve) is possible except -through continuity of substance. Mere physical contact suffices to -excite the nerve; but if there be an interruption of continuity in the -nerve itself, no stimulus-wave passes across that line. Cut a nerve, -and bring the divided surfaces once more into close contact, there will -still be such a solution of continuity as to arrest the stimulus-wave, -mere physical contact not sufficing for the propagation. Whereas across -the cut ends of a divided nerve, even visibly separated, the electric -current easily passes. This necessity for the vital continuity of -tissue in the propagation of stimulation must always be borne in mind. -The presence of a membrane, however delicate, or of any tissue having -a different molecular constitution, suffices to arrest or divert the -wave. I conceive, therefore, that it is absolutely indispensable that -a nerve should terminate in and _blend_ with a muscle or a centre, -otherwise no stimulation of muscle or centre will take place through -the nerve. - -[Illustration: Fig. 13.] - -53. The difference between excitation from contact and stimulation -from continuity may be thus illustrated. In Fig. 13 we see the legs -of a frog attached to the spine by the lumbar nerves (_l_), and lying -on the muscles (_m_) of one leg is the nerve (_c_) of another frog’s -leg. Applying the electrodes to (_l_), the muscles (_m_) are violently -contracted; not only so, but their contraction excites the other nerve -(_c_), and the leg attached to this nerve is thereby thrown into -contraction. This “secondary contraction,” as Dubois Reymond calls it, -might be supposed to be due to a diffusion of the electrical current; -but that it is due to a change in the muscles (_m_) is proved by -delicate experiments showing that the movements in the detached leg are -of precisely the same kind as those in the legs directly stimulated. -If there is only a muscular shock in the one case, there is only a -muscular shock in the other; if there is tetanus in the one, there is -tetanus in the other; if the muscles of the first leg are fatigued -and respond slowly and feebly, the response of the second is slow and -feeble. Moreover, the secondary contraction may be produced by chemical -or mechanical stimulus, as well as by the electrical. - -54. Although the contraction of a muscle is thus seen to be capable -of exciting a nerve in contact with it, the reverse is not true: we -can produce no contraction in a muscle by exciting a nerve simply in -contact with the muscle, and not penetrating its tissue and terminating -there. Accordingly we always find a nerve when about to enter a muscle -or a centre losing its _protecting_ envelopes; it gradually becomes -identified as a protoplasmic thread with the protoplasm of the muscle -or the centre. - -55. Neurility, then, is the propagation of molecular change. Two -offices are subserved by the nervous system, which may respectively be -called Excitation--the disturbance of molecular _tension_ in tissues, -and consequent liberation of their energies; and Co-ordination--the -direction of these several energies into combined actions. Thus, when -the muscle is in a given state of molecular tension, the stimulation of -its nerve will change that state, causing it to contract if it be in -repose. But this stimulation, which will thus cause a contraction, will -be arrested, if at the same time a more powerful stimulation reaches -the antagonist muscle, or some distant centre: then the muscle only -_tends_ to contract. - - -ORIGIN OF NERVE-FORCE. - -56. After this brief account of Neurility we may pass to the -consideration of its origin. Are we to understand that this property -belongs to the nerves themselves in the sense in which Contractility -belongs to the muscles? or are we to accept the teaching which assigns -the origin of “nerve-force” to the ganglia, and regards the nerves -simply as passive conductors of a force developed in the cells? - -57. It is now many years since I ventured to criticise the reigning -doctrine, and to urge the necessity Of consistently carrying out the -distinction between Property and Function. I called attention to the -positive evidence which contradicted the idea of passive conduction; -and pointed out the illusory nature of the favorite analogy, in which -ganglia were likened to batteries, and nerves to the conducting wires. -But the old image still exerts its empire; and writers are still -found speaking of the brain as a telegraphic bureau, the ganglia as -stations, and the nerves as wires. In the cells of the gray substance -they place a constantly renewing reservoir of nerve-force. There the -force is elaborated, stored up, and from thence directed along the -nerves. The sensory nerve “transmits an impression to the brain”--as -the wire transmits a message to the bureau. The motor nerve, in turn, -“transmits the mandates of the will”--and all is clear! Clear, until -we come to translate metaphors into visible facts, or try to conjure -up some mental image of the process. For myself, I can only conceive -nerve-force as the activity of the nerve, and not of something -_else_. This becomes still more evident when I find that the activity -is equally manifest after its imaginary source has been removed. -Transmitting impressions, or messages, implies as a preliminary that -there should be an impressible agent, or a _message-sender_, at the -periphery. No one supposes that simply touching one end of a wire -would send an “impression” or a “message” to the battery; or that -without the battery this touch would evolve a current. The battery is -indispensable; in _it_ is evolved the current which the wire transmits. -Not so the ganglion, or brain. Remove the wire from its connection with -the battery, and it is a bit of wire, nothing more. But remove a nerve -from its connection with a ganglion, and it is still active as nerve, -still displays its Neurility when excited, still moves the muscle as -before. The amputated limb will move when its nerves are stimulated, -just as when a reflex from its centre moved it. Every one knew the -fact; it was staring them in the face, yet they disregarded it. Even -the old anatomist, Willis, had recorded experiments which ought to have -opened their eyes. He tied the phrenic nerve, and found that, when -he irritated it below the ligature, the diaphragm moved; but when he -irritated it above the ligature, no movement followed. Since his days, -thousands of experiments have shown that the presence of a ganglion is -not necessary to the action of a nerve.[100] - -58. Of course an explanation was ready. The nerve was said to have been -“endowed with force” from its ganglion during their vital connection; -and this force, stored up in the nerve, was disposable for some time -after separation from the ganglion. We need not pause to criticise this -misty conception of one part “endowing” another with force; the plain -facts afford the best answer. There seemed, indeed, a confirmation -of the hypothesis in the fact that although the nerve separated from -its ganglion was capable of excitation, yet after a few excitations -it was exhausted, and ceased to stimulate the muscle. It seemed like -the piece of magnetized iron which would act as a temporary magnet, -though quickly losing this borrowed power. But the whole fabric -fell--or ought to have fallen--when extended observation discovered -that this exhausted nerve would, if left in repose, _recover_ its -lost power. A nerve preserves its excitability as long as it preserves -its structural integrity, and recovers its power in recovering that -integrity. The length of time varies.[101] Gratiolet found the muscles -in the leg of a tortoise, which had been amputated a week before, -contract when the nerves were irritated; and Schiff found the divided -nerve of a winter frog excitable at the end of three weeks. Even -after all excitability has disappeared, it will reappear if arterial -blood be injected; just as muscles which have already begun to assume -cadaveric rigidity recover their contractility after transfusion. Nor -is this all. The separated nerve finally degenerates, and loses all its -structural characters and physiological properties; yet under favorable -conditions it will regenerate--recover its structures and properties; -and this even apart from a centre, as Vulpian showed. Very noticeable -is the fact that the force said to be produced in the centre, and only -“conveyed” by the nerve, vanishes gradually from the centre to the -periphery, and recovers from the periphery to the centre--the part of -the nerve which is farthest from the centre being excitable when the -part nearest the centre is still inexcitable. Again, when a nerve is -pinched, contraction in the muscle follows; but the pinch has for a -time so disturbed the structural integrity of the nerve (at that spot) -that no irritant applied to the spot, or _between_ it and the centre, -will be followed by contraction, whereas _below_ the spot an irritation -takes effect. This is another form of the experiment of Willis. Even in -its normal state, the nerve has different degrees of excitability in -different parts of its course,--a fact discovered by Pflüger which is -quite irreconcilable with the hypothesis of passive conduction. Doubts -have been thrown on Pflüger’s interpretation,[102] namely, that there -is an avalanche-like accumulation of energy proportionate to the length -of the stimulated portion; but the fact remains, that one and the -same irritant applied successively to two different points of a nerve -does not irritate the muscle in the same degree. Munk also finds the -velocity of transmission in a motor nerve increases as it approaches -its termination in the muscle.[103] - -59. Nothing can be more unlike the conduction of an electric current -than this excitation of Neurility; nothing more accordant with the -idea of it as a vital property of the tissue. The notion of its being -derived from a centre is on a par with the notion first successfully -combated by Haller,[104] that the muscle derived its Contractility -from the nerves; or the analogous notion that the electric organ -in fishes derived its property from the brain. Indeed, it was in -support of the hypothesis that the brain was a battery, and nerves -the conductors, that the phenomena observed in electrical fishes were -frequently cited. The electric organ was seen to be connected with -the brain; its discharges were under the control of the animal, and -were destroyed on one side when the brain on the corresponding side -was destroyed. But Charles Robin long ago suggested, what indeed ought -never to have been doubted, that the brain was not the source of the -electricity; but that the tissue of the electric organ itself had this -special property, which the nerve merely called into activity. The -suggestion has been experimentally verified by M. Moreau, who divided -all the nerves supplying the electric organ on one side, and, having -thus cut off all communication with the brain, produced electrical -discharges by irritating the nerves; precisely as the muscles are made -to contract when the divided nerves are irritated. Had the experiment -ceased here, it might have been interpreted on the old hypothesis: the -electric organ might be supposed to have a certain amount of electric -force condensed in it, stored up there, as it is said to be in the -nerves, and discharged when the organ is irritated. But experiment has -decided this point also. Electric fishes notoriously exhaust their -power by a few discharges, and recover it after repose. When M. Moreau -had exhausted his mutilated fishes, he replaced them in the water, -and allowed them repose. On again irritating the divided nerves, the -discharges were again produced.[105] - -60. On all sides the idea of nerves deriving their power from another -source than their own substance is seen to be untenable. _A priori_ -this might have been concluded. Neurility is the vital property of -nerve-tissue. “Nerve-force” is nerve-action--molecular changes in the -nerve itself, not in some remote substance. That nerve and centre are -vitally connected is true; and what their physiological relations are -will hereafter be examined; but we must dismiss the idea of nerves -having the relation to centres that electrodes have to batteries. - -61. In proposing the term Neurility, I not only wished to get rid of -the ambiguities which hovered round “nerve-force” and “nerve-current,” -but to recall the physiological principle that properties are -dependent on structures; and therefore that the special property of -nerve-tissue is conditioned by its structure. Neurility is, of course, -an abstraction; but so is _the_ nerve an abstraction. The concrete -manifestations are the several nerve-actions. These we classify and -specify. One class we call sensory, another class motor; not because -the nerve-action itself is different, but because it is in each class -in a different functional relation to other parts. In classing men -as governors and governed, employers and employed, we do not suppose -anthropological distinctions, but only differences in their social -functions. - -62. This is the modification of the Law of Bell to which reference was -made in § 26. It replaces the idea of two different kinds of nerve, -sensory and motor, by that of two different anatomical connections. I -need not reproduce here the argument with which I formerly criticised -the supposed distinction between sensory and motor nerves; because -the old idea is rapidly falling into discredit, and physiologists so -eminent as Vulpian and Wundt have explicitly announced their adhesion -to the principle of identity,--a principle which, as Vulpian truly -remarks, dominates the whole physiology of the nervous system.[106] - - -THE HYPOTHESIS OF SPECIFIC ENERGIES. - -63. One development of the theory of Bell, respecting the different -kinds of nerve, has been the still accredited hypothesis that each -nerve has a “specific energy,” or quality, in virtue of which it -acts and reacts only in one way. The optic nerve, no matter how -stimulated, only responds by a sensation of color, the auditory nerve -only by a sensation of sound; and so on. This hypothesis, which (as -I learn from a correspondent)[107] was originally propounded by Bell -himself, was developed and made an European doctrine by Johannes -Müller, first in his remarkable treatise, _Über die phantastischen -Gesichtserscheinungen_ (1826), and afterwards in his _Physiology_. -Like all good hypotheses, it has been fruitful; and Helmholtz -still holds it to be of extraordinary importance for the theory of -perception. Although combated by a few physiologists, it has kept its -place firm in the general acceptance; no doubt because it forms a ready -explanation of the facts. But, as I often have to remark, _explanation_ -is not _demonstration_.[108] - -64. The first criticism to be made on the hypothesis is that it -commits the error of confounding function with property, assigning as -a specific quality of the nerve the reaction of the organ innervated. -Thus Müller speaks of the specific energy as “the essential condition -of the nerves in virtue of which they see light and hear sound.” -But the optic nerve no more _sees_, than the liver-nerve _secretes_ -bile. That the optic nerve is one element in the mechanism on which -vision depends, is all that we can say, Müller declares that it is -not sufficient to assume each nerve to be so constituted that it -has a susceptibility to certain stimuli rather than to others; but -that “with Aristotle we must ascribe to each a peculiar energy as -its vital quality. Sensation,” he adds, “consists in the sensorium -receiving through the medium of the nerves a _knowledge of certain -qualities_,--a condition, not of the external bodies, but of the -nerves themselves,”--and these qualities are different in different -nerves. In other words, he assumes a special substance for each special -energy. The sensation of color depends on the special Visual substance -(_Sehsinnsubstanz_); the sensation of sound on the Auditory substance -(_Hörsinnsubstanz_); and so on. - -65. We have here an hypothesis analogous to that of Innate Ideas, or -_a priori_ Forms of Thought. It is, in fact, only a reproduction of -that conception carried into the sphere of Sense. No one thinks of -assigning specific energies to the several muscles, yet a movement of -prehension is as different from a movement of extension, a peristaltic -movement is as different from a movement of occlusion, as a sensation -of sound is from a sensation of color. If movement is common to both -of the one class, feeling is common to both of the other: the forms -and mechanism are different and specific. Muscles have the common -property of contracting under stimulation; whatever be the nature of -the stimulus, each muscle has its own particular response, or mode of -reaction: the flexor always bending, never extending the limb; the -sphincter always closing, never opening the orifice. The movements -of the heart are not the same as those of the eye; both are unlike -the movements of the intestine. There are muscles which respond to -some stimuli, and not to others. Those of the eye, or of the vocal -chords, respond to impulses which would leave the masseter or biceps -unstirred. According to Marey, the hyoglossus of a frog will become -tetanic under a stimulus of only ten pulses in a second; whereas the -gastrocnemius of that same frog resists a stimulus of less than twenty -in a second. We find the retina responding to ethereal pulses which -leave the auditorius unaffected; we find the muscles of a gnat’s wing -so exquisitely susceptible that the wing beats eight thousand times in -a second,--a delicacy in comparison with which even our muscles of the -eye are coarse. - -66. The facts which the hypothesis of specific energies is called -on to explain are more consistently interpreted on the admission of -a common property in nerve-tissue, manifesting different degrees of -excitability, and entering into different mechanisms, so that the -functional results differ. A nerve which may be stimulated from the -skin will not respond at all, or not in the same way, if the stimulus -be applied under the skin. Are we to suppose that the specific energy -resides in one part of the nerve, and not in another?[109] That the -optic nerve responds to stimuli which will not sensibly excite a -motor nerve, depends on the terminal structures through which the -stimulation is excited; for the optic nerve itself, apart from the -retinal expansion, is as insensible to light as the motor nerve is. And -the specific sensation, or movement, which _results_ from stimulation -of a nerve depends not on the nerve, but on the mechanism of which the -nerve is one element. Sensations of touch, temperature, and pain are -assuredly specific; they are as unlike each other as a sensation of -taste is unlike a sensation of smell. Yet the same nerves, variously -stimulated, produce all three sensations. - -67. We conclude, therefore, that the phrase “specific energy” is an -elliptical expression for the particular office of a nerve. In this -meaning there is no obscurity. The optic nerve is not a vasomotor -nerve, the skin nerve is not a muscle nerve; the auditory nerve is a -nerve of special sensation, the vagus is a nerve of systemic sensation; -and so on. Neither movement nor sensation belongs to the nerves -themselves. - - - - -CHAPTER IV. - -SENSIBILITY. - - -68. The principles laid down in the preceding chapter are equally -applicable to the central system. But here greater difficulties await -us. We cannot expect traditional views to be easily displaced, when -they have taken such hold on the mind, as is the case with regard to -Sensibility. To admit that all nerves have a common property, and that -their functional relations depend on the organs which they innervate, -demands small relinquishment of cherished opinions. But to admit that -all nerve-centres have a common property, and that their functional -relations depend on their anatomical connections, is to sweep away at -once a mass of theoretic interpretations which from long familiarity -have acquired an almost axiomatic force. That the brain, and the brain -only, is the source and seat of Sensibility is the postulate of modern -Physiology. - -69. The question is one of extreme complexity, but may be greatly -simplified, if we can manage to reduce it to purely physiological -terms, and consider the phenomena in their objective aspect. In dealing -with nerves and their actions this was comparatively easy; we had for -the most part only physiological processes to unravel. It is otherwise -in dealing with nerve-centres--the subjective or psychological aspect -of the phenomena inevitably thrusts itself on our attention; and all -the mysteries of Feeling and Thought cloud our vision of the neural -process. Do what we will, we cannot altogether divest Sensibility of -its psychological connotations, cannot help interpreting it in terms -of Consciousness; so that even when treating of sensitive phenomena -observed in molluscs and insects, we always imagine these more or less -suffused with Feeling, as this is known in our own conscious states. - -70. Feeling is recognized as in some way or other bound up with -neural processes; but Physiology proper has only to concern itself -with the processes; and the question whether these can, and do, go on -unaccompanied by Feeling, is, strictly speaking, one which belongs -to Psychology. It demands as a preliminary that the term Feeling be -defined; and the answer will depend upon that definition, namely, -whether Feeling be interpreted as synonymous with Consciousness in the -restricted sense, or synonymous with the more general term Sentience. -If the former, then since there are unquestionably neural processes of -which we are not conscious, we must specify the particular groups which -subserve Feeling; as we specify the particular groups which subserve -the sensations of Sight, Hearing, Taste, etc.; and localize the -separate functions in separate organs. If the latter, then, since all -neural processes have a common character, we have only to localize the -particular variations of its manifestation, and distinguish sensitive -phenomena as we distinguish motor phenomena. - -71. It is absolutely certain that the Feeling we attribute to a -mollusc is different from that which we attribute to a man; if only -because the organisms of the two are so widely different, and have -been under such different conditions of excitation. If every feeling -is the functional result of special organic activities, varying with -the co-operant elements, we can have no more warrant for assuming the -existence of the same _particular_ forms of Feeling in organisms -that are unlike, than for assuming the 47th proposition of Euclid to -be presented by any three straight lines. The lines are the necessary -basis for the construction, but they are not the triangle, except when -in a special configuration. This is not denying that animals _feel_ -(in the general sense of that term), it is only asserting that their -feelings must be very _unlike_ our own. Even in our own race we see -marked differences--some modes of feeling being absolutely denied to -individuals only slightly differing from their fellows. If, however, -we admit that different animals must have different modes of Feeling, -we must also admit that the neuro-muscular activities are generically -alike in all, because of the fundamental similarity in the structures. -Whether we shall assign Feeling to the mollusc or not will depend on -the meaning of the term; but, at all events, we require some term -general enough to include the phenomena manifested by the mollusc, -and those manifested by all other animals. Sensibility is the least -objectionable term. Unless we adopt some such general designation, -physiological and psychological interpretations become contradictory -and obscure. The current doctrine which assigns Sensibility to the -brain, denying it to all other centres, is seriously defective, -inasmuch as it implies that tissues similar in kind have utterly -diverse properties; in other words, that the same nerve-tissue which -manifests Sensibility in the brain has no such property in the spinal -cord. - -72. How is this tenable? No one acquainted at first hand with the facts -denies that the objective phenomena exhibited by the brainless animal -have the same general character as those of the animal possessing a -brain: the actions of the two are identical in all cases which admit -of comparison. That is to say, the objective appearances are the -same; differing only in so far as the mechanisms are made different -by the presence or absence of certain parts. The brain not being a -necessary part of the mechanical adjustments in swimming, or pushing -aside an irritating object, the brainless frog swims and defends itself -in the same way as the normal frog. But no sooner do we pass from -the objective interpretation, and introduce the subjective element -of Feeling among the series of factors necessary to the product--no -sooner do we ask whether the brainless frog _feels_ the irritation -against which it struggles, or _wills_ the movements by which it -swims--than the question has shifted its ground, and has passed from -Physiology to Psychology. The appeal is no longer made to Observation, -but to Interpretation. Observation tells us here nothing directly -of Feeling. What it does tell us, however, is the identity of the -objective phenomena; and Physiology demands that a common term be -employed to designate the character common to the varied phenomena. -Sensibility is such a term. But most modern physiologists, under the -bias of tradition, refuse to extend Sensibility to the spinal cord, -in spite of the evidences of the spinal cord possessing that property -in common with the brain. They prefer to invoke a new property; they -assign spinal action to a Reflex Mechanism which has nothing of the -character of Sensibility, because they have identified Sensibility with -Consciousness, and have restricted Consciousness to a special group of -sensitive phenomena. - -73. Nor is it to be denied that on this ground they have a firm basis. -Every one could testify to the fact that many processes normally -go on without being accompanied by consciousness, in the special -meaning of the term. Reflex actions,--such as winking, breathing, -swallowing,--notoriously produced by stimulation of sensitive surfaces, -take place without our “feeling” them, or being “conscious” of them. -Hence it is concluded that the Reflex mechanism suffices without the -intervention of Sensibility. I altogether dispute the conclusion; and -in a future Problem will endeavor to show that Sensibility is necessary -to Reflex Action. But without awaiting that exposition we may at once -confront the evidence, by adducing the familiar fact that “unconscious” -processes go on in the brain as well as in the spinal cord; and this -not simply in the sphere of Volition, but also in the sphere of -Thought.[110] We act and think “automatically” at times, and are quite -“unconscious” of what we are doing, or of the data we are logically -grouping. We often think as unconsciously as we breathe; although from -time to time we become conscious of both processes. Yet who will assert -that these unconscious processes were independent of Sensibility? -Who will maintain that because cerebral processes are sometimes -unaccompanied by that peculiar state named Consciousness, therefore all -its processes are unaccompanied by Feeling? And if here we admit that -the Reflex mechanism in the brain is a _sensitive_ mechanism, surely we -must equally admit that the similar Reflex mechanism in the spinal cord -is sensitive? - -74. Let it be understood that Sensibility is the common property of -nerve-centres, and physiological interpretations will become clear -and consistent. Consciousness, as understood by psychologists, is not -a property of tissue, it is a function of the organism, dependent -indeed on Sensibility, but not convertible with it. There is a greater -distinction between the two than between Sensation, the reaction of -a sensory organ, and Perception, the combined result of sensory and -cerebral reactions; or than that between Contractility, the property of -the muscles, and Flying, the function of a particular group of muscles. -It is not possible to have Consciousness without Sensibility; but -perfectly possible to have Sensations without Consciousness. This will -perhaps seem as inconceivable to the reader as it seemed to Schröder -van der Kolk.[111] - -75. Let us illustrate it by the analogy of Pain. There is a vast amount -of sensation normally excited which is totally unaccompanied by the -feelings classed as painful. The action of the special senses may be -exaggerated to an intolerable degree, but the exaggeration never passes -into pain: the retina may be blinded with excess of light, and the ear -stunned with sound--the optic nerve may be pricked or cut--but no pain -results. The systemic sensations also are habitually painless, though -they pass into pain in abnormal states. Clearly, then, Pain is not the -necessary consequence of Sensibility; and this is true not only of -certain sensitive parts, but of all; as is proved in the well-known -facts of Analgesia, in which complete insensibility of the skin as -regards Pain co-exists with vivid sensibility as regards Touch and -Temperature. Hence the majority of physiologists refuse to acknowledge -that the struggles and cries of an animal, after removal of the brain, -are evidences of pain; maintaining that they are “simply reflex -actions.” This is probable; the more so as we know the struggles and -cries which tickling will produce, yet no pain accompanies tickling. -But if the struggles and cries are not evidence of pain, they are -surely evidence of Sensibility. - -76. Now for the term Pain in the foregoing paragraph substitute the -term Consciousness, and you will perhaps allow that while it may be -justifiable to interpret the actions of a brainless animal as due to a -mechanism which is unaccompanied by the _specially conditioned forms_ -of Sensibility classed under Consciousness--just as it is unaccompanied -by the specially conditioned forms of Perception and Emotion--there -is no justification for assuming the mechanism not to have been a -_sensitive_ mechanism. The wingless bird cannot manifest any Of the -phenomena of flight; but we do not therefore deny that its _other_ -movements depend on Contractility. - -77. Difficult as it must be to keep the physiological question apart -from the psychological when treating of Sensibility, we shall never -succeed in our analysis unless the two questions are separately -treated. The physiologist considers organisms and their actions -from their objective side, and tries to detect the mechanism of the -observed phenomena. These he has to interpret in terms of Matter and -Motion. The psychologist interprets them in terms of Feeling. The -actions which we _see_ in others we cannot _feel_, except as visual -sensations; the changes which we feel in ourselves we cannot see in -others, except as bodily movements. The reaction of a sensory organ is -by the physiologist called a sensation,--borrowing the term from the -psychologist; he explains it as due to the stimulus which changes the -molecular condition of the organ; and this changed condition, besides -being seen to be followed by a muscular movement, is _inferred_ to -be accompanied by a change of Feeling. The psychologist has direct -knowledge only of the change of Feeling which follows on some other -change; he infers that it is originated by the action of some external -cause, and infers that a neural process precedes, or accompanies, the -feeling. Obviously there are two distinct questions here, involving -distinct methods. The physiologist is compelled to complete his -objective observations by subjective suggestions; compelled to add -Feeling to the terms of Matter and Motion, in spite of the radical -diversity of their aspects. The psychologist also is compelled to -complete his subjective observations by objective interpretations, -linking the internal changes to the external changes. A complete theory -must harmonize the two procedures. - -78. In a subsequent Problem we shall have to examine the nature of -Sensation in its psychological aspect; here we have first to describe -its physiological aspect. To the psychologist, a sensation is simply a -fact of Consciousness; he has nothing whatever to do with the neural -process, which the physiologist considers to be the physical basis -of this fact; and he therefore regards the physiologists as talking -nonsense when they talk of “unconscious sensations,” the phrase being -to him equivalent to “unfelt feelings,” or “invisible light.” It is -quite otherwise with the physiologist, who viewing a sensation solely -as a neural process, the reaction of a sensory organ, can lawfully -speak of unconscious sensations, as the physicist can speak of -invisible rays of light,--meaning those rays which are of a different -order of undulation from the visible rays, and which may become visible -when the susceptibility of the retina is exalted. He knows that there -are different modes, and different complexities of neural process; to -one class he assigns consciousness, to the other unconsciousness. If he -would be severely precise, he would never speak of sensation at all, -but only of sensory reaction. But such precision would be pedantic and -idle. He wants the connotations of the term sensation, and therefore -uses it. - -79. The functional activity of a gland is stimulated by a neural -process reflected from a centre; by a similar process a muscle is -called into action. No one supposes that the neural process is, in -the one case secretory, in the other motory: in both it is the same -process in the nerve; and our investigation of it would be greatly -hampered if we did not disengage it from all the suggestions hovering -around the ideas of secretion and muscular action. In like manner -we must disengage the neural process of a sensory reaction from all -the suggestions hovering around the idea of Consciousness, when that -term designates a complex of many reactions. In Problem III. we shall -enter more particularly into the distinction between Sensibility and -Consciousness; for the present it must suffice to say that great -ambiguity exists in the current usage of these terms. Sometimes -Consciousness stands as the equivalent of Sensibility; sometimes as a -particular _mode_ of Sensibility known as Reflection, Attention, and -Thought. The former meaning is an extension of the term similar to -that given to the word Rose, which originally meaning Red came to be -restricted to a particular red flower; and after other flowers of the -same kind were discovered which had yellow and white petals, instead -of red, the term rose still adhered even to these. “Yellow Rose” is -therefore as great a verbal solecism as unconscious sensation. We have -separated the redness from the rose, and can then say that the color -is one thing, the flower another. By a similar process of abstraction -we separate Consciousness from Sensation, and we can then say that -there are sensations without consciousness. In consequence of this, -psychologists often maintain that to have a sensation and be conscious -of it are two different states. We are said to hear a sound, and yet -not to be conscious of hearing it. The sound excites a movement, but -it does not excite our consciousness. Now although it is true that -there are roses which are not red, it is not true that there are -roses which have no color at all. Although it is true that there are -sensations which are not of the particular mode of Sensibility which -psychologists specially designate as Consciousness, it is not true -that there are sensations which are not modes of Sensibility. - -80. And what is Sensibility which, on its subjective side, is -Sentience? In one sense it may be answered that we do not know. In -another sense it is that which we know most clearly and positively: -Sentience forms the substance of all knowledge. Being the ultimate of -knowledge, every effort must be vain which attempts to explain it by -reduction to simpler elements. The human mind, impatient of ultimates, -is always striving to pierce beyond the fundamental mysteries; and this -impatience leads to the attempts so often made to explain Sensibility -by reducing it to terms of Matter and Motion. But inasmuch as a clear -analysis of Matter and Motion displays that our knowledge of these is -simply a knowledge of modes of Feeling, the reduction of Sentience or -Sensibility to Matter and Motion is simply the reduction of Sensibility -to some of its modes. This point gained, a clear conception of the -advantages of introducing the ideas of Matter and Motion will result. -It will then be the familiar and indispensable method of explaining -the little known by the better known. The objective aspect of things -is commonly represented in the visible and palpable; because what we -can see we can also generally touch, and what we can touch we can -taste and smell; but we cannot touch an odor nor a sound; we cannot -see them; we can only connect the odorous and sonorous objects with -visible or palpable conditions. Everywhere we find sensations referred -to visible or palpable causes; and hence the desire to find this -objective basis for every change in Sensibility. The sensation, or -state of consciousness, is the ultimate fact; we can only _explain_ it -by describing its objective conditions. - -81. Thus much on the philosophical side. Returning to our physiological -point, we must say that a sensation is, objectively, the reaction -of a sensory organ, or organism; subjectively, a change of feeling. -Objectively it is a phenomenon of movement, but distinguishable -from other phenomena by the speciality of its conditions. It is a -vital phenomenon, not a purely mechanical phenomenon. Although the -molecular movement conforms, of course, to mechanical principles, and -may be viewed abstractly as a purely mechanical result, yet, because -it takes place under conditions never found in machines, it has -characters which markedly separate it from the movements of machines. -Among these differential characters may be cited that of _selective -adaptation_,[112] which is most conspicuous in volition. - -82. In the early stages of animal evolution there is no differentiation -into muscle and nerve. The whole organism is equally sensitive (or -irritable) in every part. Muscles appear, and then they are the most -sensitive parts. Nerves appear, and the seat of Sensibility has -been transferred to them; not that the muscles have lost theirs, but -their irritability is now represented by their dominant character of -Contractility, and the nerves have taken on the special office of -Sensibility. That is to say, while both muscle and nerve form integral -elements of the sensitive reaction, the process itself is analytically -conceived as a combination of two distinct properties, resident in two -distinct tissues. - -83. Carrying further this analytical artifice, I propose to distinguish -the central organs as the seat of Sensibility, confining Neurility to -the peripheral nerves. In physiological reality both systems, central -and peripheral, are one; the separation is artificial. Strictly -speaking, therefore, Neurility--or nerve-action--is the general -property of nerve-tissue, central and peripheral. But since Neurility -may be manifested by nerves apart from centres, whereas Sensibility -demands the co-operation of both, and since we have often to consider -the central process in itself, without attending to the process in the -nerves, it is well to have two characteristic terms. I shall therefore -always use the term Sensibility for the reactions of the nervous -centres,--Sentience being its psychological equivalent; although the -reader will understand that in point of fact there is no break, nor -transformation, as the wave of change passes from sensory nerve to -centre, and from centre to motor nerve: there is one continuous process -of change. But just as we analytically distinguish the sensory from -the motor element of this indissoluble process, so we may distinguish -the ingoing and outgoing stages from the combining stage. Sensibility, -then, represents the property of _combining_ and grouping stimulations. - -84. Fully aware of the misleading connotations of the term, and of the -difficulty which will be felt in disengaging it from these, especially -in reference to Consciousness, I have long hesitated before adopting -it. But the advantages greatly outweigh the disadvantages. Sensibility -has long been admitted to express the peculiar modes of reaction in -plants and animals low down in the scale. No one hesitates to speak of -a sensitive plant, or a sensitive surface. The tentacles of a polype -are said to be sensitive; though probably no one thereby means that -the polype has what psychologists mean by Consciousness. By employing -the general term Sensibility to designate the whole range of reactions -peculiar to the nerve-centres, when these special organs exist, it -will be possible to interpret all the physiological and psychological -phenomena observed in animals and men on one uniform method. The -observed variations will then be referable to varieties in organisms. - -85. Suppose, for illustration, an organism like the human except -that it is wholly deficient in Sight, Hearing, Taste, and Smell. It -has no sense but Touch--or the general reaction under contact with -external objects. It will move on being stimulated, and will combine -its movements differently under different stimulations. It will feel, -and logically combine its feelings. But its mass of feeling will be -made of far simpler elements than ours; its combinations fewer; and -the contents of its Consciousness so very different from ours that -we are unable to conceive what it will be like; we can only be sure -that it will _not_ be very like our own. This truncated Organism will -have its Sensibility; and we must assign this property to its central -nerve-tissue, as we assign our own. If now we descend lower, and -suppose an organism with no centres whatever, but which nevertheless -displays evidence of Sensibility--feelings and combinations of -movements--we must then conclude that the property specialized in -a particular tissue of the highly differentiated organism is here -diffused throughout. - -It is obvious that the sensations or feelings of these supposed -organisms will have a common character with the feelings of more highly -differentiated organisms, although the modes of manifestation are so -various. If we recognize a common character in muscular movements so -various as the rhythmic pulsation of the heart, the larger rhythm of -inspiration and expiration, the restless movements of the eye and -tongue, the complexities of manipulation, the consensus of movements in -flying, swimming, walking, speaking, singing, etc., so may we recognize -a common character in all the varieties of sensation. The special -character of a movement depends on the moving organ. The special -character of a sensation depends on the sensory organ. Contractility -is the abstract term which expresses all possible varieties of -contraction. Sensibility--or Sentience--is the abstract term which -expresses all possible varieties of sensation. - -86. The view here propounded may find a more ready acceptance when its -application to all physiological questions has been tested, and it is -seen to give coherence to many scattered and hitherto irreconcilable -facts. Meanwhile let a glance be taken at the inconsistencies of the -current doctrine. That doctrine declares one half of the gray substance -of the spinal cord to be capable only of _receiving_ a sensitive -stimulation, the other half capable only of _originating_ a motor -stimulation. We might with equal propriety declare that one half of a -muscle is capable only of receiving a contractile stimulation, and the -other half of contracting. The ingoing nerve, passing from the surface -to the posterior part of the spinal cord, excites the activity of the -gray substance into which it penetrates; with the anterior part of -this gray substance an outgoing nerve is connected, and through it -the excitation is propagated to a muscle: contraction results. Such -are the facts. In our analysis we separate the sensory from the motor -aspect, and we then imagine that this ideal distinction represents a -real separation. We suppose a phenomenon of Sensibility independent of -a phenomenon of Contractility--suppose the one to be “transformed” into -the other--and we then marvel “how during this passage the excitation -changes its nature.”[113] - -87. Before exerting ingenuity in explaining a fact, it is always well -to make sure that the fact itself is correctly stated. _Does_ the -neural excitation change its nature in passing from the posterior to -the anterior gray substance? I can see no evidence of it. Indeed the -statement seems to confound a neural process with a muscular process. -The neural process is one continuous excitation along the whole line -of ingoing nerve, centre, and outgoing nerve, which nowhere ceases -or changes into another process, until the excitation of the muscle -introduces a new factor. So long as the excitation keeps within the -nerve-tissue, it is one and the same process of change; its issue -in a contraction, a secretion, or a change in the conditions of -consciousness, depends on the organs it stimulates. - -88. I have already called attention to the artificial nature of all our -distinctions, and the necessity of such artifices. They are products of -that - - “Secondary power - By which we multiply distinctions, then - Deem that our puny boundaries are things - That we perceive, and not that we have made.”[114] - -The distinction of Central and Peripheral systems is not simply -anatomical, it has a physiological justification in this, that the -Central System is the organ of connection. Any one part of it directly -excited by an ingoing nerve propagates that excitation throughout -the whole central mass, and thus affects every part of the organism. -Therefore we place Sensibility in it. - -But this general Property subserves various Functions, according as the -Central System is variously related to different organs. This fact has -given rise to the idea that different portions of the cerebro-spinal -axis have different properties--which is a serious error. What is -certain is that the Cerebrum must have a different function from that -of the Thalami, and the Cerebellum one different from the Medulla -Oblongata; while that of the Medulla Spinalis is different from all. -Precisely on the same grounds that a muscle-nerve has a different -office from a skin-nerve, or the pneumogastric from the acoustic. -But all nerves have one Neurility in common; all centres have one -Sensibility in common. - - - - -CHAPTER V. - -ACTION WITHOUT NERVE-CENTRES. - - -89. It has long been one of the unquestioned postulates of Physiology -that no nerve-action can take place without the intervention of a -centre; and as a corollary, that all movement has its impulse--reflex -or volitional--from a centre.[115] The postulate rests on the -assumption that nerves derive their “force” from their centre. This -assumption we have seen to be erroneous. Yet, in consequence of its -acceptance, experimenters have failed to notice the many examples of -nerve-action independent of centres. Indeed, except Schiff, Goltz, and -Engelmann, I can name no one who has ventured to suggest that movements -may be excited through nerves without the co-operation of centres;[116] -nor have even they explicitly formulated the conclusion to which their -observations point. - -It is true that the majority of muscular movements are determined by a -reflex from centres; and that any break in the triple process of the -ingoing nerve, centre, and outgoing nerve, prevents such movements. -It is true that the more conspicuous and harmoniously co-ordinated -phenomena belong to this class. But it is also demonstrable that many -nerve-actions _may_, and some _do_, take place by direct stimulation -of the nerve, or direct stimulation of the muscle, without the -intervention of a centre, without even the intervention of a ganglion. -This must obviously be the case in animals which have no centres; and -even in some which have well-developed nervous centres, there is every -reason to believe that these centres often act rather in the way of -co-ordinating than of directly stimulating actions. - -90. I was first led to doubt the reigning doctrine by a surprising -observation (frequently repeated) after I had removed the whole nervous -centres from a garden snail (_Helix pomatia_). The muscular mass called -“the foot” was thrown into slow but energetic contraction whenever the -skin was pricked with the point of a scalpel, or touched with acid; -nay, even when a glass rod dipped in the acid was brought close to, -without absolutely touching, the skin, the foot curled up, and then -slowly relaxed. The same effect was produced on the “mantle”--where -there was of course no centre. But direct irritation of the muscles -under the skin produced no such contraction; only through the skin -could the stimulation take effect. In one case I observed this strange -phenomenon five hours after removal of the centres. It was a great -puzzle. At first I concluded that there must be minute ganglia in -the skin, serving as reflex-centres. I searched for them in vain; -and although a longer search on better methods might _possibly_ have -detected ganglionic cells, I soon relinquished the search, because I -had other grounds for believing that even the presence of abundant -ganglia would not suffice, until some better proof were afforded that -such ganglia were reflex-centres. - -91. That direct stimulation of the nerve suffices to move the muscles, -is familiar to all experimenters. There is no centre, or ganglion, -in the amputated leg of the frog, which nevertheless contracts -whenever the sciatic nerve is stimulated. And after the nerve has been -exhausted, and refuses to respond to any stimulus, the muscle itself -may be directly stimulated. Inasmuch as the movement depends on the -contractility of the muscles, a stimulation through centre, through -motor-nerve, or through muscle, will be followed by contraction. Let -us take a clear case of reflex action. The pupil of the eye contracts -when a beam of light falls on it, and dilates when the beam is shut -off. The path of the neural process is normally this: the light -stimulates the optic nerve, which in turn stimulates the corpora -quadrigemina; (here the nerves which move the eye are experimentally -proved to be stimulated;) and it is through these that the pupil is -caused to contract. If the optic nerve be divided, no such reflex takes -place--proving that the contraction does not, at least normally, come -from the ciliary ganglion. - -But now it is matter of observation that the pupil will contract and -dilate under the stimuli of light and darkness, when there is no such -reflex pathway open. Removal of the eye from the body obliterates -this path, cuts the eye off from all connection with the centre. -Brown Séquard removed both eyes from a frog, placed one in a dark -box, and left the other exposed to the light: the pupil of the former -was found dilated, that of the latter contracted. On reversing the -experiment, and placing the eye with contracted pupil in the dark -box, he found it there dilate, while the dilated pupil exposed to -the light contracted.[117] In frogs with very irritable tissues, I -have found not only the pupil contracting, after the whole cranial -cavity has been emptied, but even the eyelid close, on irritating -the conjunctiva[118]--yet this is one of the typical reflex actions! -I am disposed to think that even the action of swallowing may be -faintly excited by stimulation of the pharynx of a brainless frog; but -I have not observations sufficiently precise to enable me to speak -confidently. Goltz has, however, shown that after removal of brain -and spinal cord and heart, there is spontaneous and active movement -in œsophagus and stomach.[119] This will no doubt be referred to the -agency of the ganglionic plexus; but similar movements have been -observed by Engelmann in the ureter, and in isolated fragments of the -ureter in which not a ganglionic cell was present.[120] - -92. That nerves are stimulated by internal changes has long been -recognized with reference to “subjective sensations.” The divided -nerve, in that portion which remains connected with the centre, will -at times cause great pain. Obscure organic conditions, changes of -temperature, states of the blood, excite the nerves, and the patient -feels as if the surface of the amputated limb were irritated. It is -all very well to call these “subjective sensations”; that does not -alter the fact of the nerve being called into activity by other than -the normal stimuli from the surface; in like manner muscular movements -(which are not to be explained as “subjective movements”) will be -excited by organic stimuli when motor-nerves are separated from their -centres. In each case it has sufficed that the nerve should be excited; -and when excited, no matter by what means, the effect is always similar. - -93. Here are a few facts. Stimulation of the nerves which send -filaments to the chromatophores of the skin in reptiles causes the skin -to become paler, and even colorless: the color-specks disappear under -this contractile stimulus. This being known, Goltz deprived a frog of -brain, spinal cord, and heart, thus eliminating all possible influence -from them, slit up the skin of the back, and displayed the nerves which -pass from each side of the spine to the skin; these nerves he then -divided on the right side, and observed the skin on this side slowly -become paler and paler, till finally it was as yellow as wax; the left -side, having its nerves intact, retained its color. Two conclusions -seemed to him warranted by this experiment: First, that even in the -dead frog the nerves separated from their centre were still active; -secondly, that the irritation of the nerves resulting from their -section was the cause of the color-specks disappearing. This second -conclusion was strengthened when he found that the irritation was -increased when he cut the nerves bit by bit. - -It is not at present, I believe, clearly made out that the color-specks -of the Cephalopoda are in direct connection with nerves; but it is -tolerably certain that they are in some way under the influence of -nervous stimulation, directly or indirectly. D’Orbigny, indeed, goes -so far as to say they are dependent on the will of the animal.[121] -This seems very lax language; but restricting ourselves to the fact -of nervous influence, the experiments of Goltz receive further -illustration in an observation I have elsewhere recorded.[122] I found -that a strip of skin taken from the dead body of a calamary (_Loligo_) -showed the color-specks expanding and contracting with vigor. - -94. The heart is well known to beat after death, if death be not the -result of a gradual decay. Sometimes, indeed, its muscular irritability -is so active that the heart will beat for hours. E. Rousseau -observed it beating in a woman twenty-seven hours after she had been -guillotined.[123] Not only will it beat after death, but in many -animals even after removal from the body: the heart of a young puppy, -or kitten, will beat for three or four hours after its removal; that -of a full-grown dog, or cat, not one hour; whereas the beating of that -of a tortoise, or a frog, will, under proper precautions, be preserved -for days--and even after it has stopped, it may be stimulated to fresh -pulsations. - -Physiologists explain this spontaneous movement of the heart as due to -the ganglia in its substance. This explanation, which is founded on -what I cannot but regard as a purely imaginary view of the functions -of ganglionic cells, must stand or fall with that hypothesis. A long -and arduous investigation has led me to doubt whether in _any_ case -the heart’s movements are primarily due to its ganglia; at all events, -the same spontaneous movements are observed in the hearts of molluscs -and crustaceans, which are without even a trace of ganglia; and in the -hearts of mammalian embryos long before ganglia or nerve-fibres make -their appearance. Not less certain is it that movements of contraction -and dilatation are produced in the blood-vessels independently of all -central influence. This has been decisively proved by the Italian -physiologist, Mosso, when experimenting on an organ isolated from the -organism; and although the vessels have their nerve cells and fibres, -he justly doubts whether it is to these that the stimulation is due, -because the phenomena are observed after the nervous vitality has -disappeared. Goltz severed all the tissues in the leg of a rabbit, -so that the only connection of the leg with the rest of the body was -through the crural vein and artery, which kept up the circulation; yet -although the nerves of the skin were thus separated from their centre, -so that no sensation could be produced by stimulating the skin of the -leg, consequently no reflex from the centre on the vessels, Goltz found -that a marked reddening of the skin from congestion of the capillaries -followed the application of mustard to the skin. Physiologists who -believe that the constriction and dilatation of blood-vessels are due -to the action of the ganglionic cells distributed over the walls of the -vessels will explain Goltz’s observation as a case of reflex action; -but those who agree with me that such an hypothesis respecting the part -played by the cells is untenable, will class the observation among -other cases of direct stimulation. - -95. But passing from these perhaps questionable cases, let us glance -at other cases. The mobile iris of the bird displays movements after -the nerves have been divided. Even the voluntary striped muscles are -not altogether motionless. Schiff divided the hypoglossus on one side, -and found, of course, the tongue paralyzed on that side; but he also -found that on the third day after the operation some of the muscles of -that side were quivering: the agitation spread to others, till by the -end of the fourth day all the fibres were _rhythmically_ contracting. -From this time onwards, the contractions were incessant; though they -were never able to move the tongue, because the fibres did not contract -simultaneously. - -Schiff also observed that the hairs over the eyes and the “whiskers” of -cats, rabbits, and guinea pigs were for months after section of their -nerves in incessant rhythmical vibration. This was observed when the -animals were asleep as when awake. Valentin records the spontaneous -movements in the diaphragm of animals just killed; and this even after -section of the phrenic nerve. The same movements may be seen in the -operculum of fishes. Henle observed the spontaneous contractions of the -intercostal muscles; which Schiff confirms, adding that the movements -observed by him in cats and birds were not simply contractions of some -fibres, but of all the muscles, so that three or four excised ribs -rhythmically contracted and expanded. - -I have performed a great many experiments with a view of determining -this question, but the phenomena were so variable that I refrain -from adducing any,[124] and merely state the general result as one -in harmony with the foregoing examples. The great variability of the -phenomena depends upon the variable conditions of muscular irritability -and anatomical relations. When the heart of one woman is found beating -twenty-seven hours after death, while in most men and women it ceases -after a few minutes, we must be prepared to find different, and even -contradictory phenomena under varying unknown conditions. There -is, however, a general agreement among experimenters that muscular -irritability increases after separation from nerve-centres, and then -quickly decreases again. - -96. Although the stimulation of muscles usually comes _through_ a -nerve-centre, yet since the muscles do not derive their Contractility -from nerve-centres any stimulation will suffice. Now since we have -abundant proof that sensory nerves are stimulated by certain organic -changes, by poisons in the blood, excess of carbonic acid, etc., we -are justified in concluding that motor nerves will be stimulated in -like manner, and thus muscular movement be produced occasionally -without the intervention of a centre. Pressure on a motor nerve, or the -irritation which results from inflammation, will determine contraction, -or secretion directly. Recently, Erb and Westphal have disclosed -the fact that the leg will be suddenly jerked out if the patella be -gently tapped; and they prove this not to be a reflex action, because -it follows with the same certainty after the skin has been made -insensible.[125] - -There are doubtless many other phenomena which, though commonly -assigned to reflex stimulation, are really due to direct stimulation. -Research might profitably be turned towards the elucidation of this -point. Since there is demonstrable evidence that a nerve when no -longer in connection with its centre, or with ganglionic cells, may -be excited by electricity, pressure, thermal and chemical stimuli, we -must conclude that even when it is in connection with its centre, any -local irritation from pressure, changes in the circulation, etc., will -also excite it. But as such local excitations will have only local and -isolated effects, they will rarely be conspicuous. - - - - -CHAPTER VI. - -WHAT IS TAUGHT BY EMBRYOLOGY? - - -97. Subject to the qualification expressed in the last chapter, -stimulation of muscles and glands involves a neural process in ingoing -nerve, centre, and outgoing nerve. These are the triple elements of the -“nervous arc.” If muscles were directly exposed to external influences, -they would be stimulated without the intervention of a centre; but as a -matter of fact they never are thus exposed, being always protected by -the skin. Did the skin-nerves pass directly to the muscles underneath, -they would move those muscles, without the intervention of a centre; -but as a matter of fact the skin-nerves pass directly to a centre, so -that it is only _through_ a centre that they can act upon the muscles. -Were muscles and glands directly connected with sensitive surfaces, -their activity would indeed be awakened by direct stimulation; but -unless the muscles were so connected the one with the other, by -anastomosis of fibres or continuity of tissue, that the movement of -one was the movement of all, there would need to be some other channel -by which their separate energies should be combined and co-ordinated. -In the higher organisms anastomosis of muscles is rare, and the -combination is effected by means of the nerves. - -98. Although analysis distinguishes the two elements of the -neuro-muscular system, assigning separate properties to the separate -tissues, an interpretation of the phenomena demands a synthesis, so -that a movement is to be conceived as always involving Sensibility, -and a sensation as always involving Motility.[126] In like manner, -although analysis distinguishes the various organs of the body, -assigning separate functions to each, our interpretation demands their -synthesis into an organism; and we have thus to explain how the _whole_ -has different _parts_, and how these different parts are brought into -unity. Embryology helps us to complete the fragmentary indications of -Anatomy and Physiology. - -99. Take a newly laid egg, weigh it carefully, then hatch it, and when -the chick emerges, weigh both chick and shell: you will find that -there has been no increase of weight. The semifluid contents have -become transformed into bones, muscles, nerves, tendons, feathers, -beak, and claws, all without increase of substance. There has been -_differentiation_ of structure, nothing else. Oxygen has passed into -it from without; carbonic acid has passed out of it. The molecular -agitation of heat has been required for the rearrangements of the -substance. Without oxygen there would have been no development. Without -heat there would have been none. Had the shell been varnished, so as to -prevent the due exchange of oxygen and carbonic acid, no chick would -have been evolved. Had only one part of the shell been varnished, the -embryo would have been deformed. - -99_a_. The patient labors of many observers (how patient only those -can conceive who have made such observations!) have detected something -of this wondrous history, and enabled the mind to picture some of the -incessant separations and reunions, chemical and morphological. Each -stage of evolution presents itself as the consequence of a preceding -stage, at once an emergence and a continuance; so that no transposition -of stages is possible; each has its appointed place in the series -(PROBLEM I. § 107). For in truth each stage is a _process_--the sum of -a variety of co-operant conditions. We, looking forward, can foresee in -each what it will become, as we foresee the man in the lineaments of -the infant; but in this prevision we always presuppose that the regular -course of development will proceed unchecked through the regular -succession of special conditions: the infant becomes a man only when -this succession is uninterrupted. Obvious as this seems, it is often -disregarded; and the old metaphysical conception of _potential_ powers -obscures the real significance of Epigenesis. The potentiality of the -cells of the germinal membrane is simply their capability of reaching -successive stages of development under a definite series of co-operant -conditions. We foresee the result, and personify our prevision. But -that result will not take place unless all the precise changes that -are needful serially precede it. A slight pressure in one direction, -insufficient to alter the chemical composition of the tissue, may so -alter its structure as to disturb the regular succession of forms -necessary to the perfect evolution. - -100. The egg is at first a microscopic cell, the nucleus of which -divides and subdivides as it grows. The egg becomes a hollow sphere, -the boundary wall of which is a single layer of cells, all so -similar that to any means of appreciation we now possess they are -indistinguishable. They are all the progeny of the original nucleus -and yolk, or cell contents. Very soon, however, they begin to show -distinguishable differences, not perhaps in _kind_, but in _degree_. -The wall of this hollow sphere is rapidly converted into the _germinal -membrane_, out of which the embryo is formed. Kowalewsky (confirmed by -Balfour) has pointed out how in the Amphioxus the hollow sphere first -assumes an oval shape, and then, by an indentation of the under side, -with corresponding curvature of the upper side, presents somewhat -the shape of a bowl. The curvature increases, and the curved ends -approaching each other, the original cavity is reduced to a thin line -separating the upper from the under surface. The cavity of the body is -formed by the curving downwards of this double layer of the germinal -membrane. - -101. This is not precisely the course observable in other vertebrates; -but in all, the germinal membrane, which lies like a watch-glass on the -surface of the yolk, is recognizable as two distinct layers of very -similar cells. What do these represent? They are the starting-points -of the two great systems: Instrumental and Alimental. The one yields -the dermal surface; the other the mucous membrane. Each follows an -independent though analogous career. The yolk furnishes nutrient -material to the germinal membrane, and so passes more or less directly -into the tissues; but unlike the germinal membrane, it is not itself -to any great extent the seat of generation by segmentation. There are -two yolks: the yellow and the white (which must not be confounded -with what is called the _white of egg_); and their disposition may be -seen in the diagram (Fig. 14) copied from Foster and Balfour’s work. -The importance of the white yolk is that it passes insensibly into -a distinct layer of the germinal membrane, between the two primary -layers.[127] Each of the three layers of the germinal membrane has its -specific character assigned to it by embryologists, who, however, are -not all in agreement. Some authorities regard the topmost layer as -the origin of the nervous system, the epidermis, with hair, feathers, -nails, horns, the cornea and lens of the eye, etc. To the middle layer -are assigned the muscular and osseous systems, the sexual organs, etc. -To the innermost layer, the alimentary canal, with liver, pancreas, -gastric and enteric glands. Other authorities are in favor of two -primary layers: one for the nervous, muscular, osseous, and dermal -systems; the other for the viscera and unstriped muscles. Between these -two layers, a third gradually forms, which is specially characterized -as the vascular. - -[Illustration: - - Fig. 14.--_Diagrammatic section of an unincubated hen’s egg._ _bl_, - blastoderm; _w y_, white yolk; _y y_, yellow yolk; _v t_, vitelline - membrane; _x_ and _w_, layers of albumen; _ch l_, chalaza; _a ch_, - air-chamber; _i s m_, internal layer of shell membrane; _s m_, - external layer; _s_, shell. -] - -102. Messrs. Foster and Balfour, avoiding the controverted designations -of serous, vascular, and mucous layers, or of sensorial, motor -germinative, and glandular layers, employ designations which are -independent of theoretic interpretation, and simply describe the -position of the layers, namely, _epiblast_ for the upper, _mesoblast_ -for the middle, and _hypoblast_ for the under layer. From the epiblast -they derive the epidermis and central nervous system (or would even -limit the latter to the central gray matter), together with some -parts of the sense-organs. From the mesoblast, the muscles, nerves -(and probably white matter of the centres), bones, connective tissue, -and blood-vessels. From the hypoblast, the epithelial lining of the -alimentary canal, trachea, bronchial tubes, as well as the liver, -pancreas, etc.[128] Kölliker’s suggestion is much to the same effect, -namely, that the three layers may be viewed as two epithelial layers, -between which subsequently arises a third, the origin of nerves, -muscles, bones, connective tissue, and vessels.[129] - -103. The way in which the history may be epitomized is briefly this: -There are two germinal membranes, respectively representing the -Instrumental and Alimental Systems. Each membrane differentiates, by -different appropriations of the yolk substance, into three primary -layers, _epithelial_, _neural_, and _muscular_. In the epiblast, or -upper membrane, these layers represent: 1°, the future epidermis -with its derivatives--hair, feathers, nails, skin glands, and -chromatophores; 2°, the future nervous tissue; 3°, the future muscular -tissue.[130] (Bone, dermis, connective tissue, and blood-corpuscles are -subsequent formations.) - -The hypoblast, or under membrane, in an inverted order presents a -similar arrangement: 1°, the unstriped muscular tissue of viscera and -vessels; 2°, the nervous tissue of the sympathetic system; 3°, the -epithelial lining of the alimentary canal with its glands. - -Fundamentally alike as these two membranes are, they have specific -differences; but in both we may represent to ourselves the -_embryological unit_ constituted by an epithelial cell, a nerve-cell, -and a muscle-cell. All the other cells and tissues are adjuncts, -necessary, indeed, to the working of the vital mechanism, but -subordinated to the higher organites. - -104. This conception may be compared with that of His in the -division of Archiblast and Parablast assigned by him to the germ -and accessory germ.[131] We can imagine, he says, the whole of the -connective substances removed from the organism, and thus leave behind -a scaffolding in which brain and spinal cord would be the axis, -surrounded by muscles, glands, and epithelium, and nerves as connecting -threads. All these parts stand in more or less direct relation to the -nervous system. All are continuous. By a similar abstraction we can -imagine this organic system removed, and leave behind the connected -scaffolding which is formed from the accessory germ; but this latter -has only _mechanical_ significance; the truly vital functions belong to -the other system. - -105. The researches of modern histologists have all converged towards -the conclusion that the organs of Sense are modifications of the -surface, with epithelial cells which on the one side are connected with -terminal hairs, or other elements adapted to the reception of stimuli, -and are connected on the other side through nerve-fibres with the -perceptive centres. It has been shown that nerve-fibres often terminate -in (or among) epithelial cells--sensory fibres at the surface, and -motor-fibres in the glands.[132] Whether the fibres actually penetrate -the substance of the cell, or not, is still disputed. Enough for -our present purpose to understand that there is a _physiological_ -connection between the two, and above all that sensory nerves are -normally stimulated through some epithelial structure or other. - -[Illustration: - - Fig. 15.--_Transverse section of a Blastoderm incubated for - eighteen hours._ The section passes through the medullary groove, - _m e_. A, epiblast. B, mesoblast. C, hypoblast. _m f_, medullary - fold, _c h_, notochord. -] - -106. And this becomes clear when we go back to the earliest indications -of development. Look at Fig. 15, representing a transverse section of -the germinal membranes in a chick after eighteen hours’ incubation. -Here the three layers, A, B, and C, have the aspect of simple cells -very slightly differing among each other. Yet since each layer has -ultimately a progeny which is characteristically distinguishable, we -may speak of each not as what it now is, but what it will become. -Although the most expert embryologist is often unable to distinguish -the embryo of a reptile from that of a bird or of a mammal, at certain -stages of evolution, so closely does the one resemble the other, yet -inasmuch as the embryo of a reptile does not, cannot become a bird, nor -that of a bird a mammal, he is justified in looking forward to what -each will become, and in calling each embryo by its future name. On the -same ground, although we cannot point to any such distinction between -the layers of the blastoderm as I have indicated in the separation -of Instrumental and Alimental Systems, nor specify any characters by -which the cells can be recognized as epithelial, neural, and muscular, -yet a forward glance prefigures these divisions. We know that the -first result of the segmentation of the yolk is the formation of cells -all alike, which in turn grow and subdivide into other cells. We -know that these cells become variously modified both in composition -and structure, and that by such differentiations the simple organism -becomes a complex of organs. - -107. But here it is needful to recall a consideration sometimes -disregarded, especially by those who speak of Differentiation as if -it were some magical Formative Principle, quite independent of the -state of the organized substance which is formed. There is a luminous -conception--first announced by Goethe, and subsequently developed by -Milne Edwards--which regards the organism as increasing in power and -complexity by a physiological “division of labor,” very similar to -that division of employments which characterizes the developed social -organism. But the metaphor has sometimes been misleading; it has been -interpreted as indicating that Function creates Organ (see PROBLEM I. -§ 88), and as if Differentiation itself were something more than the -expression of the changes resulting from the introduction of different -elements. In the Social Organism a “division of labor” presupposes -that laborers with their labor-materials are already existing; the -change is one of rearrangement: instead of each laborer employing -his skill in doing many kinds of work, he restricts it to one kind, -which he is then able to do with less loss of time and power. Thus is -social power multiplied without increase of population, and the social -organism becomes more complex by the differentiation of its organs. It -is not precisely thus with the Animal Organism during its evolution. -Indeed to suppose that the differentiation of the germinal membrane -into special tissues and organs takes place by any such division -of employments, is to fall into the ancient error of assuming the -organism to exist _preformed_ in the ovum. The unequivocal teaching of -Epigenesis is that each part is produced out of the elements furnished -by previous parts; and for every differentiation there must be a -difference in composition, structure, or texture--the first condition -being more important than the second, the second more important than -the third. The word protoplasm has almost as wide a generality as -the word animal, and is often used in forgetfulness of its specific -values: the protoplasm of a nerve-cell is not the _same_ as that of -a blood-cell, a muscle-cell, or a connective-tissue cell, any more -than a bee is a butterfly, or a prawn a lobster. No sooner has the -specific character been acquired, no sooner is one organite formed -by differentiation, than there is an absolute barrier against any -transformation of it into any other kind of organite. The nerve-cell, -muscle-cell, and epithelial cell have a common starting-point, and a -community of substance; but the one can no more be transformed into -the other than a mollusc can be transformed into a crustacean. In the -homogeneous cellular mass which subsequently becomes the “vertebral -plates,” a group of cells is very early differentiated: this is the -rudimentary spinal ganglion, which becomes enveloped in a membrane, -and then pursues a widely different course from that of the other -cells surrounding it, so that “the same cell which was formerly an -element of the vertebral plate now becomes a nerve-cell, while its -neighbors become cartilage-cells.”[133] Indeed all the hypotheses -of transformation of tissues by means of Differentiation are as -unscientific as the hypotheses of the transformation of animals. In the -organism, as in the Cosmos, typical forms once attained are retained. -There probably was a time in the history of the animal series when -masses of protoplasm by appropriating different materials from the -surrounding medium were differentiated into organisms more complex and -more powerful than any which existed before. But it is obvious that -from a common starting-point there could have been no variations in -development without the introduction of new elements of composition: -there might have been many modifications of structure, but unless -these facilitated modifications of composition, there could never have -resulted the striking differences observed in animal organisms.[134] - -108. To return from this digression, we may liken the three primary -layers of the germinal membranes to the scattered and slightly -different masses of protoplasm out of which the animal kingdom -was developed. In this early stage there are no individualized -organites--no nerve-cells or muscle-cells. They are cells ready to -receive modifications both of composition and structure, appropriating -slightly different elements from the yolk, and according to such -appropriation acquiring different properties. And this is necessarily -so, since the different cells have not exactly the same relation to -the yolk, nor are they in exactly the same relation to the incident -forces which determine the molecular changes. The uppermost layer -(epiblast) under such variations develops into epithelium and central -nerve-tissue; the epithelial cell cannot develop into a nerve-cell, the -two organites are markedly unlike, yet both spring from a common root. -Another modification results in the development of muscle-cells from -the inner layer. - -109. Hence we can understand how the surface is sensitive even -in organisms that are without nerve-tissue; and also how even in -the highest organisms there is an intimate blending of epithelial -with neural tissues. The same indication explains the existence -of neuro-muscular cells in the _Hydra_, recorded by Kleinenberg, -and of neuro-muscular fibres in the _Beroë_, by Eimer.[135] In the -simpler organisms the surface is at once protective, sensitive, and -absorbent. It shuts off the animal from the external medium, and thus -individualizes it; at the same time it connects this individual with -the medium; for it is the channel through which the medium acts, both -as food and stimulus. The first morphological change is one whereby -a part of the surface is bent inwards, and forms the lining of the -body’s cavity. Soon there follows such a modification of structure -between the outer and inner surfaces (_ectoderm_ and _endoderm_) that -the one is mainly sensitive and protective, the other mainly protective -and absorbent. The outer surface continues indeed to absorb, but its -part in this function is insignificant compared with that of the inner -surface, which not only absorbs but secretes fluids essential to -assimilation. The inner surface, although sensitive, is subjected to -less various stimulation, and its sensibility is more uniform. - -110. The uppermost of the primary layers we have seen to be epithelial; -and we know that the first lines of the central nervous system are laid -there. A depression called the medullary groove is the first indication -of the future cerebro-spinal axis. Some writers--Kölliker, for -instance--regard this medullary groove as continuous with but different -from the epithelial layer; others maintain that it lies underneath the -epithelium, just as we see it in later stages, when the differentiation -between epithelial and nerve cell has taken place. Since no one -disputes the fact that when the groove becomes a closed canal its -lining is epithelial, one of two conclusions is inevitable: either -the cells of the primary layer develop in the two diverse directions, -epithelial and neural; or else epithelial cells can be developed on -the surface of neural cells and out of them. The latter conclusion is -one which, involving the conception of transformation, would seem to -be put out of court. I think, then, we must admit that the under side -of the primary layer of cells becomes differentiated into nerve-cells; -and this is in accordance with the observations of Messrs. Foster and -Balfour.[136] - -111. While there is this intimate morphological and physiological -blending of epithelial and neural organites, there is an analogous -relation between neural and muscular organites. As the neural layer -lies under the epithelial, the muscular lies under the neural. The -surface stimulation passes to the centre, and is reflected on the -muscles. Embryology thus teaches why a stimulus from the external -medium must be propagated to a nerve-centre before it reaches the -muscles; and why a stimulus on one part of the surface may set all the -organism in movement, by passing through a centre which co-ordinates -all movements. This, of course, only applies to the higher organisms. -In the simpler structures the sensitive surface is directly continuous -with the motor organs. - -It is unnecessary here to pursue this interesting branch of our -subject; nor need we follow the analogous evolution of the second -germinal membrane representing the Alimental System. Our attention -must be given to what is known and inferred respecting the elementary -structure of the nerves and centres, on which mainly the interest of -the psychologist settles, since to him the whole of Physiology is -merged in nerve actions. - - - - -CHAPTER VII. - -THE ELEMENTARY STRUCTURE OF THE NERVOUS SYSTEM. - - -112. The progress of science involves an ever-increasing Analysis. -Investigation is more and more directed towards the separated details -of the phenomena previously studied as events; the observed facts -are resolved into their component factors, complex wholes into their -simpler elements, the organism into organs and tissues. But while the -analytical process is thus indispensable, it is, as I have often to -insist, beset with an attendant danger, namely, that in drawing the -attention away from one group of factors to fix it exclusively on -another, there is a tendency to forget this artifice, and instead of -restoring the factors provisionally left out of account, we attempt a -reconstruction in oblivion of these omitted factors. Hence, instead -of studying the properties of a tissue in all the elements of that -tissue, and the functions of an organ in the anatomical connections -of that organ, a single element of the tissue is made to replace the -whole, and very soon the function of the organ is assigned to this -particular element. The “superstition of the nerve-cell” is a striking -illustration. The cell has usurped the place of the tissue, and has -come to be credited with central functions; so that wherever anatomists -have detected ganglionic cells, physiologists have not hesitated -to place central functions. By such interpretations the heart and -intestines, the glands and blood-vessels, have, erroneously, I think, -their actions assigned to ganglionic cells. - -It is unnecessary to point out the radical misconception which thus -vitiates a great mass of anatomical exposition and physiological -speculation. I only call the reader’s attention to the point at the -outset of the brief survey we have now to make of what is known -respecting the elementary structure of the nervous system. - - -DIFFICULTIES OF THE INVESTIGATION. - -113. So great and manifold are the difficulties of the search, that -although hundreds of patient observers have during the last forty years -been incessantly occupied with the elementary structure of the nervous -system, very little has been finally established. Indeed, we may still -repeat Lotze’s sarcasm, that “microscopic theories have an average of -five years’ duration.” This need not damp our ardor, though it ought to -check a too precipitate confidence. Nothing at the present moment needs -more recognition by the student than that the statements confidently -repeated in text-books and monographs are very often for the most part -only ingenious guesses, in which Observation is to Imagination what -the bread was to the sack in Falstaff’s tavern bill. Medical men and -psychologists ought to be warned against founding theories of disease, -or of mental processes, on such very insecure bases; and physiological -students will do well to remember the large admixture of Hypothesis -which every description of the nervous system now contains. Not that -the potent aid of Hypothesis is to be undervalued; but its limits must -be defined. It may be used as a finger-post, not as a foundation. It -may suggest a direction in which truth may be sought; it cannot take -the place of Observation. It may link together scattered facts; it -must not take the place of a fact. We are glad of corks until we have -learned to swim. We are glad of a suggestion which will for the nonce -fill up the gaps left by observation, and hold the facts intelligibly -together. And both as suggestion and colligation, Hypothesis is -indispensable. Indeed, every _discovery_ is a verified hypothesis; -and there is no discovery until verification has been gained: up -to this point it was a guess, which might have been erroneous--a -torchbearer sent out to look for a missing child in one direction, -while the child was wandering in another; only when he finds the -child can we acknowledge that the torchbearer pursued the right path. -Hypothesis satisfies the intellectual need of an explanation, but we -must be wary lest we accept this fulfilment of a need as equivalent -to an enlargement of knowledge; we must not accept explanation as -demonstration, and suppose that because we can form a mental picture -of the possible stages of an event, therefore this picture represents -the actual stages. Let us be alert, forewarned against the tendency to -seek evidence in support of a conclusion, instead of seeking to unfold -the conclusion step by step from the evidence. To seek for evidence in -support of a _guess_ is very different from seeking it in support of -a _conclusion_; which latter practice is like that of people asking -advice, and only following it when it chimes in with their desires. - -114. Is not the warning needed, when we find anatomists guided by -certain “physiological postulates,” and consequently _seeing_ only -what these postulates demand? For example, there is the postulate of -“isolated conduction,” which is said to require that every nerve-fibre -should pursue its course singly from centre to periphery. Accordingly -the fibres are described as unbranched. Whatever may be the demand -of the postulate, or the felt necessity of the deduction, the fact -is that nerve-fibres do branch off during their course at various -points; nay, it is doubtful whether any lengthy fibre is unbranched. -Other postulates demand what fact plainly denies. It is said to be -“necessary” that every cell should have at least two fibres, and that -sensory and motor nerves should be directly connected through their -respective cells. These things cannot be seen, but they are described -with unhesitating precision. Diagrams are published in which the -sensory fibres pass into the cells of the posterior horn of the spinal -cord, and these cells send off prolongations to the cells of the -anterior horn, and thence the motor fibres pass out to the muscles: -an absolutely impossible arrangement, according to our present data! -Again, the postulate that nerve-force originates in the cells, and that -nerve-functions depend on cells, required that the cells should be most -abundant where the function was most energetic. Of course they were -found most abundant in the required places--no notice whatever being -taken of the facts which directly contradicted the deduction. - -115. Among the serious obstacles to research we must reckon this -tendency to substitute Imaginary Anatomy for Objective Anatomy. I am -conscious of the tendency in myself, as I note it in others; and have -constantly to struggle against it, though not perhaps always aware of -it. Many a time have I had to relinquish plausible explanations, which -would have supported my speculations could I but have believed that -they represented the facts; but being unable to believe this, I had to -remember that hypotheses and explanations appear and disappear--only -the solid fact lives. If there is one lesson emphatically taught by -Philosophy, it is the unwisdom of founding our conclusions on our -desires rather than on the objective facts. - -116. In the following pages a constantly critical attitude is -preserved: this is simply to keep active the sense of how much is still -needed to be done before a satisfactory theory of the nervous system -can be worked out. The objective difficulties are greater than in any -other department of Anatomy. The problem is to form a precise picture -of what the organites are, and of how they are arranged in the living -tissue; yet our present means of investigation involve as a preliminary -that we should _alter_ that arrangement, _removing_ some elements of -the tissue, and _changing_ the state of others, without knowing what -were their precise state and arrangement before the change. Place a -piece of nerve-tissue under the microscope, without having subjected -it to various mechanical and chemical operations, and you can see next -to nothing of its structure. You must tear the parts asunder, and -remove the fat and nerve-sap (plasmode) before you can see anything; -you must coagulate the albumen, and otherwise chemically alter the -substances before a thin section can be made; you must get rid of -the tissues in which it is embedded, without knowing what are the -connections thus destroyed. Living neurine has no greater consistence -than cream, often no greater than oil. How, then, can thin sections -be made until this viscid substance has been hardened by alcohol or -acids? But substances thus acted on lose their constituent water, -which can no more be removed without alteration of their structure, -than it can be removed from certain salts without destruction of their -special properties. Losing their water alone, they become deformed. -They lose much more. Sometimes the loss can be estimated, as in the -case of the hyaline substance investing the nucleus during the process -of segmentation in embryonic cells, which may be seen to disappear when -a weak solution of acid is applied.[137] At other times we are unable -to say what has disappeared. Under different modes of preparation very -different appearances are observed, and anatomists are accordingly at -variance. Yet unless some hardening method be adopted little can be -seen! Stilling, who has given his life to the study, declares that no -results are reliable which are obtained from the unprepared tissue, -because the mechanical isolation of the elements destroys the textural -arrangement.[138] There is one method of hardening, and only one, which -we can be certain does not chemically alter the structure, and that -is the freezing method. The experiments of Dr. Weir Mitchell and Dr. -Richardson prove this, because they prove that the brain of the living -animal may be frozen and frozen again and again, yet recover its vital -activity when thawed. Professor Rutherford has invented an admirable -instrument for making sections of the frozen tissue, of any delicacy -that may be required; but with the thinnest section there will still be -certain difficulties of observation, unless the tissue has undergone a -staining process. Whatever is seen, however, in the frozen tissue is to -be accepted as normal. - -117. Two points must be determined before reliance can be placed on -observations of tissues chemically acted on: First, we must prove that -the forms now visible existed before the preparation--the chemical -action merely unveiling them; secondly, we must estimate the part -played by the elements which have been removed in order to make the -rest visible. We know, for example, that the nucleus often exists in -the cell, though an acid may be needed to make it visible. We also -know that cells which during life are quite free from visible granules -are distinctly granulated after death, even without external chemical -action. Imagine the explanation of a steam-engine to be attempted by -first taking it to pieces, and examining these pieces, with no account -of the coals and steam which had previously been _removed_ in order to -facilitate the examination. When we know the part played by coals and -steam, we may disregard these items of the active machine. So when we -know the part played by water, fat, amorphous substance, and plasmode, -we may describe nerve-tissue without taking these into account. - -118. “You have convinced me,” said Rasselas to Imlac, “that it is -impossible to be a poet.” My readers may, perhaps, infer from this -enumeration of the difficulties that a knowledge of the minute anatomy -of the nervous system is impossible. Not so; but a knowledge of these -difficulties should impress us with the necessity for a vigilant -scepticism, and the search after new methods. If the difficulties -are fairly faced, they may be finally overcome. What we must resign -ourselves to at present is the conviction that our knowledge is not -sufficiently accurate to be employed as a basis of deduction in the -explanation of physiological and psychological processes.[139] - -119. Having said so much, let me add that there are some positive -materials, and these yearly receive additions. The organites are -described with a general agreement as to their composition and -structure--although there is much that is hypothetical even here. -Neurine is known under two aspects: the amorphous and the figured. The -figured, which is the better known, comprises cells of different kinds, -fibres and fibrils. The amorphous, more generally called _Neuroglia_, -or nerve-cement, is less understood, and is indeed by many authorities -excluded altogether from the nerve-tissue proper, and relegated to the -class of connective tissues. - - -THE NERVE-CELL. - -120. It is unfortunate that the term nerve-cell is applied to organites -of very variable structure. Nerve-cell is a generic term of which -the species are many; under it are designated organites in different -stages--as infancy, childhood, and manhood are all included under Man. -Most commonly by nerve-cell is understood the ganglionic corpuscle, -conspicuous in its size and its prolongations, such as it appears in -the great centres, and in ganglia. It also designates smaller different -organites, sometimes called “nuclei” (_Kerne_), sometimes grains -(_Körner_). There would be advantage in designating the earlier stages -as _neuroblasts_, reserving the word _cells_ for the more developed -forms. Such a distinction would facilitate the discussion of whether -nerve-fibres had or had not their origin in cells; because while I, for -one, see very coercive evidence against the accepted notion that all -the fibres have their origin in the processes of ganglionic corpuscles, -I see no reason to doubt that both fibres and corpuscles have their -origin in neuroblasts. Of this anon. - -The cell is a composite organite, the primary element being a -microscopic mass of protoplasm, or what may more conveniently be -termed _neuroplasm_. It appears as finely granulated and striated -or fibrillated substance on a hyaline ground, with water, fat, and -diffused pigment in varying quantities. The cell contains a nucleus, -and nucleolus--sometimes two. Like other animal cells, it sometimes has -a distinct cell-wall, sometimes not. Its size and shape are variable: -sometimes distinctly visible to the naked eye, generally visible only -under the microscope.[140] It is round, oval, pyramidal, club-shaped, -pear-shaped, or many-cornered. It has one, two, three, or many -outgrowths called “processes,” and according to the processes it is -known as unipolar, bipolar, and multipolar. When there are no processes -the cell is called apolar. Some idea of these processes may be formed -if they are likened to the pseudopodia of Amœbæ and Foraminifera. -Compare Fig. 16, a nerve-cell, figured by Gerlach, with Fig. 17, one -highly magnified, in which Max Schultze’s hypothesis is represented. - -[Illustration: - - Fig. 16.--_Nerve-cell from anterior horn of spinal cord (man), - magnified 150 diameters._ _a_, cell process unbranched passing into - or joining an axis cylinder, the other processes are branched; _b_, - pigment. The nucleus and nucleolus are visible. -] - -[Illustration: Fig. 17.--_Nerve-cell from the anterior gray substance -of the spinal cord of a calf magnified 600._ _a_, the axis cylinder; -_b_, the branched process. The neuroplasm is represented as distinctly -fibrillated, with granular substance interspersed. Nucleus and -nucleolus very distinct.] - -121. Such is a general description of the nerve-cell as it is seen in -various places, and under various modes of preparation. How much is -due to preparation we cannot positively say. While we always discover -fibrine in the blood after it is withdrawn from the vessels, we know -that fibrine as such does not exist in the circulating blood. And if -neurine is a semi-liquid substance, we may doubt whether in the living -cell it is fibrillated. Doubts have been thrown even on the normal -existence of the granular substance, which has been attributed to -coagulation. Thus we know that the nucleus of the white blood-corpuscle -appears perfectly homogeneous until subjected to heat, yet at a certain -temperature (86° F.) it assumes the aspect of a fine network. Haeckel -observed the hyaline substance of the neurine in crayfish become -troubled and changed directly any fluid except its own blood-serum -came in contact with it. Leydig noticed the transparent ganglion of a -living Daphnia become darker and darker as the animal died; and I saw -something like this, after prolonged struggles of a Daphnia to escape -from a thread in which its leg was entangled. Charles Robin, indeed, -asserts that the passage from the hyaline to the finely granulated -state is a characteristic of the dying cell.[141] On the other hand, -it should be noted that Max Schultze describes a fibrillated appearance -in cells just removed from the living animal, and placed in serum. - -When, therefore, one observer describes the neuroplasm as being clear -as water, another as finely granular, and a third as fibrillated, -we must conclude that the observations refer to cells, 1°, under -different states of vitalization, or, 2°, under different modes of -preparation. On the first head we note that some nerve-cells are so -perishable that Trinchese declares he could find no cells in the -ganglia of a cuttlefish which had been dead twenty-four hours, although -they were abundant in one recently killed.[142] On the second head -we note that the changes wrought by modes of preparation cannot be -left out of consideration. Auerbach notices that the cells and fibres -apparent in the _plexus myentericus_ after an acid has been applied, -cannot be detected before that application--nothing is visible but a -pale gelatinous network, with here and there knots of a paler hue; -and I remember my surprise on examining the fresh spinal cord of a -duck-embryo, and finding no trace of cells such as I had that very -morning seen in the cord of a chick of earlier date, but which had been -soaked in weak bichromate of potash. Now we have excellent grounds for -believing that in both cases these organites were present, and that it -was the reagent which disclosed their presence in the chick; and so in -other cases we must ask whether the forms which appear under a given -mode of preparation are simply _unmasked_, or are in truth _produced_ -by the reagent? This question we can rarely answer. - -If one of the very large cells be taken from the ganglion of a living -mollusc, and be gently pressed till it bursts, the discharged contents -will be seen to be of a hyaline viscid substance, with fine granules -but no trace of fibres. Yet we must not rashly generalize from this, -and declare that in the vertebrate cells the substance is not also -fibrillated. As a good deal of speculation rests on the assumption of -the fibrillated cell-contents, I have thought it worth while to note -the uncertainty which hovers round it. - -122. Among the uncertainties must be reckoned the question as to the -cell-processes. The existence of apolar and unipolar cells is flatly -denied by many writers, who assert that the appearances are due to the -fragility of the processes. Fragile the processes are, and evidence -of their having been broken off meet us in every preparation; but the -denial of apolar and unipolar cells seems to me only an example of -the tendency to substitute hypothesis for observation (§ 114). The -“postulate” which some seem to regard as a “necessity of thought” that -every nerve-cell shall have at least two fibres, one ingoing, the other -outgoing, is allowed to override the plain evidence.[143] It originated -in the fact first noticed by Wagner and Charles Robin that certain -cells in the spinal ganglia of fishes are bipolar. The fact was rapidly -generalized, in spite of its not being verified in _other_ places; the -generalization was accepted because (by a strange process of reasoning -running counter to all physiological knowledge) it was thought to -furnish an elementary illustration of the reflex process. As the centre -had its ingoing and outgoing nerve, so the cell was held to be a centre -“writ small,” and required its two fibres, No one paused to ask, how a -cell placed in the _track_ of an ingoing nerve could fulfil this office -of a reflex centre; no one supposed that the portion of the sensory -fibre which continued its course, after the interruption of the cell, -was a motor fibre. - -What does Observation teach? It teaches that at first all nerve-cells -are apolar. Even in the cortex of the cerebrum, where (unless we -include the nuclei and grain-like corpuscles under cells) all the cells -are finally multipolar, there is not one which has a process, up to -the seventh or eighth day of incubation (in the chick); from that day, -and onwards, cells with one process appear; later on, cells with two, -and later still, with three. By this time all the apolar cells have -disappeared. They may therefore be regarded as cells in their infancy. -However that may be, we must accept the fact that apolar cells exist; -whether they can co-operate in neural functions, is a question which -must be decided after the mode of operation of cells is placed beyond a -doubt. - -123. If apolar cells are embryonic forms of cells which afterwards -become multipolar, this interpretation will not suffice for the -unipolar cells. They are not only abundant, but are mature forms in -some organs, and in some animals; though in some organs they may truly -be regarded as embryonic. Thus in the human embryo up to the fourth -month all the cells of the spinal cord are said to be unipolar,[144] -later on they become multipolar. But in birds, rabbits, dogs, and -even man, the cells in the spinal ganglia are mainly (if not wholly) -unipolar;[145] nor is there any difficulty in observing the same fact -in the œsophageal ganglia of molluscs (see Fig. 22). - -Such are the observations. They have indeed been forced into agreement -with the bipolar postulate, by the assumption that the single process -branches into two, one afferent, the other efferent.[146] But before -making observation thus pliant to suit hypothesis, it would be well to -look more closely into the evidence for the hypothesis itself. For my -own part, I fail to see the justification of the postulate; whereas -the existence of unipolar cells is an observation which has been amply -verified. - -[Illustration: Fig. 18.--_Supposed union of two nerve-cells and a -fibre._ The processes subdivide into a minute network, in which the -fibre also loses itself.] - -124. Bipolar cells abound; multipolar cells are still more abundant; -and these are the cells found in the gray substance of the neural -axis. Deiters, in his epoch-making work,[147] propounded an hypothetic -_schema_ which has been widely accepted. Finding that the large -cells in the anterior horn of the spinal cord gave off processes -of different kinds, one branched, the other unbranched, he held -that the latter process was the origin of the axis cylinder of -a nerve-fibre, whereas the branched process was protoplasm which -divided and subdivided, and formed the connection between one cell -and another. Gerlach has modified this by supposing that the minute -fibrils of the branching process reunite and form an axis cylinder -(Fig. 18). There is no doubt that some processes terminate in a fine -network; and there is a probability (not more) that the unbranched -process is always continuous with the axis cylinder of a motor nerve, -as we know it sometimes is with that of a dark-bordered fibre in the -white substances. This, though probable, is, however, very far from -having been demonstrated. Once or twice Kölliker, Max Schultze, and -Gerlach have followed this unbranched process as far as the _root_ of -a motor nerve; and they infer that although it could not be traced -further, yet it did really join an axis cylinder there. In support -Of this inference came the observations of Koschennikoff,[148] that -in the cerebrum and cerebellum, processes were twice seen continuous -with dark-bordered nerve-fibres. But the extreme rarity of such -observations amid thousands of cells is itself a ground for hesitation -in accepting a generalized interpretation, the more so since we have -Henle’s observation of the similar entrance of a _branched_ process -into the root.[149] Now it must be remembered that the branched process -is by no anatomist at present regarded as the origin of the axis -cylinder; so that if it can enter the root without being the origin of -a nerve-fibre, we are not entitled to assume that the entrance of the -unbranched process has any other significance (on this head compare -§ 145), especially when we reflect that no trustworthy observer now -professes to have followed a nerve-fibre of the posterior root right -into a multipolar cell. Figures, indeed, have been published which -show this, and much else; but such figures are diagrams, not copies of -what is seen. They belong to Imaginary Anatomy.[150] The relation of -the cell-process to the nerve-fibre will be discussed anon. - -[Illustration: - - Fig. 19.--_Anastomosing nerve-cells_ (after Gratiolet). _a_, body - of the cell; _c_, process of uniting two cells; _d_, branching - process. -] - -125. A word in passing on the contradictory assertions respecting -the anastomosis of nerve-cells. That the gray substance forms a -_continuum_ of some kind is certain from the continuity of propagation -of a stimulus. But it is by no means certain that one cell is directly -united to its neighbor by a cell-process. Eminent authorities assert -that such direct union never takes place; others, that it is a rare -and insignificant fact; others, that it is constant, and “demanded by -physiological postulates.” I will not, in the presence of distinct -affirmations, venture to deny that such appearances as are presented -in Fig. 19 may occasionally be observed; the more so as I have myself -seen perhaps half a dozen somewhat similar cases; but it is the opinion -of Deiters and Kölliker that all such appearances are illusory.[151] -Granting that such connections occur, we cannot grant this to be -the normal mode; especially now the more probable supposition is -that the connection is normally established by means of the delicate -ramifications of the branching processes. - -Imaginary Anatomy has not been content with the cells of the anterior -horn being thus united together, to admit of united action, but has -gone further, and supposed that the cells of the posterior horn, -besides being thus united, send off processes which unite them with -the cells of the anterior horn--and thus a pathway is formed for -the transmission of a sensory impression, and its conversion into a -motor impulse. What will the reader say when informed that not only -has no eye ever beheld such a pathway, but that the first step--the -direct union of the sensory nerve-fibre with a cell in the _posterior_ -horn--is confessedly not visible? - -126. The foregoing criticisms will perhaps disturb the reader who has -been accustomed to theorize on the data given in text-books; but he -may henceforward be more cautious in accepting such data as premises -for deduction, and will look with suspicion on the many theories which -have arisen on so unstable a basis. When we reflect how completely -the modern views of the nervous system, and the physiological, -pathological, and psychological explanations based on these views, -are dominated by the current notions of the nerve-cell, it is of the -last importance that we should fairly face the fact that at present -our knowledge even of the structure of the nerve-cell is extremely -imperfect; and our knowledge of the part it plays--its anatomical -relations and its functional relations--is little more than guesswork! - - -THE NERVES. - -127. We now pass to the second order of organites; and here our -exposition will be less troubled by hesitations, for although there is -still much to be learned about the structure and connections of the -nerve-fibres, there is also a solid foundation of accurate knowledge. - -[Illustration: - - Fig. 20.--_a_, axis cylinder formed by the fibrils of the cell - contents, and at _a’_ assuming the medullary sheath; _b_, naked - axis cylinder from spinal cord. -] - -A nerve is a bundle of fibres within a membranous envelope supplied -with blood-vessels. Each fibre has also its separate sheath, having -annular constrictions at various intervals. It is more correctly named -by many French anatomists a nerve-_tube_ rather than a nerve-_fibre_; -but if we continue to use the term _fibre_, we must reserve it for -those organites which have a membranous sheath, and thereby distinguish -it from the more delicate _fibril_ which has none. - -The nerve tube or fibre is thus constituted: within the sheath -lies a central band of neuroplasm identical with the neuroplasm of -nerve-cells, and known as the _axis cylinder_; surrounding this band -is an envelope of whitish substance, variously styled _myeline_, -_medullary sheath_, and _white substance of Schwann_: it is closely -similar to the chief constituent of the yolk of egg, and to its -presence is due the whitish color of the fibres, which in its absence -are grayish. The axis cylinder must be understood as the primary and -essential element, because not only are there nerve-fibrils destitute -both of sheath and myeline yet fulfilling the office of Neurility, -but at their terminations, both in centres and in muscles, the -nerve-fibres always lose sheath and myeline, to preserve only the -neuroplasmic threads of which the axis cylinder is said to be composed. -In the lowest fishes, in the invertebrates, and in the so-called -sympathetic fibres of vertebrates, there is either no myeline, or it is -not separated from the neuroplasm. - -128. Nerve-fibres are of two kinds--1°. The _dark-bordered_ or -_medullary_ fibres, which have both sheath and myeline, as in the -peripheral system; or only myeline, without the sheath, as in the -central system. 2°. The _non-medullary_ fibres, which have the sheath, -without appreciable myeline--such are the fibres of the olfactory, and -the pale fibres of the sympathetic. - -Nerve-fibrils are neuroplasmic threads of extreme delicacy, visible -only under high magnifying powers (700–800), which abound in the -centres, where they form networks. The fibrils also form the -terminations of the fibres. Many fibrils are supposed to be condensed -in one axis cylinder. This is represented by Max Schultze in Figs. 17 -and 20. - -129. As may readily be imagined, the semi-liquid nature of the -neuroplasm throws almost insuperable difficulties in the way of -accurately determining whether the axis cylinder in the living nerve -is fibrillated or not; whether, indeed, any of the aspects it presents -in our preparations are normal. Authorities are not even agreed as -to whether it is a pre-existent solid band of homogeneous substance, -or a bundle of primitive fibrils, or a product of coagulation.[152] -Rudanowsky’s observations on frozen nerves convinced him that the -cylinder is a tubule with liquid contents.[153] My own investigations -of the nerves of insects and molluscs incline me to the view of Dr. -Schmidt of New Orleans, namely, that the cylinder axis consists -of minute granules arranged in rows and united by a homogeneous -interfibrillar substance, thus forming a bundle of granular fibrils -enclosed in a delicate sheath[154]--in other words, a streak of -neuroplasm which has a fibrillar disposition of its granules. We ought -to expect great varieties in such streaks of neuroplasm; and it is -quite conceivable that in the Rays and the Torpedo there are axis -cylinders which are single fibrils, and others which are bundles, with -finely granulated interfibrillar substance.[155] - -The fibres often present a varicose aspect, as represented in Fig. 21. -It is, however, so rarely observed in the fresh tissue, that many -writers regard it (as well as the double contour) as the product of -preparation.[156] It is, indeed, always visible after the application -of water. - -We need say no more at present respecting the structure of -nerve-fibres, except to point out that we have here an organite not -less complex than the cell. - -[Illustration: - - Fig. 21.--_Nerve-fibres from the white substance of the cerebrum._ - _a_, _a_, _a_, the medullar contents pressed out of the tube as - irregular drops. -] - - -THE NEUROGLIA. - -130. Besides cells and fibres, there is the _amorphous substance_, -which constitutes a great part of the central tissue, and also enters -largely into the peripheral tissue. It consists of finely granular -substance, and a network of excessively delicate fibrils, with nuclei -interspersed. Its character is at present _sub judice_. Some writers -hold it to be nervous, the majority hold it to be simply one of -the many forms of connective tissue: hence its name neuroglia, or -nerve-cement. - -In the convolutions of the frozen brain Walther finds the cells and -fibres imbedded in a structureless semi-fluid substance wholly free -from granules; the granules only appear there when cells have been -crushed. It is to this substance he attributes the fluctuation of -the living brain under the touch, like that of a mature abscess; the -solidity which is felt after death is due to the coagulation of this -substance. Unhappily we have no means of determining whether the -network visible under other modes of investigation is present, although -invisible, in this substance. The neuroglia, as it appears in hardened -tissues, must therefore be described with this doubt in our minds. - -If we examine a bit of central gray substance where the cells and -fibres are sparse, we see, under a low power, a network of fibrils -in the meshes of which lie nerve-cells. Under very high powers we -see outside these cells another network of excessively fine fibrils -embedded in a granular ground substance, having somewhat the aspect of -hoar-frost, according to Boll. It is supposed that the first network -is formed by the ultimate ramifications of the nerve-cell processes, -and that the second is formed by ramifications of the processes of -_connective_ cells. In this granular, gelatinous, fibrillar substance -nuclei appear, together with small multipolar cells not distinguishable -from nerve-cells except in being so much smaller. These nuclei are -more abundant in the tissue of young animals, and more abundant in the -cerebellum than in the cerebrum. The granular aspect predominates the -fresher the specimen, though there is always a network of fibrils; so -that some regard the granules as the result of a resolution of the -fibrils, others regard the fibrils as the linear crystallization (so to -speak) of the granules.[157] - -131. Such is the aspect of the neuroglia. I dare not venture to -formulate an opinion on the histological question whether this -amorphous substance is neural, or partly neural and partly connective -(a substance which is potentially both, according to Deiters and -Henle), or wholly connective. The question is not at present to be -answered decisively, because what is known as connective tissue has -also the three forms of multipolar cells, fibrils, and amorphous -substance; nor is there any decisive mark by which these elements in -the one can be distinguished from elements in the other. The physical -and chemical composition of Neuroglia and Neuroplasm are as closely -allied as their morphological structure. And although in the later -stages of development the two tissues are markedly distinguishable, -in the early stages every effort has failed to furnish a decisive -indication.[158] Connective tissue is dissolved by solutions which -leave nerve-tissue intact. Can we employ this as a decisive test? No, -for if we soak a section of the spinal cord in one of these solutions, -the _pia mater_ and the membranous septa which ramify from it between -the cells and fibres disappear, leaving all the rest unaltered. This -proves that Neuroglia is at any rate chemically different from ordinary -connective tissue, and more allied to the nervous. As to the _staining_ -process, so much relied on, nothing requires greater caution in its -employment. Stieda found that the same parts were sometimes stained and -sometimes not; and Mauthner observed that in some cells both contents -and nucleolus were stained, while the nucleus remained clear, in other -cells the contents remained clear; and some of the axis cylinders were -stained, the others not.[159] Lister found that the connective tissue -between the fibres of the sciatic nerve, as well as the _pia mater_, -were stained like the axis cylinders;[160] and in one of my notes there -is the record of both (supposed) connective cells and nerve-cells being -stained alike, while the nerve-fibres and the (supposed) connective -fibres were unstained. Whence I conclude that the supposition as to -the nature of the one group being different from that of the other was -untenable, if the staining test is to be held decisive. - -132. The histological question is raised into undue importance because -it is supposed to carry with it physiological consequences which would -deprive the neuroglia of active co-operation in neural processes, -reducing it to the insignificant position of a mechanical support. I -cannot but regard this as due to the mistaken tendency of analytical -interpretation, which somewhat arbitrarily fastens on one element in a -complex of elements, and assigns that one as the sole agent. Whether -we call the neuroglia connective or neural, it plays an essential part -in all neural processes, probably a more important part than even the -nerve-cells, which usurp exclusive attention! To overlook it, or to -assign it a merely _mechanical_ office, seems to me as unphysiological -as to overlook blood-serum, and recognize the corpuscles as the only -nutrient elements. The notion of the neuroglia being a mere vehicle of -support for the blood-vessels arises from not distinguishing between -the alimental and instrumental offices. In the function of a limb, bone -is a co-operant. In the function of a centre, connective tissue is a -co-operant; so that even if we acknowledge neuroglia to be a special -form of connective tissue, it is an agent in neural processes; _what_ -its agency is, will be hereafter considered. - -Following Bidder and Kupffer, the Dorpat school proclaimed the whole -of the gray substance of the posterior half of the spinal cord to -be connective tissue; and Blessig maintained that the whole of the -retina, except the optic fibres, was connective tissue.[161] Even those -anatomists who regarded this as exaggerated, admitted that connective -tissue largely enters into the gray substance, especially if the -granular ground substance be reckoned as connective, the nerve-cells -being very sparse in the posterior region. Be it so. Let us admit -that the gray matter of the frog’s spinal cord is mainly composed of -neuroglia, in which a very few multipolar nerve-cells are embedded. -What must our conclusion be? Why, that since this spinal cord is -proved to be a centre of energetic and manifold reflex actions--even -to the extent of forcing many investigators to attribute sensation and -volition to it--this is proof that connective tissue does the work of -nerve-tissue, and that the neuroglia is more important than nerve-cells! - -Three hypotheses are maintainable--1°. The neuroglia is the amorphous -ground-substance of undeveloped tissue (neuroplasm) out of which the -cells and fibres of nerve-tissue and connective tissue are evolved. -2°. It is the product of dissolved nerve cells and fibres. 3°. It is -the undeveloped stage of connective tissue. For physiological purposes -we may adopt any one of these views, provided we keep firm hold of the -fact that the neuroglia is an essential element, and in the centres a -dominant element. To make this clear, however, we must inquire more -closely into the relations of the three elements, nerve-cells, fibres, -and neuroglia. - - -THE RELATIONS OF THE ORGANITES. - -133. In enumerating among the obstacles to research the tendency to -substitute hypothetic deductions in place of objective facts, I had -specially in my mind the wide-reaching influence of the reigning -theories of the nerve-cell. Had we a solidly established theory of the -cell, equivalent, say, to our theory of gas-pressure, we should still -need caution in allowing it to override exact observation; but insecure -as our data are, and hypothetical as are the inferences respecting -the part played by the cell, the reliance placed on deductions from -such premises is nothing less than superstition. Science will take a -new start when the whole question is reinvestigated on a preliminary -setting aside of all that has been precipitately accepted respecting -the office of the cell. This exercise of the imagination, even should -the reigning theories subsequently be confirmed, would not fail to -bring many neglected facts into their rightful place. - -I am old enough to remember when the cell held a very subordinate -position in Neurology, and now my meditations have led me to return, if -not to the old views of the cell, at least to something like the old -estimate of its relative importance. Its existence was first brought -prominently forward by Ehrenberg in 1834, who described its presence in -the sympathetic ganglia; and by Remak in 1837, who described it in the -spinal ganglia. For some time afterwards the ganglia and centres were -said to contain irregular masses of vesicular matter which were looked -on as investing the fibres; what their office was, did not appear. But -there rapidly arose the belief that the cells were minute batteries -in which “nerve-force” was developed, the fibres serving merely as -conductors. Once started on this track, Hypothesis had free way, and a -sort of fetichistic deification of the cell invested it with miraculous -powers. In many works of repute we meet with statements which may -fitly take their place beside the equally grave statements made by -savages respecting the hidden virtues of sticks and stones. We find -the nerve-cells credited with “metabolic powers,” which enable them -to “spiritualize impressions, and materialize ideas,” to _transform_ -sensations into movements, and _elaborate_ sensations into thoughts; -not only have they this “remarkable aptitude of metabolic local -action,” they can also “act at a distance.”[162] The savage believes -that one pebble will cure diseases, and another render him victorious -in war; and there are physiologists who believe that one nerve-cell has -sensibility, another motricity, a third instinct, a fourth emotion, a -fifth reflexion: they do not say this in so many words, but they assign -to cells which differ only in size and shape, specific qualities. They -describe sensational, emotional, ideational, sympathetic, reflex, and -motor-cells; nay, Schröder van der Kolk goes so far as to specify -hunger-cells and thirst-cells.[163] With what grace can these writers -laugh at Scholasticism? - -134. The hypothesis of the nerve-cell as the fountain of nerve-force -is supported by the gratuitous hypothesis of cell-substance having -greater chemical tension and molecular instability than nerve-fibre. -No evidence has been furnished for this; indeed the only experimental -evidence bearing on this point, if it has any force, seems directly -adverse to the hypothesis. I allude to the experiments of Wundt, which -show that the faint stimulus capable of moving a muscle when applied -directly to its nerve, must be increased if the excitation has to pass -through the cells by stimulation of the sensory nerve.[164] Wundt -interprets this as proving that the cells retard every impulse, whereby -they are enabled to store up latent force. The cells have thus the -office of locks in a canal, which cause the shallow stream to deepen at -particular places. I do not regard this interpretation as satisfactory; -but the fact at any rate seems to prove that so far from the cells -manifesting greater instability than the fibres, they manifest less. - -135. The hypothesis of nerve-force being developed in the ganglia, -gradually assumed a more precise expression when the nerve-cells were -regarded as the only important elements of a ganglion. It has become -the foundation-stone of Neurology, therefore very particular care -should be taken to make sure that this foundation rests on clear and -indisputable evidence. Instead of that, there is absolutely no evidence -on which it can rest; and there is much evidence decidedly opposed to -it. Neither structure nor experiment points out the cells as the chief -agents in neural processes. Let us consider these. - -Fig. 22 shows the contents of a molluscan ganglion which has been -teased out with needles. - -[Illustration: Fig. 22.--_Cells, fibres, and amorphous substance from -the ganglion of a mollusc_ (after Bucholtz).] - -The cells are seen to vary in size, but in all there is a rim of -neuroplasm surrounding the large nucleus, and from this neuroplasm -the fibre is seen to be a prolongation. The dotted substance in the -centre is the neuroglia. Except in the possession of a nucleus, there -is obviously here no essential difference in the structure of cell and -fibre. - -[Illustration: - - Fig. 23--_Fibres from the auditory nerve._ _a_, the axis cylinder; - _b_, the cellular enlargement; _c_, the medullary sheath. -] - -Now compare this with Fig. 23, representing three fibres from the -auditory nerve. - - -Here the cell substance, as Max Schultze remarks, “is a continuation -of the axis cylinder, and encloses the nucleus. The medulla commonly -ceases at the point where the axis enters the cell, to reappear at its -exit; but it sometimes stretches across the cell to enclose it also: -so that such a ganglion cell is in truth simply the nucleated portion -of the cylinder axis.”[165] There are many places in which fibres are -thus found with cells inserted in their course as swellings: in the -spinal ganglia of fishes these are called bipolar cells; they are -sometimes met with even in the cerebellum; but oftener in peripheral -nerves, where they are mostly small masses of granular neuroplasm -from which usually a branching of the fibre takes place. The point -to which attention is called is that in some cases, if not in all, -the nerve-fibre is structurally continuous with the cell contents. -The two organites--fibre and cell--differ only as regards the nucleus -and pigment. Haeckel, who affirms that in the crayfish (_Astacus -fluviatilis_) he never saw a cell which did not continue as a fibre, -thinks there is always a marked separation of the granular substance -from its “hyaline protoplasm,” and that only this latter forms the axis -cylinder. But although my observations agree with this as a general -fact, I have seen even in crayfish the granular substance prolonged -into the axis cylinder; and in other animals the granular substance is -frequently discernible. - -Indeed it may be said that anatomists are now tolerably unanimous as to -the axis cylinder being identical with the protoplasmic cell substance. -If this be so, we have only to recall the principle of identity of -property accompanying identity of structure, to conclude that _whatever -properties we assign to the cells_ (unless we restrict these to the -nucleus and pigment) _we must assign to the axis cylinders_. We can -therefore no longer entertain the hypothesis of the cells being the -fountains or reservoirs of Neurility; the less so when we reflect that -cells do not form the hundredth part of nerve-tissue: for even the -gray substance bears but a small proportion to the white; and of the -gray substance, Henle estimates that one half is fibrous, the rest is -partly cellular, partly amorphous. Those who derive Neurility from -the cells, forget that although the organism begins as a cell, and -for some weeks consists mainly of cells, yet from this time onwards -there is an ever-increasing preponderance of cell-derivatives--fibres, -tubes, and amorphous substance--and corresponding with this is the -ever-increasing power and complexity of the organism. - -136. From another point of view we must reject the hypothesis. Not -only does the evidence which points to the essential continuity in -structure of nerve cell and fibre discredit the notion of their -physiological diversity, but it is further supported by the fact -that although the whole nervous system is structurally continuous, -an immense mass of nerve-fibres have no _immediate_ connection with -ganglionic cells:--neither springing from nor terminating in such -cells, their activity cannot be assigned to them. To many readers this -statement will be startling. They have been so accustomed to hear -that every fibre begins or terminates in a cell, that a doubt thrown -on it will sound paradoxical. But there is an equivoque here which -must be got rid of. When it is said that every fibre has its “origin” -in a cell, this may be true if origin mean its _point of departure -in evolution_, for “cells” are the early forms of all organites; -but although every organite is at first a cell, and in this sense a -nerve-fibre must be said to originate in a cell, we must guard against -the equivoque which arises from calling the highly differentiated -organite, usually designated ganglionic cell, by the same name as -its starting-point. On this ground I suggest the term neuroblast, in -lieu of nerve-cell, for the earlier stages in the evolution of cell -and fibre. Both Embryology and Anatomy seem to show that cell and -fibre are organites differentiated from identical neuroblasts, with a -somewhat varying history, so that in their final stages the cell and -fibre have conspicuous differences in form with an underlying identity; -just as a male and female organism starting from identical ova, and -having essential characters in common, are yet in other characters -conspicuously unlike. The multipolar cell is not necessarily the origin -of a nerve-fibre, although it is probable that some short fibres -have their origin in the prolongations of cells. Although the latter -point has not, I think, been satisfactorily established, except in the -invertebrata, I see no reason whatever to doubt its probability; what -seems the least reconcilable with the evidence is the notion that all -fibres arise as prolongations from ganglionic cells, instead of arising -independently as differentiations from neuroblasts. The reader will -observe that my objection to the current view is purely anatomical; for -the current view would suit my physiological interpretations equally -well, and would be equally irreconcilable with the hypothesis of the -cell as the source of Neurility, so long as the identity of structure -in the axis cylinder and cell contents is undisputed. - -137. The evidence at present stands thus: There are numerous multipolar -cells which have no traceable connection with nerve-fibres; and fibres -which have no direct connection with multipolar cells. By the first -I do not mean the disputed apolar cells, I mean cells in the gray -substance of the centres which send off processes that subdivide and -terminate as fibrils in the network of the Neuroglia (Figs. 16, 18). -It is indeed generally assumed that these have each one process--the -axis-cylinder process--which is prolonged as a nerve-fibre; nor would -it be prudent to assert that such is never the case; though it would -be difficult to distinguish between a fibre which had united with a -process and a fibre which was a prolongation of a process, in both -cases the neuroplasm being identical. I only urge that the assumption -is grounded not on anatomical evidence, but on a supposed necessary -postulate. All that can be demonstrated is that some processes -terminate in excessively fine fibrils; and occasionally in thousands -of specimens processes have been traced into dark-bordered fibres. -It is true that they often present appearances which have led to -the inference that they did so terminate--appearances so deceptive -that Golgi and Arndt independently record observations of unbranched -processes having the aspect of axis cylinders being prolonged to -a considerable distance (600 μ in one case), yet these were found -to terminate _not_ in a dark-bordered fibre, but in a network of -fibrils.[166] - -138. While it is thus doubtful whether dark-bordered fibres are always -immediately connected with cells, it is demonstrable that multitudes -of fibres have only an indirect connection with cells, being developed -as outgrowths from other fibres. Dr. Beale considers that in each -such outgrowths have their origin in small neuroplasmic masses (his -“germinal matter”). That is another question. The fact here to be -insisted on is that we often find groups of cells with only two or -three fibres, and groups of fibres where very few cells exist. Schröder -van der Kolk says that in a sturgeon (_Accipenser sturio_) weighing 120 -pounds he found the spinal cord scarcely thicker than that of a frog; -the muscles of this fish are enormous, and its motor nerves abundant; -yet these nerves entered the cord by roots no thicker than a pig’s -bristle; and in the very little gray matter of the cord there was only -a cell here and there found after long search. Are we to suppose that -these rare cells were the origins of all the motor and sensory nerves? -A similar want of correspondence may be noticed elsewhere. Thus in the -spinal cord of the Lamprey my preparations show very few cells in any -of the sections, and numerous sections show none at all. Stieda counted -only eight to ten cells in each horn of some osseous fishes, except -at the places where the spinal roots emerged. In the eel and cod he -found parts of the cord quite free from cells, and in other parts found -two, three, never more than ten. In birds he counted from twenty-five -to thirty. Particular attention is called to this fact of the eel’s -cord being thus deficient, because every one knows the energetic -reflex action of that cord, each separate segment of which responds to -peripheral stimulation. - -It may indeed be urged that these few cells were the origin of all -the fibres, the latter having multiplied by the well-known process of -subdivision; and in support of this view the fact may be cited of the -colossal fibres of the electric fishes, each of which divides into -five-and-twenty fibres, and in the electric eel each fibre is said -by Max Schultze to divide into a million of fibrils. But I interpret -this fact otherwise. It seems to me to prove nothing more than that -the neuroplasm has differentiated into few cells and many fibres. -And my opinion is grounded on the evidence of Development, presently -to be adduced. If we find (and this we do find) fibres making their -appearance anywhere _before_ multipolar cells appear, the question is -settled. - -139. Dr. Beale regards the large caudate cells of the centres as -different organites from the oval and pyriform cells, and thinks they -are probably stations through which fibres having different origins -merely pass, and change their directions; and Max Schultze says that -no single fibril has been found to have a central origin; every fibril -arises at the periphery, and passes through a cell, which is thus -crossed by different fibrils.[167] (Comp. Fig. 17.) - -The teaching of Development is on this point of supreme importance. -Unhappily there has not yet been a sufficient collection of systematic -observations to enable us to speak very confidently as to the -successive stages, but some negative evidence there is. The changes -take place with great rapidity, and the earliest stages have hardly -been observed at all. Although for several successive years I watched -the development of tadpoles, the difficulties were so great, and the -appearances so perplexing, that the only benefit I derived was that of -being able the better to understand the more successful investigations -of others. Four or five days after fecundation is the earliest period -of which I have any recorded observation; at this period the cerebral -substance appeared as a finely granular matter, having numerous lines -of segmentation marking it off into somewhat spherical and oval masses, -interspersed with large granules and fat globules. Here and there -hyaline substance appeared between the segments. Similar observations -have since been recorded by Charles Robin in the earliest stages -of the Triton.[168] He says that when the external gills presented -their first indications, nuclei appeared, each surrounded by a rim of -hyaline substance, from which a pale filament was prolonged at one end, -sometimes one at both ends, and this filament subdivided as it grew -in length until it had all the appearance of an axis cylinder. This, -however, he says, is a striation, not a fibrillation; he refuses to -admit that the axis cylinder is a bundle of fibrils. He further notices -the simultaneous appearance of amorphous substance; and as this is -several days before there is any trace of a _pia mater_, or proper -connective tissue, he urges this among the many considerations which -should prevent the identification of neuroglia with connective tissue. - -In a very young embryo of a mole (I could not determine its age) the -cortex of the hemispheres showed granular amorphous substance, in -which were embedded spherical masses of somewhat paler color, which -had no nuclei, and were therefore not cells. Besides these, there were -nucleated masses (apolar cells, therefore) and more developed cells, -unipolar, bipolar, and tripolar. Not a trace of a nerve-fibre was -visible. In agreement with this are the observations of Masius and Van -Lair, who cut out a portion of the spinal cord in a frog, and observed -the regenerated tissue after the lapse of a month. It contained apolar, -bipolar, and multipolar cells, together with “corpuscles without -processes, for the most part larger than the cells, and appearing to be -mere agglomerations of granules,”--these latter I suppose to have been -what I describe as segmentations of the undeveloped substance. Gray -fibres, with a few varicose fibres, also appeared.[169] - -140. The admirable investigations of Franz Boll have given these -observations a new significance. He finds in the cerebral substance -of the chick on the third or fourth day of incubation a well-marked -separation between the neuroglia and nerve-tissue proper. Fig. 24, A, -represents three nerve-cells, each with its nucleus and nucleolus, -and each surrounded with its layer of neuroplasm. The other four -masses he regards as nuclei of connective tissue. Three days later the -distinction between the two is more marked (Fig. 24, B). Not only have -the nerve-cells acquired an increase of neuroplasm, they also present -indications of their future processes, which at the twelfth day are -varicose (Fig. 24, C). (All this while the connective corpuscles remain -unchanged.) Although Boll was unable to trace one of these processes -into nerve-fibres, he has little doubt that they do ultimately become -(unite with?) axis cylinders. - -[Illustration: Fig. 24.--_Embryonic nerve-cells._] - -[Illustration: Fig. 25.--_Embryonic nerve-fibres._] - -It is difficult to reconcile such observations with the hypothesis of -the cells being simply points of _reunion of fibrils_. We see here -multipolar cells before any fibrils appear. Respecting the development -of the white substance, i. e. the nerve-fibres, Boll remarks that in -the _corpus callosum_ of the chick the first differentiation resembles -that of the gray substance. - -The polygonal and spindle-shaped cells represented in Fig. 25, A, are -respectively starting-points of connective and neural tissues. The -spindle-shaped cells elongate, and rapidly become bipolar. This is -supposed to result in the whole cell becoming transformed into a fibre, -the nucleus and nucleolus vanishing; but the transformation is so rapid -that he confesses that he was unable to trace its stages; all that can -positively be asserted is that one or two days after the appearance -presented in Fig. 25, B, the aspect changes to that of fibrils. The -columns of polygonal cells between which run these fibrils, he regards -as the connective corpuscles described by several anatomists in the -white substance both of brain and cord, and which are sometimes -declared to be multipolar nerve-cells.[170] - -141. Dr. Schmidt’s observations on the human embryo were of course -on tissue at a very much later stage. According to him, the fibrils -of the axis cylinders are formed by the linear disposition and -consolidation of elementary granules. The fibrils thus formed are -separated by interfibrillar granules which in time become fibrils. Not -earlier than three months and a half does the formation of individual -axis cylinders begin by the aggregation of these fibrils into minute -bundles, which are subsequently surrounded by a delicate sheath.[171] - -142. With respect to the transition of the spindle-shaped cells into -fibrils, since there is a gap in the observations of Boll, and since -those of Schmidt are subsequent to the disappearance of the cells, -and in both cases all trace of nucleus has disappeared, I suggest -that we have here an analogy with what Weismann has recorded of the -metamorphoses of insects. In the very remarkable memoir of that -investigator[172] it is shown that the metamorphoses do not take place -by a gradual modification of the existing organs and tissues, but by a -_resolution_ of these into their elements, and a _reconstruction_ of -their elements into tissues and organs. The muscles, nerves, tracheæ, -and alimentary canal, undergo what may be called a fatty degeneration, -and pass thence into a mere blastema. _It is out of these ruins of the -old tissues that the new tissues are reconstructed._ On the fourth day -the body of the pupa is filled with a fluid mass--a plasma composed of -blood and dissolved tissues. The subsequent development is thus in all -essential respects a repetition of that which originally took place in -the ovum.[173] - -Two points are especially noticeable: First, that in this resolved -mass of granules and fat globules there quickly appear large globular -masses which develop a fine membrane, and subsequently nuclei. A glance -at the figure 51 of Weismann’s plates reveals the close resemblance to -the earliest stages of nerve-cells; and the whole process recalls the -regeneration of nerves and nerve-centres after their fatty degeneration. - -Secondly, the nerves reappear in their proper places in the new -muscles, and this at a time when the nerve-centres are still unformed; -so that the _whole peripheral system is completely rebuilt in absolute -independence of the central system_. The idea, therefore, that -nerve-fibres are the products of ganglia must be relinquished. This -idea is further discountenanced by Boll’s observations, which show that -the fibre-cells are from the first different from the ganglionic cells; -and by the observations of Foster and Balfour, that “fibres are present -in the white substance on the third day of incubation”; _whereas cell -processes do not appear until the eighth day_. Foster and Balfour are -inclined to believe “that even on the seventh day it is not possible -to trace any connection between the cells and fibres.” In the later -stages, the connection is perhaps established.[174] - -143. We may, I think, conclude from all this that in the higher -vertebrates the white substance of brain and cord is not the direct -product of the gray substance; in other words, that here nerve-fibres, -even if subsequently in connection with the ganglionic cells, have -an independent origin. They may grow towards and blend with cell -processes; they are not prolongations of those processes. They may be -identical in structure and property, as one muscle is identical with -another, but one is not the parent of the other. - -144. Sigmund Mayer emphatically declares that in no instance has he -traced a cell process developed into a dark-bordered nerve-fibre. -The process, he says, may often be traced for a certain distance -alongside of a fibre; but it then suddenly ceases, whereas the fibre -is seen continuing its course unaltered. Still more conclusive is the -evidence afforded by nerves having only very few fibres (2–4 sometimes -in the frog), which have, nevertheless, a liberal supply of cells, -visible without preparation. Valentin counted twenty-four cells in a -nerve which had but two fibres.[175] Now although it is possible to -explain the presence of numerous fibres with rare cells either as due -to subdivisions of fibres, or to the fibres having cells elsewhere -for their origin, it is not thus that we can explain the presence of -numerous cells which have no fibres developed from their processes. - -145. With regard to this observation of the cell process running -alongside of the fibre, the recent researches of Ranvier may throw -some light on it. He describes the cells in the spinal ganglia as all -unipolar; each single process pursues a more or less winding course -as a fibril, often blending with others, till it reaches one of the -fibres from the sensory root. It blends with this fibre at the annular -constriction of the fibre, becoming here incorporated with it, so that -a T-shaped fibre is the result.[176] If this should be confirmed, it -would reconcile many observations; but it would greatly disturb all -current interpretations. Ranvier remarks that it is no longer tenable -to suppose that the ganglionic cell is a centre, sensory or motor, -receiving the excitation or sending forth a motor impulse; for if the -fibril issuing from a cell becomes laterally soldered to a nerve-fibre, -there is no possibility of saying in which direction this cell receives -the excitation, nor in which it transmits the impulse. - -146. We have seen good reason to conclude that the essential element of -the nerve--the axis cylinder--is the same substance as the neuroplasm -which forms the essential element of the cell. At any rate, we are -quite certain that the cell process is neuroplasm. On this ground there -is no difficulty in understanding that a cell process may sometimes be -drawn out into an axis cylinder (as indeed we see to be the case in -the invertebrata and electric fishes); while again in numerous other -cases the nerve-fibre has an independent origin, being, in short, a -differentiation from the neuroplasm which has become a fibre instead -of a cell. It is clear from the observations of Rouget on Development, -and of Sigmund Mayer on Regeneration, that fibres, nuclei, and cells -become differentiated from the same neuroplasm, those portions which -are not converted into fibres remaining first as lumps of neuroplasm, -then acquiring a nucleus, and some of these passing into cells. I mean -that between fibres, nuclei, and cells there are only morphological -differences in an identical neuroplasm.[177] If this is in any degree -true, it will not only explain how fresh fibres may be developed in the -course of fibres, branching from them as from trunks, and branchlets -from branchlets, twigs from branchlets, the same conditions of growth -being present throughout; it will also completely modify the notion -of any physiological distinction between cell and fibre greater than -can be assigned to the morphological differences. We shall then no -longer suppose that the cell is the fountain whence the fibre draws its -nutrition and its “force”; and this will be equally the case even if we -admit that a cell is, so to speak, the germ from which a whole plexus -of fibres was evolved, for no one will pretend that the “force” of an -organism is directly derived from the ovum, or that the ovum nourishes -the organism. - -147. At this stage of the discussion it is needful to consider a point -which will spontaneously occur to every instructed reader, I mean the -interesting fact discovered by Dr. Waller, that when a sensory root was -divided, the portion which was still in connection with the ganglion -remained unaltered, whereas the portion which was only in connection -with the spinal cord degenerated; and _vice versa_, when a motor root -was divided, the portion connected with the cord remained unaltered, -the portion severed from the cord degenerated. The observation has -been frequently confirmed, and the conclusion drawn has been that the -cells in the ganglion of the posterior root are the nutritive centres -of posterior nerves, the cells in the anterior horn of the cord being -the nutritive centres of the anterior nerves. Another interpretation -is however needed, the more so because the fact is not constant.[178] -True of some nerves, it is not true of others. Vulpian found that -when he cut out a portion of the lingual nerve, and transplanted -it by grafting under the skin of the groin, where of course it was -entirely removed from all ganglionic influence, it degenerated, but it -also regenerated. Pathological observations convinced Meissner that -the ganglia are wholly destitute of an influence on the nutrition of -the vagus; and Schiff proved experimentally that other ganglia were -equally inoperative, since motor nerves could be separated from the -spinal cord without degeneration.[179] Not however to insist on this, -nor on the other facts of regeneration, in the absence of ganglionic -influence, let us remark that Dr. Waller’s examples would not be -conclusive unless the teaching of Embryology could be disproved. That -nerves degenerate when separated from ganglia is a fact; but it is also -a fact that muscles degenerate when separated from a nerve-centre; yet -we do not suppose the nerve-centre to nourish the muscles. And against -the fact that the sensory nerve remains unaltered only in that portion -which is connected with the ganglion, we must oppose the observations -of Kölliker and Schwalbe,[180] who affirm that none of the fibres -which enter the posterior columns of the spinal cord have any direct -connection with the cells of the ganglion on the posterior root. The -cells of this ganglion they declare to be unipolar (in the higher -vertebrates), and the fibres in connection with these cells are not -those which pass to the cord, but all of them pass to the periphery. -According to Ranvier, the fibres from the cells join the fibres of -the posterior root. Schwalbe found that if the spinal nerve be firmly -grasped and _steadily_ drawn, it will often be pulled from its sheath, -and the ganglion laid bare;[181] in this ganglion all the cells are -found undisturbed, which could not be the case had fibres from _those_ -cells entered the cord, since the traction would necessarily have -disturbed them. - - -RECAPITULATION. - -148. At the opening of this chapter mention was made of the besetting -sin of the analytical tendency, namely, to disregard the elements -which provisionally had been set aside, and not restore them in the -reconstruction of a synthetical explanation. Familiar experiences -tell us that a stimulus applied to the skin is followed by a muscular -movement, or a glandular secretion; sometimes this takes place without -any conscious sensation; sometimes we are distinctly conscious of -the stimulus; and sometimes we consciously will the movement. These -facts the physiologist tries to unravel, and to trace the complicated -processes involved. The neurologist of course confines himself -exclusively to the neural processes; all the other processes are -provisionally left out of account. But not only so: the analytical -tendency is carried further, and even in the neural process the -_organs_ are neglected for the sake of the nervous _tissue_, and the -nervous tissue for the sake of the _nerve-cell_. The consequence has -been that we have an explanation offered us which runs thus:-- - -149. The nerve-cell is the supreme element, the origin of the -nerve-fibre, and the fountain of nerve-force. The cells are connected -one with another by means of fibres, and with muscles, glands, and -centres also by means of fibres, which are merely channels for the -nerve-force. A stimulus at the surface is carried by a sensory fibre -to a cell in the centre; from that point it is carried by another -fibre to another cell; and from that by a third fibre to a muscle: -a reflex contraction results. This is the elementary “nervous arc.” -But this arc has also higher arcs with which it is in connection: the -sensory cell besides sending a fibre directly to a motor cell, also -sends one upwards to the cerebral centres; and here again there is a -nervous arc, so that the cerebral centre sends down an impulse on the -motor cells, and the contraction which results is due to a volitional -impulse. The transmission of the stimulation which in the first case -was purely physical, becomes in the latter case psychical. The sensory -impression is in one cell transformed into a _sensation_, in another -cell into an _idea_, in a third cell into a _volition_. - -150. This course is described with a precision and a confidence which -induces the inexperienced reader to suppose that it is the transcript -of actual observation. I venture to say that it is imaginary from -beginning to end. I do not affirm that no such course is pursued, -I only say no such course was ever demonstrated, but that at every -stage the requisite facts of observation are either incomplete or -contradictory. First, be it noted that the actions to be explained are -never the actions of organs so simple as the description sets forth. -It is not by single fibres and cells that the stimulus is effected, -but by complex nerves and complex centres. Only by a diagrammatic -artifice can the fibre represent the nerve, and the cell the centre. -In reality the cells of the centre (supposing them to be the _only_ -agents) act in groups, and Anatomy should therefore show them to be -mutually united in groups--which is what no Anatomy has succeeded in -showing, unless the Neuroglia be called upon. Secondly, be it noted -that the current scheme of the relations between cells and fibres is -one founded on physiological postulates, not on observation. Thirdly, -much of what is actually observed is very doubtful, because we do not -know whether the appearances are normal, or due to modes of preparation -and post-mortem changes. We cannot at present say, for instance, -whether the fibrillated appearance of cell contents and axis cylinder -represents the living structure or not. We may either suppose that -the neuroplasmic pulp splits longitudinally into fibres, or that -neuroplasmic threads resolve themselves into a homogeneous pulp--the -axis cylinder may be a condensation of many fibrils, or the fibrils may -be a resolution of the substance. - -151. Let us contrast step by step the Imaginary Anatomy found in the -text-books with the Objective Anatomy as at present disclosed by the -researches of all the chief workers. Imaginary Anatomy assumes that the -sensory fibre passes from a surface into the cells of the posterior -horn of the spinal cord. Objective Anatomy sees the fibre pass into the -gray substance, but declares that no direct entrance of a fibre into a -cell is there visible. - -Imaginary Anatomy assumes that from the sensory cells of the gray -substance pass fibres in connection with the motor cells of the -anterior horn, thus forming a direct channel through which the -excitation of a sensory cell is transmitted to a motor cell. Objective -Anatomy fails to discover any such direct channel--no such fibres are -demonstrable. - -Imaginary Anatomy assumes that from the motor cells issue fibres which -descend to the muscles and glands, and carry there the motor impulses -and the “mandates of the will.” Objective Anatomy fails to find at -the utmost more than a probability that these cells are continued -as fibres, a probability which is founded on the rare facts of cell -processes having been seen extending into the roots of the nerves, and -of a cell process having occasionally been seen elsewhere continuous -with a dark-bordered fibre. Granting, however, that this probability -represents the fact, we have thus only one part of the “nervous arc” -which can be said to have been verified. - -Imaginary Anatomy further assumes that this nervous arc is connected -with cerebral centres by means of fibres going upwards from the -posterior cells, and fibres descending downwards to the anterior -cells. Objective Anatomy sees nothing of the kind. It sees fibres -entering the gray substance, and there lost to view in a mass of -granular substance, fibrils, neuroblasts, and cells. There _may -be_ uninterrupted fibres passing upwards and downwards; but it -is impossible to see them. And if we are told that physiological -interpretations demand such a structure, we may fairly ask if this, and -this only, is the structure which is adequate to the propagation of -excitation? Now it seems to me that another kind of structure, and one -more closely agreeing with what is observed, better answers the demands -of Physiology. This will be more evident after the Laws of Nervous -Action have been expounded in the succeeding chapter. Meanwhile we may -remark that the arrangement of cells and fibres which is imagined as -the mechanism of propagation and reflexion is absolutely irreconcilable -with the teaching of Experiment: for the spinal cord may be cut through -anywhere, without destruction of the transmission of sensory and motor -excitations, provided only a small portion of gray substance be left to -establish the continuity of the axis. Divide all the substance of the -posterior half in one place, and all the substance of the anterior half -in another, yet so long as there is a portion of gray substance left -as a bridge between the lower and upper segments, the transmission of -sensory and motor excitations will take place. - -152. In other essential respects we have to note that the anatomical -evidence for the current interpretations is absolutely deficient or -contradictory. There is no adequate warrant for the assumption that all -nerves have their origin in ganglia, all fibres in cells. Such evidence -as at present exists is against that supposition, and in favor of the -supposition that both cell and fibre are differentiations of a common -neuroplasm, sometimes directly, sometimes indirectly continuous. -Fibres, and plexuses of fibres, interspersed with cells irregularly -distributed--now singly, now in small groups, now in larger and larger -groups--constitute the _figured_ elements of nerve-tissue; and even if -we set aside the _amorphous_ substance as indifferent or subordinate, -we have still no ground for assigning the supremacy, much less the sole -significance, to the cells. The grounds of this denial have been amply -furnished in our exposition. For, let it be granted that nerve-cells -are the origins of the fibres and the sources of their nutrition--a -point which is eminently disputable--this would in no sense help the -physiological hypothesis of the cell as the fountain of Neurility. If -the fibre is simply the cell-contents drawn out longitudinally, if -its essential element is identical with the essential element of the -cell, then we can no more ascribe to the cell the exclusive property -of Neurility than we can draw a lump of lead out into a wire, and then -ascribe different properties to the thin end and the thick end. But -on this point it is needless to speculate, since we have experimental -evidence proving that the nerve-fibre has its Neurility even when -separated from the cell, or even from the ganglion. - -153. It is possible--I do not see sufficient evidence for a stronger -assertion--that the cells are the nutritive sources of the fibres. They -may represent the alimental rather than the instrumental activities of -nervous life. (Compare PROBLEM I. § 42.) My contention is that in any -case they are not the supreme elements of the active tissue, and in no -sense can they be considered as _organs_. Only confusion of ideas could -for a moment permit such language, or could assign central functions -to cells which are elements of tissue. If the cell be credited with -such powers anywhere, it must be credited with them everywhere. Now I -ask what conceivable central function can be ascribed to a cell which -terminates the fibre in a peripheral ganglion, or which is merely -an enlargement in the course of a fibre in a nerve-bundle? Besides -the facts already adduced, let attention be called to this: If a -nerve-bundle from the _submucosa_ of the intestine be examined, there -appear among the fibres many nuclei (neuroblasts), and occasionally -cells, unipolar and bipolar. These cells--if we may trust the -observations of Rouget on the earliest development of nerves, and of -Sigmund Mayer on regenerated nerves--are simply more advanced stages of -evolution of the neuroblasts; but whatever their genesis may be, there -can be nothing in the nature of a central function assigned to them. - -154. It may be asked, What part can we assign to cells in neural -actions if they are apolar, unipolar, and even when multipolar, -isolated from each other, and from fibres? I confess that I have -no answer ready, not even an hypothesis. Until some rational -interpretation of the cell be given we must be content to hold an -answer in suspense. What I would urge is that we are precipitate -in assuming that the anatomical connection between one element and -another must necessarily be that of a fibre. In a semi-fluid substance, -such as neurine, continuity may be perfect without solid fibres: the -amorphous substance and the plasmode may as well transmit waves of -molecular motion from one part of the tissue to another, and therefore -from cell to cell, or from cell to fibre, as a figured substance -may. When the posterior root enters the gray substance of the cord, -there is no more necessity for its fibres passing directly into the -cells of that gray substance, in order to excite their activity, than -there is for a wire to pass from the bell to the ear of the servant, -who hears the vibrations of the bell through the pulsations of the -intervening air upon her tympanum. Look at the structure of the retina, -or the cerebellum, and you will find that the ganglionic cells which -have processes passing in a direction contrary to that whence the -stimulus arrives, have none where continuity of fibre and cell would -be indispensable on the current hypothesis. Light stimulates the -rods and cones, but there are no nerve-fibres, hitherto discovered, -passing from these to the ganglionic cells; instead of that there is -a ground-substance thickly interspersed with granules and nuclei. -_From_ the cells we see processes issue; _to_ the cells none are seen -arriving. So with the cerebellum. The large cells send their processes -upwards to the surface; but downwards towards the white substance the -processes are lost in the granular layer, which most histologists -regard as connective tissue. - -155. A mere glance at nervous tissue in any part will show that cells -are far from forming the principal constituents. In the epidermis or -a gland the cell is obviously the chief element, forming the bulk of -the tissue, and being the characteristic agent. In nerve-tissue, as in -connective tissue, the reverse is the case. We must therefore cease to -regard the cell as having the importance now attached to it, and must -rather throw the emphasis on the fibres and neuroglia. - -156. Before quitting this subject let a word be said on the amazing -classification which has attained wide acceptance (although rejected by -the most eminent authorities), founded on the size of the cells--the -large multipolar cells being specified as motor, the smaller cells as -sensory, while those of an intermediate size are sympathetic. I forbear -to dwell on the development of this notion which specifies sensational, -ideational, and emotional cells, because this does not pretend to have -a basis in observation; whereas there are anatomical facts which give -a certain superficial plausibility to the original classification. -The conception is profoundly unphysiological; yet, if the anatomical -evidence were constant, one might give it another interpretation. The -evidence is, however, not constant. Large cells are found in regions -assigned to sensory nerves, and small cells in motor regions. In the -spinal cord of the tortoise Stieda declares that the so-called motor -cells are limited to the cervical and lumbar enlargements; all the rest -of the motor region being absolutely destitute of them.[182] Again -look at the cells of the retina--no one will assign motor functions to -them--yet they are the same as those of the cerebellum and the anterior -horns of the spinal cord. (It is worth a passing mention that the -structure of the nervous parts of the retina more closely resembles -that of the cerebellum than of the cerebrum.) - -157. While our knowledge of the cell is thus far indeed from having -the precision which the text-books display, and in no sense warrants -the current physiological interpretations, our knowledge of fibres and -neuroglia is also too incomplete for theoretic purposes. We know that -the axis cylinder is the essential element; but we are still at a loss -what part is to be assigned to the medullary sheath. There is indeed a -popular hypothesis which pronounces it to be the means of _insulating_ -the fibre, and thus preserving the isolated conduction of nerve-force. -Being of a fatty nature, this insulating office was readily suggested -in agreement with the assumption that Neurility was Electricity. Now, -without discussing whether Neurility is or is not Electricity, even -admitting the former to be satisfactorily proved, I must remark that -the admission still leaves the medullary sheath incapable of fulfilling -the supposed office, since not only is there no such sheath in most of -the invertebrates and in the sympathetic nerves of vertebrates, but -even in those nerves which have the sheath it is precisely in places -where the insulation would be most needed--namely, just before the -terminations of the fibres in muscles and in centres--that the sheath -is _absent_. This is as if we tried to conduct water through a pipe -which fell short at both ends--before it left the cistern, and before -it reached the spot to be watered. If there is a tendency in Neurility -to spread wherever it is not insulated by a medullary sheath, then -before reaching the centres and the muscles, it must, on the insulating -hypothesis, dribble away! - -158. The facts expressed in the “law of isolated conduction” are -important, and are difficult of explanation; but it is obvious that -they cannot be referred to the presence of the medullary sheath. Nor -indeed will any insight into the propagation of stimulation through -the central axis be intelligible until we have reformed our anatomical -theories, and taken the Neuroglia into account. The theory which -connects every fibre directly with a cell, and every cell with another -by anastomosis--even were it demonstrated--would not explain the law -of isolated conduction. Butzke cogently remarks[183] that such a -disposition of the elements should render all neural paths invariable; -whereas the fact is that they are very variable. We learn to perform -actions, and then we unlearn them; the paths are traversed now in -one direction, now in another. Fluctuation is the characteristic -of central combinations. And for this fluctuating combination of -elements a corresponding diversity is required in the possible -channels. This seems to be furnished by the network of the Neuroglia. -See the representation copied from Butzke’s plate, and note how the -cell-process blends with the meshes of the Neuroglia. Is it fanciful -to regard this network of fibrils as having somewhat the relation of -capillaries to blood-vessels? Did we not experimentally know that the -capillaries are terminal blood-vessels, we should not suspect it from -mere examination of the structure. - -159. Having insisted that our knowledge is insufficient for any -explanation of the “law of isolated conduction,” I can only suggest a -path of research which may lead to some result. What we know is that -some stimulations are propagated from one end of the cerebro-spinal -axis to the other in definitely _restricted_ paths, while others are -_irradiated_ along many paths. In the succeeding chapter this will be -more fully considered; what we have here to note is that the manifold -irradiations of a stimulation have an anatomical substratum in the -manifold sub-divisions of the network of fibrils and the amorphous -substance in which they penetrate. - -[Illustration: Fig. 26.--_Nerve-cells with processes terminating in -neuroglia._] - -160. In conclusion, I would say, let no one place a too great -confidence in the reigning doctrines respecting the elementary -structure of the nervous system, but accept every statement as a -“working hypothesis” which has its value in so far as it links together -verified facts, or suggests new research, but is wholly without value -in so far as it is made a basis of deductions not otherwise verified. -Hypotheses are indispensable to research, but they must be accompanied -by vigilant scepticism. Imagination is only an enemy to Science when -Scepticism is asleep. - - - - -CHAPTER VIII. - -THE LAWS OF NERVOUS ACTIVITY. - - -161. The foregoing remarks have had the object of showing how little -substantial aid Psychology can at present derive from what is known -of the elementary structure of the nervous system, indispensable -as an accurate knowledge of that structure must be to a complete -analysis of its functions. This caution has been specially addressed -to those medical and psychological students whose researches leave -them insufficient leisure to pursue microscopical investigations -for themselves, and who are therefore forced to rely on second-hand -knowledge, which is usually defective in the many qualifying -considerations which keep scepticism vigilant. Relying on positive -statements, and delusive diagrams which only display what the observer -_imagines_, not what he actually _sees_, they construct on such data -theories of disease, or of mental processes; or else they translate -observed facts into the terms of this imaginary anatomy, and offer the -translation as a new contribution to Science. - -162. But little aid as can at present be derived from the teaching of -the microscope, some aid Psychology may even now derive from it. The -teaching will often serve, for instance, to correct the precipitate -conclusions of subjective analysis, which present artificial -distinctions as real distinctions, separating what Nature has united. -It will show certain organic connections not previously suspected; -and since whatever is organically connected cannot functionally be -separated, such sharply marked analytical distinctions as those of -periphery and centre, or of sensation and motion, must be only regarded -as artificial aids. The demonstration of the indissoluble union of -the tissues is a demonstration of their functional co-operation. So -also the anatomical demonstration of the similarity and continuity of -all parts of the central system sets aside the analytical separation -of one centre from another, except as a convenient artifice; proving -that cerebral substance is one with spinal substance, having the same -properties, the same laws of action. - -For the present, Psychology must seek objective aid from Physiology -and Pathology rather than from elementary Anatomy. In the paragraphs -which are to follow I shall endeavor to select the chief laws of -nervous activity which the researches of physiologists and pathologists -disclose. By these laws we may direct and control psychological -research. - - -THE ENERGY OF NEURILITY. - -163. Vitality is characterized by incessant molecular movement, both -of composition and decomposition, in the building up of structure and -the liberation of energy. The life of every organism is a complex of -changes, each of which directly or indirectly affects the statical -and dynamical relations, each being the resultant of many co-operant -forces. In the nourishment of every organite there is an accumulation -of molecular _tension_, that is to say, stored-up energy in a latent -state, ready to be expended in the activity of that organite; and this -expenditure may take place in a steady flow, or in a sudden gush. -The molecular movements under one aspect may be called convergent, -or _formative_: they build the structure, and tend to the state of -equilibrium which we call the statical condition of the organite, -i. e. the condition in which it is not active, but ready to act. -Perfect equilibrium is of course never attained, owing to the -incessant molecular change: indeed Life is inconsistent with complete -repose. Under another aspect the molecular movements may be called -_discharging_: they constitute the dynamic condition of the organite, -in which its functional activity appears. The energy is now diverted, -liberated, and the surplus, over and above that which is absorbed in -formation, instead of slowly dribbling off, gushes forth in a directed -stream. The slow formation of a secretion in a gland-cell, and the -discharge of that secretion, will illustrate this; or (if muscular -_tone_ be admitted) the incipient contraction of the chronic state, and -the complete contraction of the dynamic state, may also be cited. - -164. The discharge which follows excitation may thus be viewed as -a _directed quantity_ of molecular movement. Because it is always -strictly relative to the energy of tension, and is inevitable when -that tension attains a certain surplus over what is required in -construction, there is a limit, 1°, to the growth and evolution of -every organite, and every organism (comp. Problem I. § 118), and, 2°, -to its dynamical effect. When there is no surplus, the organite is -incapable of discharge: it is then exhausted, i. e. will not respond to -stimulus. - -165. The speciality of nerve-tissue is its pre-eminence in directive -energy. Like all other tissues, it grows, develops, and dies; but -above all others it has what we call _excitability_, or readiness in -discharging its energy in a directed stream. By its topographical -distribution it plays the functional part of exciting the activity of -other tissues: it transmits molecular disturbance from periphery to -centre, from centre to centre, and from centre to muscles, vessels, and -glands. When a muscle is excited it moves, and when a gland is excited -it secretes; but these actions end, so to speak, with themselves; the -muscle does not directly move any other muscle;[184] the gland does not -directly excite any other gland. The nerve, on the contrary, has always -a wide-spreading effect; it excites a centre which is continuous with -other centres; and in exciting one muscle, usually excites a group. -Hence the nervous system is that _which binds the different organs -into a dynamic unity_. And Comparative Anatomy teaches that there is a -parallelism between the development of this system and the efficient -complexity of the organism. As the tissues become more and more -specialized, and the organs more and more individualized, they would -become more and more unsuited to the general service of the organism, -were it not that a corresponding development of the nervous system -brought a unifying mechanism. - -The great instability of neurine, in other words, its high degree of -tension, renders it especially apt to disturb the tension of other -tissues. It is very variable; and this variability will have to be -taken into account in explaining the restriction of discharges to -particular centres. A good example of exaggerated tension is furnished -by strychnine poisoning. The centres are then so readily excitable -that a touch, or a puff of cold air on the skin, will determine -convulsions. And it is worthy of remark that for some hours after this -convulsive discharge the centres return to something like their normal -state; and the animal may then be stroked, pinched, or blown upon -without abnormal reactions. But during this interval the centres are -slowly accumulating excess of tension from the poisoned blood; and at -the close, convulsions will again follow the slightest stimulus. This -alternation of exhaustion and recrudescence is noticed by Schröder -van der Kolk in the periodicity of the phenomena exhibited in spinal -disease.[185] - - -THE PROPAGATION OF EXCITATION. - -166. Understanding, then, that the propagation of an excitation -depends on the state of tension of the tissue, and always follows -the line of least resistance, whichever that may be at the moment, -we have to inquire whether the transmission takes place only in one -direction, from periphery to centre in sensory nerves, and from centre -to periphery in motor nerves? By most physiologists this is answered -affirmatively. Indeed a special property has been assigned to each -nerve, in virtue of this imaginary limitation of centripetal and -centrifugal conduction. The “nerve-current” (accepted as a physical -fact, and not simply a metaphor) is supposed to “flow” from the -central cells along the motor nerve to the muscles; but by a strange -oversight the current is also made to “flow” _towards_ the central -cells which are said to produce it! Now although the fact may be, and -probably is, that normally the sensory nerve, being stimulated at its -peripheral end, propagates the stimulation towards the centre, and the -motor nerve propagates its central stimulation towards the periphery, -the question whether each nerve is not capable of transmission in -both directions is not thus answered. _A priori_ it is irrational to -assert that nerves fundamentally alike in composition and structure -are unlike in properties; and we might as well suppose that a train -of gunpowder could only be fired at one end, as to suppose that a -nerve could only be excited at one end. And how does the evidence -support this _a priori_ conclusion? Dubois Reymond proved that each -nerve conducted electricity in both directions; but as Neurility -has not been satisfactorily shown to be identical with the electric -current, this may not be considered decisive. Such a doubt does not -hang over the following facts. M. Paul Bert, pursuing John Hunter’s -curious experiments on animal _grafting_, has grafted the tail of -a rat under the skin of the rat’s back, the tip of the tail being -inserted under the skin, its base rising into the air, so that there -is here an inversion of the normal position. In the course of time -Sensibility gradually reappears in this grafted tail; and at the -end of about twelve months the rat not only feels when the tail is -pinched, but knows _where_ the irritation lies, and turns round to bite -the pincers.[186] Here we have a case of a sensory nerve reversed, -yet transmitting stimulation from the base to the tip of the tail, -instead of from the tip to the base, as in a normal organ. Vulpian -and Philippeaux having divided two nerves, united the central end of -the sensory nerve with the peripheral end of the motor nerve; when -the organic union was complete, and each nerve was formed out of the -halves of two different nerves, the effect of pinching one of these -was to produce simultaneously pain and movement, showing that the -excitation was transmitted upwards to the centre, and downwards to the -muscles.[187] It may be compared with a train of gunpowder having a -loaded cannon at one end and a bundle of straw at the other, when if a -spark be dropped anywhere on this train, the flame runs along in both -directions, explodes the cannon, and sets alight the straw. - -167. Indeed we have only to remember the semi-liquid nature of the -axis cylinder to see at once that it must conduct a wave of motion as -readily in one direction as in another. A liquid transmits waves in any -direction according to the initial impulse. There is consequently no -reason for asserting that because the usual direction is centripetal -in a sensory nerve, and centrifugal in a motor nerve, each nerve is -_incapable_ of transmitting excitations in both directions. And I think -many phenomena are more intelligible on the assumption that neural -transmission is in both directions. If the eye is fixed steadfastly -on a particular color during some minutes, the retina becomes -exhausted, and no longer responds to the stimulus of that color: here -the stimulation is of course centripetal. But if instead of looking -intently on the color, the mind (in complete absence of light) pictures -it intently, _this cerebral image is equally capable of exhausting the -retina_; and unless we believe that color is a cerebral, not a retinal -phenomenon (which is my private opinion), we must accept this as proof -of a centrifugal excitation of a sensory tract. Another illustration -may be drawn from the muscular sense. There may be a few sensory fibres -distributed to muscles; but even if the observations of Sachs[188] -should be confirmed, I do not think that all muscle sensations can be -assigned to these fibres, but that the so-called motor fibres must -also co-operate. When a nerve acts upon a muscle, the muscle reacts -on the nerve; and when a nerve acts on a centre, the centre reacts on -the nerve. The agitation of the central tissue cannot leave the nerve -which blends with it unaffected; the agitation of the muscular tissue -must also by a reversal of the “current” affect its nerve. Laplace -points out how the movement of the hand which holds a suspended chain -is propagated along the chain to its terminus, and if when the chain -is at rest we once more set that terminus in motion, the vibration -will remount to the hand.[189] The contraction of a muscle will not -only stimulate the sensory fibres distributed through it, but also, I -conceive, stimulate the very motor fibres which caused the contraction, -since these fibres blend with the muscle.[190] - -168. To understand this, it is necessary to remember that the -stimulation of a nerve does not arise[191] in the _changed state_ of -that nerve, but in the _process of change_, i. e. the disturbance of -the tension. The duration of the stimulation is that of the changing -process, and the intensity increases with the differential of the -velocity of change. So that when a nerve which has been excited by a -change of state returns to its former state, this return--being another -change--is a new excitation. That it is not the changed state, but the -change, which is operative, explains the fact noted by Brown Séquard: -a frog poisoned by strychnine, when decapitated and all respiration -destroyed, will remain motionless for days together, if carefully -protected from all external excitation; but its nervous system is in -such a state of tension all this time that the first touch produces -general convulsions. Freusberg also notes that if a brainless frog be -suspended by the lower jaw, and one foot be pinched, the other leg is -moved at first, then quickly droops again, and remains at rest until -the pincers are removed from the pinched foot, when suddenly all four -legs are violently moved by the _stimulation which the simple removal -produces_. Let us also add the well-known and significant fact that -if a nerve be divided rapidly by a sharp razor, neither sensation -nor motion is produced, because the intensity of a stimulus being, -to speak mathematically, _the function of the changing process_, the -duration of the process is in this case too brief. On the same ground -the application of a stimulus will excite no movement, if the force be -very slowly increased from zero to an intensity which will destroy the -nerve; but at any stage a _sudden_ increase will excite a movement. - -169. We may group all the foregoing considerations in this formula: - - LAW I. Every neural process is due to a sudden disturbance of the - molecular tension. The liberated energy is discharged along the - lines of least resistance. - -The conditions which determine the lines of least resistance are -manifold and variable. The nervous system is a continuous whole, each -part of which is connected with diverse organs; but in spite of this -anatomical diversity, the deeper uniformity causes the activity of -each part to depend on and involve the activity of every other, more -or less. By “more or less” is meant, that although the excitation of -one part necessarily affects the state of all the others, because of -their structural community, so that _each sensation and each motion -really represents a change in the whole organism_, yet the responsive -discharge determined in each organ by this change, depends on the -tension of the organ and its centre at that moment. A bad harvest -really affects the whole nation; but its effect is conspicuous on the -welfare of the poor rather than of the rich, although the price of -bread is the same to rich and poor. Nervous centres, and muscular or -glandular organs, differ in their excitability; one condition of this -greater excitability being the greater frequency with which they are -called into activity. The medulla oblongata is normally more excitable -than the medulla spinalis; the heart more than the limbs. Hence a -stimulus which will increase the respiration and the pulse may have no -_appreciable_ effect on the limbs; but some effect it must have. - -170. Imagine all the nerve-centres to be a connected group of bells -varying in size. Every agitation of the connecting wire will more or -less agitate all the bells; but since some are heavier than others, -and some of the cranks less movable, there will be many vibrations -of the wire which will cause some bells to sound, others simply to -oscillate without sounding, and others not sensibly to oscillate. -Even some of the lighter bells will not ring if any external pressure -arrests them; or if they are already ringing, the added impulses, not -being rhythmically timed, will _arrest_ the ringing. So the stimulus -of a sensory nerve agitates its centre, and through it the whole -system; usually the stimulation is mainly reflected on the group of -muscles innervated from that centre, because this is the readiest path -of discharge; but it sometimes does not mainly discharge along this -path, the line of least resistance lying in another direction; and the -discharge never takes this path without also irradiating upwards and -downwards through the central tissue. Thus irradiated, it falls into -the general stream of neural processes; and according to the state in -which the various centres are at the moment it modifies their activity. -A nervous shock--physical or mental--sensibly affects all the organs. A -severe wound paralyzes, for a time, parts far removed from the wounded -spot. A blow on the stomach will arrest the heart; a fright will do -the same. Terror relaxes the limbs, or sets them trembling; so does -a concussion: if a frog be thrown violently on the ground, all its -muscles are convulsed; but if the nerves of one limb be divided before -the shock, the muscles of that limb will not be convulsed. - -171. We are apt to regard the discharge on the moving organs as if -that were the sole response of a stimulation; but although the most -conspicuous, it is by no means the most important effect. Besides -exciting the muscles, more or less, every neural process has its -influence on the organic processes of secretion, and effects thermal -and electrical changes. Schiff has demonstrated that every sensation -raises the temperature of the brain; Nothnagel, that irritation of a -sensory nerve causes constriction of the cerebral arteries, and hence -cerebral anæmia. Brown Séquard and Lombard find the temperature of -a limb raised when its skin is pinched, and lowered when the skin -_elsewhere_ is pinched. Georges Pouchet has shown that fishes change -color according to the brightness or darkness of the ground over which -they remain; and these changes are dependent on nervous stimulation, -mainly through the eye, division of the optic nerves preventing the -change. These are so many _a posteriori_ confirmations of what _a -priori_ may be foreseen. They are cited here merely to enforce the -consideration, seldom adequately kept before the mind, that every -neural process is a change which causes other changes in the whole -organism. - - -STIMULI. - -172. Stimuli are classed as external and internal, or physical and -physiological. The one class comprises all the agencies in the -External Medium which _appreciably_ affect the organism; the other -class all the changes _in_ the organism which appreciably disturb the -equilibrium of any organ. Although the pressure of the atmosphere, for -example, unquestionably affects the organism, and determines organic -processes, it is not reckoned as a stimulus unless the effect become -appreciable under sudden variations of the pressure. In like manner -the blood is not reckoned among the internal stimuli, except when -sudden variations in its composition, or its circulation, determine -appreciable changes. Because the external stimuli, and the so-called -Senses which respond to them, are more conspicuous than the internal -stimuli and the Systemic Senses, they have unfortunately usurped too -much attention. The massive influence of the Systemic Sensations in -determining the desires, volitions, and conceptions of mankind has not -been adequately recognized. Yet every one knows the effect of impure -air, or a congested liver, in swaying the mental mood; and how a -heavy meal interferes with muscular and mental exertion.[192] What is -conspicuous in such marked effects, is less conspicuously, but not less -necessarily, present in slighter stimuli. - -173. A constant pressure on the tympanum excites no sound; only a -rhythmic alternation of pressures will excite the sensation. A constant -temperature is not felt; only changes in temperature. If Light and -Sound were as uniform as the circulation of the blood, or the pressure -of the atmosphere, we should be seldom conscious of the existence of -these stimuli. But because the changes are varied and marked, our -attention is necessarily arrested by them. The changes going on within -the tissues are too graduated to fix the attention; it is only by -considering their cumulative effects that we become impressed with -their importance. For example, the development of the sexual glands -determines conspicuous physical and moral results--we note consequent -effects on voice, hair, horns, structure of the skull and size of the -muscles, no less than the rise of new feelings, desires, instincts, -ideas. Any organic interference with the activity of the ovaries will -alter the moral disposition of the animal: suppression of this organic -process means non-development of the feelings of maternity; the moral -superstructure is absent because its physical basis is wanting. - -174. Blood supplies the tissues with their plasmodes; a constant -supply of oxygenated blood is therefore necessary to the vitality of -the tissues. But it is an error to suppose that oxygen is the special -stimulus of nerve-centres, or that their activity depends on their -oxidation; on the contrary, the deficiency of oxygen or surplus of -carbonic acid is that which stimulates. When saturated with oxygen, -the blood paralyzes respiration; when some of the oxygen is withdrawn, -respiration revives. Here--as in all other cases--we have to remember -that differences in degree readily pass into differences in kind, -so that an excess of a stimulus produces a reversal of the effect; -thus although surplus of carbonic acid excites respiratory movements, -excess of carbonic acid causes Asphyxia. Abundance of blood is -requisite for the continuous activity of nerve-centres; but while a -temporary deficiency of blood renders them more excitable, too great a -deficiency paralyzes them. Anæmia, which causes great excitability, and -convulsions (so that nerves when dying are most irritable), may easily -become the cause of the death of the tissue. There are substances which -can only be dissolved by a given quantity of liquid; if this quantity -be in excess, they are precipitated from the solution. There are -vibrations of a given order which cause each string to respond; change -the special order, and the string returns to its repose. - -In the stillness and darkness of the night we are excluded from most -of the external stimuli, yet a massive stream of systemic sensations -keeps the sensitive mechanism active, and in sleep directs the dreams. -The cramps and epileptiform attacks which occur during sleep are most -probably due to the over-excitability produced by surplus carbonic -acid. To temporary anæmia may be assigned the strange exaggeration of -our sensations during the moments which precede awakening; and the -greater vividness of dream-images. - -It is only needful to mention in passing the varied stimuli by which -cerebral changes act upon the organism. The mention of a name will -cause a blush, a brightening of the eye, a quickening of the pulse. The -thought of her absent infant will cause a flow of milk in the mother’s -breast. - -175. We may formulate the foregoing considerations in another law: - - LAW II. The neural excitation, which is itself a change, directly - causes a change in the organ innervated, and indirectly in the - whole organism. - -The significance of this law is, that although for the convenience -of research and exposition we isolate one organ from the rest of the -organism, and one process from all the co-operant processes, we have to -remember that this is an artifice, and that in reality there is no such -separation. - - -STIMULATION. - -176. Passing now from these general considerations to their special -application, we may formulate the law of stimulation: - - LAW III. A faint or moderate stimulation increases the activity - of the organ; but beyond a certain limit, increase of - stimulation diminishes, and finally arrests, the activity. - Duration of stimulation is equivalent to increase. - -A muscle stimulated contracts; if the stimulation be repeated, -the muscle becomes tetanized, and in this state has reached its -limit; a fresh stimulation then _relaxes_ the muscle. A very faint -stimulation of the vagus quickens the pulsation of the heart, but a -slight increase, or duration of the stimulation, slackens and arrests -the heart.[193] Every one knows how a moderate feeling of surprise, -pleasure, or pain quickens the heart and the respiration; and how a -shock of surprise, joy, grief, or great physical pain depresses, -and even arrests them. Excess of light is blinding; excess of sound -deafening. - -177. The nervous system is incessantly stimulated, and variably. -Hence a great variation in the excitability of different parts. While -the regular and moderate activity of one part is accompanied by a -regular flow of blood to it, so that there is a tolerably constant -rhythm of nutrition and discharge, any irregular or excessive activity -exhausts it, until there has been a nutritive restoration. We can -thus understand how one centre may be temporarily exhausted while -a neighboring centre is vigorous. Cayrade decapitated a frog, and -suspended light weights to each of its hind legs; when either leg was -stimulated, the weight attached to it was raised. After each repetition -the weight was raised less and less, until finally the weight ceased to -be raised: the centre had been exhausted. But now when the other leg, -which had been in repose, was stimulated, it energetically contracted, -and raised its attached weight; showing that its centre was not -exhausted by the action of the other.[194] - -178. This seems in contradiction with the principle that the excitation -of one centre is an excitation of all. It also seems in contradiction -with the principle urged by Herzen, that irritation of one sciatic -nerve _diminishes_ the excitability of the opposite leg; and this again -seems contradicted by the principle urged by Setschenow, that although -moderate excitation of one sciatic nerve will diminish the excitability -of the other, a powerful excitation will increase it. - -179. All three principles are, I believe, exact expressions of -experimental evidence; and their seeming contradictions may be -reconciled on a wider survey of the laws of neural activity, -interpreted according to the special conditions of each case. These -laws may be conveniently classified as laws of Discharge, and Laws of -Arrest; the second being only a particular aspect of the first. - - -THE LAW OF DISCHARGE. - -180. The physiological independence of organs, together with their -intimate dependence in the organism, and the fact that this organism is -incessantly stimulated from many sides at once, assure us _a priori_ -that the “waves” of molecular movement due to each stimulus must -sometimes interfere and sometimes blend with others, thus diverting or -neutralizing the final discharge in the one case, and in the other case -swelling the current and increasing the energy of the discharge. We -are accustomed to speak of one part “playing on another,” sympathizing -with another, and so on; but what is the process expressed in these -metaphors? When an idea, or a painful sensation, quickens the pulse, -or increases the flow of a secretion, we are not to imagine that from -a spot in the cerebrum, or the surface, there is a nerve-fibre going -directly to the heart, or the gland, transmitting an impulse; in each -case the central tissue has been agitated by a sudden change at the -stimulated point, and the discharge on heart and gland is the resultant -of this agitation along the lines of least resistance. The nerves of -the great toe, for example, pass into the spinal cord at a considerable -distance from the spot where the nerves of the arm enter it; when, -therefore, the great toe is pinched, the arm does not move by direct -stimulation of its nerves, but by the indirect stimulation which has -traversed the whole central substance. - -181. This is intelligible when we know that the whole central substance -is continuous throughout; but the difficulty arises when we have to -explain why, if this central substance is stimulated throughout, -_only_ arms and legs respond; in other words, why the toe-centre -“plays upon” the arm-centre, and not on the others? When a frog is -decapitated, if we gently touch one leg with the point of the scalpel, -the leg will move, but only this leg. Prick more forcibly, and both -legs will move. Keep on pricking, and all four legs are drawn up, and -the frog hops away. Each excitation was propagated along the cord; -but the discharge was restricted in the first case to one limb, in -the second to two, in the third it involved all the muscles of the -trunk. At the sight of a friend a dog wags his tail gently: as there -is no _direct_ connection between the optic nerves and the tail, this -playing of one centre on another must be by the agency of intermediate -centres; and we know that if the dog’s spinal cord be divided, this -excitation from the optic centre is no longer possible, yet the tail -will wag if the abdomen be tickled, or the leg pinched. Now compare the -effect on the dog produced by the sight of his master, or of a friend -accustomed to take him out. There is no longer a gentle wagging of the -tail, but an agitation of the whole body: he barks, leaps, and runs -about; the central stimulation is discharged through many outlets; and -could we test the effect, we should find an appreciable alteration -in the thermal and electrical condition of the whole organism, with -corresponding changes in circulation, secretion, etc. So different are -the consequences of two slightly different retinal impressions mingling -their stimulations with the same mass of central substance! - -182. The discharge is determined by two conditions: the state of -tension, and the energy of the stimulation. _The state of tension is -increased by every stimulation which falls short of a discharge_; that -is to say, faint and frequent stimulation augments the excitability, -whereas powerful stimulation exhausts it. When, therefore, one -wave succeeds another in the same direction, it reaches a centre -more disposed to discharge; or, as Cayrade expresses it, “a certain -agitation of the cells is necessary for the manifestation of their -property of reaction, in the same way that the concentric circles -produced on the surface of water by a falling stone are more rapid and -more numerous if a stone has already agitated the surface.” - -183. So much for the tension. What has been called the energy of the -stimulation is more complicated. It is not measurable as a simple -physical process; we cannot say that a given quantity of any external -force will determine a given discharge. It is mostly complicated by -psychical processes, and these so modify the result that instead of the -predicted discharge there is arrest, or discharge from another centre. -Press a dog’s skin with increasing violence, and the effect increases -from pleasurable to painful irritation; but whether the dog will cry -out and bite, or cry out and struggle to escape, depends upon whether -the pincher is a stranger or a friend. If you hurt a dog while removing -a thorn from its foot it will cry out, but although the pain causes it -to initiate a biting movement, by the time your hand is reached that -movement will have been changed, and the dog will lick the hand which -he knows is hurting him in the endeavor to relieve him of the thorn. -The co-operation of the mind is here evident enough. A purely psychical -process has interfered with the purely physiological process. And I -shall hereafter endeavor to show that psychical processes analogous in -kind though simpler in degree are really co-operant in actions of the -spinal cord. The dog would be said to discriminate between the pain -inflicted by a friend, and the same pain inflicted by a stranger. In -other words, the sensitive mechanism would be differently determined -in the direction of discharge, although the initial stimulation was the -same in each case. If we admit that the resulting action is in each -case the consequence of the particular group of elements co-operating, -there will be no ground for denying that analogous _discrimination_ -is manifested by the brainless animal, who also responds differently -to different external stimuli, and differently to the same stimulus -under different central conditions. The brainless frog croaks if its -back be gently stroked with the handle of a scalpel; but if the point -be used, or if the handle be roughly pressed, instead of croaking, -the frog raises his leg in defence. Here the difference in the -peripheral irritation has excited a different reaction in the centre; -and this might be interpreted as purely physical; if now the leg be -fastened, and the movement of defence be thus prevented, the frog will -employ the other leg; or adopt some other means of relieving itself -from the irritation. It was a mass of registered experiences which -determined the dog not to bite his master. An analogous registration -of experiences determines the changed reactions of the brainless frog. -But this is a point which can only be touched on in passing here, and -it is touched on merely to facilitate our exposition of the complicated -conditions of neural discharge. These may be formulated in - - 184. LAW IV. The simultaneous influence of several stimuli, each - of which separately excites the same centre, is cumulative: - stimuli then assist each other, and their resultant is their - _arithmetical_ sum. - - Simultaneous stimuli, each of which excites a different centre, - _interfere_ with each other’s energy, and their resultant is - their _algebraical_ sum. - -In this law there is a condensed expression of that composition of -forces which may either result in Discharge or Arrest. By simultaneity -is not to be understood merely the coincidence of impressions, but also -the reverberations of impressions not yet neutralized by others. Thus -when Sensibility is tested by the now common method,[195] it is found -that if one leg is withdrawn after a lapse of, say, ten pendulum beats, -the other leg, which has not been irritated, will nevertheless, on -irritation, be withdrawn in less than ten beats, provided the central -agitation caused by the first stimulation has _not yet subsided_. But, -on the contrary, the withdrawal will be considerably deferred, or -even prevented altogether, if at the same time that the leg is acted -on by the acid, a more powerful excitation takes place in some other -part of the body. In the one experiment we see simultaneous excitation -in the same centre and the same direction. In the other simultaneous -excitation in different centres. The more powerful excitation -suppresses the discharge from the less powerful; but although it -prevails, it loses just as much force as it arrests.[196] - -185. There is another very interesting experiment by Freusberg, which -must be cited here.[197] When the sciatic nerve is divided, the frog’s -leg is of course not withdrawn from the acidulated water, because in -that case no sensory excitation is propagated from the skin to the -centre; but although there is no stimulation from the skin, there is -one from the muscles, as appears in the fact that if a small weight be -suspended on this leg, the other leg is more rapidly withdrawn from the -acidulated water--the action of the muscles having affected the centre -and increased its excitability. - -186. When the motor group of one leg is moderately stimulated, the -discharge is confined to the muscles of that one leg; and according -to Herzen the excitability of the motor group of the other leg is -thereby somewhat diminished. But if the stimulation be increased, there -is an irradiation to the other group, which irradiation, although -not sufficient to excite a discharge, renders it much more _ready_ -to discharge, so that a feeble stimulus suffices. This accords with -Setschenow’s observations, and is confirmed by Freusberg’s experiment, -in which, when one leg was stimulated by acid, if the acid were not -wiped off but allowed to keep up the irritation, the other leg moved -without being irritated; and this other leg having come to rest, when -in its turn dipped in the acid, was more rapidly withdrawn than the -first leg had been on first being stimulated; showing that the central -groups had become more excitable by the stimulation of either leg. - -187. While it is intelligible that an excitation of one group should -increase the activity of neighboring groups, by an increase of the -vascular activity of the region, it is not so readily intelligible why -the feebler excitation of one group should diminish the excitability of -its neighbor; yet the facts seem to warrant both statements. - -188. The conditions which determine Discharge are obscure. We may, -however, say that anatomical and physiological data force the -conclusion that whenever the central tissue is powerfully stimulated -in any one part, there is either a discharge, or a greater tension -(tendency to discharge) in every other part; in consequence of -which, every fresh stimulus in the _same_ direction finds the parts -more prepared to react; while every fresh stimulus in a _contrary_ -direction meets with a proportional resistance. Stated thus generally, -the principle is clear enough; but the immense complication of -stimulations, and the statical variableness of the organs, renders its -application to particular cases extremely obscure. Why does the ticking -of a clock arrest the attention, even with unpleasant obtrusiveness, at -one time, and presently afterwards cease to be heard at all? Why does -the cut of a knife cause intense pain, and a far greater cut received -during the heat and agitation of a quarrel pass unfelt? Why will the -same external force excite convulsions in all the muscles, and at -another time scarcely be distinguishable? These are consequences of the -temporary condition of the centres; but there are permanent conditions -which in some organisms determine equally variable results. Thus the -shock of terror which will simply agitate one person, will develop an -epileptic attack in another, and insanity in a third; just as exposure -to cold will in one person congest the liver, in another the lungs. A -loud and sudden sound causes winking in most persons, and in many a -sort of convulsive shock. The harsh noise of a file causes a shiver in -some persons, and in others “sets the teeth on edge,” while in others -it causes an increased flow of saliva. - -189. Nerves and centres have different degrees of excitability. The -nerve-terminals in the skin are more sensitive to impressions than -those in the mucous membrane; those in the alimentary canal are more -sensitive than those in the peritoneum; and all nerve-terminals are -more sensitive than nerve-trunks. A touch on the surface of the larynx -will produce a cough, but the nerve-trunk itself may be pinched or -galvanized without producing any such reflex. Moreover, there is the -difference of grouping. If the skin of the abdomen be tickled, there -is a reflex on the adductor and extensor muscles of the leg; but these -movements are reversed if the skin of the back be tickled. Nor indeed -are these movements invariable in either case; the one series will -sometimes quite suddenly change to the other, if the irritation is kept -up. That one and the same stimulus applied to the same spot should now -excite this group and now the other, shows that _both_ motor groups -are affected, and that the discharge takes place from the one which at -the time being is in the highest tension. The alternation of tension -explains rhythmical discharge. - - -THE LAW OF ARREST. - -190. The Law of Arrest is only another aspect of the Law of Discharge, -and may be regarded as the conflict of excitations. If a stranger -enters the room where a woman lies in labor, there will often be caused -a sudden cessation of the uterine contractions.[198] Again, every one -knows how the breathing and the beating of the heart are arrested by -the idea of danger. The arrest is in each of the three cases only -temporary, because when the shock of the new stimulus has caused its -discharge (arrest), the peripheral irritation which caused the former -discharges resumes its influence, and uterus, heart, and diaphragm -begin to move again, even more energetically. Note, moreover, that not -only will the cerebral excitation arrest the spinal discharge--an idea -check the contractions of the uterus or the heart--but the reverse -also takes place. The brain of the woman may be intently occupied with -some scheme for the education or welfare of her expected child, but no -sooner do the labor pains set in, than all these cerebral combinations -are arrested. - -191. One sensation arrests another; one idea displaces another. If -the foreleg of a headless frog be irritated, the hind-leg will also -be moved by the stimulation; or _vice versa_. Here there has been a -propagation of the excitation in either direction. But if while the -legs are thus irritated, and the centres are ready to discharge, -another and more powerful irritation reach the centre--say by pinching -the skin of the back--there will be no discharge on the legs. If the -vagus be irritated, the heart is arrested; but this does not take place -if at the same time, or immediately before, the foot has been sharply -pinched. A few gentle taps on the abdomen suffice to stop the heart; -but if a drop of acid be previously placed on the skin, we tap in vain, -the heart continues to beat. Brown Séquard cites several cases in which -convulsions were arrested by irritation of sensitive surfaces;[199] -and Dr. Crichton Browne records a case of a patient in whom there was -abolition of spinal reflex, due to cerebral irritation: tickling the -soles of the feet, or pricking the toes, which normally excites reflex -movements, in this case excited none whatever. “This seems to prove -that nerve currents, set in motion by irritation of the brain, or some -of its convolutions, transmitted down the cord, may inhibit reflex -action.”[200] Examples might indefinitely be multiplied. Pinch the -skin of a rabbit between the eyes, and you will observe that pulse and -respiration are slackened; but if the tail, which is very sensitive, -be pinched, this slackening is only momentary, and is succeeded by a -quickening--unless the pain be great. Even the effect of intense pain -may be neutralized by stimulating the vagus--just as the effect of -stimulating the vagus may be neutralized by pain. Claude Bernard found -that having dropped ammonia on the eyelid of a dog, the pain caused a -convulsive closure of the lid; but on galvanizing the vagus, the lid -opened again, to be closed when the galvanism ceased.[201] When the -heart is beating faintly (as in syncope), any irritating vapor applied -to the nostrils will cause a more energetic pulsation; yet a very -irritating vapor lowers the action of the heart beating normally, and -will even arrest that of a rabbit. Over-stimulation has almost always -the opposite effect of moderate stimulation. - -192. While there seems every reason to believe that an excitation -necessarily affects the whole cerebro-spinal axis, there is no doubt -that there is a certain restriction of this irradiation to definite -paths, i. e. the responsive discharge is confined to definite groups. -Some of these restrictions are connate pathways: we bring them with us -at birth; but most of them are pathways acquired after birth. The boy -who sheds tears at parting from his mother when he goes to school, will -shed no tears when he parts from her to go to college, nay, perhaps -will shed none when he parts from her forever: not that his love has -lessened, but that the idea of such expression of it as “unmanly” has -become an organized tendency and arrests the tears. A youth of southern -race, who has not learned to be ashamed of tears, weeps freely under -such circumstances. - -193. The pathways organized at birth are not many. Examples are the -inspiration which follows expiration; the movements of coughing when -the larynx is tickled; the movements of swallowing, sneezing, etc. Even -these may be arrested for a brief time by what is called “the will”; -but when once the discharge begins in any part of the mechanism, the -whole group is necessarily involved and the action is then inevitable. -Many of the reflex actions which are universal are nevertheless -acquired. Winking, for instance, when an object approaches the eye, is -universal among us, but is never seen in infants, nor in animals. It -is even doubtful whether the drawing up of the leg when the toes are -pinched is not an acquired reflex. Doubtful, I mean, in this sense, -that although the fact of non-withdrawal is observable in infants, who -cannot localize their sensations, this may be due to the imperfect -development of their nervous system. Mr. Spalding has proved that -although the callow bird cannot fly, the mechanism of flight is no -sooner developed than the action follows at once, without any previous -tentative experiences. - -194. By experience we learn to restrict the paths of irradiation, -so as to wink with one eye while the other is unmoved, to bend one -finger while the rest are extended, to move one limb, or one group of -muscles, while the others are at rest; in short, to execute any one -particular action, and not at the same time agitate superfluously many -other organs. The boy when first learning to write is unable to prevent -the simultaneous motions of tongue and legs, which are ludicrously -irrelevant to the purpose of writing; but he learns to keep all his -organs in subjection, and only the eyes and hands active.[202] An -analogous restriction takes place in thinking. A train of thought is -kept up by the exclusion of all suggestions which are not pertinent; -and the power of the thinker is precisely this power of concentration. - - -THE HYPOTHESIS OF INHIBITORY CENTRES. - -195. The facts and their formulated laws which have just been adduced -furnish a sufficient explanation of all the phenomena of arrest -which of late years have been detached and assigned to a special -mechanism of inhibitory nerves and centres. In spite of the eminent -authorities countenancing the hypothesis of a particular set of -inhibitory nerves, and particular centres of inhibition, I must confess -that the hypothesis appears to me inadmissible; and that I side with -those physiologists who hold that each nerve and each centre has its -inhibitory action. Indeed, if the action of arrest be, as I maintain, -only another aspect of the action of discharge, the result of the -conflict of forces, to say that all centres have the property of -excitation, is to say that all have the properties of discharge and -arrest: the discharge is only the resultant of the conflict along the -line of least resistance; the arrest is the effect of the conflict -along the line of greatest resistance. The observed phenomena of -arrest are so varied and numerous that the upholders of the inhibitory -hypothesis have been forced to invent not only arresting centres, -but centres which arrest these arresting centres! Dr. Lauder Brunton -candidly remarks: “At present our notions of nervous action seem to be -getting as involved as the Ptolemaic system of astronomy, and just as -epicycles became heaped upon cycles, so nerve-centres are being added -to nerve-centres. And yet, clumsy though the system may be, it serves -at present a useful purpose, and may give real aid until a better -is discovered.” I do not think a Copernicus is needed to discover -a better. The Law of Arrest as a general neural law suffices, when -the right conception of a _centre_ as a physiological rather than an -anatomical designation is admitted. (See p. 173.) - -196. It would be out of place here to consider the conflicting evidence -which at present renders the question of the movements of the heart -one of the most unsatisfactory in the whole range of experimental -physiology. After devoting much time to it, and after writing a long -chapter on it, I suppress what I had written, and content myself with -the statement that no advantage whatever is derived from the hypothesis -of a special mechanism of arrest, unless perhaps in giving a temporary -precision to the direction of research. I mean that the search for -special centres may lead to the discovery of the particular paths to -which an impulse is restricted in any one action: as, for instance, -the vagus in retarding the pulsation of the heart. If the cerebrum can -determine a movement, and combine various movements, it is a centre of -arrest; if the cerebellum can determine and regulate movements, it is a -centre of arrest; if the medulla oblongata can determine and regulate -movements, it is a centre of arrest; if the medulla spinalis can -determine and combine movements, it is a centre of arrest; if a nerve -can dilate a constricted blood-vessel, or constrict a dilated one, it -is a nerve of arrest. In other words, every centre exerts its action -either in discharging, or in arresting the discharge of some other -centre. - -The physiological process of Arrest may be physically interpreted -as Interference;[203] not that the process in nerve-tissue is to be -understood as the _same_ as that observed in fluids, or that the -metaphor of neural waves is to be taken for more than an intelligible -picturing of the process; the difference in the two agents forbids our -admitting the resemblance to be more than analogical. Thus interpreted, -however, we see that not only will one centre arrest the action of -another, but one nerve may be made to arrest itself! I mean that, under -similar conditions of interference, the stimulation which normally -follows on external stimulus may be inhibited by a previous, or a -counter stimulation. Thus the nerve which will be stimulated by a -chemical or mechanical stimulus, wholly fails to react if a constant -current is passing through it, although this constant current does not -itself cause a constant contraction. Remove the electrodes, and then -the chemical or mechanical stimulus takes effect. Or the experiment -may be reversed: let the nerve be placed in a saline solution, and -the muscles will be at once thrown into violent contraction; if the -electrodes are now applied to the nerve, the contractions suddenly -cease, to begin again directly the electrodes are removed. - - -ANATOMICAL INTERPRETATION OF THE LAWS. - -197. The problem for the anatomist is twofold: First, given the -organ, he has to determine its function, or _vice versa_, given the -part of an organ, to determine its functional relation; secondly, -given the function, he has to determine its organ. The structural -and functional relations of nerves and centres have been ascertained -in a general way; we are quite sure that the posterior nerves carry -excitations from sensitive surfaces, that the anterior nerves carry -excitations to muscles and glands; and that the central gray substance -not only reflects a sensory excitation as a motor excitation, but -propagates an excitation along the whole cerebro-spinal axis. But when -we come to a more minute analysis of the functional activities, and -endeavor to assign their respective values to each part of the organic -mechanism, the excessive complexity and delicacy of the mechanism -baffles research. We are forced to grope our way; and the light of the -hypothetic lamps which we hold aloft as often misdirects as helps us. -The imaginary anatomy which at present gains acceptance, no doubt seems -to simplify explanations; but this seeming turns out to be illusory -when closely examined. The imagined arrangement of fibres and cells -we have seen to be not in agreement with observation; and were it -demonstrable, it would not account for the laws of propagation. Suppose -sensory fibres to terminate in cells, and fibres from these to pass -_upwards_ to other sensory cells and _transversely_ to motor cells, how -in such a connected system could irradiations take place, if the law of -isolated conduction were true? And how could isolated conduction take -place, if the excitation of a part were necessarily the excitation of -the whole? Why, for example, is pain not always irradiated? Why is it -even localized in particular spots, determining movements in particular -muscles; and when irradiation takes place, why is it circumscribed, -or--and this is very noteworthy--manifested in two widely different -places, the intercostal and trigeminal nerves? Why does the irritation -of intestinal worms manifest itself now by troubles of vision, now by -noises in the ear, and now by convulsions? - -198. Answers to such questions must be sought elsewhere. Our first -search should be directed to the anatomical data, which have hitherto -been so imprudently disregarded. Under the guidance of the laws -formulated in this chapter, let us accept the anatomical fact of a -vast network forming the ground-substance in which cells and fibres -are embedded, and with which they are continuous; let us accept the -physiological principle Of similarity of property with similarity -of composition and structure; let us accept the hypothesis that the -discharge of neural energy is dependent on the degree of stimulus -and the degree of tension at the time being--and we shall have at -least a general theory of the process, though there will still remain -great obscurities in particular applications. We shall have before -us a vast network of pathways, all equally capable of conducting an -excitation, but not all equally and at all moments open. It will always -be difficult to determine what are the conditions which at any moment -favor or obstruct particular openings. Paths that have been frequently -traversed will of course be more readily traversed again; but this very -facility will _sometimes_ be an obstacle, since it will have caused -that path to be preoccupied, or have fatigued the organ to which it -leads. - -199. Since the escape of an excitation must always be along the lines -of least resistance, an obvious explanation of the restriction to -certain paths has been to assume that some fibres and cells have -naturally greater resistance than others. But this explanation is -simply a restatement of the fact in other words. What is this greater -resistance? Why is it present in one fibre rather than in another? -We should first have to settle whether the resistance was in the -nervous pathway itself, or in the centre, or in the organ innervated; -an excitation might pass along the nervous tract, yet fail to change -the state of the centre, or the organ, sufficiently to produce an -appreciable response; and only those parts where an appreciable -response was produced would then be considered as having had the -pathways of propagation open. - -200. When we reflect on the innumerable stimulations to which the -organism is subjected from so many various points, and remember -further that _each stimulation leaves behind it a tremor which -does not immediately subside_, we shall conceive something of the -excessive complexity of the mechanism, and marvel how any order is -established in the chaos. What we must firmly establish in our minds -is that the mechanism is essentially a _fluctuating_ one, its elements -being combined, recombined, and resolved under infinite variations -of stimulation. If it were a mechanism of fixed relations, such as -we find in machines, or in the “mechanism of the heavens,” we might -accept the notion of certain organites having greater resistance as -a consequence of their structure, just as one muscle resists being -moved by the impulse which will move another. Nor is it doubtful -that such differences exist in nervous organites; but the laws of -central excitation are not interpretable by any such hypothesis, -since we know that the paths which were closed against an impulse of -considerable energy may be all open to an impulse of feebler energy, -and that a slight variation in the stimulus will be followed by a wide -irradiation. For example, a grain or two of snuff will excite the -violent and complex act of sneezing, but the nerves of the nasal cavity -may be pinched, cut, or rubbed, without producing any such result. -One group of nervous organites will fail to involve the activity of -neighboring groups; and the simple movement of a single organ is then -all that appreciably follows the stimulation; yet by a slight change in -the stimulation, the organites are somewhat differently grouped, and -the result is a complex movement of many organs. It is this fluctuation -of combination in the organites which renders education and progress -possible. Those combinations which have very frequently been repeated -acquire at last an automatic certainty. - - * * * * * - -We are now in a position to examine with more precision the extremely -important laws of nervous action which are involved in the phenomena -designated by the terms Reflex Action, Automatic Action, and Voluntary -Action. - - - - -PROBLEM III. - -ANIMAL AUTOMATISM. - - “L’organisme le plus complexe est un vaste mécanisme qui résulte de - l’assemblage de mécanismes secondaires.”--CLAUDE BERNARD. - - “Les corps vivants sont machines à l’infini.”--LEIBNITZ. - - “Noi lamentiamo con Majendie che nel linguaggio fisiologico siensi - intruse le preopinioni psicologiche col trascico inevitabile - del vocaboli, ai quali codeste preopinioni si trovano legate. - Probabilmente questa fu una delle principali cagioni degli errori e - degli equivoci anatomofisiologici, da cui non poterono svincolarsi, - a loro insaputa, i cultori sperimentali della scienza, perchè nell’ - interpretare i fenomeni osservati erano obbligati ad usare il - linguaggio di una false moneta in corso.”--LUSSANA _e_ LEMOIGNE, - _Fisiologia dei Centri Nervosi_, 1871, I. 16. - - - - -ANIMAL AUTOMATISM. - - - - -CHAPTER I. - -THE COURSE OF MODERN THOUGHT. - - -1. Modern Philosophy has moved along two increasingly divergent lines. -One, traversed by Galileo, Descartes, Newton, and Laplace, had for -its goal the absolute disengagement of the physical from the mental, -i. e. the objective from the subjective aspect of phenomena, so -that the physical universe, thus freed from all the complexities of -Feeling, might be interpreted in mechanical terms. As a preliminary -simplification of the problem this was indispensable; only by it -could the First Notion of primitive speculation be replaced by the -Theoretic Conception of scientific speculation.[204] The early -thinker inevitably invested all external objects with properties and -qualities similar to those he assigned to human beings, and their -actions he assigned to human motives. Sun, moon, and stars seemed -living beings; flames, streams, and winds were supposed to be moved -by feelings such as those known to move animals and men. Nor was any -other conception then possible: men could only interpret the unknown -by the known, and their standard of all action was necessarily drawn -from their own actions. Not having analyzed Volition and Emotion, -above all not having localized these in a neuro-muscular system, men -could not suspect that the movements of planets and plants, and of -streams and stones, had motors of a different kind from the movements -of animals. The scientific conception of inert insensible Matter was -only attained through a long education in abstraction; and is assuredly -never attained by animals, or by savages. But no sooner were vital -conditions recognized, than the difference between vital and mechanical -movements emerged. When men learned that many of their own actions -were unaccompanied either by Love or Hate, by Pleasure or Pain, and -that many were unprompted by conscious intention, while others were -unaccompanied by conscious sensation, they easily concluded that -wherever the special conditions of Feeling were absent, the actions -must have some other motors. Intelligence, Emotion, Volition, and -Sensation being one by one stripped away from all but a particular -class of bodies, nothing remained for the other bodies but insensible -Matter and Motion. This was the Theoretic Conception which science -substituted for the First Notion. It was aided by the observation -of the misleading tendency of interpreting physical phenomena by -the human standard, substituting our fancies in the place of facts, -manipulating the order of the universe according to our imagination -of what it might be, or ought to be. Hence the vigilance of the new -school in suppressing everything pertaining to the subjective aspect -of phenomena, and the insistance on a purely objective classification, -so that by this means we might attain to a knowledge of things as they -are. By thus withdrawing Life and Mind from Nature, and regarding -the universe solely in the light of Motion and the laws of Motion, -two great scientific ends were furthered, namely, a classification -of conceptions, and a precision of terms. Objective phenomena made a -class apart, and the great aim of research was to find a mathematical -expression for all varieties under this class. Masses were conceived -as aggregates of Atoms, and these were reduced to mathematical points. -Forces were only different modes of Motion. All the numberless -differences which perception recognized as _qualities_ in things, were -reduced to mere variations in _quantity_. Thus all that was particular -and concrete became resolved by analysis into what was general and -abstract. The Cosmos then only presented a problem of Mechanics. - -2. During this evolution, the old Dualism (which conceived a material -universe sharply demarcated from the mental universe) kept its -ground, and attained even greater precision. The logical distinction -between Matter and Mind was accepted as an essential distinction, -i. e. representing distinct reals. There was on the one side a group -of phenomena, Matter and Force; on the other side an unallied group, -Feeling and Thought: between them an impassable gulf. How the two -were brought into relation, each acting and reacting on the other, -was dismissed as an “insoluble mystery”--or relegated to Metaphysics -for such minds as chose to puzzle over questions not amenable to -experiment. Physics, confident in the possession of mathematical -and experimental methods which yielded definite answers to properly -restricted questions, peremptorily refused to listen to any suggestion -of the kind. And the career of Physics was so triumphant that success -seemed to justify its indifference. - -3. In our own day this analytical school has begun to extend its -methods even to the mental group. Having reduced all the objective -group to mathematical treatment, it now tries to bring the subjective -group also within its range. Not only has there been more than one -attempt at a mathematical Psychology; but also attempts to reduce -Sensibility, in its subjective no less than in its objective aspect, to -molecular movement. Here also the facts of Quality are translated into -facts of Quantity; and all diversities of Feeling are interpreted as -simply quantitative differences. - -4. Thus far the one school. But while this Theoretic Conception -stripped Nature of consciousness, motive, and passion, rendering it a -mere aggregate of mathematical relations, a critical process was going -on, which, analyzing the nature of Perception, was rapidly moving -towards another goal. Locke, Berkeley, Hume, and Kant, directing their -analysis exclusively to the subjective aspect of phenomena, soon broke -down the barriers between the physical and mental, and gradually merged -the former in the latter. Matter and its qualities, hitherto accepted -as independent realities, existing where no Mind perceived them, were -now viewed as the creations of Mind--their existence was limited to a -state of the percipient. The old Dualism was replaced by Idealism. The -Cosmos, instead of presenting a problem of Mechanics, now presented a -problem of Psychology. Beginning with what are called the secondary -qualities of Matter, the psychological analysis resolved these into -modes of Feeling. “The heat which the vulgar imagine to be in the fire -and the color they imagine in the rose are not there at all, but are in -us--mere states of our organism.” Having gained this standing-place, -there was no difficulty in extending the view from the secondary to the -primary qualities. These also were perceptions, and only existed in -the percipient. Nothing then remained of Matter save the hypothetical -unknown _x_--the postulate of speculation. Kant seemed forever to have -closed the door against the real Cosmos when he transformed it into -a group of mental forms--Time, Space, Causality, Quantity, etc. He -propounded what may be called a theory of mental Dioptrics whereby a -pictured universe became possible, as Experience by its own _a priori_ -laws moulded _itself_ into a consistent group of appearances, which -produced the illusion of being a group of realities. He admitted, -indeed, that by the operation of Causality we are compelled to believe -in a Real underlying the appearances; but the very fact that this -Causality is a _subjective law_, is proof, he said, of its not being -an _objective truth_. Thus the aim of the mechanical conception was -to free research from the misleading complexities of subjective -adulterations, and view _things as they are_ apart from their -_appearances_; but this aim seemed illusory when Psychology showed that -Time, Space, Matter, and Motion were themselves not objective reals -except in so far as they represented subjective necessities; and that, -in short, things _are_ just what they _appear_, since it is only in the -relation of external reals to internal feelings that objects exist for -us. - -5. Idealism has been the outcome of the psychological method. It -has been of immense service in rectifying the dualistic conception, -and in correcting the mechanical conception. It has restored the -subjective factor, which the mechanical conception had eliminated. -It has brought into incomparable clearness the fundamental fact that -all our knowledge _springs from_, and is _limited by_, Feeling. It -has shown that the universe represented in that knowledge, can only -be a picture of the system of things as these exist in relation to -our Sensibility. But equally with the mechanical conception it has -erred by incomplete analysis. For a complete theory of the universe, -or of any one phenomenon, those elementary conditions which analysis -has provisionally set aside must finally be restored. When Quality -is replaced by Quantity, this is an artifice of method, which does -not really correspond with fact. The quality is the fact given in -feeling, which we analytically refer to quantitative differences, -but which can never be wholly resolved into them, since it must be -presupposed throughout. One color, for example, may be distinguished -from another as having more or fewer undulations; and so we may by -abstraction, letting drop all qualitative characters, make a scale -of undulations to represent the scale of colors. But this is an -ideal figment. It is the representation of one series of feelings by -another series of different feelings. No variation of undulations will -really correspond with variation in color, unless we reintroduce the -suppressed _quality_ which runs through all color. Attempt to make one -born blind feel, or even understand, Color by describing to him the -kind of wave-movement which it is said to be, and the vanity of the -effort will be manifest. Movement he knows, and varieties of movement -as given in _tactile and muscular sensations_; but no combination and -manipulation of such experiences can give him the specific sensation -of Color. That is a purely subjective state, which he is incapable of -experiencing, simply because one of the essential factors is absent. -One set of objective conditions is present, but the other set (his -sense-organ) is defective. Without the “greeting of the spirit” -undulations cannot become colors (nor even undulations, for these -also are forms of feeling). Besides the sense-organ there is needed -the feeling of Difference, which is itself the product of past and -present feelings. The reproduction of other colors, or other shades of -color, is necessary to this perception of difference; and this involves -the element of Likeness and Unlikeness between what is produced and -reproduced. So that a certain mental co-operation is requisite even for -the simplest perception of quality. In fact, psychological analysis -shows that even Motion and Quantity, the two objective terms to which -subjective Quality is reduced, are themselves Fundamental Signatures -of Feeling;[205] so that here, as elsewhere, it is only by analytical -artifice that the objective can be divorced from the subjective. Matter -_is_ for us the Felt; its Qualities are differences of Feeling. - -6. Not that this result is to be interpreted as freeing our Theoretic -Conception from its objective side, and landing us in Idealism, -which suppresses the real universe. The denial of all reality apart -from our minds, is a twofold mistake: it confounds the conception of -general relations with particular relations, declaring that because -the External in its relation to the sentient organism can only be -what it is felt to be, therefore it can have no _other_ relations to -other individual reals. This is the first mistake. The second is the -disregard of the constant presence of the objective real in every fact -of Feeling: the Not-Self is emphatically present in every consciousness -of Self. - -The legitimate conclusion is neither that of Dualism nor of Idealism, -but what I have named Reasoned Realism (_Problems_, Vol. I. p. 201), -which reconciles Common Sense with Speculative Logic, by showing that -although the _truth_ of things (their _Wahrheit_) is just what we -perceive in them (our _Wahrnehmung_), yet their _reality_ is this, and -much more than this. _Things_ are what they are felt to be; and what -they are thought to be, when thoughts are symbols of the perceptions. -Idealism declares that they are _nothing but_ this. It is against this -_nothing but_ that Common Sense protests; and the protest is justified -by Reasoned Realism, which, taking a comprehensive survey of the facts, -thus answers the idealist: “Your synthesis is imperfect, since it -does not include _all_ the data--notably it excludes the fact of an -objective or Not-Self element in every feeling. You may, conceivably, -regard the whole universe as nothing but a series of changes in your -consciousness; but you cannot hope to convince me that I myself am -simply a change in yourself, or that my body is only a fleeting image -in your mind. Hence although I conclude that the Not-Self is to you, as -to me, undivorceable from Self, inalienable from Feeling, in so far as -it is felt, yet there must nevertheless be for both of us an existence -not wholly coextensive with our own. _My_ world may be my picture of -it; _your_ world may be your picture of it; but there is something -common to both which is more than either--an existent which has -different relations to each. _You_ are not _me_, nor is the pictured -Cosmos _me_, although I picture it. Looking at you and it, I see a vast -whole of which you are a small part; and such a part I conclude myself -to be. It is at once a picture and the pictured; at once subjective and -objective. To me all your modes of existence are objective aspects, -which, drawing from my own experience, I believe to have corresponding -subjective aspects; so that your emotions, which to me are purely -physical facts, are to you purely mental facts. And psychological -analysis assures me that all _physical facts are mental facts expressed -in objective terms_, and _mental facts are physical facts expressed in -subjective terms_.” - -7. But while Philosophy thus replaces the conceptions of Dualism and -Idealism by the conception of the Two-fold Aspect, the special sciences -in their analytical career have disregarded the problem altogether. -The mechanical theory of the universe not only simplified research by -confining itself solely to the objective aspect of phenomena, but by -a further simplification set aside all vital and chemical relations, -to deal exclusively with mechanical relations. In ascertaining the -mathematical relations of the planetary system, no elucidation could -possibly be gained from biological or chemical conceptions; the -planets therefore were provisionally stripped of everything not -mechanical. In systematizing the laws of motion, it was necessary to -disengage the abstract relations from everything in any way resembling -spontaneity, or extra-mechanical agency: Matter was therefore, by -a bold fiction, declared to be inert, and its Motion regarded as -something superadded from without. - -7_a_. And this was indispensable for the construction of those ideal -laws which are the objects of scientific research. Science, as we often -say, is the systematization of Experience under the forms of ideal -constructions. Experience implies Feeling, and certain fundamental -Signatures, all reducible to the primary discernment of Likeness and -Unlikeness. Hence Science is first a _classification_ of qualities -or discerned likenesses and differences; next a _measurement_ -of quantities of discerned likenesses and differences. Although -measurement is itself a species of classification, it is distinguished -by the adoption of a standard unit of comparison, which, being precise -and unvarying, enables us to express the comparisons in precise and -unvarying symbols. Whether the unit of length adopted be an inch, a -foot, a yard, a mile, the distance of the earth from the sun, or the -distances of the fixed stars, the quantities thus measured are symbols -admitting of one invariable interpretation. The exactness of the -mathematical sciences is just this precision and invariability of their -symbols, and is not, as commonly supposed, the source of any superior -certainty as to the facts. The classificatory sciences, which deal with -qualities rather than with quantities, may be equally _certain_, and -represent fuller _knowledge_, because involving more varied feelings, -but they cannot pretend to exactness. Even on the quantitative side, -certainty is not identical with exactness. I may be quite certain that -one block of marble is larger than another--meaning that it affects -me more voluminously--but I cannot know how much larger it is, without -interpreting my feelings by the standard of quantity--the how-muchness -as represented by that standard. The immense advantages of exact -measurement need not be insisted on. The Biological Sciences, which -are predominantly classificatory, can never rival the Cosmological -Sciences in exactness; but they may reach a fuller knowledge; and -their certainty will assume more and more the character of exactness -as methods of measurement are applied to their classifications of -qualities. The qualitative and quantitative aspects of phenomena are -handled by the two great instruments, Logic and Mathematics, the second -being only a special form of the first. These determine the general -conceptions which are derived from our perceptions, and the whole -constitute Experience. - -8. What is the conclusion to which these considerations lead? It -is that the separation of the quantitative from the qualitative -aspect of phenomena--the objective mechanical from the subjective -psychological--is a logical artifice indispensable to research; but -it is only an artifice.[206] In pursuance of this artifice, each -special science must be regarded as the search after special analytical -results; and meanwhile this method should be respected, and no -confusion of the boundaries between one science and another should be -suffered. Mechanical problems must not be confused by the introduction -of biological relations. Biological problems must not be restricted -to mechanical relations. I do not mean that the mechanical relations -present in biological phenomena are not to be sought, and, when found, -to be expressed in mechanical terms; I mean that such an inquiry must -be strictly limited to mechanical relations. Subjective relations -are not to be denied, because they are provisionally set aside, in an -inquiry into objective relations; but we must carefully distinguish -which of the two orders we are treating of, and express each in its -appropriate terms. This is constantly neglected. For example, nothing -is more common than to meet such a phrase as this: “A _sensory -impression_ is transmitted as a _wave_ of _motion_ to the brain, and -there being transformed into a state of _consciousness_, is again -reflected as a _motor_ impulse.” - -The several sciences having attained certain analytical results, it -remains for Philosophy to co-ordinate these into a doctrine which will -furnish general conceptions of the World, Man, and Society. On the -analytical side a mechanical theory of the universe might be perfected, -but it would still only be a theory of mechanical relations, leaving -all other relations to be expressed in other terms. We cannot accept -the statement of Descartes that Nature is a vast mechanism, and Science -the universal application of mathematics. The equation of a sphere, -however valuable from a geometrical point of view, is useless as an -explanation of the nature and properties of the spherical body in -other relations. And so a complete theory of the mechanical relations -of the organism, however valuable in itself, would be worthless in -the solution of a biological problem, unless supplemented by all that -mechanical terms are incompetent to express. - -9. The course of biological speculation has been similar to the -cosmological. It also began with a First Notion, which compendiously -expressed the facts of Experience. Nor can any Theoretic Conception be -finally adopted which does away with these facts, known with positive -certainty, and popularly expressed in the phrase: “I have a body, and -a soul.” We may alter the phrase either into “I _am_ a body, and I -_am_ a soul”; or into, “My body is only the manifestation of my soul”; -or, “My soul is only a function of my body”; but the fundamental -experiences which are thus expressed are of absolute authority, no -matter how they may be interpreted. That I have a body, or am a body, -is not to be speculatively argued away. That I move my arm to strike -the man who has offended me, or stretch out my hand to seize the fruit -which I see, is unquestionable; that these movements are determined by -these feelings, and are never thus effected unless thus determined, is -also unquestionable. Here are two sets of phenomena, having well-marked -differences of aspect; and they are grouped respectively under two -general heads, Life and Mind. Life is assigned to the physical -organism, or Body--all its phenomena are objective. Mind is assigned -to the psychical organism, or Soul--all its phenomena are subjective. -Although what is called my Body is shown to be a group of qualities -which are feelings--its color, form, solidity, position, motion--all -its physical attributes being what is felt by us in consequence of -the laws of our organization; yet inasmuch as these feelings have the -characteristic marks of objectivity, and are thereby referred to some -objective existence, we draw a broad line of demarcation between them -and other feelings having the characteristic marks of subjectivity, -and referring to ourselves as subjects. Psychological analysis shows -us that this line of demarcation is artificial, only representing a -diversity of aspect; but as such it is indispensable to science. We -cannot really separate in a sensation what is objective from what -is subjective, and say how much belongs to the Cosmos apart from -Sensibility, and how much to the subject pure and simple; we can only -view the sensation alternately in its objective and subjective aspects. -What belongs to extra-mental existence in the phenomenon of Color, -and what to the “greeting of the spirit,” is utterly beyond human -knowledge: for the ethereal undulations which physicists presuppose as -the cosmic condition are themselves subjected to this same greeting of -the spirit: they too are ideal forms of sensible experiences. - -10. This conclusion, however, was very slowly reached. The distinction -of aspects was made the ground of a corresponding distinction in -agencies. Each group was personified and isolated. The one group was -personified in Spirit--an existent in every respect opposed to Matter, -which was the existent represented in the other group. One was said -to be simple, indestructible; the other compound, destructible. One -was invisible, impalpable, beyond the grasp of Sense; the other was -visible, tangible, sensible. One was of heaven, the other of earth. -Thus a biological Dualism, analogous to the cosmological, replaced -the First Notion. It was undermined by advances in two directions. -Psychology began to disclose that our conception of Matter was, -to say the least, _saturated_ with Mind, its Atoms confessedly -being ideal figments; and that all the terms by which we expressed -_material qualities_ were terms which expressed _modes of Feeling_; -so that whatever remained over and above this was the unknown _x_, -which speculation required as a postulate. Idealism, rejecting this -postulate, declared that Matter was simply the projection of Mind, and -that our Body was the objectivation of our Soul. Physiology began to -disclose that all the mental processes were (mathematically speaking) -_functions_ of physical processes, i. e. varying with the variations -of bodily states; and this was declared enough to banish forever the -conception of a Soul, except as a term simply expressing certain -functions. - -11. Idealism and Materialism are equally destructive of Dualism. The -defects of particular idealist and materialist theories we will -not here touch upon; they mainly result from defects of Method. Not -sufficiently recognizing the primary fact testified by Consciousness, -namely, that Experience expresses both physical and mental aspects, -and that a Not-Self is everywhere indissolubly interwoven with Self, -an objective factor with a subjective factor, the idealist reduces -Existence to a mere panorama of mental states, and the Body to a -group in this panorama. He is thus incapable of giving a satisfactory -explanation of all the objective phenomena which do not follow in the -same order as his feelings, which manifest a succession unlike his -expectation, and which he cannot class under the order of his mental -states hitherto experienced. He conceives that it is the Mind which -_prescribes_ the order in Things; whereas experience assures us that -the order is _described_, not prescribed by us: described in terms of -Feeling, but determined by the laws of Things, i. e. the genesis of -subjective phenomena is determined by the action of the Cosmos on our -Sensibility, and the reaction of our Sensibility. He overlooks the -evidence that the mental forms or laws of thought which determine the -character of particular experiences, were themselves evolved through a -continual action and reaction of the Cosmos and the Soul, precisely as -the laws of organic action which determine the character of particular -functions were evolved through a continual adaptation of the organism -to the medium. These immanent laws are declared to be transcendental, -antecedent to all such action and reaction. - -A similar exclusiveness vitiates the materialist doctrine. Overlooking -the primary fact that Feeling is indissolubly interwoven with processes -regarded as purely physical because they are considered solely in their -objective aspect, the materialist fails to recognize the operation of -psychological laws in the determination of physiological results; -he hopes to reduce Biology to a problem of Mechanics. But Vitality -and Sensibility are coefficients which must render the mechanical -problem insoluble, if only on the ground that mechanical principles -have reference to quantitative relations, whereas vital relations are -qualitative. His error is the obverse of the vitalist’s error. The -vitalist imagines that the speciality of organic phenomena proves the -existence of a cause which has no community with the forces operating -elsewhere; so, turning his back on all the evidence, he attempts to -explain organic phenomena without any aid from Physics and Chemistry. -The materialist, turning his back on all the evidence of quite special -conditions only found at work in living organisms, tries to explain -the problem solely by the aid of Physics and Chemistry. It is quite -certain that physiological and psychological problems are not to be -solved if we disregard the laws of Evolution through Epigenesis. The -mental structure is evolved, as the physical structure is evolved. It -is quite certain that no such evolution is visible in anorganisms, -nor will any one suppose it to be possible in machines. From the -biological point of view we must therefore reject both Idealism and -Materialism. We applaud the one when it says, “Don’t confuse mental -facts by the introduction of physical hypotheses”; and the other when -it says, “Don’t darken physical facts with metaphysical mists.” We say -to both, “By all means make clear to yourselves which aspect of the -phenomena you are dealing with, and express each in its own terms. But -in endeavoring to understand a phenomenon you must take into account -all its ascertainable conditions. Now these conditions are sometimes -only approachable from the objective side; at other times only from the -subjective side.” - -12. While it is necessary to keep the investigation of a process on its -objective side, limited to objective conditions, and to express the -result in objective terms, we must remember that this is an artifice; -above all, we must remember that even within the objective limits our -analyses are only provisional, and must be finally rectified by a -restoration of all the elements we have provisionally set aside. Thus -rectified, the objective interpretation of vital and mental phenomena -has the incomparable advantage of simplifying research, keeping it -fixed on physical processes, instead of being perturbed by suggestions -of metaphysical processes. And as all physical investigation naturally -tends to reduce itself to a mechanical investigation, because Mechanics -is the science of motion, and all physical processes are motions, -we may be asked, Why should not the mechanical point of view be the -rational standing-point of the biologist? Our answer is, Because -Mechanics concerns itself with abstract relations, and treats of -products without reference to modes of production, i. e. with motions -without reference to all the conditions on which they depend. Every -physical change, if expressed in physical terms, is a change of -position, and is determined by some preceding change of position. It -is a movement having a certain velocity and direction, which velocity -and direction are determined by the velocity and direction of a force -(a pressure or a tension) compounded with the forces of resistance, -i. e. counter-pressures. Clearly, the nature of the forces in operation -must be taken into account; and it is this which the mechanical view -disregards, the biological regards. The mechanical view is fixed -on the ascertained adjustment of the parts, so that the working of -the organism may be explained as if it were a machine, a movement -here liberating a movement there. The biological view includes this -adjustment of parts, but takes in also the conditions of molecular -change in the parts on which the adjustment dynamically depends. -Mechanical actions may be expressed as the enlargement or diminution -of the angle of two levers; but chemical actions are not thus -expressible; still less vital and mental actions. - -13. The organism is on the physical side a mechanism, and so long -as the mechanical interpretation of organic phenomena is confined -to expressing the mechanical principles involved in the mechanical -relations, it is eminently to be applauded. But the organism is -something more than a mechanism, even on the physical side; or, since -this statement may be misunderstood, let me say, what no one will -dispute, that the organism is a mechanism of a very special kind, in -many cardinal points unlike all machines. This difference of kind -brings with it a difference of causal conditions. In so far as the -actions of this mechanism are those of a dependent sequence of material -positions, they are actions expressible in mechanical terms; but in -so far as these actions are dependent on vital processes, they are -not expressible in mechanical terms. Vital facts, especially facts -of sensibility, have factors neither discernible in machines nor -expressible in mechanical terms. We cannot ignore them, although for -analytical purposes we may provisionally set them aside. - - * * * * * - -In the course of the development of the mechanical theory, the history -of which has just been briefly sketched, biological problems have more -and more come under its influence. There has always been a fierce -resistance to the attempt to explain vital and sentient phenomena -on mechanical, or even physical principles, but still the question -has incessantly recurred, How far is the organism mechanically -interpretable? And while the progress of Biology has shown more and -more the machine-like adjustment of the several parts of which the -organism is composed, it has also shown more and more the intervention -of conditions not mechanically interpretable. We shall have to -consider the question, therefore, under two forms. First, whether -animals are machines, and if not, by what characters do we distinguish -them from machines? Secondly, in what sense can we correctly speak of -Feeling as an agent in organic processes? - - - - -CHAPTER II. - -THE VITAL MECHANISM. - - -14. No answer can be successfully attempted in reply to the first -of the questions which closed the last chapter until we have given -precision to certain terms of incessant recurrence. I have often -to remark on the peculiar misfortune of Psychology, that all its -principal terms are employed by different writers, and are understood -by different readers, in widely different senses: they denote and -connote meanings of various significance. All physicists mean the same -thing when they speak of weight, mass, momentum, electricity, heat, -etc. All chemists mean the same thing when they speak of affinity, -decomposition, oxygen, carbonic acid, etc. All physiologists mean the -same thing when they speak of muscle, nerve, nutrition, secretion, etc. -But scarcely any two psychologists mean precisely the same thing when -they speak of sensation, feeling, thought, volition, consciousness, -etc.; and the differences of denotation and connotation in their uses -of such terms lead to endless misunderstanding. As Rousseau says: “Les -définitions pourraient être bonnes si l’on n’employait pas les mots -pour les faire.” But since we must employ words as our signs, our -utmost care should be given to clearly marking what it is the signs -signify. - -15. The question we have now before us, whether animal actions are -interpretable on purely mechanical principles? can only be answered -after a preliminary settlement of the terms. The first of these -terms to be settled is that of mechanism, when applied to the vital -organism. If the organism is a mechanism, its actions must of course be -interpretable on mechanical principles. But this general truth requires -a special interpretation, if on inquiry we find that the organism is a -particular kind of mechanism, one which is _not_ to be classed under -the same head as inorganic machines. And this we do find. In Problem -I. § 22, will be found a statement of the radical difference between -organic and inorganic mechanisms, due to the differences in their -structures. But the differences there noted do not affect the operation -of abstract mechanical principles, which are of course manifested -_wherever_ there is a dependent sequence of material changes; and which -are the same abstract principles in the mechanism of the heavens, -the mechanism of a paper-mill, or the mechanism of an animal body. -In other words, the principles are abstract, and are abstracted from -all concrete cases by letting drop what is special to each case, -retaining only what is common to all. This procedure is indispensable -to the ideal constructions of Science. But we cannot rightly interpret -any concrete case by abstract principles alone; we must restore the -special characters which the abstraction has eliminated. The most lucid -explanation of the mechanism of the heavens will leave us quite in -the dark respecting the action of a paper-mill, until we have studied -the mill at work, ascertained its structure and mode of operation, -and therein detected what is common both to its mechanism and to the -mechanism of the heavens. Thus equipped, we approach the study of -the animal mechanism, but find ourselves wholly in the dark until we -have also ascertained its structure and mode of operation; then we -may recognize in it the principles of dependent sequence which had -been abstracted from the paper-mill and the heavens. To neglect this -concrete study, and to argue from Machinery to Life in disregard -of special conditions, is not more rational than to assume that the -movement of a piston is prompted by volition. - -16. The recognition of special differences is no denial of fundamental -identities. We do not deny the presence of phenomena in organisms -which belong to physical and chemical agencies, but we assert that -organisms have other phenomena besides these, dependent on conditions -not present in physical and chemical phenomena. The same material -elements and forces may be recognized in a moving inorganic body, -and a moving organic body; but in the latter there is a speciality -of combination with a speciality of result. Just as the same words -and laws of grammatical construction may be recognized in prose and -poetry; yet poetry is not prose, but has special rules of its own, -and special effects. In an organism, as in a machine, the adjustment -of the parts is a condition of the mechanical action; the one enables -us to explain the other. But the parts adjusted, and the consequences -of the adjustment, are unlike in the two cases. This unlikeness is -pervading and profound. One cardinal difference is that the combination -of the parts is in the machine a fixed, in the organism a fluctuating -adjustment; and this fluctuation is due to certain vital processes -subjectively known as _sensitive guidance_. Hence machines have fixed -and calculated mechanisms; whereas organisms are variable and to a -great extent incalculable mechanisms. - -17. I conceive, therefore, that a theory which reduces vital activities -to purely physical processes is self-condemned. Not that we are -to admit the agency of any extra-organic principle, such as the -hypothesis of Vitalism assumes (Prob. I. § 14); but only the agency -of an intra-organic principle, or the abstract symbol of _all_ the -co-operant conditions--the special combination of forces which result -in organization. This assures us that an organism is a peculiar kind -of mechanism, the processes in which are peculiar to it; and among -those processes there is one which results in what we call Sensibility. -This Sensibility is a factor which raises the phenomena into another -order. To overlook its presence is fatal to any explanation of the -organic mechanism. Yet it is overlooked by those who tell us that -when an impression on a nerve is conveyed to the brain, and is thence -reflected on the limbs--as when the retina of a wolf is stimulated -by the image of a sheep, and the spring of the wolf upon the sheep -follows as a “purely mechanical consequence--the whole process has -from first to last been physical.” Unless the term _physical_ is -here used to designate the _objective sequence_, as contemplated by -an onlooker, who likens the process to the sequence observable in a -machine, I should say that from first to last the process has been -_not_ physical, but _vital_, involving among its essential conditions -the peculiarly vital factor named Sensibility. The process taking place -in the wolf’s organism is one which involves conditions never found in -purely physical processes. We may indeed analytically disregard these. -We may view the process in its purely physical relations, or in its -purely chemical relations, or in its purely mathematical (mechanical) -relations. But this is the artifice of the analytical method. In -reality the process is no one of these, for it is all of these; it is a -process in a living organism, and depends on conditions only found in -living organisms--nay, in this particular case the process depends on -conditions only found in organisms like that of the wolf; for the image -of the sheep will stimulate the brain of a goat, horse, or elephant -without producing any such movement in the organism. - -18. The importance of this point must excuse my reiteration of -it. We must make clear to ourselves that the organism is in its -objective aspect a physiological mechanism, in its subjective aspect -a psychological mechanism: in both aspects it is to be radically -demarcated from all inorganic mechanisms. In it the combination -and co-ordination of movements involve conditions never present -in machines; among these conditions, there are combinations and -co-ordinations of Sensibility, which, although material processes -on the objective side, are processes believed to be only present in -organisms. We have the strongest reasons for concluding that every -feeling, every change in Sensibility, has its correlative material -process in the organism--is, in short, only the subjective aspect -of the objective organic change. What in Physiology is called -Co-ordination and has reference to movements, in Psychology may be -called Logic, having reference to feelings. But be this latter point -accepted or rejected, the one point which admits of no dispute is -that an organism is radically distinguishable from every inorganic -mechanism in that _it acquires through the very exercise of its primary -constitution, a new constitution with new powers_. Its adjustment is a -changing and developing mechanism. That is to say, a machine, however -complex its structure, is constructed once for all, and this primary -constitution is final, the adjustment of parts remaining unaltered; -and although by exercise the machine may come to work more easily, -with less friction, it never comes to work differently, to _readjust_ -its parts, and develop new capabilities. It has no _historical_ factor -manifest in its functions. It has no experience. It reacts at last -as at first. How different the organism! This has not only variable -adjustments due to internal fluctuations, it has experience which -develops new parts, and new adjustments of old parts. Every organism -has its _primary_ constitution in the adjustment of parts peculiar to -the species; it has also its _secondary_ or modified constitution, -in the adjustment which has been more or less altered by individual -experiences; it has, thirdly, its _temporary_ constitution in the -variable adjustment due to the varying state of tension which results -from varying stimulation. - -19. A word on each. There is a structural disposition of the parts -which is common to large groups of organisms, so that a corresponding -similarity is observable in the reactions of these organisms. Thus all -quadrupeds use their limbs for locomotion in very similar ways; birds -use their wings for flight in similar ways. All vertebrates swallow -their food, defend themselves, shrink when hurt, etc., in ways that are -very similar. In so far as their organizations are alike, their actions -and reactions are alike. In so far as their organizations differ, their -actions and reactions differ. The goose and the vulture are alike in -the main lines of structure; still more alike are duck and hen; yet, -owing to certain unlike characters of structure, they manifest some -marked differences in action and reaction: the goose will starve in -the presence of food which the vulture gluttonously devours, and the -vulture will refuse the vegetable food which the goose devours; the -duck plunges into the water, the hen not only refuses to enter it, -but is greatly agitated when she sees the ducklings she has hatched -plunging into it. That peculiar instincts, habits, and feelings are -rigorously determined by peculiarities in the organism, no one doubts, -when animals are in question. If this is less obvious in the case of -men, the reason is that there the influence of other factors somewhat -masks the operation of the primary constitution--these factors are the -modified and the temporary constitutions. Yet even in man it is true to -say that his feelings and actions are the result of his organization, -native and acquired. - -20. No two men are organized in all respects alike. There are -individual variations in structure, both native and acquired. These may -be too slight to be appreciable by any other test than the difference -of reaction under similar external stimuli; but the variations in the -sensibility to music, color, temperature, sexual influence, moral -influence, etc., betray corresponding differences in the organisms. -Any one variation in structure, seemingly trivial, may be the origin -of well-marked diversity in physical and moral characters. Compare -the bull with the ox, or the predatory aggressive eagle with the -cowardly vulture. Nor are the temporary modifications to be overlooked. -Antoine Cros mentions the case of a patient, a young girl, suffering -from congested liver and spleen, which of course altered the state -of her blood, and thus for a time modified her constitution. Her -moral character was greatly altered by it. She ceased to feel any -affection for father or mother; would play with her doll, but could -not be brought to show any delight in it; could not be drawn out of -her apathetic sadness. Things which previously had made her shriek -with laughter, now left her uninterested. Her temper changed, became -capricious and violent.[207] Congestion of the lungs, if unaccompanied -by congestion of the liver, never produces such effects, because not -thus altering the blood. The effects of liver congestion are familiar. -Cros cites the case of a magistrate whose liver was enlarged, and whose -skin showed a markedly bilious aspect, and in whom all affection seemed -to be dead: he did not exhibit any perversion or violence, only want -of emotive reaction. If he went to the theatre he could not feel the -slightest pleasure in it. The thoughts of his home, his absent wife -and children, were, he declared, as unaffecting to him as a problem in -Euclid. - -21. Owing to the recognized dependence of peculiar instincts and modes -of reaction on peculiarities of structure, comparative anatomists -are quite confident, when they find a portion of a skull with two -occipital condyles, that the animal to which this skull belonged had -red blood-corpuscles without nuclei, and (if a female) suckled its -young. If in that fragment of skull there remain a single tooth, it -will prove that the animal was carnivorous or herbivorous, and had, or -had not, retractile claws. From such data a general conclusion may be -formed as to the instincts and habits of the animal. The data disclose -much of the primary constitution, that is to say, the mechanism -which the animal brought with it into the world, ready prepared to -react in definite ways on being stimulated. The connate mechanism -has correlative tendencies of reaction. Some of these tendencies are -inevitably called into play by external conditions, and they continue -unaltered amid great varieties of circumstances, provided none of these -variations directly deprive them of their appropriate stimulation. -Such tendencies of the connate mechanism are styled _automatic_ (an -unfortunate metaphor, which has led to the theory of Automatism), and -include, besides the visceral reactions, the more complex reactions -of winking, breathing, swallowing, coughing, flying, walking, etc. It -is true that we learn to walk, and learn to wink, whereas the other -actions require no tentative efforts directed by experience; but the -mechanism of all these actions is already laid down in the primary -constitution, and is inevitably called into play. - -22. The instincts also belong to the connate mechanism, and in the -course of the normal experience of the animal inevitably come into -play; but, unlike the automatic tendencies of breathing, swallowing, -and coughing, they are capable of modification, or even suppression, -by alterations in the course of individual experience. The connate -mechanism of the cat determines its dread of water, and its enmity -to the dog and mouse; yet a cat will by the modifications of certain -experiences become as ready as an otter to take to the water, and -become so fond of a dog that she will allow him to tend upon her -kittens; and so indifferent to the mouse that she will let it run -over her body. All this implies a new adjustment in the nervous -centres, with new modes of reaction on sensory impressions: the -inherited mechanism has been modified. I need not dwell on the profound -modifications which the human inherited mechanism undergoes in the -course of experience--how social influences and moral and religious -teachings redirect, or even suppress, many primary tendencies; so that -“moral habits” become organized, and replace the original tendencies -of the organism. These, when organized, become the inevitable modes -of reaction, and are sometimes called secondarily automatic. It -is important to recognize this organization of experiences, this -acquisition of a secondary or modified constitution, if we would -explain psychological processes by physiological processes. Thus -the processes of Logic are automatic, they belong to the connate -primary mechanism, and their action is inevitable, invariable. The -elements of a judgment, like the elements of a perception, may vary, -and we therefore say that one judgment is false, and one perception -incomplete; but the judging process is always the same, and the -perceiving process is always the same. We may breathe pure air or -impure air, but the breathing process is in each case the same; and -judgment is as automatic as breathing, not to be altered, not to be -suppressed. Again, the moral terror at wickedness of any recognized -kind is as automatic as the instinctive terror at danger. The one has -its roots in the primary disposition called love of approbation and -its correlative dread of disapprobation: the social instinct. The -other has its root in the primary disposition called “instinct of -self-preservation,” which is really the reflex shrinking from pain: the -physiological instinct. - -23. Besides the connate and acquired mechanism, we have now to consider -the temporary and fluctuating adjustments which represent the statical -condition of the organism at each moment. The automatism of the primary -constitution is such that previous experience and conscious effort -are not needed; nor will any experience or any effort alter the mode -of reaction. If a strong light falls on the eye, the iris contracts; -if the eyeball is dry, the eyelid drops; if sound-waves beat upon the -tympanum, the stapedius muscle contracts; if the lining of the throat -be tickled, the muscles involved in coughing or in vomiting contract. -No experience is necessary for these actions, some of which are so -complicated that if we had to learn them, as we learn far simpler -actions, the organism would perish before the power was attained. Yet -all of these presuppose a certain normal state of the mechanism, any -considerable variation in which will modify or suppress them. - -24. Secondarily automatic actions are those which have been acquired -through experiences that have modified the organism, and produced a -new adjustment of parts. We learn to shield the eyes against a strong -glare of light by raising the hand; by winking we learn to shield the -eye against an approaching body; we also learn to turn the head in the -direction of a sound, and to thrust away with our hands the object that -is irritating our skin. Experience has been necessary for all these -actions, and has finally organized the tendencies to perform them, -so that the reaction is invariable, inevitable, unless controlled by -the will. If you tickle my throat, I may, or may not, push aside your -hand; but if the inside of my throat be tickled, I must cough. Here -we see the difference between the automatic and secondarily automatic -actions. The second being due to individual experience, are more or -less controllable; and whether they are or are not controlled depends -on the condition of the nerve-centres at the moment. You may tickle my -throat, or irritate my skin, without causing any movement of my hands -to thwart you, either because my nerve-centres are preoccupied by other -stimulations, and I am not conscious of the irritation, or because I do -not choose to thwart you. - -25. It should be added that some secondarily automatic actions have -become so firmly organized that we can only with great difficulty -interfere with them. Others never enter into consciousness, and are -therefore often supposed to be purely mechanical. The movement of the -eye towards the brightest light, and the convergence of the axes of -both eyes, are reflexes which, although involuntary and unconscious, -are the products of education. They do not belong to the connate -constitution, although they are so inevitably acquired by experience -that they belong to every normal child. At first the infant stares with -a blank gaze, and its eyes, though moving under the stimulus of light, -move incoherently; the axes never converge except by accident. Very -early, however, the infant’s eyes are observed to follow the movements -of a bright light; and at last they acquire so certain and rapid a -power of adjustment that the eyes shift from spot to spot, always -“fixing” the object by bringing the most sensitive part of the retina -to bear on it. The incoherent movements have become precisely regulated -movements. It is the same with speech. The vocal organs are exercised -in an incoherent babble. By degrees these movements become regulated -so as to respond definitely to definite stimuli, and words are formed, -then sentences, till finally fluent speech becomes in a great degree -automatic. The vocal muscles respond to an auditory stimulus, and the -child repeats the word it has heard, just as the eye-muscles respond -to a retinal stimulus. That we acquire the power of converging the -axes, and accommodating the lens to near objects, is not only proved by -observation of infants, but also by cases of disease. After the reflex -mechanism has been long established, so that it acts with inevitable -precision, a slight paralysis of one of the muscles has the effect of -making all objects appear in a different position; the patient trying -to touch an object, then always moves his hand on one side of it. Von -Graefe relates the case of a stonebreaker who always struck his hand -with the hammer when he tried to strike the stone. Yet this very man -_learned_ to accommodate his movements to the new impressions; so that -if his paralysis had been cured, his modified mechanism would have been -ill adapted to the new conditions, and he would once more have struck -his hand instead of the stone. - -26. This digression on the native and acquired dispositions of the -organism, while it has brought into strong light all that can be cited -in favor of regarding animal bodies as mechanisms, and their actions -as the direct consequences of mechanical adjustments, has also made -conspicuous the radical difference between an organism and a machine. -We cannot too emphatically insist on this radical difference. Between -the group of conditions involved in the structure and action of a -machine, and the group of conditions involved in the structure and -action of an organism, there are contrasts as broad as any that can be -named. To overlook these in taking account solely of the conditions -common to both groups is a serious error. On such grounds we might -insist that a tiger is a violet, because both are organisms. - -The biologist will admit that an organism is a mechanism, and (in -so far as its bodily structure is concerned) a material mechanism. -All the actions of this structure are therefore mechanical, in the -two senses of the term: first, as being the actions of material -adjustments; secondly, as being movements, and thereby included under -the general laws of motion represented in Mechanics; the abstract -laws of movement for an organic body are not different from the -abstract laws of movement for an inorganic body. So far we have been -considering the abstract relations only. No sooner do we consider the -phenomena as concrete wholes, than we find great diversity in the modes -of production of the movements in organisms and machines. Now it is -precisely the modes of production which have interest for us. We never -understand a phenomenon so as to gain any practical control over it, or -any theoretical illumination from it, unless we have mastered some of -its conditions; our knowledge of these conditions is the measure of our -power. - - - - -CHAPTER III. - -THE RELATION OF BODY AND MIND. - - -27. The second question proposed was, In what sense can Feeling be -correctly spoken of as an Agent in organic processes? This brings -us face to face with a much-debated topic, the relation of Body and -Mind; and demands a theoretic interpretation of that First Notion -which expresses universal experience, namely, that what I know as -Myself is a Body, in one aspect, and a Soul, in the other. What I -call my Body is a persistent aggregate of objective phenomena; and -my Soul is a persistent aggregate of subjective phenomena: the one -is an individualized group of experiences expressible in terms of -Matter and Motion, and therefore designated _physical_; the other an -individualized group of experiences expressible in terms of Feeling, -and therefore designated _psychical_. But, however contrasted, they -are both simply embodiments of Experience, that is to say, are Modes -of Feeling. All Existence--as known to us--is the Felt. The laws of -our organism compel us, indeed, to postulate an Existent which is -_extra mentem_--a Real not Ourselves--but the same laws debar us from -any knowledge whatever of what this _is_, or is _like_. We know Things -absolutely _in so far_ as they exist in relation to us; and that is the -only knowledge which can have any possible significance for us. - -28. It is impossible for me to doubt that I am a Body, though I may -doubt whether what is thus called is anything more than a group of -feelings. It is impossible for me to doubt that I am a Soul; though -I may doubt whether what is thus called is more than a group of -bodily functions. In separating what is unquestionable from what is -questionable, we separate the fundamental facts of consciousness -from the theoretic interpretations of those facts: no theoretic -interpretation can efface or alter the facts. Whatever Philosophy may -discover, it cannot displace the fact that I know I am a Soul, _in -every sense in which that phrase represents Experience_: I know the -Soul in knowing its concretes (feelings), and in knowing it as an -abstraction which condenses those concretes in a symbol. The secondary -question is, Whether this abstraction represents one Existent, and the -abstraction Body another and wholly different Existent, or the two -abstractions represent only two different Aspects? this may be debated, -and must be answered according to theoretic probabilities. - -29. What are the probabilities? We are all agreed that Consciousness -is the final arbiter. Its primary deliverance is simply that -of _a_ radical distinction. It is silent on the nature of the -distinction--says nothing as to whether the distinction is one of -agents or of aspects. It says, “I am a Soul.” With equal clearness -it says, “I am a Body.” It does _not_ say, “I am two things.” Nor -does the fact of a radical distinction imply more than a contrast of -aspects, such as that of convex and concave. The curve has at every -point this contrast of convex and concave, and yet is the identical -line throughout. A mental process is at every point contrasted with -the physical process assumed to be its correlate; and this contrast -demands equivalent expression in the terms of each. The identity -underlying the two aspects of the curve is evident to Sense. The -identity underlying the mental and physical process is not evident to -Sense, but may be made eminently _probable_ to Speculation, especially -when we have explained the grounds of the difference, namely, that they -are apprehended through different modes. But although I admit that -the conclusion is only one of probability, it is one which greatly -transcends the probability of any counter-hypothesis. Let us see how -this can be made out.[208] - -30. We start from the position that a broad line of demarcation must -be drawn between the mental and the physical aspect of a process, -supposing them to be identical in reality. Nothing can be more _unlike_ -a logical proposition than the physical process which is its correlate; -so that Philosophy has hitherto been forced to forego every attempt at -an explanation of how the two can be causally connected: referring the -connection to a mystery, or invoking two different agents, spiritual -and material, moving on parallel lines, like two clocks regulated to -work simultaneously. But having recognized this difference, can we not -also discern fundamental resemblances? First and foremost, we note -that there is common to both the basis in Feeling: they are both modes -of Consciousness. The Mind thinking the logical proposition is not, -indeed, in the same _state_ as the Mind picturing the physical process -which is the correlate of that logical proposition--no more than I, -who see you move on being struck, have the same feelings as you who -are struck. But the Mind which pictures the logical proposition as -a process, and pictures the physical process as a bodily change, is -contemplating one and the same event under its subjective and objective -aspects; just as when I picture to myself the feelings you experience -on being struck I separate the subjective aspect of the blow from its -objective aspect. Secondly, between the logical proposition and the -physical process there is a community of causal dependence, i. e. the -mode of grouping of the constituent elements, whereby this proposition, -and not another, is the result of this grouping, and not another. In -fact, what in subjective terms is called Logic, in objective terms is -Grouping. - -31. Let us approach the question on a more accessible side. Sensation -avowedly lies at the basis of mental manifestations. Now, rightly -or wrongly, Sensation is viewed alternately as a purely subjective -fact--a psychological process--and as a purely objective fact--the -physiological reaction of a sense-organ. It is so conspicuously a -physiological process that many writers exclude it from the domain -of Mind, assign it to the material organism, and believe that it is -explicable on purely mechanical principles. This seems to me eminently -disputable; but the point is noticed in proof of the well-marked -objective character which the phenomenon assumes. In this aspect a -sensation is simply the reaction of a bodily organ. The physiologist -describes how a stimulus excites the organ, and declares its reaction -to be the sensation. Thus viewed, and expressed in terms of Matter -and Motion, there is absolutely nothing of that subjective quality -which characterizes sensation. Yet without this quality the objective -process cannot be a sensation. Exclude Feeling, and the excitation of -the auditory organ will no more yield the sensation of Sound by its -reaction, than the strings and sounding-board of a piano when the keys -are struck will yield music to a deaf spectator. Hence the natural -inference has been that inside the organism there is a _listener_: the -Soul is said to listen, transforming excitation into sensation. This -inference only needs a more systematic interpretation and it will -represent the biological theory, which demands something _more_ than -the reaction of the sensory organ--namely, the reaction of the whole -organism _through_ the sensory organ. I mean, that no organ isolated -from the organism is capable of a _physiological_ reaction--only -of a physico-chemical reaction; and sensation depends on (_is_) -the physiological reaction. When a sense-organ is stimulated, this -stimulation is a vital process, and is raised out of the class of -physico-chemical processes by virtue of its being the indissoluble -part of a complex whole. Interfere with any one of the co-operant -conditions--withdraw the circulation, check respiration, disturb -secretion--and the sense-organ sinks from the physiological to the -physical state; it may then be brought into contact with its normal -stimuli, but no stimulation (in the vital sense) will take place, there -will be no vital reaction. - -Condensing all vital processes in the symbol Vitality, we may say -Vitality is requisite for every physiological process. A parallelism -may be noted on the subjective side: all the sentient processes may be -condensed in the one symbol Sensibility (Feeling), and we must then -say, No psychological process is possible as an isolated fact, but -demands the co-operation of others--it is a _resultant_ of all the -contemporaneous conditions of Sensibility in the organism. In ordinary -language this is what is meant by saying that no impression can become -a sensation without the intervention of Consciousness--an ambiguous -phrase, because of the ambiguity of the term Consciousness, but the -phrase expresses the fact that in Sensation a process in the organism -is necessary to the reaction of the organ. - -32. Having recognized the distinction between the two processes -objective and subjective, physical and mental, we have recognized -the vanity of attempting to assign their limits, and to say where -Motion ends and Feeling begins, or how Feeling again changes into -Motion. The one does _not_ begin where the other ends. According to the -two-clock theory of Dualism, the two _agents_ move on parallel lines. -On the theory of Monism the two _aspects_ are throughout opposed. Both -theories explain the facts; which explanation is the most congruous -with experience? Against the first we may object that the hypothesis of -two Agents utterly unallied in nature wants the cardinal character of -a fertile hypothesis in its unverifiableness: it may be true, we can -never know that it is true. By the very terms of its definition, the -Spirit--if that mean _more_ than an abstract expression of sentient -states--is beyond all sensible experience. This is indeed admitted by -the dualists, for they postulate a Spirit merely because they cannot -otherwise explain the phenomena of Consciousness. Herein they fail to -see that even their postulate brings no explanation, it merely restates -the old problem in other terms. - -33. Up to the present time these same objections might have been urged -with equal force against Monism. Indeed, although many philosophers -have rejected the two-clock theory of Leibnitz, they have gained a very -hesitating acceptance for their own hypothesis of identity. To most -minds the difficulty of imagining how a physical process could _also_ -be a psychical process, a movement also be a feeling, seemed not less -than that of imagining how two such distinct Agents as Matter and Mind -could co-operate, and react on each other, or move simultaneously on -parallel lines. Although for many years I have accepted the hypothesis -of Monism, I have always recognized its want of an adequate reply to -such objections. Unless I greatly deceive myself, I have now found -a solution of the main difficulty; and found it in psychological -conditions which are perfectly intelligible. But knowing how easily one -may deceive one’s self in such matters, I will only ask the reader to -meditate with open-mindedness the considerations now to be laid before -him, and see if he can feel the same confidence in their validity. - -34. One of the early stages in the development of Experience is the -separation of Self from the Not-Self. I look out on “the vast extern -of things,” and see a great variety of objects, included in a visible -hemisphere. All these objects in various positions, having various -forms and colors, I believe to be wholly detached from, and in every -way unallied to, Myself. And what is that Self? It is my Body as a -visible and tangible object, separated from all other visible and -tangible objects by the constant presence of feelings connected with -it and its movements, and not connected with the other objects. This -constant presence of feelings is referred to a Soul, which I then -separate from my Body, as an Inner Self; and from this time onwards I -speak of the Body as _mine_, and learn to regard it in much the same -light as other outer objects. In my naïve judgment the external objects -are supposed to exist _as_ I see and touch them, whether I or any one -else see and touch them or not: they in no sense belong to the series -of feelings which constitute the Me. And since my Body resembles these -objects in visible and tangible qualities, and also in being external -to my feelings, it also takes its place in the objective world. Thus -arises the hypothesis of Dualism which postulates a _Physis_, or -object-world, and an _Æsthesis_, or subject-world: two independent -existents, one contemplated, the other contemplating. - -35. Philosophy, as we know, leads to a complete reversal of this -primitive conclusion, and shows that the _contemplated_ is a _synthesis -of contemplations_, the Physis being _also_ the Æsthesis. Psychological -investigation shows that the objects supposed to _have_ forms, -colors, and positions within an external hemisphere, have these -only in virtue of the very feelings from which they are supposed -to be separated. The _visible_ universe exists only _as seen_: the -objects are Reals conditioned by the laws of Sensibility. The space -in which we see them, their geometrical relations, the light and -shadows which reveal them, the forms they affect, the lines of their -changing directions, the qualities which distinguish them,--all these -are but the externally projected signs of feelings. They are signs -which we interpret according to organized laws of experience; each -sign being itself a feeling connected with other feelings. We project -them outside according to the “law of eccentric projection”--which is -only the expression of the fact that one feeling is a sign of some -other, and is thereby _ideally detached_ from it. According to this -law I say, “my Body”; just as I say, “my House”; or, “my Property.” -Misled by this, Dualism holds that in the very fact of detaching my -Body from my Self, calling it _mine_, is the revelation of a distinct -entity within the body. But that this is illusory, appears in the -application of this same law of eccentric projection to sensations -and thoughts, which are called _mine_, as my legs and arms are mine. -If it is undeniable that I say _my_ Body--and thus ideally detach the -Body from the Soul--it is equally undeniable that I say _my_ Soul; and -from what is the Soul detached? In presence of this difficulty, the -metaphysician may argue that neither Body nor Soul can be coextensive -with its manifestations, but demands a noumenal Real for each--a -_substratum_ for the bodily manifestations, and a _substratum_ for the -mental manifestations. This, however, is an evasion, not a solution of -the difficulty. If we postulate an unknown and unknowable noumenon, -we gain no insight: first, because Philosophy deals only with the -known functions of unknown quantities, and therefore leaves the _x_ -out of the calculation; secondly, because, granting the existence of -these noumena, we can have no rational grounds for asserting that they -are not of one and the same nature; for we have no grounds for _any_ -assertion whatever about them. And if it be urged against this, that -Consciousness testifies to a distinction, I answer that on a closer -scrutiny it will be found to testify to nothing more than a diversity -of manifestation. All therefore that comes within the range of -knowledge is, How does this diversity arise? - -36. There are two ways, and there are only two, in which differences -arise. These are, 1°, the _modes of production_ of a product, and, -2°, our _modes of apprehension_ of the product. Things may be very -different, and yet to our apprehension indistinguishable, so that -we regard them as identical; and they may be identical, yet appear -utterly unlike. A mechanical bird may seem so like a living bird, and -their actions so indistinguishable to the spectator, that he will not -suspect a difference, or suspecting it, will not be able to specify -it. Of both objects, so long as his modes of apprehending them are -circumscribed, he can only say what these imply: he sees familiar -forms, colors, and movements, which he interprets according to the -previous experiences of which these are the signs. But by varying the -modes of apprehension, and gaining thus a fuller knowledge, he finds -that the two products have very different modes of production; hence he -concludes the products to be different: the mechanism of the one is not -the organism of the other; the actions of the mechanical bird are not -the actions of the living bird. The fuller knowledge has been gained -by viewing the objects under different relations, and contemplating -them _in_ their modes of production, not as merely visible products. He -sees the mechanism performing by steel springs, wheels, and wires, the -work which the organism performs by bones, muscles, and nerves; and the -farther his analysis of the modes of production is carried, the greater -are the differences which he apprehends. - -37. Now consider the other side. One and the same object will -necessarily present very different aspects under different subjective -conditions, since it is _these_ which determine the aspect. The object -cannot be to Sight what it is to Hearing, to Touch what it is to -Smell. The vibrations of a tuning-fork are seen as movements, heard -as sounds. In current language the vibrations are said to cause the -sounds. Misled by this, philosophers puzzle themselves as to how a -material process (vibration) can be transformed into a mental process -(sensation), how such a cause can have so utterly different an effect. -But I have formerly[209] argued at some length that there is no -transformation or causation of the kind supposed. The tuning-fork--or -that Real which in relation to Sense is the particular object thus -named--will, by one of its modes of acting on my Sensibility through -my optical apparatus, determine the response known as _vibrations_; -but it is not this response of the optical organ which is transformed -into, or causes the response of the auditory organ, known as _sound_. -The auditory organ knows nothing of vibrations, the optical nothing of -sounds. The responses are both modes of Feeling determined by organic -conditions, and represent the two different relations in which the -Real is apprehended. The Real _is_ alternately the one and the other. -And if the one mode of Feeling has a physical significance, while the -other has a mental significance, so that we regard the vibrations as -objective facts, belonging to the external world, and the sounds as -subjective facts, exclusively belonging to the internal world, this is -due to certain psychological influences presently to be expounded. -Meanwhile let us fix clearly in our minds that both vibrations and -sounds are modes of Feeling. My consciousness plainly assures me -that it is I who see the one, and hear the other; not that there are -two distinct subjects for the two distinct feelings. Add to which, -manifold uncontradicted experiences assure me that the occasional -cause--the objective factor--of the one feeling, is also the cause of -the other, and not that the two feelings have two different occasional -causes. From both of these undeniable facts we must conclude that the -difference felt is simply a difference of aspect, determined by some -difference in the modes of apprehension. - -38. Assuming then that a mental process is only another aspect -of a physical process--and this we shall find the more probable -hypothesis--we have to explain by what influences these diametrically -opposite aspects are determined. From all that has just been said we -must seek these in the modes of apprehension. There can be no doubt -that we express the fact in very different terms; the question is, -What do these terms _signify_? Why do we express one aspect in terms -of Matter and Motion, assigning the process to the objective world; -and the other aspect in terms of Feeling, assigning the process to the -subjective world? - -Let the example chosen be a logical process as the mental aspect, -and a neural process as its physical correlate. The particular -proposition may be viewed logically, as a grouping of experiences, -or physiologically, as a grouping of neural tremors. Here we have -the twofold aspect of one and the same reality; and these different -aspects are expressed in different terms. We cannot be too rigorous -in our separation of the terms; for every attentive student must have -noted how frequently discussions are made turbid by the unconscious -_shifting of terms_ in the course of the argumentation. This is not -only the mistake of opponents who are unaware of the shifting which has -occurred in each other’s minds, so that practically the adversaries -do not meet on common ground, but cross and recross each other; it is -also the mistake of the solitary thinker losing himself in the maze -of interlacing conceptions instead of keeping steadily to one path. -Only by such shifting of terms can the notion of the physical process -causing, or being transformed into, the mental process for a moment -gain credit; and this also greatly sustains the hypothesis of Dualism, -with its formidable objections: How can Matter think? How can Mind act -on Matter causing Motion? - -39. Those who recognized that the terms Matter and Mind were -abstractions mutually exclusive, saw at once that these questions, -instead of being formidable, were in truth irrational. To ask if -Matter could think, or Mind move Matter, was a confusion of symbols -equivalent to speaking of a yard of Hope, and a ton of Terror. Although -Measure and Weight are symbols of Feeling, and in _this_ respect are -on a par with Hope and Terror, yet because they are objective symbols -they cannot be applied to subjective states, without violation of the -very significance they were invented to express. No one ever asks -whether a sensation of Sound can be a sensation of Color; nor whether -Color can move a machine, although Heat can, yet the one is no less a -sensation than the other. On similar grounds no one should ask whether -Matter can think, or Mind move Matter. The only rational question is -one preserving the integrity of the terms, namely, whether the living, -thinking organism presents itself to apprehension under the twofold -aspect--now under the modes of Feeling classified as objective or -physical; now under the modes classified as subjective or mental. - -40. We are told that it is “impossible to imagine Matter thinking,” -which is very true; only by a gross _confusion_ of terms can Thought -be called a property of cerebral tissue, or of Matter at all. We -may, indeed, penetrate beneath the terms which relate to aspects, -and recognize in the underlying reality not two existences, but one. -Our conceptions of this reality, however, are expressed in symbols -representing different classes of feelings, objective and subjective; -and to employ the terms of one class to designate the conceptions of -the other is to frustrate the very purposes of language. Matter and -Mind, Object and Subject, are abstractions from sentient experiences. -We know them as abstractions, and know the concrete experiences from -which they are abstracted. Philosophers, indeed, repeatedly assure us -that we neither know what Matter is nor what Mind is, we only know the -_phenomenal products_ of the action and reaction of these two unknown -noumena. Were this so, all discussion would be idle; we could not say -whether Matter was or was not capable of thinking, whether Mind was or -was not the same as Matter, we could only abstain from saying anything -whatever on the topic. What should we reply to one who asked us to -name the product of two unknown quantities? So long as _x_ and _y_ are -without values their product must be without value. If the value of -_x_ be known, and that of _y_ unknown, then the product still remains -unknown: _x_ + _y_ = _x_ + 0 = _x_. Therefore, unless the Objective -aspect were the _equivalent_ of the Subjective aspect, it could never -be subjectively present. Feeling is but another aspect of the Felt. - -41. It is because we do know what Matter is, that we know it is -_not_ Mind: they are symbols of two different modes of Feeling. If -we separate the conception of citizenship from the conception of -fatherhood, although the same man is both citizen and father, how much -more decisively must we separate the conception of Matter, which -represents one group of feelings, from the conception of Mind, which -represents another? One element in the former is common to the whole -group, namely, the reference to a Not-Self, induced by the sensation of -Resistance, which always ideally or sensibly accompanies the material -class. The axiom, I feel, _ergo_ I exist, has its correlative:--I act, -_ergo_ there are other existents on which I act; and these are not -wholly Me, for they resist, oppose, exclude me; yet they are also one -with Me, since they are felt by me. In my Feeling, that which is not Me -is Matter, the objective aspect of the Felt, as Mind is the subjective -aspect. - -But since Hunger and Thirst, Joy and Grief, Pain and Terror, are also -_felt_, yet are never classed under the head of Matter, the grounds of -the classification of feelings have to be expressed. Professor Bain -makes the distinction between Matter and Mind to rest solely on the -presence or absence of Extension: this is the decisive mark: Matter -he defines as the Extended. The definition is inadequate. When I see -a dog and its image reflected in a pool, or see a dog and think of -another, in the three cases dog, image, and idea have Extension; but -I recognize the dog as a material fact, the idea as a mental fact; -and although the image of the dog has material conditions by which -I am optically affected, just as the idea has material cerebral -conditions, I recognize a marked difference between them and the dog, -due to the different modes of apprehension. The dog is known as a -persistent reality, which, when Sight is supplemented by Touch, will -yield sensations of Resistance, and thus disclose its materiality. The -image vanishes if I attempt to touch it; I see its outlines waver and -become confused with every disturbance of the surface of the pool; -the idea vanishes when another idea arises; whence I conclude that -neither has material reality, because neither has the Resistance which -characterizes the Not-Self. The image and the idea may be referred to -material conditions, but so may pains, terrors, volitions, yet these -are all without Extension, simply because they are not visual feelings. - -42. Matter does not represent all feelings, but only the objective -sensibles; and these are not all characterized by Extension, but only -those which directly or indirectly involve optico-tactical experiences -accompanied by muscular experiences. Matter is primarily the Visible -and Resistant; and secondarily, whatever can be imagined as such; -so that ether, molecules, and atoms, although neither visible nor -tangible, are ranged under the head of Matter. Color is a feeling as -Sound and Scent are feelings, and although material conditions are -equally presupposed in all three, yet Color alone has Extension, and -because it can be imaged it has a more objective character than the -others, which having no lines and surfaces, want the optical conditions -for the formation of images, and are less definitely connected with -tactical and muscular experiences. Nevertheless, since Sound and Scent -are obviously associated with objects seen and touched, they have a -degree of materiality never assigned to such feelings as Hunger and -Thirst, Pleasure, Terror, and Hope. - -43. When we refer feelings to material conditions, we follow the -natural tendency to translate the little known in terms of the better -known, and employ the symbols Matter and Motion, because these furnish -the intellect with images, i. e. definite and exact elements to operate -with. In hearing a sound, there is nothing at all like “vibrations,” -nothing like “aerial waves” and “neural processes,” given in that -feeling; but on attempting to _explain_ it, we remove it from the -sphere of Sensation to carry it into the sphere of Intellect, and -we must change our symbols in changing our problem; here our only -resource is to translate the subjective state into an _imaginable_ -objective process, which can only be expressed in terms of Matter -and Motion. What we _heard_ as Sound is then _seen_ as Vibration. -When we are optically or mentally contemplating vibrations and neural -processes, we are supplanting one source of feeling by another, -translating an event in another set of symbols. But we can no more hear -the sound in seeing the vibrations, than a blind man can see the fly -in the amber which he feels with his fingers, or than we can feel the -amber he holds, while we are only looking at it. The phrase “material -conditions of Feeling” sometimes designates the objective aspect of the -subjective process, and sometimes the agencies in the external medium -which co-operate with the organism in the production of the feelings. -In each case there is an attempt to explain a feeling by intelligible -symbols. - -44. The Animal probably never attempts such explanation; satisfied with -the facts, it is careless of their factors. Man is never satisfied: -is restless in the search after factors; and having found them, seeks -factors of these factors; so that Lichtenberg felicitously calls him -“_das rastlose Ursachenthier_”--“the animal untiring in the search -for causes.” And thus sciences arise: we translate experiences into -geometrical, physical, chemical, physiological, and psychological -terms--different symbols of the different modes of apprehending -phenomena. - -45. “I see an elephant.” In other words, I am affected in a certain -way, and interpret my affection by previous similar experiences, -expressing these in verbal symbols. But I want an explanation, and -this the philosopher vouchsafes to me by translating my affection into -his terms. He takes me into another sphere--tells me of an undulating -Ether, the waves of which beat upon my retina--of lines of Light -refracted by media and converged by lenses according to geometric -laws--of the formation thereby of a tiny image of the gigantic elephant -on my retina as on the plate of a camera-obscura--this, and much -more, is what _he_ sees in _my_ visual feeling, and he bids me see it -also. Grateful for the novel instruction, I am compelled to say that -it does not alter my vision of the elephant, does not make the fact -a whit clearer, does not indeed correspond with what I feel. It is -outside knowledge, valuable, as all knowledge is, but supplementary. -It is translation into another language. And when I come to examine -the translation, I find it very imperfect. I ask my instructor: Is -it the tiny image on my retina which I see, and not the big elephant -on the grass? And how do I see this retinal image, which you explain -to be upside down?--how is it carried from my retina to my mind? I -have no consciousness of tiny reversed image, none of my retina, -only of a fact of feeling, which I call “seeing an elephant.” The -camera-obscura has no such feeling--it reflects the image, it does -not see the object. Here my instructor, having reached the limit -of his science,[210] hands me over to the physiologist, who will -translate the fact for me in terms not of Geometry, but of Anatomy -and Physiology. The laws of Dioptrics cease at this point: the image -they help to form on the retina is ruthlessly dispersed, and all its -beautiful geometric construction is lost in a neural excitation, which -is transmitted through semifluid channels of an optic tract to a -semifluid ganglion, whence a thrill is shot through the whole brain, -and is there _transformed_ into a visual sensation. Again I fancy I -have gained novel instruction of a valuable kind; but it does not -affect my original experience that I am enabled to translate it into -different terms; the less so because I cannot help the conviction that -the translation is imperfect, leaving out the essential points. If a -phrase be translated for me into French or German, I gain thereby an -addition to my linguistic knowledge, but the experience thus variously -expressed remains unaffected. When the fact is expressed in geometrical -or physiological terms, the _psychical process_ finds no adequate -expression. Neither in the details, nor in the totals, do I recognize -any of the qualities of my state of feeling in seeing the elephant. -I do not see the geometrical process, I do not see the anatomical -mechanism, I see the elephant, and am conscious only of that feeling. -You may consider my organism geometrically or anatomically, and bring -it thus within the circle of objective knowledge; but my subjective -experience, my spiritual existence, that of which I am most deeply -assured, demands another expression. Nay more, on closely scrutinizing -your objective explanations, it is evident that a psychical process -is _implied_ throughout--such terms as undulations, refractions, -media, lenses, retina, neural excitation, overtly refer, indeed, to -the material objective aspect of the facts, but they are themselves -the modes of Feeling by which the facts are apprehended, and would not -exist _as such_ without the “greeting of the spirit.” - -46. What, then, is our conclusion? It is, that to make an adequate -explanation of psychical processes by material conditions we must first -establish an equivalence between the subjective and objective aspects; -and, having taken this step, we must complete it by showing wherein the -difference exists; having established this entity and diversity, we -have solved the problem. - -Let us attempt this solution. When I speak to you, the spoken words -are the same to you and to me. You hear what I hear, you apprehend -what I apprehend. But there were muscular movements of articulation -felt by me and not felt by you; to feel these you also must articulate -the words; but so long as you merely hear the words, there is a -difference in our states of feeling. Some of my movements you can see, -others you can imagine; but this is not my feeling of them, it is your -optical equivalent of my muscular feeling. On a similar assumption of -equivalence, a neural process is made to stand for a logical process. -In thinking a proposition, we are logically grouping verbal symbols -representative of sensible experiences; and this is a quite peculiar -state of Consciousness, wholly unlike what would arise in the mental or -visual contemplation of the neural grouping, which is its physiological -equivalent. But this diversity does not discredit the idea of their -identity; and although some of my readers will protest against such an -idea, and will affirm that the logical process is not a process taking -place in the organism at all, but in a spirit which uses the organism -as its instrument, I must be allowed in this exposition to consider -the identity established, my purpose being to explain the diversity -necessarily accompanying it. Therefore, I say, that although a logical -process is identical with a neural process, it must appear differently -when the modes of apprehending it are different. While you are thinking -a logical proposition, grouping your verbal symbols, I, who mentally -_see_ the process, am grouping a totally different set of symbols: to -you the proposition is a subjective state, i. e. a _state_ of feeling, -not an _object_ of feeling: to become an object, it must be apprehended -by objective modes: and this it can become to you as to me, when we see -it as a process, or imagine it as a process. But obviously your state -in seeing or imagining the process must be different from your state -when the process itself is passing, since the modes of apprehension -are so different. There may be every ground for concluding that a -logical process has its correlative physical process, and that the two -processes are merely two aspects of one event; but because we cannot -apprehend the one aspect as we apprehend the other, cannot _see_ the -logical sequence as we _see_ the physical sequence, this difference in -our modes of apprehension compels us to separate the two, assigning -one to the subjective, the other to the objective class. Between the -sensible perception of an object and the reproduced image of the object -there is chiefly a quantitative difference in the physiological and -psychological processes: the image is a faint sensation. Yet this -quantitative difference brings with it the qualitative distinction -which is indicated in our calling the one a sensation, the other a -thought. The consequence has been that while all philosophers have -admitted the sensation to be--at least partly--a process in the bodily -organism, the majority have maintained that the thought is no such -process in the organism, but has its seat in a spirit independent of -the organism. - -47. The states of Feeling which are associated with other states -characterized as objective because overtly referring to a Not-Self, we -group under the head of Matter: we assign material conditions as their -antecedents. Whereas states of Feeling which are not thus associated we -group under the head of Mind, and assign internal conditions as their -antecedents. Color and Taste are very different states of Feeling, yet -both are spontaneously referred to external causes, because they are -associated with visual and tactical states; whereas Hunger, Nausea, -Hope, etc., have no such associations, and their material conditions -are only theoretically assigned. - -Our intelligible universe is constructed out of the elements of Feeling -according to certain classifications, the broadest of which is that -into external and internal, object and subject. The abstractions Matter -and Mind once formed and fixed in representative symbols, are easily -accredited as two different Reels. But the separation is ideal, and -is really a distinction of Aspects. We know ourselves as Body-Mind; -we do not know ourselves as Body _and_ Mind, if by that be meant two -coexistent independent Existents; and the illusion by which the two -Aspects appear as two Reals may be made intelligible by the analysis -of any ordinary proposition. For example, when we say “this fruit -is sweet,” we express facts of Feeling--actual or anticipated--in -abstract terms. The concrete facts are these: a colored feeling, a -solid feeling, a sweet feeling, etc., have been associated together, -and the colored, solid, sweet group is symbolized in the abstract -term “fruit” But the color, solidity, and sweetness are also abstract -terms, representing feelings associated in other groups, so that we -find “fruit” which has no “sweetness”; and “sweetness” in other things -besides “fruits.” Having thus separated ideally the “sweetness” from -the “fruit”--which in the concrete sweet-fruit is not permissible--we -easily come to imagine a real distinction. This is the case with the -concrete living organism when we cease to consider it in its concrete -reality, and fix our attention on its abstract terms--Body and Mind. We -then think of Body apart from Mind, and believe in them as two Reals, -though neither exists apart. - -There is no state of consciousness in which object and subject are -not indissolubly combined. There is no physical process which is -not indissolubly bound up with the psychical modes of apprehending -it. Every idea is either an image or a symbol--it has therefore -objective reference, a material aspect. Every object is a synthesis -of feelings--it has therefore subjective reference, a material -aspect. Thus while all the evidence points to the identity of Object -and Subject, there is ample evidence for the logical necessity of -their ideal separation as Aspects. This I have explained as a case -of the general principle which determines all distinctions--namely, -the diversity in the modes of production of the products, -which--subjectively--is diversity in the modes of apprehending them. -The optico-tactical experiences are markedly different from the other -experiences, as being more directly referred to the Not-Self which -resists; and because these lend themselves to ideal constructions by -means of images and symbols, it is these experiences into which we -translate all the others when we come to explain them and assign their -conditions. For--and this is the central position of our argument--all -interpretation consists in translating one set of feelings in the terms -of another set. We condense sets of feelings in abstract symbols; to -_understand_ these we must reduce them to their concrete significates. -They are signs; we must show what they are signs of. - -Now the symbols Object and Subject are the most abstract we can employ. -Because they are universal, they represent what cannot in reality be -divorced. We can, indeed, ideally separate ourselves from the Cosmos; -in the same way we can ideally separate our inner Self or Soul from our -outer Self or Body; and again our Soul from its sentient states, our -Body from its physical changes. But not so in reality. The separation -is a logical artifice, and a logical necessity for Science. - -The necessity will be obvious to any one who reflects how the ideal -constructions of Science demand precision and integrity of terms. The -problem of Automatism brings this very clearly into view. The question -is, Can we translate all psychological phenomena in mechanical terms? -If we _can_, we ought; because these terms have the immense advantage -of being _exact_, dealing as they do with quantitative relations. But -my belief is that we cannot--nay, that we cannot even translate them -all into physiological terms. The distinction between quantitative and -qualitative knowledge (p. 354) is a barrier against the mechanical -interpretation. Physiology is a classificatory science, not a science -of measurement. Nor can the laws of Mind be deduced from physiological -processes, unless supplemented by and interpreted by psychical -conditions individual and social. - - - - -CHAPTER IV. - -CONSCIOUSNESS AND UNCONSCIOUSNESS.[211] - - -48. Science demands precision of terms; and in this sense Condillac -was justified in defining it, “_une langue bien faite_.” The sciences -of Measurement are exact because of the precision of their terms, and -are powerful because of their exactness. The sciences of Classification -cannot aspire to this precision, and therefore, although capable of -attaining to a fuller knowledge of phenomena than can be reached -by their rivals, this advantage of a wider range is accompanied by -the disadvantage of a less perfect exposition of results. While -physicists and chemists have only to settle the significance of the -facts observed, biologists and social theorists have over and above -this to settle the significance of the terms they employ in expressing -the facts observed. Hence more than half their disputes are at bottom -verbal. - -This is markedly the case in the question of Automatism. One man -declares that animals are automata; another that they are conscious -automata; and while it is quite possible to hold these views and not -practically be in disagreement with the views of ordinary men, or -indeed with the views of spiritualist and materialist philosophers, -we can never be sure that the advocates of Automatism do not mean -what they are generally understood to mean. If a man says that by an -automaton he does not here mean a machine, such as a steam-engine or -a watch, but a vital mechanism which has its parts so adjusted that -its actions resemble those of a machine; and if he adds that this -automaton is also conscious of some of its actions, though unconscious -of others, we can only object to his using terms which have misleading -connotations. If he mean by “conscious automata,” that animals are -mechanisms moved on “purely mechanical principles,” their consciousness -having nothing whatever to do with the production of their actions, -then indeed our objection is not only to his use of terms, but to his -interpretation of the facts. - -49. The questions of fact are two: Are animal mechanisms rightfully -classed beside machines? and, Is consciousness a coefficient in the -actions of animal mechanism? The first has already been answered; the -second demands a preliminary settlement of the terms “conscious,” -“unconscious,” “voluntary,” and “involuntary.” The aim of Physiology -is to ascertain the particular combinations of the elementary parts -involved in each particular function--in a word, the mechanism of -organic phenomena; and the modern Reflex Theory is an attempt to -explain this mechanism on purely mechanical principles, without the -co-operation of other principles, especially those of Sensation and -Volition. It is greatly aided by the ambiguity of current terms. We are -accustomed to speak of certain actions as being performed unconsciously -or involuntarily. We are also accustomed to say that Consciousness -is necessary to transform an impression into a sensation, and that -Volition is the equivalent of conscious effort. When, therefore, -unconscious and involuntary actions are recorded, they seem to be -actions of an insentient mechanism. The Reflex Theory once admitted, a -rigorous logic could not fail to extend it to all animal actions. - -50. I reject the Reflex Theory, on grounds hereafter to be urged, -but at present call attention to the great ambiguity in the terms -“conscious” and “unconscious.” In one sense no definition of -Consciousness can be satisfactory, since it designates an ultimate -fact, which cannot therefore be made more intelligible than it is -already. In another sense no definition is needed, since every one -knows what is meant by saying, “I am conscious of such a change, -or such a movement.” It is here the equivalent of Feeling. To be -conscious of a change, is to feel a change. If we desire to express -it in physiological terms, we must define Consciousness--“a function -of the organism”; and this definition we shall find eminently useful, -because the organism being a vital mechanism, and the integrity of that -mechanism being necessary for the integrity of the function, while -every variation of the mechanism will bring a corresponding variation -of the function, we shall have an objective guide and standard in -our inquiries. Organisms greatly differ in complexity, yet because -they also agree in the cardinal conditions of Vitality, among which -Sensibility is one, we conclude that they all have Feeling; but the -Feeling of the one will differ from that of another, according to the -complexity of the sentient mechanism in each. The perfection of this -mechanism lies in the co-ordination of its parts, and the consensus of -its sentient activities; any disturbance of that consensus must cause -a modification in the total consciousness; and when the disturbance -is profound the modification is marked by such terms as “insanity,” -“loss of consciousness,” “insensibility.” These terms do not imply -that the sentient organs have lost their Sensibility, but only that -the disturbed mechanism has no longer its normal consensus, no longer -its normal state of Consciousness. Each organ is active in its own -way so long as its own mechanism is preserved; but the united action -of the organs having been disturbed, their _resultant_ function has -been altered. Hence in a fit of Epilepsy there is a complete absence -of some normal reactions, with exaggeration of others. In a state of -Coma there is no spontaneity--none of the manifold adaptations of the -organism to fluctuating excitations, external and internal, observable -in the normal state. The organism still manifests Sensibility--but -this is so unlike the manifestations when its mechanism is -undisturbed (and necessarily so since the Sensibility varies with -the mechanism) that it is no longer called by the same name. In the -normal organism Sensibility means Feeling, or Consciousness; but in -the abnormal organism there is said to be a “loss of Consciousness.” -What the physiologist or the physician means by the phrase “loss of -Consciousness” is intelligible, and for his purposes unobjectionable. -He observes many organic processes going on undisturbed--the -unconscious patient breathes, secretes, moves his limbs, etc. These -processes are referred to the parts of the mechanism which are not -disturbed; they are obviously independent of that adjustment of the -mechanism which by its _consensus_ has the special resultant named -Consciousness; he therefore concludes that these, and many other -organic processes, which are neither accompanied nor followed by -_discriminated_ feelings, are the direct consequences of the stimulated -mechanism. He never hesitates to adopt the popular language, and say, -“We sometimes act unconsciously, perceive unconsciously, and even think -unconsciously, all by the simple reflex of the mechanism.” - -Now observe the opening for error in this language. The actions are -said to go on unconsciously, and, because unconsciously, as pure -reflexes, which are then assigned to an insentient mechanism, and -likened to the actions of machines. But, as I hope hereafter to make -evident, the reflex mechanism necessarily involves Sensibility; and -therefore reflex actions may be unaccompanied by Consciousness--in -one meaning of that term--without ceasing to be sentient, the feelings -are operative, although not discriminated. On the other hand, there is -another and very general meaning of the term Consciousness, which is -the equivalent of Sentience. - -51. In discussing Automatism, or the Reflex Theory, it is absolutely -necessary that we should first settle the meaning we assign to the -term Consciousness. The laxity with which the term is used may be seen -in the enumeration occupying six pages of Professor Bain’s account of -the various meanings. Psychology is often said to be “the science of -the facts of Consciousness”; and the Brain is often assigned as “the -organ of Consciousness.” Yet there are many mental processes, and many -cerebral processes, which are declared to be unconscious. Obviously if -Consciousness is the function of the Brain, there can be no cerebral -activity which is unconscious; just as there can be no activity of the -lungs which is not respiratory. Usage therefore points to a general -and a special sense of the term. The general usage identifies it -with Sensibility, in its subjective aspect as Sentience, including -all psychical states, both those classed under Sensation, and those -under Thought. These states are the “facts of consciousness” with -which Psychology is occupied. In the special usage it is distinguished -from all other psychical states by a peculiar reflected feeling of -Attention, whereby we not only _have_ a sensation, but also _feel_ that -we have it; we not only think, but are conscious that we are thinking; -not only act, but are conscious of what we do. It is this which Kant -indicates when he defines it “the subjective form accompanying all our -conceptions (_Begriffe_)”; and Jessen when he defines it “the internal -knowing of our knowing, an in itself reflected knowing.”[212] - -52. We shall often have to recur to this general and this special -meaning, both of which are too firmly rooted for any successful attempt -to displace them. The fact that some organic processes and some -mental processes take place now consciously and now unconsciously, -i. e. now with the feeling of reflected attention, and now with no -such feeling, assuredly demands a corresponding expression; nor, in -spite of inevitable ambiguities, is there ground for regretting that -the expression chosen should be only an extension of the expression -already adopted for all other states of Sentience. A sentient or -conscious state can only be a state of the sentient organism, itself -the unity of many organs, each having its Sensibility. There is -more or less consensus, but there is no introduction of a new agent -within the organism, converting what was physical impression into -mental reaction. From first to last there has been nothing but -neural processes, and combinations of such processes--which, viewed -subjectively, are sentient processes. Thus the gradations of sensitive -reaction are Sentience, Consentience, and Consciousness, which are -represented in the Logic of Feeling and the Logic of Signs. The -familiar term Conscience will then represent the Logic of Conduct. -Thus understood, we may say that a man sometimes acts unconsciously, -or thinks unconsciously, although his action and thought are ruled -by Consentience, as he sometimes acts and thinks unconscientiously, -although he is not without obedience to Conscience on other occasions. -The feeling which determines an action is _operative_, although it -may not be _discriminated_ from simultaneous feelings. When this -is the case, we say the feeling is unconscious; but this no more -means that it is a purely physical process taking place outside the -sphere of Sentience, than the immoral conduct of a man would be said -to be mechanical, and not the conduct of a moral agent. There is -undoubtedly a marked distinction expressed in the terms Consciousness -and Unconsciousness, but it is not that of contrasts such as Mental -and Physical, it is that of grades such as Light and Darkness. Just -as Darkness is a positive optical sensation very different from mere -privation--just as it replaces the sensation of Light, blends with -it, struggles with it, and in all respects differs from the _absence_ -of all optical sensibility in the skin; so Unconsciousness struggles -with, blends with, and replaces Consciousness in the organism, and is -a positive state of the sentient organism, not to be confounded with a -mere negation of Sentience; above all, not to be relegated to merely -mechanical processes. - -52 _a_. Remember that, strictly speaking, Consciousness is a -psychological not a physiological term, and is only used in Physiology -on the assumption that it is the subjective _equivalent_ of an -objective process. To avoid the equivoque of “unconscious sensation,” -we may substitute the term “unconscious neural process”; and as all -neural processes imply Sensibility, which in the subjective aspect is -Sentience, we say that Sentience has various modes and degrees--such -as Perception, Ideation, Emotion, Volition, which may be conscious, -sub-conscious, or unconscious. When Leibnitz referred to the fact of -“obscure ideas,” and modern writers expressed this fact as “unconscious -cerebration,” the first phrase did not imply a process that was other -than mental, the second phrase did not imply a process that was other -than physiological: both indicated a mode of the process known as -Consciousness under other modes. There are different neural elements -grouped in Ideation and Emotion; there are different neural elements -grouped in Consciousness, Sub-consciousness, and Unconsciousness; but -one tissue with one property is active in all. - -53. The nervous organism is affected as a whole by every affection -of its constituent parts. Every excitation, instead of terminating -with itself--as is the case in most physical processes--or with the -motor impulse it excites, is propagated throughout the continuous -tissue, and thus sends a _thrill_ throughout the organism. The wave -of excitation in passing onwards beats against variously grouped -elements--temporary and permanent centres--disturbing their balance -more or less, and liberating the energy of some, increasing the tension -of others, necessarily affecting all. Those groups which have their -energy liberated set up processes that are either _discriminated_ -as sensations, or are blended with the general stream, according -to their _relative_ energy in the consensus. Thus the impulse on -reaching the centres for the heart, lungs, legs, and tail excites -the innervation of these organs; but as these are only parts of the -organism, and as all the parts enter the consensus, and Consciousness -is the varying resultant of this ever-varying consensus, the -thrill which any particular stimulus excites will be unconscious, -sub-conscious, or conscious, in proportion to the extent of the -_irradiated_ disturbance, which will depend on the statical conditions -of the centres at the moment. A sound sends a thrill which excites -emotion, causes the heart to beat faster, the muscles to quiver, the -skin-glands to pour forth their secretion; yet this same sound heard -by another man, or the same man under other conditions, physical or -historical, merely sends a faint thrill, just vivid enough to detach -itself as a sensation from the other simultaneous excitations; and -the same sound may excite a thrill which is so faint and fugitive as -to pass unconsciously. Physiological and psychological inductions -assure us that these are only differences of degree. The same kind -of physiological effect accompanies the conscious and unconscious -state. Every sensory impression, no matter whether discriminated or -not, affects the circulation and develops heat. The blood-vessels of -the part impressed expand, vessels elsewhere contract--a change in -the blood pressure has been effected, which of course implies that -the whole organism has been affected. Delicate instruments show that -at the time a sensation is produced the temperature of the brain is -raised. The same is true of ideation. Mosso has invented a method of -registering the effect of thought on the circulation. He finds ideation -accompanied by a contraction of the peripheral vessels proportionate -to the degree of intellectual effort. A young man translating Greek -showed greater contraction than when he was translating Latin. During -sound sleep--when we are said to be unconscious--sudden noises -always cause contraction of the peripheral vessels. Psychological -observation assures us that the conscious and unconscious states -were both consentient, and were both operative in the same degree. -The absorbed thinker threads his way through crowded streets, and is -sub-conscious and unconscious of the various sights, sounds, touches, -and muscular movements which make up so large a portion of his sentient -excitation at the time; yet he deftly avoids obstacles, hears the -sound of a hurried step behind him, recognizes an interesting object -directly it presents itself, and can even recall in Memory many of the -uninteresting objects which he passed in sub-conscious and unconscious -indifference. - -54. On all grounds, therefore, we must say that between conscious, -sub-conscious, and unconscious states the difference is only of -degree of complication in the neural processes, which by relative -preponderance in the consensus determine a relative discrimination. We -can only discriminate one thrill at a time; but the neural excitations -simultaneously pressing towards a discharge are many; and the -conditions which determine now this, and now the other excitation to -predominate by its differential pressure, are far beyond any mechanical -estimate. I mention this because the advocates of the Reflex Theory -maintain that the neural processes are the same whether a sensation be -produced or not; and that since the same actions follow the external -stimulation whether sensation be produced or not, this proves the -actions to be purely mechanical. I reply, the neural processes are -_not_ the same throughout in the two cases--otherwise the effects would -be the same. You might as well say, “Since the explosion of the gun -is the same, whether shotted or not, a blank cartridge will kill”; -but if you tell me that your gun killed the bird, I declare that the -cartridge was _not_ a blank one. Whether the explosion of the gun -_also_ produced terror in one bystander, curiosity in a second, and -attracted no notice from a third, will be altogether another matter. -In like manner the sensory impression which determines a movement may -or may not be accompanied or followed by _other_ sentient states; the -fact of such movement is evidence of its sentient antecedent; and an -external stimulus that will produce _this_ neural process, and this -consequent movement, must produce a feeling, although not necessarily a -discriminated sensation. Now since, for discrimination, _other_ neural -processes must co-operate, we cannot say that in the two cases _all_ -the neural processes have been the same throughout; nor because of this -difference can we say that the process of the undiscriminated sensation -is a mechanical, not a sentient process. In the next problem this point -will be argued more fully. - -55. The need of recognizing Consciousness and Consentience as degrees -of energy and complexity in sentient states is apparent when we -consider animal phenomena. Has a bee consciousness? Has a snail -volition? or are they both insentient mechanisms? All inductions -warrant the assertion that a bee has thrills propagated throughout its -organism by the agency of its nerves; and that some of these thrills -are of the kind called sensations--even discriminated sensations. -Nevertheless we may reasonably doubt whether the bee has sentient -states resembling otherwise than remotely the sensations, emotions, -and thoughts which constitute human Consciousness, either in the -general or the special sense of that term. The bee feels and reacts on -feelings; but its feelings cannot closely resemble our own, because -the conditions in the two cases are different. The bee may even be -said to think (in so far as Thought means logical combination of -feelings), for it appears to form Judgments in the sphere of the Logic -of Feeling--το νοητικὸν; although incapable of the Logic of Signs--το -διανοητικον. We should therefore say the bee has Consentience, but -not Consciousness--unless we accept Consciousness in its _general_ -signification as the equivalent of Sentience. The organism of the bee -differs from that of a man, as a mud hut from a marble palace. But -since underlying these differences there are fundamental resemblances, -the functions of the two will be fundamentally alike. Both have the -function of Sentience; as mud hut and palace have both the office of -sheltering. - -56. The question of Volition will occupy us in the next chapter. -Restricting ourselves here to that of Consciousness, and recalling -the distinction of the two meanings of the term, we now approach -the question of Unconsciousness. Are we to understand this term as -designating a purely physical state in contrast to the purely mental -state of Consciousness; or only as designating a difference of degree? -This is like asking whether Light and Darkness are both optical -feelings, or one an optical feeling and the other a physical process? -On the Reflex Theory, no sooner does a vital and mental process pass -from the daylight of Consciousness, or twilight of Sub-consciousness, -into the darkness of Unconsciousness, than the whole order of phenomena -is abruptly changed, they cease to be vital, mental, and lapse into -physical, mechanical processes. The grounds of this conclusion are, -first, the unpsychological assumption that the unconscious state is -out of the sphere of Sentience; and secondly, the unphysiological -assumption that the Brain is the only portion of the nervous system -which has the property of Sensibility. Restate the conclusion in -different terms and its fallacy emerges: “organic processes suddenly -cease to be organic, and become purely physical by a slight change -in their _relative_ position in the consensus; the organic process -which was a conscious sensation a moment ago, when its energy was not -balanced by some other process, suddenly falls from its place in the -group of organic phenomena--sentient phenomena--to sink into the group -of inorganic phenomena now that its energy is balanced.” Consider the -parallel case of Motion and Rest in the objective sphere. They are two -functions of the co-operant forces, one dynamic, the other static; -although markedly distinguishable as functions, we know that they are -simply the co-operant forces now unbalanced and now balanced; what -we call Rest is also a product of moving forces, each of which is -operant, and will issue in a definite resultant when its counter-force -is removed. Motion and Rest are correlatives, and both belong to the -sphere of Kinetics. In like manner Consciousness and Unconsciousness -are correlatives, both belonging to the sphere of Sentience.[213] Every -one of the unconscious processes is operant, changes the general state -of the organism, and is capable of at once issuing in a discriminated -sensation when the force which balances it is disturbed. I was -unconscious of the scratch of my pen in writing the last sentence, but -I am distinctly conscious of every scratch in writing this one. Then, -as now, the scratching sound sent a faint thrill through my organism, -but its relative intensity was too faint for discrimination; now that I -have redistributed the co-operant forces, by what is called an act of -Attention, I hear distinctly every sound the pen produces. - -57. The inclusion of Sub-consciousness within the sentient sphere is -obvious; the inclusion of Unconsciousness within that sphere may be -made so, when we consider its modes of production, and compare it -with the extra-sensible conception of molecules and atoms. The Matter -which is sensible as masses, may be resolved into molecules, which lie -beyond the discrimination of sense; and these again into atoms, which -are purely ideal conceptions; but because molecules are _proved_, and -atoms are _supposed_, to have material properties, and to conform to -sensible canons of the objective world, we never hesitate to class them -under the head of Matter; nor do we imagine that in passing beyond the -discrimination of Sense they lose their objective significance. They -are still physical, not mental facts. So with Sentience: we may trace -it through infinite gradations from Consciousness to Sub-consciousness, -till it fades away in Unconsciousness; but from first to last the -processes have been those of a sentient organism; and by this are -broadly distinguished from all processes in anorganisms. The movement -of a limb has quite different modes of production from the movement of -a wheel; and among its modes must be included those of Sensibility, -a peculiarly vital property. Oxidation may be slow or rapid, -manifesting itself as combustion, heat, or flame, but it is always -oxidation--always a special chemical phenomenon. And so the neural -process of Sentience, whether conscious, sub-conscious, or unconscious, -is always a state of the sentient organism. If a material process does -not change its character, and become spiritual, on passing beyond the -range of sensible appreciation, why should a psychical process become -material on passing beyond the range of discrimination? If we admit -molecules as physical units, sentient tremors are psychical units. -The extra-sensible molecules have indeed their subjective aspect, -and only enter perception through the “greeting of the spirit.” The -sentient tremors have also their objective aspect, and cannot come -into existence without the neural tremors, which are their physical -conditions. - -58. It is only by holding fast to such a conception that we can escape -the many difficulties and contradictions presented by unconscious -phenomena, and explain many physiological and psychological processes. -Descartes--followed by many philosophers--identified Consciousness -with Thought. To this day we constantly hear that to have a sensation, -and to be conscious of it, is one and the same state; which is only -admissible on the understanding that Consciousness means Sentience, -and Sentience the activity of the nervous system viewed subjectively. -Leibnitz pointed out that we have many psychical states which are -unconscious states--to have an idea and be conscious of it, are, he -said, not one but two states. The Consciousness by Descartes erected -into an essential condition of Thought, was by Leibnitz reduced to an -accompaniment which not only may be absent, but in the vast majority -of cases is absent. The teaching of most modern psychologists is -that Consciousness forms but a small item in the total of psychical -processes. Unconscious sensations, ideas, and judgments are made to -play a great part in their explanations. It is very certain that in -every conscious volition--every act that is so characterized--the -larger part of it is quite unconscious. It is equally certain that -in every perception there are unconscious processes of reproduction -and inference--there is much that is _implicit_, some of which cannot -be made explicit--a “middle distance” of sub-consciousness, and a -“background” of unconsciousness. But, throughout, the processes are -those of Sentience. - -59. Unconsciousness is by some writers called _latent_ Consciousness. -Experiences which are no longer manifested are said to be stored up in -Memory, remaining in the Soul’s picture-gallery, visible directly the -shutters are opened. We are not conscious of these feelings, yet they -exist as latent feelings, and become salient through association. As a -metaphorical expression of the familiar facts of Memory this may pass; -but it has been converted from a metaphor into an hypothesis, and we -are supposed to _have_ feelings and ideas, when in fact we have nothing -more than a modified _disposition_ of the organism--temporary or -permanent--which when stimulated will respond in this modified manner. -The modification of the organism when permanent becomes hereditary; and -its response is then called an instinctive or automatic action. And as -actions pass by degrees from conscious and voluntary into sub-conscious -and sub-voluntary, and finally into unconscious and involuntary, we -call them volitional, secondarily automatic, and automatic. If any one -likes to say the last are due to latent consciousness, I shall not -object. I only point to the fact that the differences here specified -are simply differences of degree--all the actions are those of the -sentient organism. - -60. Picture to yourself this sentient organism incessantly stimulated -from without and from within, and adjusting itself in response to such -stimulations. In the blending of stimulations, modifying and arresting -each other, there is a fluctuating “composition of forces,” with -ever-varying resultants. Besides the stream of direct stimulations, -there is a wider stream of indirect or reproduced stimulations. -Together with the present sensation there is always a more or less -complex group of revived sensations, the one group of neural tremors -being organically stimulated by the other. An isolated excitation is -impossible in a continuous nervous tissue; an isolated feeling is -impossible in the consensus or unity of the sentient organism. The term -Soul is the personification of this complex of present and revived -feelings, and is the substratum of Consciousness (in the general -sense), all the particular feelings being its _states_. To repeat an -illustration used in my first volume, we may compare Consciousness to -a mass of stationary waves. If the surface of a lake be set in motion -each wave diffuses itself over the whole surface, and finally reaches -the shores, whence it is reflected back towards the centre of the lake. -This reflected wave is met by the fresh incoming waves, there is a -blending of the waves, and their product is a pattern on the surface. -This pattern of stationary waves is a fluctuating pattern, because of -the incessant arrival of fresh waves, incoming and reflected. Whenever -a fresh stream enters the lake (i. e. a new sensation is excited from -without), its waves will at first pass over the pattern, neither -disturbing it nor being disturbed by it; but after reaching the shore -the waves will be reflected back towards the centre, and there will -more or less modify the pattern. - - - - -CHAPTER V. - -VOLUNTARY AND INVOLUNTARY ACTIONS. - - -61. Much of what has been said in the preceding chapter respecting -the passive side of the organism is equally applicable to the active -side. Our actions are classed as voluntary and involuntary mainly in -reference to their being consciously or unconsciously performed; but -not wholly so, for there are many involuntary actions of which we are -distinctly conscious, and many voluntary actions of which we are at -times sub-conscious and unconscious. I do not propose here to open the -long and arduous discussion as to what constitutes Volition, my present -purpose being simply that of fixing the meaning of terms, so that the -question of Automatism may not be complicated by their ambiguities. -“Voluntary” and “involuntary” are, like “conscious” and “unconscious,” -correlative terms; but commonly, instead of being understood as -indicating differences of degree in phenomena of the same order, they -are supposed to indicate differences of kind--a new agent, the Will, -being understood in the one case to direct the Mechanism which suffices -without direction in the other. - -62. This interpretation is unphysiological and unpsychological, -since it overlooks the fact that both voluntary and involuntary -actions belong to the same _order_ of phenomena, i. e. those of the -sentient organism. Both involve the same _efficient_ cause, i. e. -co-operant conditions. We draw a line of demarcation between the two -abstractions--as between all abstractions--but the concrete processes -they symbolize have no such demarcation. Just as the thought which at -one moment passes unconsciously, at another consciously, is in itself -the same thought, and the same neural process; so the action which at -one moment is voluntary, and at another involuntary, is itself the same -action, performed by the same mechanism. The incitation which precedes, -and the feeling which accompanies the action, belong to the accessory -mechanisms, and may be replaced by other incitations and other -feelings; as the fall of an apple is the same event, involving the same -conditions, i. e. efficient cause, whether the _occasional_ cause be a -gust of wind or the gardener’s scissors, and whether the fall be seen -and heard or not. I may utter words intentionally and consciously, and -I may utter the same words automatically, unconsciously; I may wink -voluntarily, and wink involuntarily. There are terms to express these -differences; but they do not express a difference in the efficient -agencies. - -63. Many writers seem to think that the involuntary actions belong -to the physical mechanical order, because they are not stimulated by -cerebral incitations, and cannot be regulated or controlled by such -incitations--or as the psychologists would say, because Consciousness -in the form of Will is no agent prompting and regulating such actions. -But I think this untenable. The actions cannot belong to the mechanical -order so long as they are the actions of a vital mechanism, and so long -as we admit the broad distinction between organisms and anorganisms. -Whether they have the special character of Consciousness or not, -they have the general character of sentient actions, being those -of a sentient mechanism. And this becomes the more evident when we -consider the gradations of the phenomena. Many, if not all, of those -actions which are classed under the involuntary were originally of -the voluntary class--either in the individual or his ancestors; but -having become permanently organized dispositions--the pathways of -stimulation and reaction having been definitely established--they have -lost that volitional element (of hesitation and choice) which implies -regulation and control. But even here a slight change in the habitual -conditions will introduce a disturbance in the process which may -awaken Consciousness, and the sense of effort, sometimes even causing -control. An instinctive or an automatic action may be thus changed, -or arrested. Take as an example one of the unequivocally automatic -actions, that of Breathing. It is called automatic because, like the -actions of an automaton, it is performed by a definitely constructed -mechanism, always working in the same way when stimulated and left to -itself. There must of course be a sense of effort in every impulse -which has resistance to overcome, organs to be moved; but the mechanism -of Breathing is so delicately adjusted, that the sense of effort is -reduced to a minimum, and we are unconscious of it, or sub-conscious -of it. Nevertheless, without altering the rate or amplitude of the -inspirations and expirations, we become distinctly conscious of them, -and, moreover, within certain limits we can control them, so that the -Breathing passes from the involuntary to the voluntary class. - -64. Pass on to other examples. What action can be more involuntary than -the rhythmic movements of the heart and the contractions of the iris? -Compared with the actions of the tongue or limbs, these seem riveted -by an iron necessity, freed from all consciousness and control. Yet -the movements of the heart are not only stimulated by sensations and -thoughts, they are also capable of being felt; and the movements both -of heart and iris are not wholly removed from our control. That we do -not habitually control (that is, _interfere_ with) the action of the -heart, the contraction of the iris, or the activity of a gland, is -true; it is on this account that such actions are called involuntary; -they obey the immediate stimulus. But it is an error to assert that -these actions _cannot_ be controlled, that they are altogether beyond -the interference of other centres, and cannot by any effort of ours -be modified. It is an error to suppose these actions are essentially -distinguished from the voluntary movement of the hands. We have -acquired a power of definite direction in the movements of the hands, -which renders them obedient to our will; but this acquisition has been -of slow laborious growth. If we were asked to use our toes as we use -our fingers--to grasp, paint, sew, or write with them, we should find -it not less impossible to control the movements of the toes in these -directions, than to contract the iris, or cause a burst of perspiration -to break forth. Certain movements of the toes are possible to us; but -unless the loss of our fingers has made it necessary that we should -use our toes in complicated and slowly acquired movements, we can do -no more with them than the young infant can do with his fingers. Yet -men and women have written, sewed, and painted with their toes. All -that is requisite is that certain links should be established between -sensations and movements; by continual practice these links _are_ -established; and what is impossible to the majority of men, becomes -easy to the individual who has acquired this power. This same power -can be acquired over what are called the organic actions; nevertheless -the habitual needs of life do not _tend_ towards such acquisition, -and without some strong current setting in that direction, or some -peculiarity of organization rendering it easy, it is never acquired. -In ordinary circumstances the number of those who can write with their -toes is extremely rare, the urgent necessity which would create such a -power being rare; and rare also are the examples of those who have any -control over the movement of the iris, or the action of a gland; but -both rarities exist. - -It would be difficult to choose a more striking example of reflex -action than the contraction of the iris of the eye under the stimulus -of light;[214] and to ordinary men, having no link established which -would guide them, it is utterly impossible to close the iris by any -effort. It would be not less impossible to the hungry child to get -on the chair and reach the food on the table, until that child had -_learned_ how to do so. Yet there are men who have learned how to -contract the iris. The celebrated Fontana had this power; which is -possessed also by a medical man now living at Kilmarnock--Dr. Paxton--a -fact authenticated by no less a person than Dr. Allen Thomson.[215] Dr. -Paxton can contract or expand the iris at will, without changing the -position of his eye, and without an effort of adaptation to distance. - -To move the ears is impossible to most men. Yet some do it with ease, -and all could learn to do it. Some men have learned to “ruminate” their -food; others to vomit with ease; and some are said to have the power of -perspiring at will.[216] Now, if once we recognize a link of sensation -and motion, we recognize a possible source of control; and if the -daily needs of life were such that to fulfil some purpose the action -of the heart required control, we should learn to control it. Some -men have, without such needs, learned how to control it. The eminent -physiologist, E. F. Weber of Leipzig, found that he could completely -check the beating of his heart. By suspending his breath and violently -contracting his chest, he could retard the pulsations; and after -three or five beats, unaccompanied by any of the usual sounds, it was -completely still. On one occasion he carried the experiment too far, -and fell into a syncope. Cheyne, in the last century, recorded the case -of a patient of his own who could at will suspend the beating of his -pulse, and always fainted when he did so. - -65. It thus appears that even the actions which most distinctly bear -the character recognized as involuntary--uncontrollable--are only so -because the ordinary processes of life furnish no necessity for their -control. We do not learn to control them, though we could do so, to -some extent; nor do we learn to control the motions of our ears, -although we could do so. And while it appears that the involuntary -actions can become voluntary, it is familiar to all that the voluntary -actions tend, by constant repetition, to become involuntary. Thus -involuntary actions, under certain limitations, may be controlled; on -the other hand, the voluntary are incapable of being controlled under -the urgency of direct stimulation. Both are reflexes. - -Inasmuch as almost all actions are the products of stimulated -nerve-centres, it is obvious that these actions are reflex--reflected -from those centres. It matters not whether I wink because a sensation -of dryness, or because an idea of danger, causes the eyelid to close: -the act is equally reflex. The nerve-centre which supplies the eyelid -with its nerve has been stimulated; the stimuli may be various, the -act is uniform. At one time the stimulus is a sensation of dryness, -at another an idea of danger, at another the idea of communicating -by means of a wink with some one present; in each case the stimulus -is reflected in a muscular contraction. Sensations excite other -sensations; ideas excite other ideas; and one of these ideas may issue -in an action of control. But the restraining power is limited, and -cannot resist a certain degree of urgency in the original stimulus. I -can, for a time, restrain the act of winking, in spite of the sensation -of dryness; but the reflex which sets going this restraining action -will only last a few seconds; after which, the urgency of the external -stimulus is stronger than that of the reflex feeling--the sensation of -dryness is more imperious than the idea of resistance--and the eyelid -drops. - -If a knife be brought near the arm of a man who has little confidence -in the friendly intentions of him that holds it, he shrinks, and the -shrinking is “involuntary,” i. e. in spite of his will. Let him have -confidence, and he does not shrink, even when the knife touches his -skin. The idea of danger is not excited in the second case, or if -excited, is at once banished by another idea. Yet this very man, who -can thus repress the involuntary shrinking when the knife approaches -his arm, cannot repress the involuntary winking when the same friend -approaches a finger to his eye. In vain he prepares himself to resist -that reflex action; in vain he resolves to resist the impulse; no -sooner does the finger approach, than down flashes the eyelid. Many -men, and most women, would be equally unable to resist shrinking on the -approach of a knife: the association of the idea of danger with the -knife would bear down any previous resolution not to shrink. It is from -this cause that timorous women tremble at the approach of firearms. An -association is established in their minds which no idea is powerful -enough to loosen. You may assure them the gun is not loaded; “_that_ -makes very little difference,” said a naïve old lady to a friend of -mine. They tremble, as the child trembles when he sees you put on the -mask. These illustrations show that the urgency of any one idea may, -like the urgency of a sensation, bear down the resistance offered by -some other idea; as the previous illustrations showed that an idea -could restrain or control the action which a sensation or idea would -otherwise have produced. According to the doctrines current, the Will -is said to be operative when an idea determines an action; and yet all -would agree that the winking which was involuntary when the idea of -danger determined it, was voluntary when the idea of communicating with -an accomplice in some mystification determined it. - -66. There is no real and essential distinction between voluntary and -involuntary actions. They all spring from Sensibility. They are all -determined by feeling. It is convenient, for common purposes, to -designate some actions as voluntary; but this is merely a convenience; -no psychological nor physiological insight is gained by it; an analysis -of the process discloses no element in a voluntary action which is -not to be found in an involuntary action--except in the origin or -degree of stimulation. In ordinary language it is convenient to mark a -distinction between my raising my arm because I will to raise it for -some definite purpose, and my raising it because a bee has stung me; it -is convenient to say, “I _will_ to write this letter,” and “this letter -is written against my will--I have no will in the matter.” But Science -is more exacting when it aims at being exact; and the philosopher, -analyzing these complex actions, will find that in each case certain -muscular groups have been set in action by different sensational or -ideational stimuli. The action itself is that of a neuro-muscular -mechanism, which mechanism works in the same way, whatever be the -source of the original impulse. The stimulation may be incited -directly from the periphery, or indirectly from a remote centre; and -the action may be arrested by a peripheral or central stimulation: -the reflex which ordinarily follows the excitation of a sensory nerve -will be modified, or arrested, if some other nerve be at the same time -stimulated. (See Law of Arrest, _Prob._ II. § 190.) - -67. All actions are reflex, all are the operations of a mechanism, -all are sentient, because the mechanism has Sensibility as its vital -property. In thus preserving the integrity of the order of vital -phenomena, and keeping them classified apart from physical and chemical -phenomena, we by no means set aside the useful distinctions expressed -in the terms voluntary and involuntary; any more than we set aside the -distinction of vertebrate and invertebrate when both are classed under -Animal, and separated from Plant, or Planet. - -The mechanisms of the special Senses respond in special reactions; -the mechanisms of special actions have also their several responses. -The tail responds to stimulation with lateral movements, the chest -with inspiration and expiration, and so on. These responses are called -automatic, and have this in common with the actions of automata that -they are uniform, and do not need the co-operation of Consciousness, -though they do need the operation of Sensibility, and are thereby -distinguished from the actions of automata. The facial muscles, and -the limbs, also respond to stimulation in uniform ways, but owing to -the varieties of stimulation the actions are more variable, and have -more the character of volitional movements. With this greater freedom -of possible action comes the eminently mental character of _choice_. -In the cerebral rehearsal of an act not yet performed--its mental -prevision--as when we intend to do something, yet for the moment -arrest the act, so that there is only a nascent excitation of the -motor process, there is a peculiar state of Consciousness expressive -of this state of the mechanism: we call the prevision a _motive_--and -it becomes a _motor_ when the intention is realized, the nascent -excitation becomes an unchecked impulse. The abstract of all motives we -call Will. A motive is a volition in the sphere of the Intellect. In -the sphere of Emotion it is a motor. Hence we never speak of the Will -of a mollusc, or the motives of an insect, only of their sensations and -motors. Yet it is obvious that the reflex in operation when a snail -shrinks at the approach of an object is essentially similar to the -reflex in operation when the baby shrinks, and this again is still more -similar to that in operation when the boy shrinks: the boy has the idea -of danger, which neither baby nor snail can have; the idea is a motive, -which can be controlled by another idea; the baby and the snail can -have no such motive, no such control--are they therefore automata? - -68. If I see that a donkey has wandered into my garden, the motive -which determines me to take a stick and with it drive the donkey -away is a cerebral rehearsal of the effects which will follow my -act. The sight of the donkey has roused disagreeable feelings, -and these suggest possible means of alleviation; out of these -possibilities--reproductions of former experiences--I choose one. -But if I seize the stick with which some one is threatening me, I do -not pause to choose, I snatch automatically without hesitation. Yet -this unreflecting automatic act is itself as truly volitional as my -seizing the stick to drive away the donkey--it is the motor which has -been organized in me by previous experiences--it is the consequence -of an emotion, not of a deliberation; and it has not been determined -by any clear prevision of consequences. Feeling inspires, and feeling -guides my movements, so that if my snatch has missed the stick, I -snatch again, or duck under. This is the kind of Volition we ascribe -to animals. It is a great part of our own. By insensible degrees, acts -which originally were prompted by motives sink into the automatic -class prompted by motors. When an angry man snatches up a knife, doffs -bystanders aside, and rushes on his enemy to stab him, he does not -distinctly prefigure the final result, he only obeys each motor, and -is conscious of each step; but had he planned the murder he would have -foreseen the end, and this prevision would have been the motive. The -angry man is struck with horror at the sight of the bleeding corpse, -and passionately declares he did not _mean_ to kill. Nor did he will -the consequences of his act, yet he certainly willed each separate -step--he recognized the knife, saw the bystanders, knew they would -interfere with him, willed to push them aside. He may be right in -declaring that the act was involuntary; but assuredly it was not purely -mechanical. - -69. Again, we are not conscious of the separate sensations which guide -speech or writing; we cannot properly be said to will the utterance -of each tone, or the formation of each letter. Are these processes -mechanical and not volitional? By no means. We know that they were -laboriously learned by long tentative efforts, each of which was -accompanied by distinct consciousness. We also know that now when the -mechanism is so easy in its adjustment as to suggest automatism, there -needs but a slight alteration in the conditions to make us distinctly -conscious of the processes--the wrong word spoken, or one letter ill -formed, suffices to arrest the easy working of the mechanism. A similar -mechanism operates in thinking, which also lapses from the conscious -and voluntary to the unconscious and involuntary state. The logical -process of Judgment is as purely a reflex from one neural group to -another, as the physiological process of co-ordination. In ordinary -thinking we are as little conscious of the particular steps--our -interest being concentrated on the result--as we are of the particular -stages of an action. The adjustments of the mechanism of Reproduction -and Association are _set_ going by a motive, and _kept_ going by -psychological motors. And here--as in bodily actions--there is often -a conflict between motive and motors--between the foreseen result, -and the available means of reaching it--the motors usually prevailing -because they represent the active side of the mechanism. Thus when an -oculist wishes to examine a patient’s eye, he does not tell him to give -a particular direction to his eye, knowing that the _motive_ to do so -will not suffice; instead of this he simply moves his own hand in the -desired direction, certain that the eye will by reflex irresistibly -follow it. Nay, there are sometimes such anomalies of innervation -that the eye, instead of obeying the motive, moves in a contrary -direction. Meschede mentions a patient whose movements were mostly of -this anomalous kind: when he willed to move the eyes to the right, they -moved to the left; when he willed to move them up, they moved down. It -was thus also with his hands and feet. Yet he was distinctly conscious -that his intention had been frustrated, and that he acted “because he -could not help it.”[217] How insensibly a motive sinks into a motor, -that is to say, a voluntary into an involuntary act, may be recognized -in speech, writing, singing, walking, etc., and in the incessant -movements of the eye in fixing objects. Aubert has well remarked -that we only give definite movements to the eye when we wish to see -an object distinctly. Whenever the indistinct vision suffices--as in -walking through the streets occupied in conversation or thought--we -make no such movements; but no sooner does any object excite our -attention, than the effort to fix that object at once excites the -necessary reflex.[218] - -70. By the Will, then, we must understand the abstract generalized -expression of the impulses which determine actions, when those -impulses have an ideal origin; by Volition the still more generalized -expression of all impulses which determine actions. The one class is -that of _motives_ with ideal elements; the other that of _motors_ with -sensational or emotional elements. But both are mental states, both -are neural processes in a sentient organism; neither is mechanical, -except in so far as all actions are expressible in mechanical terms. -For convenience we class actions as reflex, automatic, involuntary, -unconscious, voluntary, and conscious. If we separate the reflex -from the voluntary, we need not therefore dissociate the former from -Sensibility; and the reason why we ought not to separate it is that we -know it to be sense-guided from first to last, although the sensations -may escape discrimination. The feeling of Effort, which was formerly -felt when an action was performed, may have become so minimized -that it is too faint for more than a momentary consciousness, too -evanescent for the memory to retain it; yet the feeling must always -be operant when its mechanism is in action. The ease with which the -mechanism works does not change the adjustment of its elements, nor -alter its character. The facile unobtrusive performance of a vital -function does not change it from a vital to a mechanical act. Mr. -Spencer seems to me to express himself ambiguously when he says: -“Just as any set of psychical changes originally displaying Memory, -Reason, and Feeling cease to be conscious, rational, and emotional -as fast as they by repetition grow closely organized, so do they at -the same time pass beyond the sphere of Volition. Memory, Reason, -Feeling, and Will disappear in proportion as psychical changes become -automatic”[219]--for while it is perfectly true that we only call those -psychical changes “automatic” which have lost the special qualities -called “conscious, rational, and emotional,” it is not less true that -they remain from first to last _psychical_ changes, and are thereby -distinguished from _physical_ changes. To suppose that they pass from -the psychical to the physical by frequent repetition would lead to the -monstrous conclusion that when a naturalist has by laborious study -become so familiarized with the specific marks of an animal or plant -that he can recognize at a glance a particular species, or recognize -from a single character the nature of the rest, the rapidity and -certainty of this judgment proves it to be a mechanical, not a mental -act. The intuition with which a mathematician sees the solution of a -problem would then be a mechanical process, while the slow and bungling -hesitation of the tyro in presence of the same problem would be a -mental process: the perfection of the organism would thus result in its -degradation to the level of a machine! - -The operations of the intellect may furnish us with an illustration. -Ideas are symbols of sensations. The idea of a horse is an abstraction -easily traceable to concrete sensations, yet as an abstraction is -so different a state of feeling that we only identify it with its -concretes by a careful study of its stages of evolution, namely, -sensation, image, reproduced images resembling yet differing from the -original sensation, a coalescence of their resemblances, and finally -the substitution of a verbal symbol for these images. With this symbol -the intellect operates, and sometimes operates so exclusively with it -that not the faintest trace of image or sensation is appreciable--the -word horse takes the place of the image in the sequence of sensorial -processes, just as the image takes the place of the sensation. It does -this as a neural equivalent. In the same way we substitute verbal -symbols for a bag of sovereigns when we pay a creditor with a check; -he pays the check away to another; and this monetary equivalent passes -from hand to hand without a single coin making its appearance. Does -the transaction cease to be commercial, monetary, in this substitution -of signs? No; nor does a process cease to be psychical when an image -is substituted for a sensation, and a verbal symbol for an image. This -every one will admit. Must we not go further, and extend the admission -to automatic actions which originally were voluntary, and have now lost -all trace of ideal prevision, and almost all traces of accompanying -consciousness? _The motor mechanism has its symbols also_; in this -sense, that whereas the action which at first needed complex sensorial -processes to set it going and keep it going, is now determined by a -single one of those processes taking the place of their resultant. When -a practised accountant runs his eye up a column of figures, he does -not pause to realize the values of those figures by decomposing the -symbols into their numerical units, he simply groups one symbol with -another according to their intuited relations, and the final result is -reached with a certainty not less, and a rapidity far greater, than if -it had been reached by step-by-step verification. It is thus with the -pianoforte-player. It is thus with all automatic performances, except -those dependent on the connate adjustments of the mechanism. - - - - -CHAPTER VI. - -THE PROBLEM STATED. - - -71. If the preceding attempt to disengage the question from the -ambiguities of its terms has been successful, we shall find little -difficulty in rationally interpreting all the facts adduced in favor -of Animal Automatism, without having recourse to a mechanical theory -of biological phenomena. The objections to that theory are that it -employs terms which have very misleading _connotations_ even when they -do not _denote_ phenomena of widely different orders; so that the moral -repugnance commonly felt at the attempt to treat the animal organism as -if it were a machine, is sustained by the intellectual repugnance at -the attempt to explain biological phenomena on principles derived from -phenomena of a simpler order. - -Remark, in passing, this piquant contradiction: the Automaton theory -of Descartes, when applied to the animals, generally excited ridicule -or repulsion; whereas the far more inconsistent and mechanical -theory of Reflex Action has been almost universally welcomed as a -great discovery, though it banishes the Sensibility which Descartes -preserved. And further, the philosophers who most loudly protested -against the idea that animals were machines, were the philosophers -who most insisted that these animals were made, not evolved--planned -by their maker, as a watch is planned by its maker, with a distinct -purpose and prevision in the disposition of every part; whereas the -philosophers who most emphatically reject this notion of organisms -being made, are often those who liken organisms to machines. - -72. The paradox propounded by Descartes loses much of its strangeness -when we understand his meaning. Its terms are infelicitous because of -their misleading connotations. When he says that all the actions of -animals which seem to be due to Consciousness are in fact produced on -the same principles as those of a machine, he means that animals have -not souls to direct their actions; but since, on being questioned, he -is ready to admit that animals have sensation, perception, emotion, and -memory, his denial of their souls practically comes to much the same as -the ordinary position that animals have not Thought nor Consciousness -of Self.[220] The admission of sensation is, however, quite enough to -mark the essential difference between an organism and a machine. - -73. It was really a great step taken by Descartes when he directed -attention to the fact that all animal actions were executed in -strict conformity with mechanical principles, because both before -his time, and since, we may observe a great disregard of the animal -mechanism, and a disposition to interpret the phenomena on metaphysical -principles. But the connotations of the term “machine” were such as to -lead the mind away from the special conditions of the vital mechanism, -and fix it exclusively on the general conditions of machinery. Hence -his opponents misunderstood him, and some of his followers made the -same oversight, and ended by eliminating sensation altogether. In -pursuance of this mechanical point of view, to the exclusion of the -biological, Thought and even Consciousness have been eliminated from -among the organic agencies, and are said to have no more influence in -determining even human actions than the whistle of the steam-engine has -in directing the locomotive. There are thus two _meta_physiological -theories. According to the one, Consciousness directs indeed the -actions of the organism, but is not itself an organic process--it sits -apart, like a musical performer playing on an instrument. According -to the other, it is not a directing agency, but an accessory product -of certain organic processes, which processes may go on quite as well -without any accompaniment and interference of Consciousness. - -74. Two observations arise here. First, we observe a want of due -recognition of the objective and subjective aspects, and their -respective criteria. Secondly, we observe mental facts of irresistible -certainty interpreted by material hypotheses of questionable value; -and not only so, but a higher validity is assigned to the material -hypotheses than to the mental facts they are invented to explain. That -we are conscious, and that our actions are determined by sensations, -emotions, and ideas, are facts which may or may not be explained by -reference to material conditions, but which no material explanation -can render more certain. That animals resemble us in this as in -other respects is an induction of the highest probability. It is -also a fact that many actions take place, as we say, unconsciously -and involuntarily; and that some take place now consciously, now -unconsciously. These facts also we endeavor to explain: and when -we find that some of the unconscious and involuntary actions take -place after the brain has been removed, this is interpreted on the -material hypothesis of the brain being the sole seat of sensation -and consciousness; and is urged in favor of the hypothesis that -consciousness cannot be an agent in the mechanism. Here the confusion -of objective and subjective aspects is patent. Consciousness as a -subjective fact cannot be a material or objective fact. But may it not -be another aspect of that which is objective? So long as we are dealing -with the objective aspect, we have nothing but material processes in a -material mechanism before us. A change within the organism is caused -by a neural stimulation, and the resulting action is a reflex on the -muscles. Here there is simply a transference of motion by a material -mechanism. There is in this no evidence of a subjective agency; -there could be none. But when we come to investigate the process, we -find that it differs from similar processes in anorganisms, by the -necessary co-operation of special conditions, and among these--the -vital conditions--there are those which in their subjective aspect we -express not in terms of Matter and Motion, but in terms of Feeling, -i. e. not in objective but in subjective terms. I see a stone move on -being struck; I also see a man shrink on being struck, and hear a dog -howl on being kicked. I do not infer that the stone feels as the man -and dog feel, because I know the stone and the dog to be differently -constituted, and infer a corresponding difference in their reactions. I -infer that the man and dog feel, because I know they are like myself, -and conclude that what I feel they feel, under like conditions. - -75. Descartes says that animals are sensitive automata. They _always_ -act as we _sometimes_ act, i. e. when we are not conscious of what we -do, as in singing, walking, playing the piano, etc. We are said to do -these things mechanically, automatically, and hence the conclusion that -these actions are those of a pure mechanism. But it would be truer to -say that we never act mechanically, we always act organically. “When -one who falls from a height throws his hands forwards to save his -head,” says Descartes, “it is in virtue of no ratiocination that he -performs this action” (that depends on the definition: in the Logic -of Feeling there is a process of ratiocination identical with that in -the Logic of Signs). “It does not depend upon his _mind_” (again a -question of definition), “but takes place merely because his senses -being affected by _present danger_” (senses, then, have a perception -of danger?) “some change arises in his brain which determines the -animal spirits to pass thence into the nerves in such a manner as is -required to produce this motion, in the same way as in a machine, and -without his mind being able to hinder it. Now since we observe this in -ourselves, why should we be so much astonished if the light reflected -from the body of a wolf into the eye of a sheep has the same force to -excite in it the motion of flight?” - -Here, both in the case of the man and the sheep, there is presupposed -the very mental experience which is denied. The young child will -not throw out its arm to protect itself; but after many experiences -of falling and stumbling, there is an organized perception of the -impending danger, and the means of averting it, and it is this which -determines the throwing out of the arms. If this is not a mental -fact--a process of judgment--then the logical conclusion by which a -financier on hearing a war rumor orders his broker to sell stock, is -not a mental fact. The light reflected from the body of a wolf would -not disturb the sheep unless its own, or its _inherited_ organized -experience were ready there to respond. But this organized experience, -you say, enters into the mechanism? Yes; but it cannot be made to -enter into the mechanism of an automaton, because however complex that -mechanism may be, and however capable of variety of action, it is -constructed solely for definite actions on calculated lines: all its -readjustments must have been foreseen, it is incapable of adjusting -itself to unforeseen circumstances. Hence every interruption in the -prearranged order either throws it out of gear, or brings it to a -standstill. It is regulated, not self-regulating. The organism, on the -contrary--conspicuously so in its more complex forms--is variable, -self-regulating, incalculable. It has _selective adaptation_ (p. -221) responding readily and efficiently to novel and unforeseen -circumstances; _acquiring_ new modes of combination and reaction. An -automaton that will learn by experience, and adapt itself to conditions -not calculated for in its construction, has yet to be made; till it -is made, we must deny that organisms are machines. Automatism in the -organism implies Memory and Perception. A sudden contact--a sudden -noise--a vague form seen in the twilight will excite the mechanism -according to its organized experiences. We start automatically, before -we automatically interpret the cause; we start first, and then ask, -What is that? But we do not always start at sounds or sights which have -no association with previous experiences. The child and the man both -see the falling glass, but the child does not automatically stretch out -a hand to save the glass. Having once learned the action of swimming or -billiard-playing, we automatically execute these; without consciously -remembering the rules, we unconsciously obey them; each feeling as it -rises is linked on to another, each muscle is combined with others in a -remembered synthesis. - -76. Kempelen’s chess-player surprised the public, but every instructed -physiologist present knew that in some way or other its movements were -directed by a human mind; simply because no machine could possibly have -responded to the unforeseen fluctuations of the human mind opposed to -it. Even the mind of a dog or a savage would be incompetent to pass -beyond the range of its previous experiences, incompetent to seize the -significance of an adversary’s moves on the chessboard. Now just as -we conclude that mental agency is essential to a game of chess, so we -conclude that Sensibility is essential to the fluctuating responses -of an organism under unforeseen circumstances. We can conceive an -automaton dog that would bark at the presence of a beggar; but not of -an automaton dog that would bark one day at the beggar and the next -day wag his tail, remembering the food and patting that beggar had -bestowed. Since all we know of machines forbids the idea of their -being capable of adjusting their actions to new circumstances, or of -evoking through experience new powers of combination, we conclude that -wherever this capability of adaptation is present there is an agency in -operation which does not belong to the class of mechanical agencies. -Goltz has shown that a frog deprived of its brain manifests so much of -vision as enables it to avoid obstacles--leaping to the right or to -the left of a book placed in its path. This Professor Huxley regards -as purely mechanical:--“Although the frog appears to have no sensation -of light, visible objects act upon the motor mechanism of its body.” -Should we not rather conclude that if the frog had no sensation, -no such effect would follow? because although a machine _might_ be -constructed to respond to variations of light and shadows, none could -be constructed (without Sensibility) to respond to the fluctuating -conditions as an organism responds.[221] Were the reflex actions -of the organism purely mechanical--i. e. involving none of those -fluctuating adjustments which characterize Sensibility--the effect -would be uniform, and proportional to the impact; but it is variable, -and proportional to the static condition of the nervous centres at the -moment. Exaggerate this--by strychnine, for instance--and the slightest -touch on the skin will produce general convulsions. Lower it--by an -anæsthetic--and no reflex at all will follow a stimulus. In anæsthesia -of the mucous membrane, no reflex of the eyelid, no secretion of -tears, follows on the irritation of the membrane; no sneezing follows -irritation of the inside of the nose; no vomiting follows irritation of -the fauces. - -77. The question has long ceased to be whether the organism is a -mechanism. To the physiologist it is this before all things. To the -psychologist also it has of late years more and more assumed this -character; because even when he postulates the existence of a spiritual -entity _in_ the organism but not _of_ it, he still recognizes the -necessity of a mechanism for the execution of the acts determined by -the spirit; and when the psychologist adopts the theory of spiritual -phenomena as the subjective aspect of what objectively are material -phenomena, he of course regards the bodily mechanism and the mental -mechanism as one and the same real. - -This settled, the problem of Automatism may be thus stated: Granting -the animal organism to be a material mechanism, and all its actions -due to the operation of that mechanism, are we to conclude that it is -an automaton essentially resembling the automata we construct, the -movements of which may, or may not, be _accompanied_ by Feeling, but -are in no case _determined_ by Feeling? - -Descartes says that animals are sensitive automata. Professor Huxley -says that both animals and men are sensitive and conscious automata; -so that misleading as the language of Descartes and Professor Huxley -often is in what its terms connote, we do them great injustice if -we suppose them to have overlooked the points of difference between -organisms and machines which have been set forth with so much emphasis -in a preceding chapter; and the reader is requested to understand that -without pretending to say how much the inevitable connotation of their -language expresses their opinions, and how much it may have only led -to their being misunderstood, my criticisms are directed against this -connotation and this interpretation. - - - - -CHAPTER VII. - -IS FEELING AN AGENT? - - -78. Descartes having attributed all animal actions to a sensitive -mechanism, and indeed all human actions to a similar mechanism, -endeavored to reconcile this hypothesis with the irresistible facts -of Consciousness--which assured us that _our_ actions, at least, were -determined by Feeling. To this end he assumed that man had a spiritual -principle over and above the sentient principle. The operation of this -principle was, however, limited to Thought; the actions themselves were -all performed by the automatic mechanism; so that, in strict logic, the -conclusion from his premises was the same for man as for animals. - -This conclusion Professor Huxley announced in his Address before the -British Association, 1874[222]--to the great scandal of the general -public, which did not understand him aright; and to the scandal also of -a physiological public, which, strangely enough, failed to see that it -was the legitimate expression of one of their favorite theories--the -celebrated Reflex Theory. Now although it is quite open to any one to -reject the premises which lead to such a conclusion, if he sees greater -evidence against the conclusion than for the premises, it is surely -irrational to accept the premises as those of scientific induction, -and yet reject the conclusion because it endangers the stability of -other opinions? For my own part, I do not accept the premises, and my -polemic will have reference to them. - -79. Professor Huxley adopts certain Theses which represent the views -generally adopted by physiologists; to which he adds a Thesis which is -adopted by few, and which he only puts forward hypothetically. Against -these positions I place Antitheses, less generally adopted, but which -in my belief approximate more nearly to the inductions of experience. - - _Theses._ _Antitheses._ - - I. There can be no sensation I. There is sensation without - without consciousness. consciousness, if consciousness - means a special mode of Sentience. - - II. There can be no II. The co-operation of the brain - consciousness without the is only necessary for a special - co-operation of the brain. mode of Sentience; other modes are - active when the brain is inactive. - - III. Sensation and Consciousness III. Unless the molecular changes - are in some inexplicable way be limited to the brain as the - caused by molecular changes in _occasional_ cause, there is - the brain, following upon these no _following_ of sensation or - as one event follows another, motion, no causal link between the - the causal link between motion two; but the neural process _is_ - and sensation being a mystery. the sensation, viewed objectively, - the sensation is the neural - process, viewed subjectively. In - this antithesis, Neural Process - is not limited to the brain, but - comprises the whole sensitive - organism as the _efficient_ cause. - - IV. All actions which take place IV. All actions are the actions of - unconsciously are reflex, and a reflex mechanism, and all are - reflex actions are the operation sentient, even when unconscious; - of an insentient mechanism; they are therefore never purely - they are therefore as purely mechanical, but always organical. - mechanical as those of automata. - - V. The animal body is a reflex V. Sentience being necessary to - mechanism; even when the reflex action, it is necessarily - brain co-operates with the an agent. - other centres, and produces - consciousness, this product is - not an agent in determining - action, it is a collateral - result of the operation. - -80. The first four Theses are those current in our textbooks, so -that it is only the fifth which will have the air of a paradox. Nor, -as a paradox, is it without advocates. Schiff long ago suggested it -hypothetically. Hermann mentions it as entertained by physiologists, -whom he does not name.[223] Laycock, and, if I remember rightly, Dr. -Drysdale, have insisted on it; and Mr. Spalding has proclaimed it with -iterated emphasis. Of the Antitheses nothing need be said here, since -the whole of this volume is meant to furnish their evidence. - -I have already stated that my polemic is against the views that -Professor Huxley is _supposed_ to hold by those whom his expressions -mislead, rather than against the views I imagine him really to hold. -I have little doubt that he would disavow much that I am forced to -combat, although his language is naturally interpreted in that sense. -But I do not know in how far he would agree with me, and in the -following remarks I shall confine myself to what seems to be the plain -interpretation of his words, since _that_ is the interpretation which -has been generally adopted, and which I most earnestly desire to refute. - -81. To begin with this passage. After stating the views of Descartes, -he says: “As actions of a certain degree of complexity are brought -about by mere mechanism, why may not actions of still greater -complexity be the result of a more refined mechanism? What proof is -there that brutes are other than a superior race of marionnettes, which -eat without pleasure, cry without pain, desire nothing, know nothing, -and only simulate intelligence as a bee simulates a mathematician?” -What proof? Why, in the first place, the proof which is implied in -the “more refined mechanism” required for the greater complexity of -actions. In the next place, the proof that the organism of the brute is -very different from the mechanism of a marionnette, and is so much more -like the organism of man, that since we know man to eat with pleasure -and cry with pain, there is a strong presumption that the brute eats -and cries with somewhat similar feelings. - -82. Having stated the hypothesis, Professor Huxley says he is not -disposed to accept it, though he thinks it cannot be refuted. His chief -reason for not accepting it is that the law of continuity forbids -the supposition of any complex phenomenon suddenly appearing; the -community between animals and men is too close for us to admit that -Consciousness could appear in man without having its beginnings in -animals. Finding that animals have brains, he justly concludes that -they also must have brain functions; and they also therefore must -be credited with Consciousness. This argument seems to me to have -irresistible cogency; and to be destructive not only of the automaton -hypothesis, but equally of the hypothesis on which the Reflex Theory -is founded. If the law of continuity forbids the sudden appearance of -Consciousness, the law of similarity of property with similarity of -structure forbids the supposition that central nerve-tissue in one -part of the system can suddenly assume a totally different property -in another part. If the brain of an animal, a bird, a reptile, or a -fish--and _a fortiori_ if the œsophageal ganglia of an insect or a -mollusc--may be credited with Sensibility, because of the fundamental -similarity of these structures with the structures of the human brain, -then surely the spinal cord must be credited with Sensibility; for the -tissue of the spinal cord is more like that of the brain, than the -brain of a reptile is like the brain of a man. The sudden disappearance -of all Sensibility, on the removal of one portion of the central -nervous system, would be a violation of the law of continuity. And if -it be said that Consciousness is not the same as Sensibility, but is a -specially evolved function of a specially developed organ, the answer -will be that this is only a difference of mode, and that the existence -of Sensibility is that which renders the automaton and reflex theories -untenable. - -83. Professor Huxley would probably admit this; for however his -language may at times seem to point to another conclusion, and is so -far ambiguous, he has expressed the view here maintained with tolerable -distinctness in the following passage, to which particular attention is -called:-- - -“But though we may see reason to disagree with Descartes’ hypothesis, -that brutes are unconscious machines, it does not follow that he -was wrong in regarding them as automata. _They may be more or less -conscious sensitive automata_; and the view that they are such -conscious machines is that which is implicitly or explicitly adopted -by most persons. When we speak of the actions of the lower animals -being guided by instinct and not by reason, what we really mean is that -though they feel as we do, yet their actions are the results of their -physical organization. We believe, in short, that they are machines, -one part of which (the nervous system) not only sets the rest in motion -and co-ordinates its movements in relation with changes in surrounding -bodies, but is provided with a special apparatus the function of which -is the calling into existence of those states of consciousness which -are termed sensations, emotions, and ideas.” - -84. To say that they are “conscious automata” seems granting all that -I demand; but there are two objectionable positions which the phrase -conceals: first, that Consciousness is not a coefficient; and secondly, -that Reflex Action is purely mechanical. - -Professor Huxley nowhere, I think, establishes the distinction -between Consciousness as a term for a special mode of Feeling, and -Consciousness as the all-embracing term for sentient phenomena. His -language always implies that an action performed unconsciously is -performed mechanically; which may be acceptable if by unconsciously be -meant insentiently. I hold that whether consciously or unconsciously -performed, the action is equally vital and sentient. In the case he has -cited of a soldier now living who is subject to periodic alternations -of normal and abnormal states, in the latter states all the actions -being said to be “unconscious,” we have only to read the account to -recognize ample evidence of Sentience. Here is a descriptive passage:-- - -85. “His [the soldier’s in the abnormal state] movements remain free, -and his expression calm, except for a contraction of the brow, an -incessant movement of the eyeballs, and a chewing motion of the jaws. -The eyes are wide open, and their pupils dilated. If the man happens -to be in a place to which he is accustomed he walks about as usual; -but if he is in a new place, or if obstacles are intentionally placed -in his way, he stumbles against them, _stops, and then feeling over -the objects with his hands, passes on one side of them_. He offers -no resistance to any change of direction which may be impressed upon -him, or to the forcible acceleration or retardation of his movements. -He eats, drinks, smokes, walks about, dresses and undresses himself, -rises and goes to bed at the accustomed hours. Nevertheless pins may be -run into his body, or strong electric shocks sent through it, without -causing the least indication of pain; no odorous substance, pleasant or -unpleasant, makes the least impression; he eats and drinks with avidity -whatever is offered, and takes asafœtida or vinegar of quinine as -readily as water; no noise affects him; and light influences him only -under certain conditions.” - -There is no one of these phenomena that is unfamiliar to students of -mental disease. The case is chiefly remarkable from the periodicity of -the recurrence of the abnormal state. I have collected other cases of -the kind, and may hereafter find a fitting occasion to quote them.[224] -The anæsthesia and “unconsciousness” noted, no more prove the actions -performed by this soldier to have been purely mechanical, i. e. -undetermined by sensation, than anæsthesia and unconsciousness prove -somnambulists and madmen to be machines. In the pathological state -called “ecstasy” there is a considerable diminution of sensibility to -external stimuli; with a concentration on certain feelings, images, -trains of thought, exhibiting itself in expressions of emotion. -“Les malades,” says a master, “paraissent entièrement absorbés par -leurs mouvements intérieurs, ils refusent généralement de manger, et -spécialement la volonté de l’âme semble complètement enchainée.”[225] - -86. Observe that while this soldier exhibits such insensibility to -certain stimuli, he unequivocally exhibits sensibility to other -stimuli. All his acts show sense-guidance. Sight and Touch obviously -regulate his movements. And when he feels objects placed in his way, -and then passes beside them, wherein does this differ from the normal -procedure of sensitive organisms? wherein does it resemble automata? -Dr. Mesmet--from whose narrative the case is cited--remarks that the -sense of Touch seems to persist “and indeed to be more acute and -delicate than in the normal state”; upon which Professor Huxley has -this comment:--“Here a difficulty arises. It is clear from the facts -detailed that the nervous apparatus by which in the normal state -sensations of touch are excited is that by which external influences -determine the movements of the body in the abnormal state. But does the -state of consciousness, which we term a tactile sensation, accompany -the operation of this nervous apparatus in the abnormal state? or -is consciousness utterly absent, the man being reduced to a pure -mechanism? It is impossible to obtain direct evidence in favor of the -one conclusion or the other; all that can be said is that the case of -the frog shows that the man may be devoid of any kind of consciousness.” - -87. It is here we are made vividly aware of the absolute need there is -to disengage the terms employed from their common ambiguities. All the -evidence of a tactile sensation which can possibly be furnished, on the -objective side, is furnished by the actions of this soldier; to doubt -it would be to throw a doubt on the sensibility of any animal unable -to _tell_ us what it felt; nay, even a man if he were dumb, or spoke -a language we could not understand, could give us no other proof. We -conclude that the soldier had tactile sensations, because we see him -guided by them as we ourselves are guided by tactile sensations; we -know that he is an organism, not a machine, and therefore reject the -inference that he has become reduced to a “pure mechanism” because -it is inferred that his consciousness is absent. And on what is this -inference grounded? 1°, The belief that the brain is the sole organ -of consciousness (Sentience)--a belief flatly disproved by the facts, -which show Sentience when the brain has been removed; and 2°, the -belief that the decapitated frog, because it avoids obstacles and -redirects its leaps to avoid them, does so without Sentience. According -to the definition we adopt, we may either say that the decapitated -frog, and the soldier in his abnormal state, act without consciousness, -or with it. But what does not seem permissible is to deny that their -actions exhibit the clearest evidence of _sense-guidance_, and the -kind of volition which this sense-guidance implies; and this is quite -enough to separate them from actions of automata. When a man ducks his -head to avoid a stone which he sees falling towards him, he assuredly -has a sensation, i. e. there is a grouping of neural elements, which -subjectively is a sensation, and this originates a grouping of other -neural elements, the outcome of which is a muscular movement, which -subjectively is a motor sensation: _this_ grouping would not have -been originated unless the particular grouping had preceded it; nor -would the simple retinal stimulus have excited this sensation unless -the nerve-centres had been attuned to such response by many previous -experiences: the ignorant child would not duck its head on seeing -the stone approach. In our familiar use of the word Consciousness it -would be correct to say that the man ducks his head “unconsciously”; -and yet expressing the fact in psychological language, we also say: -He ducks his head because _remembering_ the pain of former similar -experiences, he _knows_ that if the stone strikes him he will again -be hurt as before, therefore he _wills_ to avoid it; expressing it -in physiological language we may say: The man acts thus because he -is so organized that a particular neural process is the stimulus of -a particular central discharge; and he became thus organized through -a long series of anterior adjustments responding to stimuli, each -adjustment being the activity of the vital organism. - -88. There can be no doubt that the soldier had perceptions, and that -these perceptions guided his movements; whether these shall be called -“states of consciousness” or not, is a question of terms. Now since -we know that _certain actions are uniformly consequent on certain -perceptions_, we are justified in inferring that _whenever the -actions are performed, the perceptions preceded them_: this inference -may be erroneous, but in the absence of positive evidence to the -contrary it is that which claims our first assent. Is it evidence to -the contrary that the perception may have stimulated the action, yet -been unaccompanied by the special mode named consciousness? Not in -the least. We learn to read with conscious effort; each letter has -to be apprehended separately, its form distinguished from all other -forms, its value as a sign definitely fixed, yet how very rarely are -we “conscious” of the letters when we read a book? Each letter is -perceived; and yet this process passes so rapidly and smoothly, that -unless there be some defect in a letter, or the word be misspelled, -we are not “conscious” of the perceptions. Are we therefore reading -automata?[226] - -We are said to walk unconsciously at times; and the continuance of the -movement is said to be due to reflex action. But it is demonstrable -that the cutaneous sensibility of the soles of the feet is a primary -condition. If the skin be insensible, the walking becomes a stumble. In -learning to walk, or dance, the child fixes his eyes on his feet, as he -fixes them on his fingers in learning to play the piano. After a while -these registered sensations _connected_ with the muscular sense suffice -to guide his feet or his fingers; but not if feet or fingers lose their -sensibility. - -89. With these explanations let us follow the further details of this -soldier’s abnormal actions:-- - -“The man is insensible to sensory impressions made through the ear, -the nose, the tongue, and, to a great extent, the eye; nor is he -susceptible to pain from causes operating during his abnormal state. -Nevertheless it is possible _so to act upon his tactile apparatus as -to give rise to those molecular changes in his sensorium which are -ordinarily the causes of associated trains of ideas_. I give a striking -example of this process in Dr. Mesmet’s words: ‘Il se promenait dans -le jardin, on lui remet sa canne qu’il avait laissé tomber. Il la -palpe, promène à plusieurs reprises la main sur la poignée coudée de -sa canne--devient attentif--semble prêter l’oreille--et tout à coup -appelle, “Henri! les voilà!” Et alors portant la main derrière son -dos comme pour prendre une cartouche, il fait le mouvement de charger -son arme, se couche dans l’herbe à plat ventre dans la position d’un -tirailleur, et suit avec l’arme épaulée tous les mouvements de l’ennemi -qu’il croit voir à courte distance.’ In a subsequent abnormal period -Dr. Mesmet caused the patient to repeat this scene by placing him in -the same conditions. Now in this case the question arises whether the -series of actions constituting this singular pantomime was accompanied -by the ordinary states of consciousness, the appropriate trains of -ideas, or not? Did the man dream that he was skirmishing? or was he in -the condition of one of Vaucanson’s automata--_a mechanism worked by -molecular changes in the nervous system_? The analogy of the frog shows -that the latter assumption is perfectly justifiable.” - -90. Before criticising this conclusion let me adduce other -illustrations of this dreamlike activity. “A gentleman whom I attended -in a state of perfect apoplexy,” says Abercrombie, “was frequently -observed to adjust his nightcap with the utmost care when it got into -an uncomfortable state: first pulling it down over his eyes, and -then turning up the front of it in the most exact manner.” According -to the current teaching, these actions, which seem like evidence -of sensation, are nothing of the kind, because--the patient was -“unconscious”; that is to say, because he did not exhibit one complex -kind of Sensibility, it is denied that he exhibited another kind! -he did not feel discomfort, nor feel the movements by which it was -rectified--because he could not speak, discuss impersonal questions, -nor attend to what was said to him! Abercrombie cites other cases: “A -gentleman who was lying in a _state of perfect insensibility_ from -disease of the brain” (note the phrase, which really only expresses -the fact that external stimuli did not create their normal reactions) -“was frequently observed even the day before his death to take down -a repeating watch from a little bag at the head of his bed, put it -close to his ear and make it strike the hour, and then replace it in -the bag with the greatest precision. Another whom I saw in a state of -profound apoplexy, from which he recovered, had a perfect recollection -of what took place during the attack, and mentioned many things which -had been said in his hearing when he was supposed to be in a state of -perfect unconsciousness.” Dr. Wigan also tells of a lady whom he knew, -and who was actually put in a coffin, under the belief that she was -dead when in a trance. Her sense of hearing was then preternaturally -acute. In her second-floor bedroom she heard what the servants said -in her kitchen. When her brother came to see her and he declared she -should not be buried until putrefaction set in, she felt intense -gratitude and a gush of tenderness, but was unable to move even an -eyelid as a manifestation of her feeling. Suddenly all her faculties -returned. Dr. Wigan adds that he visited the Countess Escalante, one -of the Spanish refugees, who remained in a similar state for a short -period, during which she saw her husband and children, and was quite -conscious of all they did and said--but did not recognize them as her -own. She was absolutely without the power of moving a finger or of -opening her mouth. Dr. Neil Arnott told me of a similar case in his -practice. In these last cases we learn that consciousness--in its -ordinary acceptation--was present, though bystanders could see no trace -of it. And very often in cases where Consciousness, or at any rate -Sensibility, is clearly manifested, its presence is denied, because the -patient on recovering his normal condition is quite unable to remember -anything that he felt and did. Under anæsthetics patients manifest -sensation, but on awaking they declare that they felt nothing--of -what value is their declaration? M. Despine tells us of a patient who -under chloroform struggled, swore, and cried out, “_Mon Dieu! que -je souffre!_” yet when the operation was over, and he emerged from -the effects of the chloroform, he remembered nothing of what he had -felt.[227] - -91. Returning now to Dr. Mesmet’s soldier, and to the conclusion that -his dreamlike acts were no more than the actions of one of Vaucanson’s -automata, surely we are justified in concluding, first, that these -actions were not of the same kind as those of an automaton, since they -were those of a living organism; secondly, that they present all the -evidence positive and inferential which Sensibility can present in -the actions we observe in another, and do not feel in ourselves; and -thirdly, if with physiologists we agree that the mechanism of these -actions is “worked by molecular changes in the nervous system,” there -is some difficulty in understanding how Consciousness, which is said -to be caused by such changes, could have been absent--how the _cause -could operate yet no effect be produced_. - -92. What automata can be made to perform is surprising enough, but -they can _never_ be made to display the fluctuations of sense-guided -actions, such as we see in the report of Dr. Mesmet’s soldier:-- - -“The ex-sergeant has a good voice, and had at one time been employed -as a singer at a café. In one of his abnormal states he was observed -to begin humming a tune. He then went to his room, dressed himself -carefully, and took up some parts of a periodical novel which lay -on the bed, as _if he were trying to find something_. Dr. Mesmet, -suspecting that he was seeking his music, made up one of these into a -roll and put it into his hand. _He appeared_ satisfied, took up his -cane, and went down stairs to the door. Here Dr. Mesmet turned him -round, and he walked quite contentedly in the opposite direction. The -_light of the sun_ shining through a window happened to fall upon -him, and _seemed to suggest the footlights of the stage_ on which he -was accustomed to make his appearance. He stopped, opened his roll of -imaginary music, put himself in the attitude of a singer, and sang with -perfect execution three songs one after the other. After which he wiped -his face with his handkerchief and drank without a grimace a tumbler of -strong vinegar-and-water.” - -93. Epileptic patients have frequently been observed going through -similar dreamlike actions in which only those external stimuli which -have a relation to the dream seem to take effect.[228] We interpret -these as phenomena of _disordered_ mental action, the burden of proof -lies on him who says they are phenomena of pure mechanism. A mail-coach -does not suddenly cease to be a mail-coach and become a wheelbarrow -because the coachman is drunk, or has fallen from the box. The horses, -no longer guided by the reins, may dash off the highroad into gardens -or ditches; but it is their muscular exertions which still move the -coach. - -Can any one conceive an automaton acting as the sergeant is described -to be in the following passage?-- - -“Sitting at a table he took up a pen, felt for paper and ink, and began -to write a letter to his general, in which he _recommended himself for -a medal_ on account of his good conduct and courage. It occurred to -Dr. Mesmet to ascertain experimentally how far vision was concerned in -this act of writing. He therefore interposed a screen between the man’s -eyes and his hands; under these circumstances he _went on writing for -a short time, but the words became illegible, and he finally stopped_. -On the withdrawal of the screen, he _began to write again where he had -left off_. The substitution of water for ink in the inkstand had a -similar result. He stopped, _looked at his pen, wiped it on his coat_, -dipped it in the water, and began again, with the same effect. On one -occasion he began to write upon the topmost of ten superposed sheets -of paper. After he had written a line or two, this sheet was suddenly -drawn away. _There was a slight expression of surprise_, but he -continued his letter on the second sheet exactly as if it had been the -first. This operation was repeated five times, so that the fifth sheet -contained nothing but the writer’s signature at the bottom of the page. -Nevertheless, when the signature was finished, his eyes turned to the -top of the blank sheet, and he went through the form of reading over -what he had written, a movement of the lips accompanying each word; -moreover, with his pen _he put in such corrections as were needed_.” - -94. Dr. Mesmet concludes that “his patient sees some things and not -others; that the sense of sight is accessible to all things which -are brought into relation with him by the sense of touch, and, on the -contrary, is insensible to things which lie outside this relation.” -In other words, the sensitive mechanism acts, but acts abnormally. -This is precisely what is observed in somnambulists. Yet Professor -Huxley, who makes the comparison, appears to regard both states as -those in which the organism is reduced to a mere mechanism, because -on recovering their normal state the patients are unconscious of what -has passed; and because the frog, without its brain, also manifests -analogous phenomena. Neither premise warrants the conclusion. I -have already touched on the unconsciousness of past actions; let me -add the case of Faraday, who was assuredly not an automaton when he -prepared and delivered a course of lectures which were nevertheless so -entirely obliterated from his memory that the next year he prepared and -delivered the same course once more, without a suspicion that it was -not a new one. As to the frog, I must leave that case till I come to -examine the evidence on which the hypothesis of the purely mechanical -nature of spinal action rests. - -95. The point never to be left out of sight is that actions which are -known to be preceded and accompanied by sensations do not lose their -special character of Sentience, as actions of a sentient mechanism, -because they are not also preceded and accompanied by that peculiar -state which is specially called Consciousness, i. e. attention to the -passing changes (comp. p. 403). When we see a man playing the piano, -and at the same time talking of something far removed from the music, -we say his fingers move unconsciously; but we do not conclude that -he is a musical machine--muscular sensations and musical sensations -regulate every movement of his fingers; and if he strikes a false -note, or if one of the notes jangles, he is instantly conscious of -the fact. Either we must admit that his brain is an essential part -of the mechanism by which the piano was played, and its function an -essential agent in the playing; or else we must admit that the brain -and its function were not essential, and therefore the playing would -continue if the brain were removed. In the latter case, we should have -a musical automaton. That a particular group of sensations, such as -musical tones, will set going a particular group of muscular movements, -without the intervention of any _conscious_ effort, is not more to be -interpreted on purely mechanical principles, than that a particular -phrase will cause a story-teller to repeat a familiar anecdote, or an -old soldier “to fight his battles o’er again.” - -96. Let us now pass to another consideration, namely, whether -Consciousness--however interpreted--is legitimately conceived as a -factor in the so-called conscious and voluntary actions; or is merely a -_collateral result_ of certain organic activities? To answer this, we -must first remember that Consciousness is a purely subjective process; -although we may believe it to be objectively a neural process, we are -nevertheless passing out of the region of Physiology when we speak of -Feeling determining Action. Motion may determine Motion; but Feeling -can only determine Feeling. Yet we do so speak, and are justified. For -thereby we implicitly declare, what Psychology explicitly teaches, -namely, that these two widely different aspects, objective and -subjective, are but the two faces of one and the same reality. It -is thus indifferent whether we say a sensation is a neural process, -or a mental process: a molecular change in the nervous system, or a -change in Feeling. It is either, and it is both, as I have elsewhere -explained.[229] There it was argued that the current hypothesis of a -neural process _causing_ the mental process--molecular movement being -in some mysterious way _transformed_ into sensation--is not only -inconceivable, but altogether unnecessary; whereas the hypothesis -that the two aspects of the one phenomenon are simply two different -expressions, now in terms of Matter and Motion, and now in terms of -Consciousness, is in harmony with all the inductive evidence. - -97. “It may be assumed,” says Professor Huxley, “that molecular -changes in the brain are the causes of all the states of consciousness -of brutes. Is there any evidence that these states of consciousness -may conversely cause those molecular changes which give rise to -muscular motion? I see no such evidence. The frog walks, hops, swims, -and goes through his gymnastic performances, quite as well without -consciousness, and consequently without volition, as with it; and if a -frog in his natural state possesses anything corresponding with what -we call volition, there is no reason to think that _it is anything but -a concomitant of the molecular changes in the brain_, which _form part -of the series involved in the production of motion_. The consciousness -of brutes would appear to be related to the mechanism of their body -simply as a collateral product of its working, and to be _as completely -without any power of modifying that working as the steam-whistle which -accompanies the work of a locomotive engine is without influence -upon its machinery_. Their volition, if they have any, is an emotion -_indicative_ of physical changes, not a _cause_ of such changes.” -Particular attention is called to the passages in italics. In the first -is expressed a view which seems not unlike the one I am advocating, but -which is contradicted by the second. Let us consider what is implied. - -98. When Consciousness is regarded solely under its subjective aspect -there is obviously no place for it among material agencies, regarded -as objective. So long as we have the material mechanism in view we -have nothing but material changes. This applies to the frog, with -or without its brain; to man, supposed to be moved by volition, or -supposed to move automatically. The introduction of Consciousness is -not the introduction of another agent in the series, but of a new -aspect; the neural process drops out of sight, the mental process -replaces it. The question whether we have any ground for inferring -that in the series there is included the particular neural state which -subjectively is a state of Consciousness, must be answered according -to the evidence. Well, the evidence shows that the actions do involve -the co-operation; and this Professor Huxley expresses when he says that -the molecular changes in the brain form part of the series involved in -the production of motion. Whether we regard the process objectively -as a series of molecular changes, or subjectively as a succession of -sentient changes, the sum of which is on the one side a motor impulse, -on the other a state of consciousness, we must declare Consciousness -to be an agent, _in the same sense that we declare one change in the -organism to be an agent in some other change_. The facts are the same, -whether we express them in physiological or in psychological terms. The -physiologist, having only the material aspect of the organism in view, -says, “A cerebral process initiates a motor process”; the psychologist -says, “A sensation determines an action.” Unless the two processes have -been linked together by an organic disposition, native or acquired, -there will be no such motor process following the cerebral process. -A dog standing outside the gate is unable to ring the bell, though -having seen another dog ring it, he may wish to do so; but the cerebral -process (his wish) is not linked on to the needful motor process--he -has not learned to realize the wish; whereas the other dog, having by -trial hit upon the right mode of directing his muscles, has registered -this experience, and can ring the bell. The organized disposition -which enables the dog to do this may truly enough be called a -modification of the mechanism; but what we have here to note is that a -sensation originally determined the movement, and always determines it. - -99. It is the unfortunate ambiguity of the word Consciousness, and -the questionable hypothesis of the brain being the sole seat of -Sensibility, which darken this investigation. Because animals, after -the brain has been removed, are seen to perform certain actions -as deftly as before, they are said to perform these without the -intervention of Consciousness; when all that is proved by the facts is -that these actions are performed without the intervention of the brain. -In support of this explanation, examples are cited of unconscious -actions performed by human beings. But if we assign Sensibility not to -one part of the nervous system exclusively, but to the whole, we can -readily understand how the loss of a part will be manifested by very -marked changes in the reactions of the whole, and yet not altogether -prevent the reactions of the parts remaining intact. An animal must -respond somewhat differently with and without a brain. One marked -difference is the spontaneity of the actions when the brain is intact, -and the loss of much spontaneity when the brain is injured or removed. -Cerebral processes prompt and regulate actions, as the pressure of the -driver on the reins prompts and regulates the movements of the horses; -but the carriage is moved by the horses and not by the driver; and the -action is executed by the motor mechanism, whether the incitation arise -in a cerebral process or a peripheral stimulation. - -100. If we admit that Consciousness is itself an organic process, -accompanying the molecular changes as a convex surface accompanies -a concave, we must also admit that its fluctuations are adjustments -and readjustments of the organic mechanism, and that the actions are -the effects of these--their resultants. The loss of the brain must -obviously cause a great disturbance in these adjustments. We may call -that a loss of Consciousness, if we choose to limit the term to one -_mode_ of sentient reaction. But this loss of a mode does not change -those reactions which persist so as to convert them into purely -mechanical reactions. A troop of soldiers may have lost its directing -officer, but will fight with the old weapons and the old intelligence, -though not with the same convergence of individual efforts. A frog or a -pigeon no more acts as _well_ without a brain as with a brain, than the -troop of soldiers fights as well without an officer. - -101. Having thus claimed a place for Consciousness in the series of -organic processes, let us now see whether it has a place among the -active agencies. According to Professor Huxley it is not itself an -agent, but only the “collateral product of the working of the machine.” -It accompanies actions, it does not direct them. It is an index, not a -cause. - -Surely it seems more accurate to say that it accompanies _and_ directs -the working? It accompanies the working in two senses: first, as the -subjective aspect of the objective process; secondly, as the change -which produces a subsequent change, that is to say, the movements -initiated by a feeling are themselves also _felt as they pass_; and -this feeling enters into the general stream of simultaneous excitations -out of which new movements and feelings arise; or to express it -physiologically, the sensory impressions determine muscular movements, -which in turn react on the nerve-centres, and these reactions -blend with the general excitation of reflected and re-reflected -processes.[230] Since every change in Consciousness is a change in -the sentient organism, which objectively is a change in the nervous -centres, the working of the mechanism being itself a dependent series -of such changes, each movement must have a reflected influence on the -general state. This reflected influence may be viewed as a collateral -product of the working; but there is no real analogy between it and -the whistle of the steam-engine, because this reflected influence -demonstrably _does_ intervene in the _subsequent_ movements. The -feeling which accompanies or follows a particular movement cannot -indeed modify _that_ movement, since that is already set going, or -has passed; here there is some analogy to the steam-whistle; but the -analogy fails in the subsequent history: no movements whatever of -the steam-engine are modified by the whistle which accompanies the -working of that engine; yet how the reflected influence modifies the -working of the organism! If the hand be passing over a surface, there -is, accompanying this movement, a succession of muscular and tactile -feelings which may be said to be collateral products. But the feeling -which _accompanies_ one muscular contraction _is itself the stimulus_ -of the next contraction; if anywhere during the passage the hand -comes upon a spot on the surface which is wet or rough, the change in -feeling thus produced, although a collateral product of the movement, -instantly changes the direction of the hand, suspends or alters the -course--that is to say, the _collateral product of one movement becomes -a directing factor in the succeeding movement_. Now this is precisely -what no automaton can effect, unless for changes that are prearranged. -A steam-engine drives its locomotive over the rails, be they smooth -or rough, entire or broken; it whistles as it goes, but no whistling -directs and redirects its path. - -102. Volition is said to be an “emotion indicative of physical changes, -not a cause of such changes.” Here it is necessary to understand in -what sense the term cause is employed. I should prefer stating the -proposition thus: a volition is a state of the sentient organism, -indicative of physical changes which have taken place, and of changes -which will take place. Because it is the _expression_ of the first -group of changes, it cannot be their _origin_; but it can be, and is -the origin of the second group, which it initiates. The indignation -excited by an insult or a blow is not the origin of the emotion or -the pain, but it is the origin of the actions which are prompted by -this sentient state. In fact no sooner do we admit that the organism -is a sentient mechanism, than the conclusion is irresistible that -Sensibility is a factor in the working of that mechanism. - -103. “Much ingenious argument,” says Professor Huxley, “has at various -times been bestowed upon the question: How is it possible to imagine -that volition which is a state of consciousness, and as such has not -the slightest community of nature with matter and motion, can act upon -the moving matter of which the body is composed, as it is assumed to do -in voluntary acts? But if, as is here suggested, the voluntary acts of -brutes--or in other words, the acts which they desire to perform--are -as purely mechanical as the rest of their actions, and are simply -accompanied by the state of consciousness called volition, the inquiry, -so far as they are concerned, becomes superfluous. Their volitions -do not enter into the chain of causation of their actions at all.... -As consciousness is brought into existence only as the consequence -of molecular motion in the brain, it follows that it is an indirect -product of material changes. The soul stands related to the body as the -bell of a clock to the works, and consciousness answers to the sound -which the bell gives out when it is struck.” This has been answered in -the foregoing pages; nor do I think the reader who has recognized the -ambiguity of the term Consciousness, and the desirability of replacing -it in this discussion by the less equivocal term Sentience, will need -more to be said. - -104. The important question whether reflex actions are insentient, and -therefore mechanical, will occupy us in the next problem. The question -of Automatism which has been argued in the preceding chapters, may, -I think, be summarily disposed of by a reference to the irresistible -evidence each man carries in his own consciousness that his actions -are frequently--even if not always--determined by feelings. He is -quite certain that he is not an automaton, and that his feelings are -not simply collateral products of his actions, without the power of -modifying and originating them. Now this fundamental fact cannot be -displaced by any theoretical explanation of its factors. Nor would -this fundamental truth be rendered doubtful, even supposing we were to -grant to the full all that is adduced as evidence that _some_ actions -were the result of purely mechanical processes without sentience at -all. I am a conscious organism, even if it be true that I sometimes act -unconsciously. I am not a machine, even if it be true that I sometimes -act mechanically. - - - - -PROBLEM IV. - -THE REFLEX THEORY. - - “Si omnes patres sic, et Ego non sic.”--ABELARD, _Sic et Non_. - - “Will man bestimmen wo der Mechanismus aufhört und wo der Wille - anfängt so ist die Frage überhaupt falsch gestellt. Denn man setzt - hier Begriffe einander gegenüber die gar keine Gegensätze sind. - Vorgebildet in den mechanischen Bedingungen des Nervensystems sind - _alle_ Bewegungen.”--WUNDT, _Physiologische Psychologie_. - - “Sollte die so durchsichtige Homologie zwischen Hirn and - Rückenmark, wie solche sich schlagend in Bau und Entwicklung - darthut, wesentlich andere physiologische Qualitäten - bedingen?”--LUSCHINGER in _Pflüger’s Archiv_, Bd. XIV. 384. - - - - -THE REFLEX THEORY. - - - - -CHAPTER I. - -THE PROBLEM STATED. - - -1. The peculiarity of the Reflex Theory is its exclusion of Sensibility -from the actions classed as reflex; in consequence of which, the -actions are considered to be “purely mechanical.” - -No one denies that most of the reflex actions often have conscious -sensations preceding and accompanying them, but these are said not -to be essential to the performance of the actions, because they may -be absent and the actions still take place. It is notorious that we -breathe, wink, swallow, etc., whether we are conscious of these actions -or not. Our conclusion therefore is that these peculiar states of -Consciousness are _accessory_, not essential to the performance of -these actions. The fact is patent, the conclusion irresistible. But -now consider the equivoque: because an action takes place without our -being conscious of it, the action is said to have had no sensation -determining it. This, which is a truism when we limit Consciousness to -one of the special modes Of Sensibility, or limit sensation to this -limited Consciousness, is a falsism when we accept Consciousness as -the total of all combined sensibilities, or Sensation as the reaction -of the sensory mechanism. That a reflex action is determined by the -sensory mechanism, no one disputes; whether the reaction of a sensory -mechanism shall be called a sensation or not, is a question of terms. -I have shown why it must be so called if anything like coherence is to -be preserved in physiological investigations; and I have more than once -suggested that the fact of intellectual processes taking place at times -with no more consciousness than reflex actions, is itself sufficient to -show that a process does not lapse from the mental to the mechanical -sphere simply by passing unconsciously. - -Inasmuch as an organism is a complex of organs, its total function must -be a complex of particular functions, each of which may analytically -be treated apart. Vitality is the total of all its physiological -functions, and Consciousness the total of all its psychological -functions. But inasmuch as it is only in its relation to the whole that -each part has functional significance, and cannot therefore be isolated -in reality, as it is in theory--cannot live by itself, act by itself, -independently of the organism of which it is an organ, there is strict -accuracy in saying that no particular sensation can exist without -involving Consciousness; for this is only saying that no sensory organ -can react without at the same time involving a reaction of the general -sensorium. But since this general sensorium is simultaneously affected -by various excitations each of which is a force, every sensation, -perception, emotion, or volition is a _resultant_ of the composition -of these forces; and as there can be only one resultant at a time, to -be replaced by another in swift succession, this one represents the -_state_ of Consciousness, and this state may or may not be felt under -the peculiar _mode_ named “Consciousness,” in its special meaning. In -other words, the reaction of a sensory organ is always sentient, but -not always consentient. - -2. Let us illustrate this by the sensation of musical tone. When -we hear a tone we are affected not only by the fundamental tone, -representing the vibrations of the sounding body as a whole, but -also by the harmonics or overtones, representing the vibrations of -the several parts of that whole. It is these latter vibrations which -give the tone its timbre, or peculiar _quality_; and as the harmonics -are variable with the variable structure of the vibrating parts, two -bodies which have the same fundamental tone may have markedly different -qualities. There are some tones which are almost entirely free from -harmonics; that is to say, their harmonics are too faint for our ear to -appreciate them, though we know that the vibrations must be present. -Apply this to the excitations of the sensorium. Each excitation will -have its fundamental feeling, and more or less accompanying thrills of -other feelings: it is these thrills which are the harmonics, giving to -each excitation its specific quality; but they may be so faint that no -specific quality is discriminated. A fly settles on your hand while you -are writing, the faint thrill which accompanies this excitation of your -sensory nerve gives the specific sensation of tickling, and this causes -you to move your hand with a jerk. If your attention is preoccupied, -you are said to be unconscious of the sensation, and the jerk of -your hand is called a reflex action; but if your attention is not -preoccupied, or if the thrill is vivid, you are said to be conscious -of the sensation, and the action is no longer reflex, but volitional. -Obviously here the difference depends not on the sentient excitation by -an impression on the nerve, but on the state of the general sensorium -and its consequent reaction. Had not the impression been carried to the -sensorium, no movement would have followed the fly’s alighting on your -hand, because no sensation (sensory reaction) would have been excited; -the hypothesis of a purely mechanical reflex is quite inadmissible. - -3. Or take another case. It sometimes happens that we fall asleep -while some one is reading to us aloud. The sounds of the reader’s -voice at first awaken the familiar thrills which give the tones their -quality, and the words their significance; but gradually as sleep -steals over us, the organism ceases to react thus; the words lose more -and more of their significance, the tones lose more and more of their -harmonics; at last we pass into the state of unconsciousness--we cease -to hear what is read. But do we cease to feel? We have not _heard_, -but we have been _affected_ by the sounds. Not by distinguishable -sensations; nevertheless a state of the general Sensibility has been -induced. To prove that we have been affected is easy. Let the reader -suddenly cease, and if our sleep be not too profound, we at once awake. -Now, unless the sound of his voice had affected us, it is clear that -the cessation of that could not have affected us. Or let us suppose -our sleep to be unbroken by the cessation of the sound; even this will -not prove that we have been unaffected by the sounds, it will merely -prove that those sounds, or their cessation, did not excite a conscious -state. For let the reader, in no louder tone, ask, “Are you asleep?” -and we start up, with round eyes, declaring, “Not at all.” Nay, should -even this question fail to awaken us, the speaker need only utter some -phrase likely to excite a thrill--such as, “There’s the postman!” or, -“I smell fire!” and we start up. - -I remember once trying the experiment on a wearied waiter, who had -fallen asleep in one of the unoccupied boxes of a tavern. His arm -rested on the table, and his head rested on his arm: he snored the -snore of the weary, in spite of the noisy laughter and talk of the -guests. I called out “Johnson,” in a loud tone. It never moved him. I -then called “Wilson,” but he snored on. No sooner did I call “waiter,” -than he raised his head with a sleepy “_yessir_.” Now, to suppose, in -this case, that he had _no_ sensation when the words “Johnson” and -“Wilson” reached his ears, but had a sensation when the word “waiter” -reached his ears, is to suppose that two similar causes will not -produce a similar effect. The dissyllable “Johnson” would excite as -potent a reaction of his sensory organ as the dissyllable “waiter”; -but the thrills--the reflex feelings--were different, because the word -“Johnson” was not associated in his mind with any definite actions, -whereas the word “waiter” was so associated as to become an automatic -impulse.[231] - -4. Two sisters are asleep in the same bed, and a child cries in the -next room. The sounds of these cries will give a similar stimulus -to the auditory nerve of each sister, and excite a similar sensory -reaction in each. Nevertheless, the one sister sleeps on undisturbed, -and is said not to hear the cry. The other springs out of bed, and -attends to the child, because she being accustomed to attend on the -child and soothe it when crying, the primary sensation has excited -secondary sensations, thrills which lead to accustomed actions. Could -we look into the mind of the sleeping sister, we should doubtless find -that the sensation excited by the child’s cry had merged itself in -the general stream, and perhaps modified her dreams. Let her become a -mother, or take on the tender duties of a mother, and her vigilance -will equal that of her sister; because the cry will _then_ excite a -definite reflex feeling, and a definite course of action. But this very -sister, who is so sensitive to the cry of a child, will be undisturbed -by a much louder noise; a dog may bark, or a heavy wagon thunder along -the street, without causing her to turn in bed.[232] - -Although during sleep the nervous centres have by no means their -full activity, they are always capable of responding to a stimulus, -and sensation will always be produced. When the servant taps at your -bedroom door in the morning, you are said not to hear the tap, if -asleep; you do not perceive it; but the sound reaches and rouses you -nevertheless, since when the second tap comes, although no louder, you -distinctly recognize it. In etherized patients, sensation is constantly -observed returning before any consciousness of what is going on -returns. “I was called,” says Mr. Potter, “to give chloroform to a lady -for the extraction of ten teeth. The first five were extracted without -the slightest movement, but as the operation proceeded, sensation -returned, and I was obliged to use considerable force to keep her in -the chair during the extraction of the last tooth. She came to herself -very shortly after, and was delighted to find she had got over all her -troubles without having felt it the least in the world.”[233] - -5. We do not see the stars at noonday, yet they shine. We do not see -the sunbeams playing among the leaves on a cloudy day, yet it is by -these beams that the leaves and all other objects are visible. There -is a general illumination from the sun and stars, but of this we are -seldom aware, because our attention falls upon the illumined objects, -brighter or darker than this general tone. There is a sort of analogy -to this in the general Consciousness, which is composed of the sum of -sensations excited by the incessant simultaneous action of internal -and external stimuli. This forms, as it were, the daylight of our -existence. We do not habitually attend to it, because attention falls -on those particular sensations of pleasure or of pain, of greater -or of less intensity, which usurp a prominence among the objects of -the sensitive panorama. But just as we need the daylight to see -the brilliant and the sombre forms of things, we need this living -Consciousness to feel the pleasures and the pains of life. It is -therefore as erroneous to imagine that we have no other sensations than -those which we distinctly recognize--as to imagine that we see no other -light than what is reflected from the shops and equipages, the colors -and splendors which arrest the eye. - -The amount of light received from the stars may be small, but it is -present. The greater glory of the sunlight may render this starlight -inappreciable, but it does not render it inoperative. In like manner -the amount of sensation received from some of the centres may be -inappreciable in the presence of more massive influences from other -centres; but though inappreciable it cannot be inoperative--it must -form an integer in the sum. - -6. The reader’s daily experience will assure him that over and above -all the particular sensations capable of being separately recognized, -there is a general stream of Sensation which constitutes his feeling -of existence--the Consciousness of himself as a sensitive being. The -ebullient energy which one day exalts life, and the mournful depression -which the next day renders life a burden almost intolerable, are -feelings not referable to any of the particular sensations, but arise -from the massive yet obscure sensibilities of the viscera, which form -so important a part of the general stream of Sensation. Some of these -may emerge into distinct recognition. We may feel the heart beat, the -intestines move, the glands secrete; anything _unusual_ in their action -will force itself on our attention. - -“What we have been long used to,” says Whytt, “we become scarcely -sensible of; while things which are new, though much more trifling, -and of weaker impression, affect us remarkably. Thus he who is wont to -spend his time in the country is surprisingly affected, upon first -coming into a populous city, with the noise and bustle which prevail -there: of this, however, he becomes daily less sensible, till at length -he regards it no more than they who have been used to it all their -lifetime. The same seems to be the case also with what passes within -our bodies. Few persons in health feel the beating of their heart, -though it strikes against their ribs with considerable force every -second; whereas the motion of a fly upon one’s face or hands occasions -a very sensible and uneasy titillation. The pulsation of the great -_aorta_ itself is wholly unobserved by us; yet the unusual beating of a -small artery in any of the fingers becomes very remarkable.” - -7. A large amount of sensation is derived from the muscular sense, yet -we are not aware of the nice adjustments of the muscles, regulated by -this sensibility, when we sit or walk. No sooner are we placed in an -exceptional position, as in walking on a narrow ledge, than we become -distinctly aware of the effort required to preserve equilibrium. It is -not the novelty of the position which has increased our sensibility; -that has only caused us to attend to our sensations. In like manner, -the various streams of sensation which make up our general sense -of existence, separately escape notice until one of them becomes -obstructed, or increases in impetuosity. When we are seated at a -window, and look out at the trees and sky, we are so occupied with the -aspects and the voices of external Nature, that no attention whatever -is given to the fact of our own existence; yet all this while there -has been a massive and diffusive feeling arising from the organic -processes; and of this we become distinctly aware if we close our -eyes, shut off all sounds, and abstract the sensations of touch and -temperature--it is then perceived as a vast and powerful stream of -sensation, belonging to none of the special Senses, but to the System -as a whole. It is on this general stream that depend those well-known -but indescribable states named “feeling well” and “feeling ill”--the -_bien être_ and _malaise_ of every day. Of two men looking from the -same window, on the same landscape, one will be moved to unutterable -sadness, yearning for the peace of death; the other will feel his soul -suffused with serenity and content: the one has a gloomy background, -into which the sensations excited by the landscape are merged; the -other has a happy background, on which the sensations play like -ripples on a sunny lake. The tone of each man’s feeling is determined -by the state of his general consciousness. Except in matters of pure -demonstration, we are all determined towards certain conclusions as -much by this general consciousness as by logic. Our philosophy, when -not borrowed, is little more than the expression of our personality. - -8. Having thus explained the relation of particular sensations to the -general state of Consciousness considered as the function of the whole -organism, we may henceforward speak of particular sentient states, as -we speak of particular organs and functions, all the while presupposing -that the organs and functions necessarily involve the organism, since -_apart_ from the organism they have no such significance. The reaction -of a sensory organ is therefore always a sentient phenomenon. Apart -from the living organism there can be no such vital reaction, but only -a physical reaction. It is commonly supposed that sensation is simply -the molecular excitation of the cerebrum; yet no one will maintain -that if the cerebrum of a corpse be excited, by a galvanic current -sent through the optic nerve, for instance, this excitation will be a -sensation. Whence we may conclude that it is not the physical reaction -or stimulus which constitutes sensation, but the physiological reaction -of the living organism. - -9. Now this is the point which the advocates of the Reflex Theory, -implicitly or explicitly, always deny. Let us trace the origin of the -fallacy, if possible. When we remove the eye from a recently killed -animal, and let a beam of light fall on it, the pupil contracts. This -is a purely mechanical action; no one would suggest that a sensation -determined it. When we remove the leg, and irritate its nerve, the leg -is jerked out. This is also a purely mechanical action. When we remove -the brain from an animal, and pinch its toes, the leg is withdrawn -or the pincers are pushed aside. Is this equally a purely mechanical -action? And if not, why not? - -The Reflex Theory would have us believe that all three cases were -mechanical, at least in so far as they were all destitute of sentient -co-operation, the ground for this conclusion being the hypothesis that -the brain is the exclusive seat of sensation. The Reflex Theory further -concludes that since these, and analogous actions, are performed when -the brain is removed, they, being thus independent of sentience, may -be performed when the brain is present without any co-operation of -sentience. The grounds for this conclusion being the facts that in -the normal state of the organism there are many actions of which we -are sometimes conscious, and at other times unconscious; and some -actions--such as the dilatation and contraction of the pupil--of which -we are never conscious. This observation of parts detached from the -organism seems confirmed by observation of actions passing in our -own organisms, both converging to the conclusion that the actions in -question are purely mechanical, involving no sentience whatever. We are -taught, therefore, that there is besides the sentient mechanism, to -which all conscious actions are referred, a reflex mechanism, to which -all unconscious actions are referred. The cerebro-spinal axis, acting -as a whole, constitutes the first; the spinal axis, acting without the -co-operation of the cerebrum, constitutes the second. - -10. Before proceeding with our exposition of the theory it may be -well to state two considerations which must be constantly in view. If -it should appear that there is any reasonable evidence for refusing -to limit Sensibility to the cerebrum--and this evidence I shall -adduce--the Reflex Theory must obviously be remodelled. Nor is this -all. We might see overwhelming evidence in favor of the hypothesis that -the cerebrum is the exclusive seat of Sensibility, and still reject as -a fallacy the conclusion that because certain actions can be performed -in the absence of the cerebrum, therefore those actions in the normal -organism are likewise performed without cerebral co-operation. I -mean that it is a fallacy to conclude from the contractions of the -pupil, and the jerking of the leg, when eye and leg are detached -from the organism, that therefore when eye and leg form integral -parts of the organism, such contractions and jerkings are mechanical -reflexes without sentient conditions. And the fallacy is analogous -to that which would conclude from the observations of a mechanical -automaton, that similar appearances in a vital organism were equally -automatic and mechanical. So long as both sets of phenomena are -apprehended simply as they appear to the sense of sight, they may be -indistinguishable; but no sooner do we apprehend them through other -modes, and examine the _modes of production_ of the phenomena, than -we come upon cardinal differences. A limb detached from the organism -is like a phrase detached from a sentence: it has lost its vital -significance, its functional value, in losing its connection with the -other parts. The whole sentence is necessary for the slightest meaning -of its constituent words, and each word is a language-element only -when ideally or verbally connected with the other words required to -form a sentence; without subject, predicate, and copula, no sentence -can be formed. So the organic connexus of parts with a living whole is -necessary for the simplest function of each organ; and a limb, or any -other part, is a physiological element only when (ideally or really) -an integral of a vital whole. The organism may be truncated by the -removal of certain parts, as the sentence may be abbreviated by the -removal of certain phrases; but so long as subject, predicate, and -copula remain, there is a meaning in the sentence; and so long as the -organic connexus needful for vitality remains, there will be vital -function. The eye detached from the organism is no longer a part of -the living whole, it no longer lives, its phenomena cease to be vital, -its movements cease to have sentient conditions. The movements of the -pupil may seem to be the same as those of the living eye; but when we -come to examine their modes of production, we learn that they are not -the same. The stimulus of light falling on the eye in the two cases -necessarily has a different effect, because the effect is the result of -the co-operating causes, and the co-operation in the one case is that -of a lifeless organ, in the other that of a living organism. So long as -the eye forms an integral part of the organism, every stimulus acting -on the eye necessarily acts on the organism, and every reaction of the -organ is necessarily conditioned by the state of the organism. Further, -every stimulation of a sensory nerve necessarily affects the general -sensorium, since the whole nervous system is structurally continuous -and functionally co-operant. (See Prob. II. § 16.) Therefore, the -stimulation of the eye, although too faint to be discriminated as a -conscious sensation, must enter as a sentient tremor into the general -stream of Sentience; and although we have no test delicate enough to -reveal this operation, we know the _obverse_ operation of conscious -sensation on the movements of the pupil--in surprise, for example, the -pupil is dilated. - -11. There are still stronger reasons for asserting that the spinal -reflexes are necessarily conditioned by the general state of the -sensorium, so that in the normal organism we cannot legitimately -exclude them from Sentience; and the Reflex Theory is therefore -unphysiological, even on the hypothesis that the cerebrum is the -exclusive seat of Sensibility. This hypothesis, however, seems to -me untenable; and all the observed facts which it is invented to -explain admit of a far more consistent explanation. It is irrational -to suppose that a limb, detached from the body, _felt_ the stimulus -which caused its muscles to contract. The limb is not a living -organism, having a sentient mechanism in its nervous mechanism. Not -less irrational is it to suppose that when the limb forms an integral -part of a living organism, with a sentient mechanism of nerves and -nerve-centres, this organism does not react on the stimulus which -excites the muscles of the limb to contract; nor, pursuing the same -train of reasoning, is it irrational to suppose that when this living -organism has been mutilated, and certain parts destroyed, which do -not in their destruction prevent the connexus of the rest, but leave -intact a sentient mechanism of nerves and nerve-centres, then also this -truncated organism still reacts as a whole, still feels the stimulus -which causes the muscles of the limb to contract. Hypothesis for -hypothesis, we may at least say that the one is as reasonable as the -other. And I shall be disappointed if, when the reader has gone through -all the evidence hereafter to be adduced, he does not conclude that -the hypothesis which assigns Sensibility to the nervous mechanism as a -whole is not the more acceptable of the two. - -12. Let us now pursue our exposition of the Reflex Theory. All that -we have endeavoured to establish respecting the essential identity of -the processes in conscious and unconscious states, and voluntary and -involuntary actions,--an identity which does not exclude differences of -degree corresponding with these different terms,--is ignored or denied -in the Reflex Theory. Whereas I suppose all processes to be reflex -processes, some of them having the voluntary, others the involuntary -character, physiologists generally distinguish the involuntary as -reflex, and invent for this class a special mechanism. According to -Marshall Hall, who originated the modern form of this theory, actions -are divisible into four distinct classes: the _voluntary_, dependent -on the brain; the _involuntary_, dependent on the irritability of -the muscular fibre; the _respiratory_, wherein “the motive influence -passes in a _direct line_ from one point of the nervous system to -certain muscles”; and the _reflex_, dependent on the “true spinal -system” of _incident-excitor_ nerves, and of _reflex-motor_ nerves. -These last-named actions are produced when an _impression_ on the -sensitive surface is conveyed, by an excitor-nerve, to the spinal -cord, and is there _reflected_ back on the muscles by a corresponding -motor-nerve. In this process _no_ sensation whatever occurs. The action -is purely reflex, purely _excito-motor_--like the action of an ordinary -mechanism.[234] - -Müller, who shares with Marshall Hall the glory of having established -this classification, thinks that although the absence of sensation is -a characteristic of the reflex actions, these actions may be, and are -at times, accompanied by sensation. “The view I take of the matter is -the following: Irritation of sensitive fibres of a spinal nerve excites -primarily a centripetal action of the nervous principle conveying the -impression to the spinal cord; if the centripetal action can then be -continued to the _sensorium commune_, a true sensation is the result; -if, on account of division of the cord, it cannot be communicated to -the sensorium, it still exerts its whole influence upon the cord; in -both cases a reflex motor action may be the result.”[235] - -13. It is needless nowadays to point out that the existence of a -distinct system of excito-motor nerves belongs to Imaginary Anatomy; -but it is not needless to point out that the Imaginary Physiology -founded on it still survives. The hypothetical process seems to me not -less at variance with observation and induction, than the hypothetical -structure invented for its basis. We have already seen that what -Anatomy positively teaches is totally unlike the reflex mechanism -popularly imagined. The sensory nerve is not seen to enter the spinal -cord at one point, and pass over to a corresponding point of exit; it -is seen to enter the gray substance, which is continuous throughout the -spinal cord; it is there lost to view, its course being untraceable. -Nor does the physiological process present the aspect demanded by the -theory: it is not that of a direct and uniform reflexion, such as -would result from an impression on one spot transmitted across the -spinal cord to a corresponding motor-nerve. The impression is sometimes -followed by one movement, sometimes by another very different movement, -each determined by the state of neural tension in the whole central -system. - -Even the facts on which the Reflex Theory is based are differently -interpreted by different physiologists. Van Deen, for instance, -considers that Reflexion takes place without Volition, but not -without Sensation; and Budge, that it takes place without perception -(_Vorstellung_). And when it is remembered that most of the reflex -actions will be accompanied by distinct consciousness whenever -attention is directed to them, or the vividness of the stimulation -is slightly increased, it becomes evident that the absence of -Consciousness (discrimination) is not the differentia of Reflex action. - -14. Nor can the absence of spontaneity be accepted as a differentia. -_All_ actions are excited by stimulation, internal or external. What -are called the spontaneous actions are simply those which are prompted -by internal, or by not recognizable stimuli; and could we see the -process, we should see a neural change initiated by some stimulation, -whether the change was conscious and volitional, or unconscious and -automatic. The dog rising from sleep and restlessly moving about, -is acting spontaneously, whether the stimulation which awakens him -be a sensation of hunger, a sensation of sound, the sharp pain of a -prick, or a dash of cold water. If he wags his tail at the sight of -his master, or wags it when dreaming, the stimulation is said to be -spontaneous; but if after his spinal cord has been divided the tail -wags when his abdomen is tickled, the action is called reflex. In all -three cases there has been a process of excitation and reflexion. - -15. The advocates of the Reflex Theory insist that spontaneity is -always absent in brainless animals; whence the conclusion that the -brain is the exclusive organ of sensation. But the fact asserted is -contradicted by the evidence. No experimenter can have failed to -observe numberless examples of spontaneity in brainless animals. Many -examples have already been incidentally noticed in previous pages. Let -me add one more from my notes: I decapitated a toad and a triton, and -divided the spinal cord of another triton and a frog. At first the -movements of the decapitated animals were insignificant; but on the -second day the headless toad was quite as lively as the frog; and the -headless triton little less so than his companion with cord divided -but brain intact. I have, at the time of writing this, a frog whose -cord was divided some weeks ago. He remains almost motionless unless -when touched; he is generally found in the same spot, and in the same -attitude to-day as yesterday, unless touched, or unless the table be -shaken. He occasionally moves one of the forelegs; occasionally one of -the hind-legs; but without changing his position. If he were brainless, -this quiescence would be cited in proof of the absence of spontaneity -in the absence of the brain; but this conclusion would be fallacious, -and is seen to be so in the spontaneous movements of his companion who -has _no_ brain. - -16. With spontaneity is associated the idea of volition, and with -volition _choice_. Now I admit that it is complicating the question to -ask any one to conceive a headless animal choosing one action rather -than another; but it is equally difficult to reconcile ourselves to -the idea of “choice” in contemplating the actions of a mollusc. In -what sense we can speak of the volition of a mollusc or an insect has -already been considered (p. 408). When a man in a fit of coughing -seizes a glass of water to allay the tickling in his throat, we have -no hesitation in declaring this to be volitional--and the remedy to -be _chosen_. But when a brainless animal adopts some _unusual_ means, -after the failure of the usual means, to allay an irritation, we still -hesitate to call the action volitional. I see, however, no objection to -calling it the adaptation of a sensitive mechanism which is markedly -unlike any inorganic mechanism. - -Place a child of two or three years old upon his back, and tickle -his right cheek with a feather. He will probably move his head away. -Continue tickling, and he will rub the spot with his right hand, -_never_ using the left hand for the right cheek, so long as the right -hand is free; but if you hold his right hand, he will use the left. -Does any one dispute the voluntary character of these actions? - -Now compare the actions of the sleeping child under similar -circumstances, and their sequence will be precisely similar. This -contrast is the more illustrative, because physiologists generally -assume that in sleep consciousness and volition are _suspended_. -They say: “The brain sleeps, the spinal cord never; volition and -sensation may be suspended, but not reflex action.” This proposition is -extremely questionable; yet it is indispensable to the reflex theory; -because unless sensation and volition _are_ suspended during sleep, we -must admit that they can act, without at the same time calling into -activity that degree of sensibility which is supposed to constitute -consciousness. The child moves in his sleep, defends himself in his -sleep; but he is not “aware” of it. - -“Children,” says Pflüger, “sleep more soundly than adults, and seem -to be more sensitive in sleep. I tickled the right nostril of a -three-year-old boy. He at once raised his right hand to push me away, -and then rubbed the place. When I tickled the left nostril he raised -the left hand. I then softly drew both arms down, and laid them close -to the body, embedding the left arm in the clothes, and placing on it a -pillow, by gentle pressure on which I could keep the arm down without -awakening him. Having done this I tickled his left nostril. He at once -began to move the imprisoned arm, but could not reach his face with -it, because I held it firmly though gently down. He now drew his head -aside, and I continued tickling, whereupon he raised the _right_ hand, -and with it rubbed the _left_ nostril--an action he never performed -when the left hand was free.” - -17. This simple but ingenious experiment establishes one important -point, namely, that the so-called reflex actions observed in sleep -are determined by sensation and volition. The sleeping child behaves -exactly as the waking child behaved; the only difference being in -the energy and rapidity of the actions. If the waking child felt and -willed, surely the sleeping child, when it performed precisely similar -actions, cannot be said to have felt nothing, willed nothing? It is -not at one moment a sentient organism, and at the next an insentient -mechanism. - -It is possible to meet this case by assuming that the child was nearly -awake, and that a dim consciousness was aroused by the tickling, so -that the cerebral activity was in fact awakened. But, plausible as -this explanation may be (and I am the more ready to admit it because I -believe the brain always co-operates when it is present), it altogether -fails when we come to experiments on decapitated animals. If any one -will institute a series of such experiments, taking care to compare the -actions of the animal before and after decapitation, he will perceive -that there is no more difference between them than between those of the -sleeping and the waking child. - -18. Even more striking is the following experiment, devised by Pflüger, -which I have verified, and varied, many times: A frog is decapitated, -or its brain is removed.[236] When it has recovered from the effect of -the ether, and manifests lively sensibility, we place it on its back, -and touch, with acetic acid, the skin of its thigh just above the -_condylus internus femoris_. (Let the reader imagine his own shoulder -burnt at the point where it can be reached with the thumb of the same -arm, and he will realize the operation.) No sooner does the acid begin -to burn than the frog stretches out the _other_ leg, so that its body -is somewhat drawn towards it. The leg that has been burnt is now bent, -and the back of the foot is applied to the spot, rubbing the acid -away--just as your thumb might rub your shoulder. This is very like -the action of the tickled child, who always uses the right hand to rub -the right cheek, unless it be held; but when the child’s right hand is -prevented from rubbing, the left will be employed; and precisely this -do we observe with the brainless frog: prevent it from using its right -leg, and it will use its left! - -This has been proved by decapitating another frog, and cutting off -the foot of the leg which is to be irritated. No sooner is the acid -applied, than the leg is bent as before, and the stump is moved to and -fro, as if to rub away the acid. But the acid is not rubbed away, and -the animal becomes restless, as if trying to hit upon some other plan -for freeing himself of the irritation. And it is worthy of remark that -he often hits upon plans very similar to those which an intelligent -human being adopts under similar circumstances. Thus, the irritation -continuing, he will sometimes cease the vain efforts with his stump, -and stretching that leg straight out, bends the _other_ leg over -towards the irritated spot, and rubs the acid away. But, to show how -far this action is from one of “mere mechanism,” how far it is from -being a direct reflex of an impression on a group of muscles, the -frog does not _always_ hit even on this plan. Sometimes it bends its -irritated leg more energetically, and likewise bends the body towards -it, so as to permit the spot to be rubbed against the flank--just as -the child, when both his hands are held, will bend his cheek towards -his shoulder and rub it there. - -19. It is difficult to resist such evidence as is here manifested. The -brainless frog “chooses” a new plan when the old one fails, just as -the waking child chooses. And an illustration of how sensations guide -and determine movements, may be seen in another observation of the -brainless frog, when, as often happens, it does not hit upon either of -the plans just mentioned, but remains apparently restless and helpless; -if under these circumstances we perform a part of the action for it, -_it will complete what we have begun_: if we rub the irritated leg, at -some distance from the spot where the acid is, with the foot of the -other, the frog suddenly avails itself of this _guiding sensation_, and -at once directs its foot to the irritated spot. - -In these experiments on the triton and the frog, the evidence of -sensation and volition is all the stronger, because the reactions -produced by irritations are not uniform. If when a decapitated animal -were stimulated it always reacted in _precisely the same way_, and -never chose _new means_ on the failure of the old, it would be -conceivable to attribute the results to simple reflex action--i. e. the -mechanical transference of an impulse along a prescribed path. It is -possible so to conceive the breathing, or the swallowing mechanism: the -impression may be directly reflected on certain groups of muscles. But -I cannot conceive a machine suddenly striking out new methods, when the -old methods fail. I cannot conceive a machine thrown into disorder when -its accustomed actions fail, and in this disorder suddenly lighting -upon an action likely to succeed, and continuing _that_; but I can -conceive this to be done by an organism, for my own experience and -observation of animals assures me that this is always the way new lines -of action are adopted. And this which is observed of the unmutilated -animal, I have just shown to be observed of the brainless animal; -wherefore the conclusion is, that if ever the frog is sentient, if -ever its actions are guided by sensation, they are so when its brain is -removed. - -20. Schröder van der Kolk thinks that Pflüger was deceived in -attributing sensation and volition to the frog, because the reflex -actions are, he says, so nicely adapted to their ends, that they are -undistinguishable from voluntary actions. The mechanism is such that, -by means of the communications established between various groups of -cells, all these actions adapted to an end may be excited by every -stimulus. But I deny the fact. I deny that all the actions are awakened -by every stimulus. Only some few are awakened, and those are not -always the same, nor do they follow the same order of succession. One -decapitated frog does not behave exactly like another under similar -circumstances; does not behave exactly like himself at different -seasons; unlike a machine, he manifests spontaneity in his actions, and -volition in the direction of his actions. - -21. The reader will notice that my illustrations show these actions of -the brainless animal to have the same external characters as those of -the unmutilated animals. I am therefore not here concerned to prove -the psychical nature of these actions, unless it be granted that the -unmutilated animal has sensation and volition. This of course can -only be inferred, not proved. But the inference must not be allowed -in the one case and refused in the other. Young rabbits and puppies -when taken from their mothers manifest discomfort by restless movement -and whining. Do they feel the discomfort they thus express? If ever -rabbits and puppies may be said to feel, we must answer, Yes. Well, -if the brain be removed from rabbits and puppies, precisely similar -phenomena are observed when these young animals are taken from -their mothers. “I observed the motions, which seemed the result of -discomfort, quickly cease when I warmed the young rabbit by breathing -on it. After a while it was completely at rest, and seemed sunk in -deep sleep; occasionally, however, it moved one of its legs without -any external stimulus having been applied, and this not spasmodically, -but in the manner of a sleeping animal.”[237] Is this cessation of -the restlessness, when warmth is restored, not evidence of sensation? -We see an infant restless, struggling, and squalling; and we believe -that it is hungry, or that some other sensations agitate it; it is -put to the breast, and its squalls subside; or a finger is placed in -its mouth, and it sucks that, in a peaceful lull, for a few moments, -to recommence squalling when the finger yields no satisfaction. If we -accept these as signs of sensation, I do not see how we can deny such -sensation to the brainless animal which will also cease to cry, and -will suck the delusive finger. - -22. One of the earliest advocates of the Reflex Theory sums up -his observations in these words: “It is clear that brainless -animals, although without sensation, because not endowed with -mind, nevertheless, by means of external impressions which operate -incessantly on them, perform all the acts and manifest all the activity -of the sentient animal; everything that is effected sensationally -and volitionally, they effect by means of the organic forces of the -impressions.”[238] Call Sensibility one of the organic forces, if you -please, but so long as the acts performed are not only the same as -those of a sentient animal, but are performed by the same mechanism, -they have every claim to the character of sensational acts which can be -urged in the case of these animals when the brain is present. And the -only reason on which this claim is disputed is the assumed loss of all -sensation with the loss of the brain. Here, therefore, lies the central -point to be determined. - - - - -CHAPTER II. - -DEDUCTIONS FROM GENERAL LAWS. - - -23. The evidence is of two kinds: deductions from the general laws of -nervous action, and inductions from particular manifestations. The -former furnish a presumption, the latter a proof. - -The central process which initiates a reflex action may be excited -by the external stimulation of a peripheral nerve, by the internal -stimulation of a peripheral nerve, or by the irradiation from some -other part of the central tissue. The last-named stimulations are -the least intelligible, because they are so varied and complex, -and so remote from observation; among them may be placed, 1°, the -organized impulses of Instinct and Habit, with their fixed modes of -manifestation; 2°, the organized impulses of Emotion, which are more -variable in their manifestations, because more fluctuating in their -conditions; 3°, the organized impulses of Intellect, the most variable -of all. Whether we shrink on the contact of a cold substance or on -hearing a sudden sound,--at the sight of a terrible object,--at the -imaginary vision of the object,--or because we feign the terror which -is thus expressed,--the reflex mechanism of shrinking is in each case -the same, and the neural process discharged on the muscles is the same; -but the state of Feeling which originated the change--or, in strictly -physiological terms, the inciting neural process which preceded this -reflex neural process--was in each case somewhat different, yet in each -case was a mode of Sensibility. - -24. The property of Sensibility belongs to the whole central tissue; -and we have every reason to believe that unless it is excited no reflex -takes place, whereas when it is exaggerated--as in epilepsy, or under -strychnine--the reflex discharges are convulsive. When anæsthetics are -given, consciousness first disappears, and then reflexion. When the -sensorium is powerfully excited by _other_ stimuli, the normal stimulus -fails to excite either consciousness or reflexion. Hence our conclusion -is that for consciousness, on the one hand, and _normal_ reflexion, on -the other, the proximate condition is a change in the sensorium; or--to -phrase it more familiarly--Feeling is necessary for reflex action. - -The difficulty in apprehending this lies in the ambiguity of the -term Feeling. Many readers who would find no difficulty in admitting -Sensibility as a necessary element in reflex action, will resist the -idea of identifying Sensibility with Feeling. But this repugnance must -be overcome if we are to understand the various modes of Sensibility -which represent Feeling in animals, and its varieties in ourselves. We -understand how the general Sensibility manifests itself in markedly -different sensations--how that of the optic centre differs from that -of the auditory centre, and both from a spinal centre. The tones of a -violin are not the same as the tones of a violoncello, both differ from -the tones of a key-bugle: yet they all come under the same general laws -of tonality. So, as I often insist, the tissues in brain and cord being -the same, their properties must be the same, their laws of excitation, -irradiation, and combination the same, through all the varieties in -their manifestations due to varieties of innervation. Hence it is -that there are reflex cerebral processes no less than reflex spinal -processes: the motor impulse from, the hemispheres on the _corpora -striata_, or from posterior gray substance on anterior gray substance, -is similar to that from the anterior gray substance on the motor -nerves. The difference in reflexes arises from the terminal organs; as -the difference in sensations arises from the surfaces stimulated. But -not only are there reflex processes in the brain, of the same _order_ -as those in the cord, there are volitional processes in the cord of -the same order as those in the brain. And in both the processes are -sometimes conscious, sometimes unconscious. No evidence suggests that -in the conscious action there is a sensorial process, and a purely -physical process in the unconscious action--only a different _relation_ -of one sensorial process to others. - -25. Let us contrast a cerebral and a spinal process, in respect to the -three stages of stimulation, irradiation, and discharge. A luminous -impression stimulates my retina, this excites my sensorium, in which -second stage I am conscious of the luminous sensation; the final -discharge is a perception, or a mental articulation of the _name_ of -the luminous object. But the irradiation may perhaps not have been -such as to cause a _conscious_ sensation, because the requisite neural -elements were already grouped in some other way; in this case there is -an unconscious discharge on some motor group, and instead of perceiving -and naming the luminous object, I move my head, or my band, or my -whole body, avoiding the object, or grasping at it. A third issue is -possible: the irradiation, instead of exciting a definite perception, -or a definite movement, may be merged in the stream of simultaneous -excitations, and thus form the component of a group, and the discharge -of this group will be a perception or a movement. - -It is the same with a spinal process. An impression on the skin is -irradiated in the cord, and the response is a movement, of which we -are conscious, or unconscious. Here also a third issue is possible: -the irradiation may be merged in a stream of simultaneous excitations, -modifying them and modified by them, thus forming a component in some -ulterior discharge. - -26. The obstacle in the way of recognizing that cerebral processes and -spinal processes are of the same order of sensorial phenomena, and have -the same physiological significance when considered irrespective of the -group of organs they call into activity, is similar to the obstacle -which has prevented psychologists from recognizing the identity of the -logical process in the combinations of Feeling and the combinations -of Thought, i. e. the Logic of Feeling and the Logic of Signs. This -obstacle is the fixing attention on the diversity of the effects when -the same process operates with different elements. Because the spinal -cord manifests the phenomena of sensation and volition, we are not to -conclude that it also manifests ideation and imagination; any more -than we are to conclude that a mollusc is capable of musical feelings -because it is affected by sounds. - -27. The careless confusion of general properties with special -applications of those properties, and of functions with properties, has -been a serious hindrance to the right understanding of Sensibility and -its operations. Instead of recognizing that the nervous system has one -general mode of reaction, which remains the same under every variety -of combination with other systems, physiologists commonly lose sight -of this general property, and fix on one mode of its manifestation as -the sole characteristic of Sensibility. Sometimes the mode fixed on -is Pain, at other times Attention. Thus, when an animal manifests no -evidence of pain under stimulations which ordinarily excite severe -pain, this is often interpreted as a proof that _all_ sensation is -absent; and if with this absence of pain there is--as there often -is--clear evidence of the presence of some other mode of sensibility, -the contradiction is evaded by the assumption that what here looks like -evidence of sensation is merely mechanical reflexion. One would think -that Physiology and Pathology had been silent on the facts of analgesia -without anæsthesia, and of so much conscious sensation which is -unaccompanied by pain.[239] Who does not know that a patient will lose -one kind of sensibility while retaining others--cease to feel pain, -yet feel temperature, or be insensible to touch, yet exquisitely alive -to pain?[240] Inasmuch as Sensibility depends on the condition of the -centres, an abnormal condition will obviously transform the reaction -of the centres into one very unlike the normal reaction. For example, -Antoine Cros had a patient who was quite unable to feel the sensation -of cold on her left side--every cold object touching her skin on that -side was felt as a very hot one; whereas a hot object produced “the -sort of sensation which followed the application of an intermittent -voltaic current.”[241] Thus also the experiments of Rose[242] and -others have exhibited the effects of a dose of Santonine in causing all -objects to be seen as yellow in one stage, and violet in another. - -28. If, then, certain alterations in the organic conditions are -accompanied by a suppression or perversion of some modes of -Sensibility, without suppressing the rest, it is but rational to -suppose that profound disturbances of the organic mechanism, such -as must result from the removal of the brain, will also suppress or -pervert several modes of Sensibility, and yet leave intact those -modes which belong to the intact parts of the mechanism. Assuming -that the spinal centres with the organs they innervate are capable of -reacting under certain modes of sensation, these will not necessarily -be suppressed by removal of the brain--all that will thereby be -suppressed is their co-operation with the brain. I know it will be -said that precisely this co-operation is necessary for sensation; and -that the spinal reactions are simple reflexions in which sensation has -no part. This, however, is the position I hope to turn. Meanwhile my -assumption is that sensation necessarily plays a part in the reflex -actions _of the organism_, and when that organism is truncated, its -actions are proportionately limited, its sensations less complex. The -spinal cord, separated from encephalic connections, cannot react in the -special forms of Sensation known as color, scent, taste, sound, etc., -because it does not innervate the organs of these special senses, nor -co-operate with their centres. But it can, and does, react in other -modes: it innervates skin and muscles; and the sensibilities, thus -excited, it can also _combine_ and _co-ordinate_. It has its Memory, -and its Logic, just as the brain has: both no longer than they are -integral parts of an active living organism: neither when the organism -is inactive or dead. We do not expect the retina to respond in sounds, -nor the ear to respond in colors: we expect each organ to have its -special mode of reaction. What is common to both is Sensibility. -What is common to brain and cord is Sensibility--and the laws of -Grouping. Instead of marvelling at the disappearance of so many modes -of Sensibility when the brain is removed, our surprise should be to -find so many evidences of Sensibility remaining after so profound a -mutilation of the mechanism. - -29. The current hypothesis, which assumes that the brain is the sole -organ of the mind, the sole seat of sensation, is a remnant of the -ancient hypothesis respecting the Soul and its seat; and on the whole -I think the ancient hypothesis is the more rational of the two. If the -Soul inhabits the organism, using it as an instrument, playing on its -organs as a musician plays on his instrument, we are not called upon -to explain the mode of operation of this mysterious agent; but if the -Soul be the subjective side of the Life, the spiritual aspect of the -material organism, then since it is a synthesis of all the organic -forces, the consensus of all the sentient phenomena, no one part can -usurp the prerogatives of all, but all are requisite for each. And -this indeed is what few physiologists would nowadays dispute. In spite -of their localizing sensation in the cerebral cells, they would not -maintain that the cerebral cells, nor even the whole brain, could -produce sensation--if _detached_ from the organism; the cheek of the -guillotined victim may have blushed when struck, but who believes that -the brain felt the insult, or the blow? Obviously, therefore, when we -read that thought is “a property of the gray substance of the brain, as -gravitation is of matter,” or that the brain is the exclusive organ of -Sensation, the writers cannot consistently carry out their hypothesis -unless they silently reintroduce other organs as co-operating agents; -for a neural process in the cerebrum is _in itself_ no more a -sensation than it is a muscular contraction, or a glandular secretion: -the muscles must co-operate for the contraction, the gland for the -secretion, the neural process being simply the exciting cause. In -like manner the Sensorium is necessary for the sensation, the neural -process--in cerebrum, or elsewhere--being simply the exciting cause. - -30. And what is the Sensorium? A long chapter would be required -to state the various opinions which have been held respecting its -_seat_, although amid all the disputes as to the organ, there has been -unanimity as to the function, which is that of converting stimulations -into sensations. I cannot pause here to examine the contending -arguments, but must content myself with expounding the opinion I hold, -namely, that the Sensorium is the _whole_ of the sensitive organism, -and not any one isolated portion of it. When light falls on the optic -organ, or air pulses on the auditory organ, the reaction of each organ -determines the _specific_ character of the sensation, _but no such -sensation is possible unless there be a reaction of the organism_; -and the nature of the product will of course vary with the varying -factors which co-operate--a simple organism, a truncated organism, an -exhausted or otherwise occupied organism, will react differently from -a complex, a normal, or an unoccupied organism. Detach the optic organ -with its centre from the rest of the organism, and no normal sensation -of Sight will result from its stimulation; and in a lesser degree this -is equally true of a stimulation of the optic organ when the sensorium -is exhausted, or powerfully affected by other stimuli. Because of the -great importance of the cerebrum, and its predominance in the nervous -system, it has been supposed to constitute the whole of the sensorium, -in spite of the evidence of varied Sensibility after the cerebrum has -been removed. I do not wish to understate the cerebral importance (see -p. 166), yet I must say that the modern phrase _cerebration_, when -employed as more than a shorthand expression of the complex processes -which a cerebral process initiates, and when taken as the objective -equivalent of Consciousness or of Thought, seems to me not more -justifiable than to speak of Combustion as the equivalent of Railway -Transport. The railway wagons will not move unless the fuel which -supplies the boiler be ignited; the organism will not think unless the -cerebrum excites this peculiar mode of Sensibility by its action on -the organs. _It is the man, and not the brain, that thinks_: it is the -organism as a whole, and not one organ, that feels and acts. - -31. Consciousness, or Sensation, is a complex product not to be -recognized in any _one_ of its factors. Cerebral processes and spinal -processes are the elements we analytically separate, as muscular -contractions are the elements of limb-movements. The synthetic unity -of these elements is a reflex; this we analytically decompose into -a sensation and a movement; and then we speak of sensation as the -reaction of the sensory organ, the movement as the reaction of the -muscular organ. By a similar procedure we separate the stimulation of -a sensory nerve from the reaction of the sensory organ, and that from -the reaction of the sensorium; and in this way we may come to regard -Cerebration as Thought. But those who employ this artifice should -remember that the organism is not an assemblage of organs, made up of -parts put together like a machine. The organs are differentiations of -the organism, each evolved from those which preceded it, all sharing in -a common activity, all _inter_-dependent. - -32. That co-operation of the Personality which is conspicuous in -conscious actions is also inductively to be inferred in sub-conscious -and unconscious actions. We know that a man reacts on an impression -according to his physical and mental state at the moment--that through -his individuality he feels differently, and thinks differently from -other men, and from himself at other epochs, and in other states. -Because he resembles other men in many and essential points we -conclude that he will resemble them in all; but observation proves -this conclusion to be precipitate. Other men see a blue color in the -sky, or feel awe at sight of the setting sun; but he has perhaps -not learned to discriminate this sensation, is not conscious of the -blue; nor has he learned to feel awe at the setting sun. Why--having -normally constructed eyes--does he not see the blue of the sky? For the -same reason that a dog, or an infant, fails to see it. The color has -no _interest_ for him (and all cognition is primarily emotion), nor -has this want of personal interest been rectified from an impersonal -source: he has never been taught to distinguish the color of the sky; -and his eye wanders over it with the indifferent gaze with which a -savage would regard a Greek codex. - -33. The point here insisted on, namely, that every reaction on an -impression is indirectly the reaction of the whole organism, and that -no organ detached from the organism has more significance than a word -detached from a sentence, is of far-reaching importance, and peculiarly -worthy of attention in considering the Reflex Theory, because almost -all the evidence urged in support of that theory presupposes the -legitimacy of concluding what takes place in the organism from what -is observed in an organ detached from its normal connections. No -experimental proof is necessary to show that many actions take place -unconsciously; the fact is undisputed. But does unconsciously mean -insentiently? It is certain that the unconscious actions take place in -a sentient organism, and involve organic processes of the same _order_ -as the actions which are conscious. It is also certain that many -sentient processes take place unconsciously. For thousands of years men -used their eyes, and saw as their descendants see, yet were unconscious -of the blue sky and green of the grass. Were their visual reactions -not of the same _order_ as our own? So far as the optic apparatus -is concerned, there cannot be a doubt on the point; yet in them the -sensorium having a somewhat different disposition--the neural elements -being differently combined--their reactions correspondingly differed. -They too had optical Sensibility, and visual sensations; but they did -not feel precisely what we feel. - -34. I have chosen these somewhat remote illustrations for the sake of -their psychological interest; but I might have confined myself to more -familiar examples. Thus the contents of the consciousness of a man born -blind cannot be _the same_ as the contents of one who has had visual -experiences, which will enter into the complex of every conscious -state, because the visual organs will have affected his sensorium; -nevertheless in the organism of the blind man there are conditions -so similar to those of other men, and his experiences will have been -so similar, that in spite of the modifications due to the absence of -visual experiences, his consciousness will in the main resemble theirs. -But now let us in imagination pursue this kind of modification, let us -take away hearing, taste, and smell, and we shall have proportionately -simplified the contents of consciousness--the reactions of the -sensorium--in thus simplifying the organism. There still will remain -Touch, Temperature, Pain, and the Systemic Sensations. There will still -remain an organism to react on impressions. So long as there is a -living organism, however truncated, there is a sentient mechanism. When -the brain has been removed, the removal causes both a _disturbance_ of -function and a _loss_ of function; the mechanism has been seriously -interfered with; yet all those parts of the mechanism which still -co-operate manifest their physiological aptitudes. The animal can live -without its brain, _ergo_ it can feel without its brain. Observation -proves this, for it discovers the brainless animal manifesting various -sensibilities, and combining various movements. The vision of the -brainless animal is greatly impaired, but it nevertheless persists. -The intelligence is greatly impaired, the spontaneity is reduced to a -minimum; but still both intelligence and spontaneity are manifested. - -35. The physiologist has only two conclusions open to him. Either -he holds Sensation to be a _property_ of nerve-tissue--and in that -case he must assign it to the spinal cord as to the brain; or else -he holds Sensation to be a _function_ of an organ--and in that case, -although analytically he may decompose the organism into separate -organs, assigning special sensations to the reactions of each, he must -still admit that in reality these organs only yield sensations as -component parts of the organism. The notion of a separate organ, such -as the brain, being the exclusive seat of sensation is thus seen to be -untenable. - -In popular phrase, “it is not the eye which sees, but the mind behind -the eye.” It is not the stimulus which is the _object_ felt--it is the -change in consciousness--the reaction of the sensorium. No one would -propound the absurdity that the retinal cells _see_, or the auditory -cells _hear_ (although by a conventional ellipsis these cells are said -to be “percipient” of colors and sounds), yet many writers have no -hesitation in asserting that the cerebral cells are the seats of these -and all other sensations. In a hundred treatises may be read the most -precise description of the transformation of molecular changes in the -retinal cells into molecular changes in the cerebral cells, where, it -is said, “we know that the stimulations become sensations.” Now who -knows this? How can it be known? Nay, who, on reflection, fails to see -that this cannot be so? If a sensation of sight were not much _more_ -than a molecular change in the cerebrum stimulated by a molecular -change in the optic tract, three conclusions would follow, each of -which is demonstrably erroneous:-- - -I. The cerebrum in a decapitated animal would respond by a sensation of -sight to a retinal stimulation. - -II. The animal deprived of its cerebrum could not respond by a -sensation of sight to a retinal stimulation. - -III. The same retinal stimulation would always produce the same -cerebral process and the same sensation; whereas the sensation depends -on the condition of the sensorium at the time. - -36. The difference between the Reflex Theory and that here upheld is -important in its general relations, and yet turns on a point which may -easily appear insignificant. The Reflex Theory asserts that when a -sensory nerve is stimulated, the excitation of the centre may either -subdivide into two waves, one of which passes directly to the brain -and there awakens sensation, the other passes over to the motor-roots -and causes muscular contractions; or, instead of thus subdividing, the -wave may pass at once to the motor-nerves, and then there is movement -without sensation. This is obviously a restatement in anatomical terms -of the observed fact that some reflexes take place consciously and -some unconsciously. But what evidence is there for this anatomical -statement? We have seen that there is none. According to all we -actually know, and reasonably infer, the continuity of tissue and the -irradiation of excitation are such that the stimulus wave must always -affect the whole system, so that brain and cord being structurally -united, their reactions must co-operate with varying energy dependent -on their statical conditions at the time.[243] - -37. The physiological fact that the irradiation is _restricted_ to -certain paths, and therefore only certain portions of the whole system -are excited to discharge--the fact that stimulation takes effect along -the lines of least resistance--is that which gives the Reflex Theory -its plausible aspect. But this fact of restriction is not dependent on -an _anatomical_ disposition of structure, it is, as we have already -seen (PROBLEM II. § 166), dependent on a fluctuating physiological -disposition--a temporary statical condition of the centres. And it -enables us to understand why the reflex action which is at one moment -a distinctly conscious or even a volitional action, is at another -sub-conscious or unconscious. When an object is placed in the hand of -an infant the fingers close over it by a simple reflex. This having -also been observed in the case of an infant born without a brain,[244] -one might interpret it as normally taking place without brain -co-operation, were there not good grounds for concluding that normally -the brain must co-operate. Thus if the object be placed in the hand of -a boy, or a man, the fingers will close, or not close--not according to -an anatomical mechanism, but according to a physiological condition: -if the attention preoccupy his sensorium elsewhere, his fingers will -probably close, probably not; if his sensorium be directed towards the -object, either by the urgency of the sensitive impression, or by some -one’s pointing to the object, the fingers will close or not close, -just as he chooses--perhaps the hand will be suddenly drawn away. The -centre of innervation for the fingers is in the cord, and from this -comes the final discharge of the sensitive stimulation; but the neural -processes which preceded this discharge, and were consequent on the -stimulation, were in each case somewhat different. In each case the -impression on the skin was carried to the cord, and thence irradiated -throughout the continuous neural axis, restricted to certain paths by -the resistance it met with, but blending with waves of simultaneous -excitations from other sources, the final discharge being the resultant -of these component forces. We may suppose the brain to be the seat -of consciousness, and yet not conclude that the brain was unaffected -because the fingers closed unconsciously; any more than we conclude -that the retina of the unoccupied eye is unaffected by light when with -the other we are looking through a microscope, and only _see_ objects -with this eye--though directly we attend to the impressions on the -other eye we see the objects which before were unseen. We know that the -muscles of the back are all involved in walking, standing, etc., but we -are seldom conscious of their co-operation till rheumatism or lumbago -makes us painfully alive to it. - -38. The two main positions of the Reflex Theory are, 1°, that -reflex actions take place without brain co-operation,--as proved by -observation of decapitated animals; 2°, that they take place without -brain co-operation,--as proved by our being unconscious of them. - -To these the answers are: 1°. The proof drawn from observation of -decapitated animals is defective, because the conditions of the -organism are then abnormal--there is a disturbance of the mechanism, -and a loss of some of its components. The fact that a reflex occurs -in the absence of the brain is no proof that reflexes when the brain -is present occur without its participation. 2°. The absence of -consciousness cannot be accepted as proof of the brain not being in -action, because much brain-work is known to pass unconsciously, and -there are cerebral reflexes which have the same characters as spinal -reflexes. - -39. A prick on the great toe traverses the whole length of the spinal -axis with effects manifested in various organs--the muscles of the -limb, the heart, the chest, the eyes, etc. The leg is withdrawn, -the heart momently arrested, the eyes turned towards the source of -irritation, the thoughts directed towards relief. These effects can -be observed--there are others which lie beyond our observation, and -can only be revealed by delicate experimental tests. But even the -observable effects are very fluctuating, because they depend on -fluctuating conditions. All we can say is, that so long as there is -continuity of structure, there must be continuity of excitation; -and the brain structurally connected with the centre of a sensory -impression, must necessarily co-operate more or less in the reactions -of that centre. In other words, the brain, although not the exclusive -seat of sensation, plays a part in every particular sensation, so long -as it forms a part of the stimulated organism. - -40. This view being so widely opposed to the views current in -physiological schools, I was gratified to find Dr. Crichton Browne led -by his researches to a conclusion not unlike it in essential features. -In his essay on the Functions of the Optic Thalami[245] (well worthy -of attention on other grounds) he says: “Allowing the spinal cord a -power of independent action, it may still be that it generally acts -reflexly through, or in association with, a superior centre. The -sensorial ganglia can undoubtedly act alone in a reflex manner, but -they almost invariably consult the cerebrum before dealing with the -impressions which they receive; so it may be that the spinal cord, -though capable of spontaneous reaction, may yet commonly refer to some -higher seat of compound co-ordination before sending forth an answer -to any message brought to it.” What is here stated as a possible and -occasional process, I consider to be a necessary and universal process. -Dr. Browne acutely remarks that if “what may be termed the encephalic -loop were an integral part of every reflex act, then the influence of -an intracranial lesion in checking reflex action would not be difficult -to understand”--and we may add the notorious influence of the brain in -arresting reflex actions, and modifying them by the will, which is only -explicable on the supposition that the cerebral and spinal centres are -functionally associated. Dr. Browne further remarks: “In experimenting -upon myself I have sometimes thought that when the toe is pricked the -sensation of pain actually precedes the movement of withdrawal; and -in experimenting upon patients with sluggish nervous systems I have -certainly noticed that after the pricking of the toe the little cry of -pain has anticipated the muscular contractions of the leg. Now this cry -of pain is a secondary reflex act through the sensorial centre; it is -the result of a discharge from efferent nerves from the summit of what -we have spoken of as the encephalic loop line; and we should certainly -not expect that it would be developed earlier than the primary -reflexion upon the motor apparatus, unless indeed what we have regarded -as the primary reflexion really itself took place by way of the loop -line.” - -41. The difference between a voluntary and involuntary act is not, I -conceive, that in the one case the brain co-operates and in the other -is inactive, but that while in both the brain co-operates, the state -of the sensorium known as mental prevision or ideal stimulation, is -present in the one, and absent or less conspicuous in the other. So -likewise the difference between a normal reflex action accompanied, and -the same action unaccompanied by consciousness, is not that the brain -co-operates in the one and is inactive in the other, but that the state -of the sensorium is somewhat different in the two cases. Movements -which originally were voluntary and difficult of execution--accompanied -therefore by brain co-operation--become by frequent repetition -automatic, easy of execution, and unconscious--they are then said to -depend on the direct action of the established mechanism. Granted. But -what are the components of this mechanism? Are they not just those -centres and organs which at first effected the movements? In becoming -easy and automatic, the movements do not _change their mechanism_--the -moving organs and the motor conditions remain what they were; all that -is changed is the degree of consciousness, i. e. the _state_ of the -sensorium which precedes and succeeds the movement. It is this which -constitutes the difficulty of the question. Some readers may consider -that all is conceded when unconsciousness is admitted. But this is -not so. My present argument is the physiological one that the brain -co-operates in reflex actions whenever the brain is structurally united -with the reflex centres; the psychological question as to whether -consciousness is also involved in this brain co-operation must be -debated on other grounds; and we have already seen that consciousness -operates in gradations of infinite delicacy. - -Observe a man performing some automatic action, such as planing a -deal board, or cutting out a pattern, which he has done so often that -he is now able to do it “mechanically.” It is certain that his brain -co-operates, and that he could not act thus with an injured brain; -yet he is said to act unconsciously, his brain occupied elsewhere as -he whistles, talks to bystanders, or thinks of his wife and children. -Yet the brain is acting as an overseer of his work, attentive to every -stroke of the plane, every snip of the scissors; and this becomes -evident directly his attention is otherwise absorbed by an interesting -question addressed to him, or an interesting object meeting his eye: -then the work pauses, his hands are arrested, and the automatic action -will only be resumed when his attention is released--when he has -answered your question, or satisfied himself about the object. - -42. This is a step towards understanding the co-operation of the brain -even in those connate reflexes which were not originally voluntary -acts, but were from the first organized tendencies, and are capable -of being realized in the absence of the brain. I admit that it is -difficult to find proof of brain co-operation here, though I think -the anatomical and physiological evidence render it highly probable. -But distinct proof to the contrary would not suffice for the Reflex -Theory--would not prove that reflex actions were insentient--unless -there had previously been proved that which seems to me contradicted -by the clearest and most massive evidence, namely, that the brain is -the sole seat of sentience. This contradictory evidence we will now -furnish. - - - - -CHAPTER III. - -INDUCTIONS FROM PARTICULAR OBSERVATIONS. - - -43. In the last chapter we surveyed the deductive evidence, from which -the conclusion was that Reflexion necessarily involves Sensibility, -but not necessarily any one particular _mode_ of Sensibility, such -as Consciousness, Pain, Discomfort, Attention, or the reaction of -any one of the special Senses. Although each or all of these modes -may be involved in the sensorial process which determines a reflex -act, each or all may be absent. Such is the fact of observation. This -fact is interpreted on the hypothesis that Reflexion is the exclusive -property of the spinal cord, as Sensation is of the brain. When we -come to examine the evidence for this hypothesis, we find it to move -in a circle: the brain is said to be the exclusive seat of sensation, -because reflex actions can be effected after its removal; and reflex -actions are said to be insentient because they take place in the -absence of the brain. - -A gentleman was one day stoutly asserting that there were no -gold-fields except in Mexico and Peru. A nugget, dug up in California, -was presented to him, as evidence against his positive assertion. -He was not in the least disconcerted. “This metal, sir, is, I own, -extremely _like_ gold; and you tell me that it passes as such in the -market, having been declared by the assayers to be undistinguishable -from the precious metal. All this I will not dispute. Nevertheless, -the metal is not gold, but _auruminium_; it cannot be gold, _because_ -gold comes only from Mexico and Peru.” In vain was he informed that -the geological formation was similar in California and Peru, and the -metals similar; he had fixed in his mind the conclusion that gold -existed _only_ in Mexico and Peru: this was a law of nature; he had no -reasons to give why it should be so; but such had been the admitted -fact for many years, and from it he would not swerve. He was not fond -of new-fangled notions, which, after all, would only lead us back to -the exploded errors of the past. To accept the statement that gold was -to be found elsewhere than in Mexico and Peru, would be to return to -the opinion of the ancients, who thought there was gold in the upper -regions of Tartary! - -Sensation is not tangible, assayable, like gold. We can understand, -therefore, that the very men who would make merry with the -_auruminium_, would accept easily such a phrase as “reflex action.” -The decapitated animal defends itself against injury, gets out of -the way of annoyances, cleans itself, performs many of its ordinary -actions, but is said to do these things without that Sensibility which, -if its head were on, would guide them. Even before the Reflex Theory -was invented this line of argument was used. Gall, referring to the -experiments of Sue, previously noticed, says that “Sue confounds the -effects of Irritability with those of Sensibility.”[246] Not gold, dear -sir, but _auruminium_! - -44. On investigating the phenomena we soon come upon two classes which -must cause hesitation. We find that the brain has its reflex processes, -of the same order as those of the cord; we find that these processes -may be conscious or unconscious, voluntary or involuntary; so that we -can no longer separate brain from cord on the ground of Reflexion. In -this respect, at least, the two are mechanisms with similar powers. -Turning now to the other class of phenomena, we find that precisely as -the brain is an organ of Reflexion, the cord is an organ of Sensation. -All the evidence we can have, from which to infer the presence of -sensation, is furnished by the sensorial processes in the cord. Remove -the brain, and the animal still manifests Sensibility, and this in -degrees of energy and complexity proportional to the mechanisms still -intact: some of these manifestations have the character of volitional -actions, some of automatic actions, some of Memory, Judgment, and -selective Adaptation. These we observe not indeed with the energy and -variety of such manifestations when the brain co-operates, since the -disturbance of the organism which is the consequence of the brain’s -removal--or the meagreness of the organism which is the correlative -of the brain never having been developed--must of course involve a -corresponding difference in the observed phenomena; but the point here -brought forward is that phenomena of the same _order_ are manifested by -organisms with or without a brain. - -45. Let us go seriatim through the evidence of these two classes:-- - - -CEREBRAL REFLEXES. - -While Theory separated the actions of the cord from those of the brain -on the ground of their being at times unconscious and involuntary, -Observation disclosed that this distinction could not be maintained. - -This step was taken by Dr. Laycock in 1840. In a striking paper[247] -read by him at the British Association in 1844, he brought together the -evidence on which his view was founded. The idea has been adopted and -illustrated in the writings of Dr. Carpenter, who now calls the action -“unconscious cerebration.” - -“I was led to this opinion,” Dr. Laycock says in announcing his view, -“by the general principle that the ganglia within the cranium, being -a continuation of the spinal cord, must necessarily be regulated as -to their reaction on external agencies by laws identical with those -governing the spinal ganglia and their analogues in the lower animals. -If, therefore, the spinal cord is a centre of reflexion, the brain must -also be one.” It is a matter of regret that Dr. Laycock did not extend -this principle, and declare that whatever was true of the _properties_ -of the cranial centres must also be true of the spinal centres; if the -brain have Sensibility, the spinal cord must also have it. - -Dr. Laycock refers to the curious phenomena of Hydrophobia in proof -that reflex actions may be excited by the optic nerves, or by a mere -idea of water. When a mirror was presented to a patient, the reflexion -of the light acting on his retina, in the manner of a reflexion -from the surface of water, produced a convulsive sobbing, as in the -attempt to swallow water, and the patient turned aside his head with -expressions of terror. Money was given him to induce him to look a -second time, but before he had looked a minute the same effect was -produced. - -The _idea_ of water excited similar convulsions. No sooner was it -suggested that the patient should swallow a little water than he seemed -frightened, and began to cry out. By kindly encouragements he was -brought to express his willingness to drink, but the _sound_ of the -water, as it was poured out again, brought on convulsions. In another -case, “on our proposing to him to drink, he started up, and recovered -his breath by a deep convulsive inspiration. On being urged to try, -he took a cup of water in one hand and a spoon in the other. With as -expression of terror, yet with great resolution, he filled the spoon -and proceeded to carry it to his lips; but before it reached his mouth -his courage forsook him, and he was forced to desist. He repeatedly -renewed the attempt, but with no more success. His arm became rigid and -immovable whenever he tried to raise it to his mouth, and he struggled -in vain against this spasmodic resistance.” - -In 1843 Griesinger--who appears to have known nothing of Dr. Laycock’s -paper--published his remarkably suggestive memoir on Psychical -Reflexes,[248] in which he extends the principle of Reflexion to all -the cerebro-spinal centres. The whole course of subsequent research -has confirmed this view; so that we may say with Landry, “L’existence -du pouvoir réflexe dans l’encéphale ou dans quelques unes de ses -parties établit une nouvelle analogie entre le centre nerveux cranien -et la moelle épinière.”[249] Indeed we have only to consider the -Laughter which follows a ludicrous idea, or the Terror which follows -a suggestion of danger,--the varying and involuntary expression of -Emotion,--and the curious phenomena of Imitation and Contagion,--to see -how large a place cerebral reflexion occupies. - -46. The existence of cerebral reflexion having been thus made manifest, -Dr. Carpenter classed all reflex actions under three heads: 1°, the -excito-motor, determined by the spinal cord; 2°, the sensori-motor, -determined by the ganglia at the base of the brain; 3°, ideo-motor, -determined by the brain. From all these Consciousness is absent. From -the first, he supposes Sensation to be absent. As an artifice, such -a classification may have its value, but it is physiologically and -psychologically misleading. It sustains the hypothesis of an imaginary -excito-motor mechanism. It restricts Sensibility to one of its many -modes. It fails altogether to connect Sensation with Thought, the Logic -of Feeling with the Logic of Signs. - -47. The view of Sensibility as common to the whole cerebro-spinal axis -is by no means new. Robert Whytt maintained it. Prochaska held that -the spinal cord formed the greater part of the _sensorium commune_; -and he adduced, in proof, the familiar facts of sensibility manifested -by headless animals. The next writer whom I can discover to have -held this opinion is J. J. Sue,--the father of the celebrated French -romance-writer,--who, in 1803, conceived that his experiments proved -the spinal cord to be capable of replacing, to a certain extent, the -functions of the brain.[250] Next came Legallois,[251] who undertook -to show, by a series of experiments, that the principle of sensation -and movement, in the trunk and extremities, has its seat in the spinal -cord. The mere division of the cord, he said, produces “the astonishing -result of an animal, in which the head and the body enjoy separate -vitality, the head living as if the body did not exist, and the body -living as if the head did not exist. Guinea-pigs, after decapitation, -seem very sensitive to the pain caused by the wound in the neck; they -alternately carry first one hind-leg and then the other, to the spot, -as if to scratch it. Kittens also do the same.” - -A few years afterwards, 1817, Dr. Wilson Philip concluded that “the -spinal marrow possesses sensorial power, as appears from very simple -experiments”; but he held the brain to be the _chief_ source of -sensorial power.[252] The following year, Lallemand supported this -opinion by the very curious phenomena exhibited by infants born without -brains: these infants breathed, swallowed, sucked, squalled, and gave -very unequivocal signs of sensibility. The value of such observations -consists in disproving the objection frequently urged against the -evidence of decapitated animals, namely, that in these animals the -spinal cord preserves the remains of a sensibility endowed by the brain. - -Longet here places an observation recorded by Beyer. A new-born infant, -whose brain, during the birth, had been completely extirpated (to save -the mother’s life), was wrapped in a towel, and placed in the corner -of the room, as a lifeless mass. While the surgeon was giving all his -care to the mother, he heard with horror a kind of murmur proceeding -from the spot where the body had been placed. In three minutes a -distinct _cry_ was heard. The towel was removed, and, to the surprise -of all, this brainless infant was seen struggling with rapid movement -of its arms and legs. It cried, and gave other signs of sensibility for -several minutes.[253] - -In 1828 Calmeil arrived at the same conclusion as that reached by -Legallois, Wilson Philip, and Lallemand. Indeed when, in 1833, the -Reflex Theory appeared, this opinion was so firmly rooted, that -we find Mr. Grainger combating it as the established error of the -day. He takes as much pains to show that physiologists are wrong in -attributing sensation to the spinal cord, as I am here taking to show -that they were right.[254] “It is, indeed, apparent,” he says, “that -the whole question concerning the truth or falsehood of the theory -which attributes the reflex power to the spinal cord hinges upon the -correctness or incorrectness of the received doctrines respecting the -seat of sensation and volition; so that until those doctrines are -proved to be false, it is impossible to establish the hypothesis of Dr. -Hall.”[255] - -The reader is requested to take note of this, because when we come to -the evidence which proves the spinal cord to be a centre of sensation, -we shall find that the _only_ ground for rejecting that evidence is the -assumed truth of the Reflex Theory, coupled with the assumption of the -brain being the exclusive seat of sensation. Whereas if the evidence -proves that the spinal cord _is_ a sensational centre, then the Reflex -Theory is destroyed, and cannot be urged against such evidence. - -48. Thus many of the facts which prove the sensational function of -the spinal cord were known, and even a vague conception of their real -significance was general, until the Reflex Theory came to explain -all such facts as the results of mechanical adjustment, and of a new -nervous principle called “Reflexion.” For many years this theory has -reigned, and met with but little opposition. Yet the true doctrine has -not wanted defenders in Germany. Nasse[256] denied that decapitated -animals showed no spontaneity; he asserted that they exhibited clear -signs of mental activity. Carus sarcastically pointed out that the -_word_ “reflex” was replacing “irritability,” as a key to unlock all -puzzles; and he took up a position which is very similar to the one -occupied in these pages, namely, that the spinal cord being formed of -gray matter as well as of fibres, it must have sensibility and power of -reacting on nervous stimulus, no less than conductibility; that, in -fact, it is a centre, and must act like all other nerve-centres.[257] -J. W. Arnold opposed the Reflex Theory in a very remarkable little -work, in which he vindicates the claim of the spinal cord as a sensory -and motor centre, although denying to its actions any volitional -character.[258] This was in 1844. Eleven years elapsed without any -further opposition, when Edward Pflüger, in 1853, published his work -on the Sensorial Functions of the spinal cord.[259] In this work he -recurred to the old views of Prochaska and Legallois; but although he -attacked Marshall Hall with merciless severity, he did not point out -the fundamental error of the Reflex Theory, which theory he seems to -accept. Nor did he give his views that philosophical and anatomical -basis which could alone render his interpretations acceptable. Added to -this, the tone of asperity in which his work was written, created some -prejudice against him; and thus, while many admitted his facts, they -rejected his conclusions.[260] - -In 1858 Professor Owen read a paper of mine at the Leeds meeting of -the British Association, on “The spinal cord as a centre of Sensation -and Volition,” in which a rapid indication of my point of view, and -an account of some experiments to illustrate it, were given--_not_, I -believe, conclusive to any of the audience. Indeed, the subject was -too vast to be discussed in such a paper; and my object was rather to -excite new inquiry, than to make converts to a view which could only be -embraced after a thorough reinvestigation of the dominant theories. - -In 1859 appeared Schiff’s work;[261] and here we find a large space -allotted to the discussion of Pflüger’s doctrine. Schiff, whose -immense experience as an experimentalist, and whose acuteness and -caution every one will highly estimate, frankly pronounces in favor -of the sensational character of spinal actions; but he denies that -they are volitional, and objects strongly to the introduction of -any such idea as that of “psychical activity.” He thinks it utterly -untenable to suppose that impressions have reactions in the brain -which they have not in the spinal cord:--if one has sensibility, the -other must have it; and he thinks that, so far from the actions of the -cord being distinguishable from those of the brain by the character -of “reflexion,” and depending on a mechanical arrangement--_all_ -actions, cerebral or spinal, are reflex; _all_ depend on a mechanical -arrangement.[262] - -Since that time there has been the remarkable work of Goltz, so -often cited in these pages,[263] and his subsequent experiments on -dogs, which (although he does not decisively adopt the views of -Pflüger) furnish ample evidence that sensation and volition cannot be -exclusively localised in the brain. - -49. Heubel’s interesting experiments[264] show that a frog may be -thrown into a state of profound sleep by the withdrawal of all external -stimulation, and in this state will remain lying on its back for hours. -Now this position is one so very uncomfortable that, when awake, the -frog will not retain it a moment, if free to turn round; and when -asleep, a prick on the toe, a sudden noise, or a beam of light will -awaken it, causing it to turn. That is to say, the withdrawal of the -normal stimuli so lowers the sensibility of the frog’s nerve-centres, -that he does not feel the effects of the unusual position, but feels -them directly the centres are stimulated into activity. All this is -intelligible enough on the supposition of the state of sleep being -dependent on a lowering of the cerebral activity. But what shall we -say on learning that precisely the same phenomena are manifested by a -brainless frog? Every one knows that the brainless frog is intolerant -of lying on its back, and immediately turns round, if placed on it. Yet -the brainless frog may be thrown into deep sleep by the same exclusion -of external stimuli; from which he also will be awakened by a prick, -a noise, or a beam of light; and no sooner is he awakened than he at -once turns round. Were the brainless frog incapable of sensation, a -prick on his toe would cause a simple reflex withdrawal of the leg; -but this is not the effect; on the contrary, the stimulus excites the -whole spinal cord, and whatever sensation of discomfort may be caused -by the abnormal position of the limbs in an uninjured awakened frog, is -excited in the brainless frog. - -50. I need not swell this chapter with examples of Sensibility in -animals deprived of the brain; many have already been given, and -any text-book of Physiology will supply more. No one disputes the -observations, only the inference that these manifestations were -sentient: they are said to have been merely mechanical reflexes. If, -however, we can detect in them _some_ evidence of what all recognize as -peculiarly characteristic of Mind, the mechanical interpretation will -be less plausible. - -At the outset the reader must be warned against exaggerating and -distorting the bearing of my remarks, and must not suppose that I -disregard the vast differences between the Logic of Signs which -belongs to Thought, and the Logic of Feeling which belongs to -Sensation, nor suppose that I look upon the spinal cord as a mental -organ having the _same_ functions as the brain. All that I wish to -establish is the common character of spinal and cerebral processes, -modified as each is by the character of the actions initiated by the -process. - -51. This premised, let us begin with the evidence of - - -DISCRIMINATION. - -Although this process is usually regarded as purely psychological, it -must obviously have its physiological side; we find it in Sensation as -in Ideation, and may expect to find it in unconscious as in conscious -processes--in a word, in all sensorial processes whatever. Place a -bit of marble on your tongue, and it will be touched, but not tasted: -the sensations of contact and temperature will excite reflexes, but -little or no reflexes from parotid and salivary glands. A difference in -sensation has a corresponding difference in reflex action; which may be -made evident by removing the tasteless marble, and replacing it by a -pinch of carbonate of lime, i. e. the marble in another state reduced -to a powder: this will excite a sensation of taste, and a secretion -from the glands. In both cases your sentient organism was affected, but -it reacted differently because the difference of the stimulation was -discriminated: consciously or unconsciously, you _felt_ differently. -Again: touch the back of your mouth with your finger, or a feather, and -a convulsive contraction of the gullet responds, followed by vomiting, -if the excitation be renewed. Yet these same nerves and muscles respond -by the totally opposite action of swallowing, if instead of the -stimulation coming from your finger, it come from the pressure of food -or drink. - -Analogous experiments on animals without their brains yield similar -results.[265] The salivary secretion and the ordinary reactions of -Taste are provoked by sapid substances. Still more conclusive are the -observations made on a dog whose spinal cord has been divided, and -who therefore according to the reigning ideas is incapable of feeling -any impression made on parts below the section. A pencil inserted in -the rectum causes a reaction of the muscles energetically resisting -the entrance of this foreign body; yet this rectum so sensitive in -its reaction on the stimulus of the pencil, responds by the totally -different reaction--the relaxation of the muscles--on the stimulus of -fæcal matters. - -52. “This is all mechanical,” you say? Mechanical, no doubt, as all -actions are; but the question here is whether among the conditions of -the mechanical action Sensibility has a place? The answer can only be -grounded on induction. The actions of the dog are analogous to the -actions which you know were sentient in yourself. There was in both a -discrimination, in both a corresponding reaction. I admit that what is -here called “discrimination” is the application of a logical term to a -mechanical process; I admit that if the spinal mechanism is insentient, -the fact of discrimination may still be manifested; but I conceive -that the many and coercive grounds for admitting that the mechanism is -sentient gain further support in the evidence of discrimination. Every -particular sensation has its corresponding reaction; and although this -has been acquired during ancestral or individual experiences, so that -in the majority of cases there is no consciousness accompanying the -operation, this, as we have seen, is not a valid argument against the -existence of a sensorial process. We have only to lower the Sensibility -of the cord by anæsthetics, or to _preoccupy_ its energies by some -other excitation, and the reaction fails. - - -MEMORY. - -53. “But discrimination, if not a purely physical process, implies -Memory?” No doubt. And what is Memory--on its physiological side--but -an organized tendency to react on lines previously traversed? As -Griesinger truly says: “There is Memory in all the functions of the -central organs, including the spinal cord. There is one for reflex -actions, no less than for sense-images, words, and ideas.” Gratiolet -makes a similar assertion.[266] Indeed if, as we have seen, reflex -actions are partly connate, and partly acquired, it is obvious that the -second class must involve that very reproduction of experiences, which -in the sphere of Intellect is called Memory. - -There is assuredly something paradoxical at first in this application -of the terms of the Logic of Signs, yet the psychologist will find -it of great service. But if the terms discrimination and memory -be objected to, they may be replaced by some such phrase as the -“adaptation of the mechanism to varying impulses.” On its objective -side, Discrimination is Neural Grouping; on its subjective side, it is -Association of experiences. - - -INSTINCT. - -54. If we can detect evidences of Volition and Instinct in the -absence of the brain, our thesis may be considered less questionable. -And such evidence there is. Goltz decapitated a male frog (in the -pairing season), and observed that it not only sought, grasped, and -energetically embraced a female, but could always discriminate a -female from a male. Thus when a male frog closely resembling a female -in size and shape was presented to this decapitated animal, he clasped -it, but rapidly let it go again, whereas even the dead body of a -female was held as in a vice. Goltz tried to _delude_ this brainless -animal in various ways, always in vain. Only a female would be held -in his embrace. Goltz then presented a female in a reversed position, -so that the head was grasped by the male. Now here, had there been -simply a reflex machine, incapable of sentient discrimination, the -clutched female would have been held in this position, just like any -other object which excited the reflex; there would have been no “sense -of incongruity,” such as Goltz noticed in his frog, who at once began -a series of movements by which he was enabled, without letting the -female escape, to bring her into the proper position. To render this -observation still more significant, I may add that Goltz did not find -all male frogs act thus--many relinquished the female thus improperly -presented to them. Such phenomena observed in frogs possessing brains, -would be accepted as evidence of sexual instinct and volition. - -Further: Goltz removed the brain from a frog, which he then held -under water, gently pressing the body so as to drive the air out of -its lungs; the body being then heavier than the water sank to the -bottom, where it remained motionless. He repeated this procedure with -another frog, not brainless but blinded. This one sank also, but in a -few minutes rose to the surface to breathe. This difference naturally -suggests that the brainless frog was insensible of the condition which -in the other caused a movement of relief. The one felt impending -suffocation, the other felt nothing. Such was the interpretation of a -German friend in whose presence I repeated the experiment. But I had -been instructed by Goltz, and bade my friend wait awhile. He did so, -and saw the brainless frog slowly rise to the surface and breathe there -like his blinded companion. So that the only difference observable was -in the lessened sensibility of the brainless frog. - -55. But Goltz records a still more conclusive case. In a large vessel -of water he inverted a glass jar also containing water, which could -then only be retained in the jar by atmospheric pressure. Through the -neck of this inverted jar he thrust a blinded frog, not having pressed -the air out of its lungs. It rose at once in the jar, touching the -inverted bottom with its nose, and when the necessity of fresh air -was felt, the frog began restlessly feeling about the surface of its -prison till an issue was found in the neck of the jar, through which it -dashed into the vessel, and at once rose to the surface of the water -to breathe. In this observation are plainly manifested the stimulation -of uneasy sensation, the volition of seeking relief, and the -discrimination of it when found. If this frog was a sentient mechanism, -what shall we say to the fact that a brainless frog was observed to -go through precisely the same series of actions? Goltz pertinently -remarks: “So long as physiologists satisfied themselves that the -brain was the sole organ of sensation, it was easy to declare all the -actions of the brainless animal to be merely reflex. But now we must -ask whether the greater part of these actions are not due to the _power -of adaptation_ in the central organs, and are therefore to be struck -out of the class of simple reflexes? If I bind one leg of a brainless -frog and observe that he not only sees an obstacle, but crawls aside -from it, I must regard these movements as regulated by his central -power of adaptation; but now suppose I unbind the leg and remove the -obstacle, then if I prick the frog he hops forward. Must I now declare -this hop to have been a simple reflex? Not at all. In both cases the -physiological processes have been similar.” - - * * * * * - -56. There are no doubt readers who will dismiss all evidence drawn -from experiments on frogs, as irrelevant to mammals and man. Let us -therefore see how the evidence stands with respect to animals higher -in the scale, endowed with less questionable mental faculties. In a -former chapter (PROBLEM II. § 29) we recorded the marked results of -removing the cerebral hemispheres; and at the same time suggested that -these by no means justified the conclusion usually drawn respecting -the hemispheres as the exclusive seat of sensation. And this on two -grounds: First, because the absence of some sensitive phenomena does -not prevent the presence of others: the mutilated organism is still -capable of manifesting Sensibility in those organs which remain intact. -Secondly, because were the mutilation followed by total destruction of -Sensibility, this would not prove Sensibility in the normal organism to -have its seat in the part injured. If the removal of a pin will destroy -the chronometric action of a watch, we do not thence infer that the -chronometric action was the function of this pin. And this objection -has the greater force when we remember that one hemisphere may be -removed without the consequent loss of a single function, and both may -be removed without the loss of several functions usually ascribed to -cerebral influence.[267] - -57. Consider the analogous effects of injuries to or removal of -the Cerebellum, in causing disturbance of locomotion, whence the -conclusion has been drawn that the Cerebellum is the exclusive organ -of muscular co-ordination, in spite of the unquestionable evidence -that very many muscular co-ordinations still persist after this organ -is removed. What is the part played by the Cerebellum I do not pause -here to examine.[268] I only say that the movements of swimming, -sucking, swallowing, breathing, crying, micturition, defecation, -etc., are co-ordinated as well after removal of the Cerebellum as -they were before, and that consequently _their_ co-ordination has not -its seat in the Cerebellum. The parallelism is obvious. Removal of -the Cerebrum causes a disturbance in the combination of sensations, -and the execution of certain sense-guided actions, but causes little -appreciable disturbance in others. Removal of the Cerebellum causes -a disturbance in the combination of certain muscular sensations, and -the execution of certain co-ordinated actions, with little appreciable -disturbance in others. - -58. So little have the facts been surveyed and estimated in their -entirety that there is perhaps no subject on which physiologists are -more agreed than on the function of the Cerebellum being that of -co-ordination. Yet consider this decisive experiment. I etherized -three healthy frogs, from one I removed the entire cranial centres; -from another I removed only the cerebellum; and, leaving the third -in possession of an intact encephalon, I made two sections of the -posterior columns of the spinal cord. The two first hopped, swam, -used their legs in defence, and exhibited a variety of muscular -co-ordinations, although in both the supposed organ of co-ordination -was absent. Whereas the third, which had this organ intact, and -was capable of moving each limb separately, and each pair of limbs -separately, was utterly incapable of moving all four simultaneously. -Why was this? Obviously because in the first two frogs the motor -mechanism remained intact, and only the cerebral and cerebellar -influence was removed; in the third frog the sensory part of the -motor mechanism had been divided, and no combination of the limbs was -possible. - -59. Physiological induction agrees with anatomical induction in -assigning to the cerebrum and cerebellum the office of _incitation_ -and _regulation_ rather than of _innervation_; for, as we have seen, -no nerve issues directly from them (PROBLEM II. § 7). Consequently the -effects of injuries to these centres are losses of spontaneity and of -complexity in the manifestations. Inasmuch as in the intact organism -all sensory impressions are propagated throughout the nervous centres, -the reactions of these highest centres will enter into the complex of -every adjusted movement; so the abolition of these centres will be the -dropping of a link in the chain, the abolition of a special element -in the complex group. The organs which are still intact will react, -each in its own way, on being stimulated; but the reaction will be -without the modifying influence of the absent centres. For instance, -the retinal stimulation from a luminous impression normally calls up a -cluster of associated feelings derived originally from other senses, -and a perception of the object is associated with emotions of desire, -terror, etc., according to the past history of the organism, and its -organized reactions, due to hereditary or acquired experiences. It -is these which form the complex feeling discharged in the particular -movement of prehension, or flight. Remove the brain, and there can be -no longer _this_ cluster of associated neural groups excited; there -will be therefore no emotion, simply the visual sensation, and such a -movement as is directly associated with it. The brainless dog moans -when hurt, it does not bark at the cat which it nevertheless sees, -and avoids as a mere obstacle in its path; the cat will cry, it will -not mew. The present pain moves the vocal organs, but does not revive -associated experiences. All those combinations by which a series of -dependent actions result from a single stimulation are frustrated when -the mechanism is disturbed, so that the mutilated animal can no longer -recognize its prey or its enemy, to feed on the one and fly from the -other; no longer builds its habitation, or rears its offspring. It -can still live, feed, sleep, move, and defend itself against present -discomfort; it cannot find its food, or protect itself against -prospective discomfort. We must supply the place of its Intelligence. -We must give it the food, and protect it from injuries. - -There is therefore ample evidence to show that what is specially known -as Intelligence is very imperfect after the cerebral influence has been -abolished; but this does not prove the Cerebrum to be the exclusive -seat of Intelligence, it only proves it to be an indispensable factor -in a complex of factors. Still less does it prove the Cerebrum to be -the exclusive seat of Sensation, Instinct, Volition; for these may be -manifested after its removal, although of course even these will be -impaired by the loss of one factor. - -60. And here an objection must be anticipated. In spite of the -familiar experience that one mode of Sensibility may be destroyed -without involving the destruction of other modes, there is a -general belief--derived from a mistaken conception of what is really -represented by the unity of Consciousness--that Consciousness -disappears altogether when it disappears at all; and hence, since -Sensation is supposed to imply Consciousness, it also cannot be -divisible, but must vanish altogether if it vanish at all. The first -answer is that Sensation as an abstraction is neither divisible nor -indivisible; but as a generalized expression of concrete sensorial -processes it is reducible to these processes, and divisible as -they are. No one doubts that we may lose a whole class of special -sensations--sight, hearing, pain, temperature, etc.--yet retain all -the others. No one doubts that we may lose a whole class of registered -experiences--forget a language, or lose memory of places so familiar as -the streets of the small town we inhabit, or of faces so familiar as -those of friends and relatives, while the names of these streets and -friends are still remembered when the sounds are heard. Yet sensation -and intelligence are not wholly lost. The mind is still erect amid -these ruins.[269] - -61. This premised, let us consider the experimental evidence. Flourens -declares that when he removed the whole of the Cerebrum from pigeons -and fowls, they lost _all_ sensation, _all_ perception, _all_ instinct, -and _all_ volition. They lived perfectly well for months after the -operation, if the food were placed in their mouths; but they never -_sought_ their food; they never _took_ it, even when their beaks were -plunged into it: they could swallow, and digest the grains; but they -had no instinct to make them seek, no volition to make them pick up -the grains. They _saw_ nothing, although the iris remained irritable; -they heard nothing; they could not smell. A state of stupor came on, -resembling that of deep sleep. All voluntary action ceased. If they -were thrown into the air, they flew; if irritated, they moved away; but -if left to themselves, they remained motionless, with the head under -the wing, as in sleep. Now, inasmuch as these effects always ensue -when the Cerebrum is removed, and _never_ when only the Cerebellum is -removed, he concludes that all instincts, volitions, and sensations -“belong exclusively to the cerebral lobes.” - -But all experimenters do not agree in other points named by Flourens; -nor in the conclusions he has drawn. On the contrary, it is very -certain, and we find evidence even in Flourens himself, that all -instincts and all sensations are _not_ destroyed by the removal of the -cerebral lobes. - -62. Let us hear Bouillaud on this subject.[270] He repeated the -experiment of Flourens, removing the whole of the Cerebrum from -the Brain of a fowl; and he thus records his observations: “This -fowl passes the greater part of her time asleep, but she awakes at -intervals, and _spontaneously_. When she goes to sleep, she turns her -head on one side and buries it in the feathers of the wing; when she -awakes, she shakes herself, flaps her wings, and opens her eyes. In -this respect there is no difference observable between the mutilated -and the perfect bird. She does not seem to be moved at all by the -noise made round about her, but a very slight irritation of the skin -suffices to awaken her instantaneously. When the irritation ceases, -she relapses into sleep. When awake, she is often seen to cast stupid -glances here and there, _to change her place, and walk spontaneously_. -If put into a cage, _she tries to escape_; but she comes and goes -without any purpose, or rational design. When either foot, wing, -or head is pinched, she withdraws it; when she is laid hold of, she -_struggles to escape, and screams_; but no sooner is she liberated than -she rests motionless. If severely irritated, she screams loudly; but -it is not only to express pain that she uses her voice, for it is by -no means rare to _hear her cackle and cluck a little spontaneously_; -that is to say, when no external irritation affects her. Her stupidity -is profound; she knows neither objects nor places, nor persons, and is -completely divested of memory in this respect: not only does she not -know how to seek or take food, she does not even know how to swallow it -when placed in her beak--it must be pushed to the throat. Nevertheless -her indocility, her movements, her agitation, attest that she _feels_ -the presence of a strange body. Inasmuch as external objects excite in -her no idea, no desire, she pays no attention to them; but she is not -absolutely deprived of the power of attention, for if much irritated -her attention is awakened. She knows not how to escape an enemy, nor -how to defend herself. All her actions, in a word, are blind, without -reflexion, without knowledge.” - -In this recital, the evidence both of _sensation_ and _instinct_ is -incontestable, to any unprejudiced mind. Bouillaud, in commenting -on his observations, remarks, that assuredly _all_ sensation was -not destroyed, since the sensibilities of touch and pain were very -manifest. Nor is it certain, he says, that the fowl heard nothing, saw -nothing. It is true that she stumbled against objects, and knew not how -to avoid them. She opened her eyes on awaking, looked about, and showed -a sensibility in the pupil to light; which, he thinks, is incompatible -with the absence of all sensation of sight - -63. The experiments of Longet[271] seem decisive on this latter point. -Having removed the whole of the Cerebrum from a pigeon, he observed -that whenever he approached a light brusquely to its eyes, there was -contraction of the pupil, and even winking; but, what was still more -remarkable, “when I gave a rotatory motion to the candle, and at such -a distance that there could be no sensation of heat, the pigeon made -a similar movement with its head. These observations, renewed several -times in the presence of persons who were at my lectures, left no -doubt of the persistence of sensibility to light after removal of the -cerebral lobes.” We have only to think of the baby following with its -eyes the light moved before it, to understand the kind of impression -produced by the candle on the pigeon. Longet also declares that his -experiments prove the existence of sensations of sound, after removal -of the whole cerebrum. - -64. Dr. Dalton, giving the results of numerous experiments he -performed, says that removal of the Cerebrum plunges the animal in -“a profound stupor, in which he is _almost_ entirely inattentive to -surrounding objects.... Occasionally the bird opens its eyes with a -vacant stare, stretches his neck, perhaps shakes his bill once or -twice, or smoothes down the feathers upon his shoulders, and then -relapses into his former apathetic condition. This state of immobility, -however, is _not_ accompanied by the loss of sight, of hearing, or of -ordinary sensibility. _All these functions remain, as well as that -of voluntary motion._ If a pistol be discharged behind the back of -the animal, he at once opens his eyes, moves his head half round, and -gives evident signs of having heard the report; but he immediately -becomes quiet again, and pays no further attention to it. Sight is also -retained, since the bird will sometimes fix its eye on a particular -object, and watch it for several seconds together.”[272] - -While, therefore, Flourens concludes from his experiments that the -Cerebrum is the seat of _all_ sensation and all volition; and Bouillaud -concludes that it is most probably the seat of _none_; Dr. Dalton -concludes that the functions of the Cerebrum are restricted to those -usually classed as intellectual. “The animal,” he says, “is still -capable, after removal of the hemispheres, of receiving sensations -from external objects. But these sensations appear to make upon -him no lasting impression. He is incapable of connecting with his -perceptions any distinct succession of ideas. He hears, for example, -the report of a pistol, but he is not alarmed by it; for the sound, -although distinctly perceived, does not suggest any idea of danger or -injury. The memory is altogether destroyed, and the recollection of -sensations is not retained from one moment to another. The limbs and -muscles are still under the control of the will; but the will itself -is inactive, because apparently it lacks its usual mental stimulus and -direction.”[273] - -Dr. Dalton reminds us how disturbance of the cerebral functions in -human beings recalls these observations on animals. “In cases of -impending apoplexy, or of softening of the cerebral substance, among -the earliest and most common phenomena is a loss or impairment of -the memory. The patient forgets the names of particular objects, or -particular persons; or he is unable to calculate numbers with his usual -facility. His mental derangement is often shown in the undue estimate -which he forms of passing events. He is no longer able to appreciate -the true relation between different objects and different phenomena. -Thus he will show an exaggerated degree of solicitude about a trivial -occurrence, and will pay no attention to other matters of importance. -As the difficulty increases, he becomes careless of the directions and -advice of his attendants, and must be watched and managed like a child -or an imbecile. After a certain period he no longer appreciates the -lapse of time, and even loses the distinction between day and night. -Finally, when the injury to the hemispheres is complete, the senses may -still remain active and impressible, while the patient is completely -deprived of intelligence and judgment.”[274] - -65. Having seen how far other experimenters are from confirming the -conclusions of Flourens, let us glance at his record of observations, -and we shall find there evidence that _all_ sensation and _all_ -volition cannot be localized in the Cerebrum. Speaking of a fowl whose -Cerebrum was removed the day before, he says: “She shakes her head -and feathers, sometimes even she cleans and sharpens them with her -beak; sometimes she changes the leg on which she sleeps, for, like -other birds, she sleeps habitually resting upon one leg. In all these -cases she seems like a man asleep, who, without quite waking, changes -his place, and reposes in another, from the _fatigue_ occasioned by -the previous posture: he selects one more _comfortable_, stretches -himself, yawns, shakes himself a little, and falls asleep again.... On -the third day the fowl is no longer so calm; she comes and goes, but -without motive and without an aim; and if she encounters an obstacle -on her path, she knows not how to avoid it.”[275] In his second work -he remarks of a Duck operated on in the same way: “As I mentioned last -year _à propos_ of fowls, the duck walks about oftener, and for a -longer time together, when it is fasting, than when it is fed.” - -Here he observes the unmistakable evidence of feelings of Hunger, -Fatigue, and Discomfort in animals which, according to him, have lost -_all_ sensation. He also observes the operation of instinct (cleaning -the feathers), and of spontaneous activity (walking about), in animals -said to have lost _all_ instinct and _all_ volition. - -66. Still more decisive are the observations recorded by other -experimenters. Leyden removed the hemispheres _and_ the ganglia at -their base from a hen; yet this hen moved about and clucked. Meissner -noticed that a pigeon whose hemispheres had been removed always uttered -its _coo_, and showed restlessness at the usual feeding-time.[276] -Voit carefully extirpated the cerebrum from some pigeons, and kept -them for many months in health. For the first few weeks they exhibited -the well-known stupor. Then they began to shake this off, open their -eyes, walk, and fly about _spontaneously_. They gave unmistakable -signs of seeing and hearing. But the chief defect was in the inability -to feed themselves, and the complete insensibility to danger. They -also manifested signs of sexual feeling with lively cooings; though -quite unable to gratify their desires.[277] Vulpian having removed -the cerebrum, optic thalami, and corpora striata from a young rabbit, -found that on pinching its tail it cried out and struggled to -escape; and a rat thus mutilated not only struggled and cried when -pinched, but manifested strong emotion. “Il est très craintif, très -impressionable; il bondit pour peu qu’on le touche; le moindre bruit le -fait tressaillir. Un certain bruit d’appel fait avec les lèvres, ou un -soufflet brusque imitant celui qu’emettent les chats en colère excitent -chez le rat une vive émotion.”[278] - -67. There are several well-authenticated cases on record of children -born without a vestige of brain, and others with only a vestige, who -nevertheless manifested the ordinary signs of sensation. I will cite -but one, and it shall be one for which an illustrious physiologist, -Panizza, is the guarantee. A male infant, one of twins, who lived but -eighteen hours, during that period manifested such unquestionable signs -of Sensibility as the following: the pupils contracted under light, -sharp sounds caused flutterings, and a bitter solution when placed in -the mouth was instantly rejected. This infant had not a vestige of -cerebrum, cerebellum, or cerebral ganglia. The medulla oblongata was -normal. There were no olfactory nerves, and the optic nerves terminated -in a little mass of membrane.[279] - -68. The observations of Lussana and Lemoigne are both extensive and -precise, and the conclusion at which they arrive is that the removal -of the Cerebrum is the abolition of Intelligence and Instinct, but is -not the abolition of Sensation. Whereas Rolando, and after him Renzi, -consider that only the Intelligence is abolished, the supposed loss -of Instinct being really nothing more than the loss of the directive -influence which makes the Instinct to be executed. - -69. Here it becomes needful to understand - - -THE MECHANISM OF INSTINCT. - -Were we dealing with an ordinary mechanism, and the disturbances -produced in its actions by the removal of any part, we should attribute -all observed effects to _interference with the conditions of dependent -sequence_: we should infer that the actions were imperfectly performed, -or wholly abolished, because their requisite mechanical conditions were -disturbed. Let us be equally precise in dealing with the physiological -mechanism. If we have deprived it of an organ in which certain -combinations are effected, we must expect to find all actions which -were dependent on such combinations to be now impossible; but all the -actions which are not directly dependent on these combinations may -still be possible. The actions of feeding, for example, are determined -by certain sensations, when these are present in a particular sequence, -but not otherwise; the sensation of sight does not suffice, because -the animal must not only _see_ the food, he must _perceive_ it. The -action of defence and flight are also determined by certain sensations, -but only when these are connected in a certain sequence: the brainless -animal will defend itself, or move out of the way, under the stimulus -of unpleasant sensation; but will not be moved by a _prospective_ -injury, because he fails to associate it with the sight of the -threatening object. In the same way a blind man shrinks at the actual -contact of the heated poker, but does not shrink at the approach of -that poker which he does not see. We do not deny him the possession -of the so-called instinct of Self-preservation on this ground; why -deny it to the brainless animal? The brainless fish or frog swims when -placed in the water, because the sensation from the _moving_ water[280] -sets going the swimming mechanism. To call this a “swimming instinct” -may seem extravagant; yet it is as fully entitled to the name as -Self-defence is, or the Alimentary Instinct. In all three cases there -is a connate mechanism set going by appropriate feelings. - -70. Since all admit that there is an Alimentary Instinct, let us see -what kind of mechanism it implies. There must be a state of feeling -called Hunger, which--combined with other feelings--determines certain -muscular adjustments in the search, recognition, capture, and finally -the swallowing of the food:--a very complex series of actions, which -lead to and sustain one another until the desire is gratified. On the -mental side there are three constituents, all indispensable: the -hunger must be felt, the food must be discriminated, the desire must -be gratified; on the physical side there are also the indispensable -arrangements of the motor mechanism. Now it is obvious that the -_entire_ mechanism of this instinct cannot be localized in the brain, -even if its mental elements are localized there; and there is reason -to believe that even the mental elements--the feelings of hunger, -discrimination, and gratification--are not exclusively localized there. -The brainless animal manifests if not the feeling of Hunger, at any -rate that feeling of discomfort which is the basis of Hunger. The -restlessness is that of a hungry animal. Now we know that some of the -Systemic Sensibility is preserved, for we see the animal breathing, -swallowing, urinating, sleeping, preening its feathers, changing its -attitude, resting on one leg after the fatigue of the other, etc. We -may therefore infer that other systemic sensations, such as Hunger and -Thirst, arise under the usual conditions. - -71. We have noted an indication of Hunger; but on further observation -we discover that although the food is eaten, if brought within reach -of that portion of the feeding mechanism which is still intact, yet -the second step--the feeling of recognition--is wanting. The animal -fails to perceive the food brought under his eyes, or even placed in -his mouth; unless the back part of the mouth be touched, no swallowing -takes place. Hence the animal can no longer feed himself, and is -therefore said to have lost his instinct. But although the mechanism -of the instinct has been _disturbed_, its action is not wholly -abolished. The brain is necessary for that combination of adjustments -which normally accompany the perception of food through sight and -scent; and its absence of course frustrates such combination; but we -shall presently see that although certain sensible marks by which a -perception is guided are absent, others may still be present, and -suffice. - -72. Before adducing examples let me say that we cannot legitimately -attribute the abeyance of an instinct solely to the absence of the -brain, 1°, because we observe a similar abeyance of the instinct and -frustration of perception, even when the brain is present, and the -animal is in its normal state. 2°. On the other hand, some instincts -are unmistakably manifested, and some perceptions excited, after the -brain has been removed. In fact, all that is needful is that some of -the mental elements of such perception and such instinct be preserved; -and this is the case so long as the leading element is present. - -73. On the first point consider this unequivocal example. A healthy, -hungry frog may be placed in a vessel in which lie a quantity of dead -flies. He sees these flies, but sight is not enough; to him they are -only so many black spots, in which he does not recognize his food, -because the flies do not move, and the _leading element_ in his -perception of food is not a _colored_ form, but a _moving_ form. Hence -this frog, in spite of brain and an intact organism, will starve amidst -appropriate food. Whereas the frog that will not snap at motionless -flies snaps at any other small moving object, though it be not his -food. Goltz observed one incessantly snapping at the moving tentacles -of a slug which was in the vessel--as if that were possible food! Not -only the stupid frog, but the more intelligent carnivora will starve -in the presence of appropriate food which is unrecognized, because the -leading element in the recognition is absent. The cat will not eat a -dead mouse, unless she has killed it herself. Predatory animals must -capture their food--unless the scent of blood excites their alimentary -instinct. So intimately is this sensation of a moving object connected -with the predatory impulse, that the cat which is unexcited by the dead -mouse cannot resist springing on a moving ball. We need not suppose the -cat to mistake this ball for food; but we must suppose that, accustomed -to pounce upon moving food, it is unable to resist the impulse of this -leading sensation. - -74. The _presence_ of the brain not sufficing, in the absence of the -leading sensation, we shall now see that the _absence_ of the brain -will not prevent the execution of the instinctive action, if the -leading sensation be present. The brainless bird sees a heap of grain, -or a pan of water, but no more recognizes them by sight alone than the -frog recognizes the dead flies; yet if the bird’s feet be placed in -the water, _this_ sensation will suffice to make him drink; if placed -amid the grain, this sensation will (sometimes) suffice to make him -feed. Lussana and Lemoigne state that their brainless pigeons ate and -drank with avidity when their feet were placed in grain and water.[281] -M. Krishaber removed the hemispheres from a pigeon, and observed that -when his beak was thrust into a heap of hempseed the head was quickly -withdrawn, whereas when the beak was plunged into water the bird drank -eagerly. Every day he was forced to feed the bird by pouring the seed -into its throat, but every day it drank when the beak was thrust into -the pan of water.[282] Brücke noticed that his brainless hen, which -made no attempt to peck at the grain under her very eyes, began pecking -if the grain were thrown on the ground with force, so as to produce a -rattling sound. The sensation of hearing was here more perfect than -that of vision, and sufficed to awaken the state of feeling necessary -to initiate the pecking movement.[283] - -75. Somewhat analogous phenomena are observed in Aphasia. The patient -can see printed or written letters, and even copy them; but he cannot -read, i. e. interpret, these symbols; as the birds see the grain, but -cannot connect this sensation with others. These letters and words, -which the patient cannot interpret when _seen_, he can interpret when -_heard_; he can not only understand them when spoken, but write them -if they are dictated to him. The birds recognize the grain and water -(or act as if they did) when other sensations than those of sight -are excited. Sound is the leading element in Language, both spoken -and written. We hear the words even when we see them, but we do not -see them when we hear them. The visible symbols are accessory and -subordinate. But to the born deaf the visible symbols dominate. How one -sensation will determine a particular group of movements which cannot -be effected by any other stimulus is abundantly illustrated in disease -no less than in experiment. Here is a very luminous example: Gratiolet -had a patient for six months under his eye incapable of articulating a -single word, owing to the incoherence of her incessant utterance--she -babbled sounds, but could not group the syllables into a recognizable -word. Yet she could sing the words of any song she knew, the musical -sensations being sufficient to guide her vocal organs. “Ainsi la -mémoire, infidèle dans le cas où les mots étaient des idées, devenait -claire et précise quand les mots étaient des chansons.”[284] - -76. These illustrations plainly tell how the brainless animal may -starve amid his food, failing to perceive it because the leading -sensation is not excited; and how the same animal may manifest his -feeding instinct if the mechanism be set going by a leading sensation. -We are told, indeed, that in the absence of the brain the actions are -mechanical reflexes from impressions, and not comparable with the -complex processes determined by perception. I think, however, that the -only difference is in degree of complexity: a combination of touch, -temperature, and muscular movement will be simpler than one which also -combines sight, smell, and the revived images of associated sensations. -The sight of a sheep affects the instinctive mechanism of a wolf _only_ -when combined with the leading element of smell. Place a stuffed sheep -in a field, and no wolf will approach and spring on it, whereas the -blind wolf will find and capture the real sheep; and I believe that -were it practicable to remove the brain without injury to the organ of -scent and the powers of locomotion, the wolf would track and capture -the living sheep. - -77. The outcome of this discussion is that the mechanism of each -instinct is the adjustment of the organs which effect the instinctive -action; and this adjustment is not simply a cerebral process, but -a complex of _many_ sensorial processes; consequently the instinct -cannot be exclusively localized in the brain, although the cerebral -process may be a very important element in the adjustment. This is -true even on the supposition that in speaking of Instinct we refer -only to the state of feeling which originates the action--separating -the psychological from the physiological aspect of the phenomenon. For -the brain _minus_ the organism is obviously incapable of feelings; -whereas the organism _minus_ the brain is obviously capable of -sensibilities adequate to determine the actions. Thus the feeling -of hunger which prompts the alimentary actions does not arise if -the animal is satiated, nor does the sexual feeling which prompts -generative actions arise when the animal is castrated; but each arises -when the organism is in a particular state. In vain will food be placed -before the satiated animal, or a female before the castrated male; -food and female are seen and recognized, but no desires are excited, -in spite of the brain and its supposed instincts. On the contrary, -when the brain is removed, the need of the organism for food is felt, -and this need determines restless movements, which are directed by -certain other sensations, and the instinctive action of feeding is -finally effected; although, of course, the removal of the brain has -so disturbed the normal mechanism of the instinct that the action is -imperfect. Renzi says that an animal deprived of its brain has lost -the intelligence which enables it to seek and seize its food, but not -the instinct, since it still has the desire for food. The following -experiment may illustrate this. Renzi wounded superficially one optic -thalamus of a frog without injuring the external margin, or optic -tract. The frog showed no appreciable loss of sight, but hopped timidly -away whenever approached. Then both thalami were divided transversely, -the optic tract still being spared. This frog remained motionless -under every threat. It manifested no alarm, and even when directly -irritated, only crawled or hopped away like a brainless frog. Sight -still so far remained that obstacles were avoided.[285] Now since this -animal’s brain was intact, and its organs of movement were capable -of responding to stimulation, how are we to explain the loss of its -instinct of self-preservation? The frog perceived no danger in a -threatening approach, yet perceived an obstacle and avoided it, getting -under it if there were room enough, crawling beside it if that was -the easier escape. Why did one vision prompt the movements of escape, -and another fail? Was it not that in the one case the normal pathway -was still open, in the other closed? We know that one injury will -destroy the perception of color without destroying that of light and -shadow; so one injury may destroy the combination of neural processes -necessary for the perception of a _danger_, without destroying those -necessary for the perception of a _hindrance_. If all actions depend -on their mechanical conditions, they must be disturbed according to -the disturbance of the conditions. Nothnagel found that after removing -the _nucleus lentiformis_ on both sides of a rabbit, leaving all the -rest of the encephalon intact, the rabbit hopped when its tail was -pinched; yet although starting at the sound when hands were loudly -clapped, did not hop as a normal rabbit does; nor although closing his -eyes when a light was brought near them, did he ever move aside. No -feeling of danger was excited by sound or sight. In striking contrast -are the phenomena manifested by a rabbit whose _corpora striata_ have -been removed: it is with difficulty made to hop by pinching its skin, -whereas noises and sights cause it to make terrified bounds.[286] - -78. No sooner do we analyze the conditions of an instinct than we -see the error of regarding instincts as localized in the brain. The -cerebral process is only one factor in the product--an important -factor, no doubt, since the cerebrum is the supreme centre of -incitation and regulation; but its absence does not wholly carry -away the activity of the mechanism, sentient and motor, on which the -instincts depend, it only carries away one source of stimulation and -regulation. - -79. An instinct depends on a connate mechanism. Let us glance for a -moment at a parallel case of an ordinary reflex action, also dependent -on a connate mechanism, say that of sneezing. When the inner surface -of the nose is stimulated by snuff, or other irritant, the nasal -branch of the trigeminus is excited, and the effects are first a deep -inspiration, then a closure of the respiratory orifices by the tongue, -which in turn excites a spasmodic expiration. But the same effects -are producible from quite different stimulations--namely, that of the -ciliary nerves on sudden exposure to a glare of sunshine--or of the -skin nerves on a sudden draught of cold air. Brücke remarks that there -is perhaps no spot on the surface of the body from which this reflex -may not be excited in very sensitive people. He knew a gentleman who -always sneezed when in winter he laid hold of a cold door-bell; and the -fit of sneezing was only arrested by giving him a crust of bread or -something hard to gnaw. Now just as the connate mechanism of sneezing -may be set in action by a variety of stimulations, so may the connate -mechanism of an instinct. - - -ACQUISITION. - -80. Not only may Discrimination and Instinct be manifested in the -absence of the brain, but even the acquisition of new modes of -reaction, such as are classed under Learning through Experience. -The objection is sometimes urged that animals without their brains -only manifest single reactions on stimulation--the pinched foot -is withdrawn, and then remains motionless until again pinched. -But although the stimulation does not excite a consecutive series -of movements, because there is no cerebrum to react in successive -stimulation, this does not prove the absence of sensation in the one -movement which is excited. If my hand be lying on the table, and -something irritates it, my hand is withdrawn, and then remains as -motionless as the limb of the brainless animal, _until_ some fresh -stimulation, external or internal, moves it. Although removal of -the brain causes a manifest reduction in the variety and succession -of the movements, all experimenters are agreed that animals acquire -a certain dexterity in executing actions which they had previously -failed to carry out after removal of their brains. “There is,” says -Freusberg, “a decided improvement acquired in the reactions of the -motor centres after division of the spinal cord, not indeed in vigor, -but in delicacy. Removed from the regulating influence of the brain, -the legs acquired through practice a power of self-regulation.” Nor -is this wonderful: pathways are made easy by repetition of impulses, -and new adaptations form new adjustments. It is thus all learning is -effected--intelligent, and automatic. Nor is there any force in the -objection that the power thus acquired speedily disappears, so that if -the stimulations are effected at long intervals the reactions do not -manifest their acquired dexterity. The spinal centres forget, as the -cerebral centres forget; but they also remember, i. e. they learn. -Because an animal shows to-day none of the aptitude it acquired three -days ago, we are not to deny that it had once acquired the aptitude it -has now lost. Attempt to teach a child to read by giving it spelling -lessons of two or three minutes at intervals of two or three months, -and little will the acquisition be! - - * * * * * - -81. Hitherto we have been considering phenomena manifested in the -absence of the cerebral hemispheres, because it is in these that the -majority of writers place the sensorium. There are, indeed, many -authoritative writers who regard the ganglionic masses at the base of -the cerebrum, and even those of the medulla oblongata, as participating -in this sensorial property, which they refuse to the lower ganglia in -the spinal cord. I cannot follow their logic. The cerebrum is by its -position as a centre of centres, and its detachment from all direct -innervation of organs, so different from the rest of the neural axis, -that we can understand how it should be assigned a special function; -although being of the same tissue as the other ganglionic masses, it -must have the same property. And what that special function is I shall -hereafter endeavor to set forth. But that the upper region of the -spinal axis should differ so profoundly from the lower region as to -be the seat of psychical processes, while the lower region is simply -the seat of mechanical processes, is what I cannot understand, so -long as the anatomical structure and physiological properties of the -two regions are seen to be identical. The various centres innervate -various organs, and have consequently various functions. As each centre -is removed, we observe a corresponding loss of function--the organism -is truncated, but continues to manifest such functions as have still -their mechanisms intact. Let us suppose the brain or upper regions of -the cord detached from the lower regions by a section of the cord; the -animal will still live, and perform almost all its functions in the -normal way, but there will be little or no consensus between the lower -and the upper regions. Granting Sensibility to both, we must still see -that the sensation excited in one will not be felt in the other. And -this is the ground on which physiologists deny that the lower regions -have Sensibility. Without pausing here to examine this point, which -will occupy us in the next chapter, I assume that the positive evidence -of Sensibility suffices to discredit that argument; and in furtherance -of that assumption will cite an example of sensation and volition -manifested by the lower portion of the cord when separated from the -brain and upper portion. - -82. The function of Urination is one which notoriously belongs to -the voluntary class, in so far as it is initiated or arrested by a -voluntary impulse, and it is one which, according to the classic -teaching, has its centre in the brain. The grounds on which this -cerebral centre is assigned are very similar to those on which other -functions are assigned to cerebral centres, namely, observation of the -suppression of the function when the pathway between certain organs and -the brain is interrupted. But the careful experiments of Goltz[287] -have demonstrated that the “centre” of Urination is not in the brain, -but in the lower region of the cord. When the cord is completely -divided, Urination is performed in the _normal_ way--not passively, -not irregularly, but with all the characters of the active regular -function. And, what is also noticeable, this function is so intimately -dependent on Sensibility that it will be arrested--like any other -function--by a sensation excited from the periphery--to be resumed when -the irritation ceases. Now this arrest from a stimulation of sensory -nerves takes place when the brain is cut off from the spinal centre, -just as when the brain is in connection with it. - -The same is true of Defecation, and the still more complex functions -of Generation and Parturition. I can only refer the reader to the -very remarkable case of Goltz’s bitch with the spinal cord divided -in the lumbar region, if evidence be wanted for the performance of -complex functions so long as the spinal centres were intact. It is -true that Goltz considers these functions to have been independent -of _sensation_; but that is because he has not entirely emancipated -himself from the traditional views; for my purpose it is enough that he -admits the functions to be dependent on sensorial processes. - - * * * * * - -83. To sum up the evidence, we may say that observation discloses a -surprising resemblance in the manifestations of the cord and brain. In -both there are reflex processes, and processes of arrest; in both there -are actions referable to conscious and unconscious processes; in both -depression and exaltation are produced by the same drugs; in both there -are manifestations interpretable, as those of Discrimination, Logic, -Instinct, Volition, Acquisition, Memory; in both there is manifestation -of Sensibility--how then can we deny Sensation to the one if we accord -it to the other? - - - - -CHAPTER IV. - -NEGATIVE INDUCTIONS. - - -84. I fancy some reader exclaiming: “All your reasoning, and all your -marshalled facts, are swept away by the irresistible evidence of human -patients with injured spinal cords, whose legs have manifested reflex -actions, and who nevertheless declared they had _no sensation whatever_ -in them. We can never be sure of what passes in an animal; but man can -tell us whether he feels an impression, or does not feel it; and since -he tells us that he does not feel it, _cannot_, however he may _try_, -we conclude that reflex action may take place without sensation.” - -As this is the one solitary fact which is held to negative the mass of -evidence, anatomical and physiological, in favor of the Sensibility of -the spinal cord, it is necessary that we should candidly examine it. -No reader will suppose that during the twenty years in which I have -advocated the doctrine expounded in this volume, I have not been fully -alive to the one fact which prevented the general acceptance of the -doctrine. From the first it has seemed to me that the fact has been -misinterpreted. - -85. Certain injuries to the spinal cord destroy the connection of -the parts below the injury with the parts above it; consequently no -impression made on the limbs below the injured spot is transmitted -to the brain, nor can any cerebral incitation reach those limbs. The -patient has lost all consciousness of these limbs, and all control -over them. Hunter’s patient on being asked if he felt any pain when the -prick caused his leg to kick, answered, “No: but you see my leg does.” -This answer has been regarded as a drollery; I think it expressed -a physiological truth. For on the assumption that the whole of the -cerebro-spinal axis had one uniform _property_, corresponding with -its uniform structure, and various _functions_, corresponding with -the variety of organs it innervates, a division of this axis would -necessarily create two independent seats of Sensibility, and interrupt -the consensus of their functions. In such a case it would be absurd to -expect that the cerebral segment could be affected by, or co-operate -with, what affected the spinal segment. - -Now, when a man has a diseased spinal cord, the seat of injury causes, -for the time at least, a division of the whole group of centres into -two independent groups. For all purposes of sensation and volition it -is the same as if he were cut in half; his nervous mechanism _is_ cut -in half. How then can any cerebral control be obeyed by his legs; how -can any impression on his legs be felt by his cerebrum? As well might -we expect the man whose arm has been amputated, to feel the incisions -of the scalpel, when that limb is conveyed to the dissecting-table, as -to feel by his brain impressions made upon parts wholly divorced from -organic connection with the brain. - -86. But, it may be objected, this is the very point urged. The man -himself does not feel the impressions on his legs when his spine has -been injured; he is as insensible to them as to the dissection of his -amputated arm. Very true. _He_ does not feel it. But if the amputated -arm were to strike the anatomist who began its dissection, if its -fingers were to grasp the scalpel, and push it away, or with the thumb -to rub off the acid irritating one of the fingers, I do not see how -we could refuse to admit that the _arm_ felt although the _man_ did -not. And this is the case with the extremities of a man whose spine is -injured. _They_ manifest every indication of sensibility. In the frog -and pigeon the legs manifest the unmistakable control which we ascribe -to volition. It is true that the man himself, when interrogated, -declares that he feels nothing; the cerebral segment has attached to -it organs of speech and expressive features, by which _its_ sensations -can be communicated to others; whereas the spinal segment has _no_ such -means of communicating _its_ sensations; but those which it _has_, it -_employs_. You can ask the cerebral segment a question, which can be -heard, understood, and answered; this is not the case with the spinal -segment: yet if you _test_ its sensibility, the result is unequivocal. -You cannot ask an animal whether it feels, but you can test its -sensibility, and that test suffices. - -87. The question we have to decide, therefore, is not whether a -patient, with an injured spine, can feel impressions on, or convey -voluntary impulses to, limbs below the seat of injury--for as respects -the nervous mechanism these limbs are separated from him, no less -than if actual amputation had taken place--the question is, whether -these separated limbs have any sensibility? And the answer seems to -me unequivocally affirmative. I assert, therefore, that if there is -ample evidence to show that the spinal centres have sensibility, when -separated from the cerebral centres, such evidence can in no respect be -weakened by the fact that a man with an injured spine is unconscious -of impressions made below the seat of injury; since such a fact -necessarily follows from the establishment of two centres: the parts -above are then not sensitive to impressions on the parts below; nor are -the parts below sensitive to impressions on the parts above; but each -segment is sensitive to its own affections. - -88. Every one knows that there are animals, low down in the scale, -which may be cut in two, each half continuing to live, and each capable -of reproducing its lost segments. Would any one, seeing these separated -halves move and manifest ordinary signs of sensibility, venture to say -that the one half was a living, the other an insentient, mechanism? -And since the one half had eyes, mouth, tentacles, etc., while the -other half had none of these, would the observer be surprised that -the functions of the one differed from those of the other in these -respects? Why, then, should he not conclude the same of the two halves -of the human mechanism, when disease had divided them? - -89. The man, you urge, does not feel the prick on his leg. This is -true, because “the man” here designates the seeing, hearing, tasting, -smelling, talking, thinking group of organs--to the exclusion of the -limb or limbs which are no longer in sensitive connection with this -group. When a leg is amputated “the man” remains--a truncated man, -indeed, yet still one having all the distinguishing human characters. -Yet obviously in strict language we can no longer say that the man is -the _same_ as he was. “Man” or “animal” means the complex whole; and -each anatomically separable part forms one constituent of that whole. -The medulla oblongata and spinal cord innervate certain parts; the -mesencephalon innervates others; the cerebrum rises above the whole. -If after removing one limb, then another, we continued truncating the -organism till we left only the head, should we call _that_ the man? -Clearly not. Should we even suppose that the intact brain--the supposed -seat of sensation and volition--still felt, and willed? Clearly not. -There is absolutely no evidence, however faint, of the isolated head -manifesting any sensational and volitional phenomena; whereas there -is ample evidence of the truncated spinal cord manifesting some of -these phenomena. And this is intelligible when we understand that the -nerve-centres stimulate into action the organs they innervate, but do -not by themselves play any other part. - -90. “The man” then does not feel the prick on his leg, but his leg -feels it. The man has no consciousness of what takes place outside the -sphere of his sensitive mechanism; and the leg is now outside that -sphere. Consciousness--as distinguished from Sentience in general--we -have seen to be a resultant of the composition of forces co-operating -at the moment; the Sensibility of the spinal cord in the regions below -the injury cannot _now_ enter into that composition. It is detached -from the upper organs. But inasmuch as the organs it innervates are -still living and active, the functions of this detached portion are -still displayed. We have seen the dog with divided cord capable of -Urination, Defecation, Generation, etc.; its hinder legs, though not -moving in a consensus with the forelegs, yet moved independently; and -all the normal reflexes of the parts followed on stimulations. To say -that “the dog” showed no signs of Sensibility when its hinder limbs -were irritated, is identifying “the dog” with the anterior half of the -organism which was not in connection with the posterior half. It is -equally true that the posterior half showed no signs of Sensibility -when the anterior was irritated. The two halves were united by the -circulation, nutrition, etc., but disunited as to sensation and -volition. - -91. Do I then suppose the separated half of an animal to feel pain and -pleasure, hope and terror? The reader who has attentively followed -the exposition will be at no loss to answer. Pain, pleasure, hope, -and terror, are special modes of Sensibility, dependent on particular -neural combinations. The organs comprised in the anterior half of the -animal furnish the main conditions for these special modes, whereas -the organs comprised in the posterior half furnish few or none of -those--they contain none of the special Senses, and they are without -the chief combining centre, the brain. But since we know that a large -amount of normal Sensation is wholly without the special characters -of pain, pleasure, hope, or terror, we need not hesitate to assign -Sensation to the spinal cord because these characters are absent. - -92. All I contend for is that the spinal centres have Sensibility -of the same _order_ as the cerebral centres; and that in the normal -organism this Sensibility enters as a factor into the general -Consciousness--no one portion of the nervous system being really -independent of all the others, all co-operating in every result. Over -and over again I have had to insist that the property of Sensibility -is only the general condition of Sensation; and that each particular -sensation receives its _character_ from the organs innervated, _plus_ -the reaction of the whole organism. Obviously, therefore, the peculiar -character of a sensation, or “state of consciousness,” must vary with -the variations in either of these factors. To say that every segment of -the spinal cord has Sensibility, is not saying that an excitation of -that segment will produce a particular sensation of definite character; -because for this definite character there is needed the co-operation of -all those parts of the mechanism which enter into the complex product. - - * * * * * - -93. And here attention must be called to a double fallacy pervading -the arguments on the other side. It is always assumed that the -reactions of an organ, or part of the organism, when separated from -the rest, are typical of their reactions when forming constituents -of the normal organism. Nothing of the kind. The movement of a -muscle or a limb separated from the body may resemble that movement -when normally effected--but only as the movements of a mechanical -bird resemble those of a living bird: the modes of production are -different. So that were we to grant the postulate of the brain -being the exclusive seat of sensation, we should still deny that an -action which was effected after removal of the brain was typical of -the action effected when the brain was present. The leg of Hunter’s -patient jerked when the skin was irritated; but this action could not -be altogether the same as the similar action in a leg united with the -rest of the sensitive mechanism. Nor is this all. The leg may have -been insensible, the spinal segment which innervated it may have been -wholly without Sensibility, and still we should have to question the -logic which extended such an inference to the very different and far -more complex actions of decapitated animals. On this ground:--The -leg is, by the hypothesis, insensible because cut off from all -connection with the sensitive mechanism. But this is not the case -with the decapitated animal: there still remain the essential parts -of a sensitive mechanism--all the chief organs are still in activity, -still manifesting their functions. Decapitation has produced a great -disturbance in the mechanism, and has removed an important centre; but -nevertheless every impression excites a connected group of centres, and -this group responds. - - * * * * * - -94. In conclusion, unless we adopt the opinion that -Sensation--Consciousness--Sensibility, is something not belonging to -the physiological properties of the nervous system in a vital organism -(the opinion held by spiritualists), there seems no alternative but -to adopt the opinion advocated in this volume, namely, that the -physiological properties of the nervous system are inseparable from -every segment of that system; and the functions are the manifestation -of those properties as determined by the special organs with the -co-operation of all. - - - - -FOOTNOTES - - -[1] WORDSWORTH. - -[2] Crystals not only grow by assimilation, but even repair injuries, -with a certain superficial resemblance to the repair of animal tissues. -Thus, according to the experiments of JORDAN cited by Sir JAMES PAGET -(_Lectures on Surgical Pathology_, I. 153, and 2d ed. p. 115), an -octohedral crystal of alum, if fractured and replaced in a motherlye -will in a few days exhibit a complete restoration of the original form. -The whole crystal increases, but the increase is greatest on the broken -edge, and the octohedral form is completely renewed. (Comp. § 113.) - -[3] Cited by DRYSDALE, _Life and the Equivalence of Force_, Part II. p. -149. - -[4] RANKE, _Die Lebensbedingungen der Nerven_, 1868, p. 80. - -[5] “Il n’y a peut être pas un seul phénomène chimique dans l’organisme -qui se fasse par les procédés de la chimie de laboratoire; en -particulier il n’y a peut être pas une oxydation qui s’accomplisse par -fixation directe d’oxygène.”--CLAUDE BERNARD. - -[6] Dr. MADDEN, in his essay _On the Relation of Therapeutics to -Medicine_, 1871, p. 5, gives a remarkable illustration of what may be -called the frustration of chemical affinity effected by mechanical -conditions. “Before calico can be printed, every loose particle of -cotton must be removed from the surface in order that the colored inks -may not run. This removal is effected by passing the calico over and in -contact with a red-hot iron cylinder, and by regulating the rapidity -with which the cylinder revolves, the intense heat burns off the loose -fibres, yet does no injury to the woven cloth. In other words, the -changes in the relation of the high temperature and the cotton are -too rapid to admit of the fibre combining with the oxygen. Let the -rate of revolution be reduced but very little, and the calico would -burst into flames.” Any one who has snuffed a candle with his fingers -will understand this. Dr. Madden further instances certain fulminates -which can be detonated in contact with gun-cotton without causing it -to explode--the extreme rapidity with which the fulminates expand is -too great to enable the gun-cotton to adjust its movements to this new -motion. Precisely the same kind of thing occurs in organized matter. If -the rate of its changes be reduced below a certain point, the ordinary -chemical affinities will assert themselves. - -[7] I am often reminded of the surprising movements of particles of -carbonate of lime in water which my friend Professor PREYER showed -me during a visit to Bonn. He had removed one of the concretions, -usually found in connection with nerves along the spine of old frogs, -and crushed it in water; under the microscope the seeming spontaneity -and variety of the movements of the particles was such that had we -not known their origin we should certainly have attributed them to -vitality: no infusoria could have moved with more seeming spontaneity. -It is hardly physiological to conclude that because fragments of tissue -manifest ambœbiform movements therefore they are alive (STRICKER, -art. _Die Zelle_ in his _Handbuch der Lehre von den Geweben_, 1868, -p. 7), or that the heart removed from the body is _alive_ because it -still beats. LIEBERKÜHN, _Ueber Bewegungserschsinungen der Zellen_, -1870, pp. 357–359, cites examples of such movements in undeniably dead -substances. For Life, we demand not only Movement, but Functional -Activity. - -[8] TELESIUS, _De Natura Rerum_, 1586, V. 184. TELESIO might have been -saved from the mistake had he attended to what NIPHUS had said on -the point in his _Expositio subtilissima_, 1559, p. 245. Comp. also -PHILELPHUS, _Epist. Familiarum_, 1502, p. 253, _verso_. - -[9] The authorities just cited are ARISTOTLE, _De Anima_, Lib. -II. c. I. KANT, _Kritik der Urtheilskraft_. MÜLLER, _Physiology_. -BEALE, _Bioplasm_, and _Introduction to Todd and Bowman’s Anatomy_. -SCHELLING, _Erster Entwurf_, and _Transcendent. Idealismus_. BICHAT, -_Recherches sur la Vie et la Mort_. STAHL, _Theoria Vera Medica_. -DUGÈS, _Physiologie Comparée_. BÉCLARD, _Anatomie Générale_. LAMARCK, -_Philosophie Zoologique_. COMTE, _Cours de Philosophie Positive_. -OWEN’S _Hunterian Lectures_, 1854. HERBERT SPENCER, _Principles of -Biology_. - -[10] FLETCHER, as quoted by DRYSDALE, _Life and the Equivalence of -Force_, Part II. p. 120. - -[11] ROBIN et VERDEIL, _Traité de Chimie Anatomique_, 1853. - -[12] PAGET, _Lectures on Surgical Pathology_, p. 14. - -[13] Comp. HAECKEL, in _Siebold und Kölliker’s Zeitschrift_, 1865, p. -342, and his _Generelle Morphologie_, 1866, I, 135, 336. - -[14] In the _Archiv für mikros. Anatomie_, 1865, p. 211. - -[15] Here organization is the simplest form of all--molecular organized -structure, which in the higher forms becomes tissue structure, -and organ structure. The word _structure_ properly means orderly -arrangement of different materials; and molecular structure refers -to the different proximate principles which constitute the organized -substance. Usually, however, the word _structureless_ indicates the -absence of _visible_ arrangement of the parts; a cell has structure -since it has nucleus and protoplasm. - -[16] In the cell-theory established by SCHLEIDEN and SCHWANN, in 1838, -and which has formed the basis of modern histology, the cell-wall -was endowed with an importance which can no longer be upheld now -that the existence of independent organisms, and of cells, without -a trace of enveloping membrane has been abundantly observed. Cells -without walls were first described by COSTE in the _Comptes Rendus_, -1845, p. 1372. They were also described by CHARLES ROBIN in 1855, -_Dict. de la Médicine_, art. _Cellule_. But little notice was taken -until MAX SCHULTZE, in his famous essay, _Ueber Muskelkörperchen -und was man eine Zelle zu nennen habe_, which appeared in _Reichert -und Du Bois Reymond’s Archiv_, 1861,--BRUECKE, in his memoir, _Die -Elementarorganismen_, 1861,--and LIONEL BEALE, in his _Structure of the -Simple Tissues_, 1861,--all about the same time began the reform in -the cell-theory which has effected a decisive change in the classical -teaching. LEYDIG claims, and with justice, to have furnished important -data in this direction (_Vom Bau des thierischen_ _Körpers_, 1864, I. -p. 11). The student interested in this discussion should consult MAX -SCHULTZE, _Das Protoplasma der Rhizopoden und der Pflanzenzellen_, -1863; HAECKEL, _Die Radiolarien_, 1862; the controversial papers by -REICHERT, in his _Archiv_ (beginning with the Report of 1863), and MAX -SCHULTZE, in his _Archiv für mikros. Anat._, with HENLE’S judgment in -his _Jahresberichte_, and KÜLLIKER’S summing-up in the last edition of -his _Gewebelehre_. For a full yet brief history of the cell-theory see -DRYSDALE, _The Protoplasmic Theory of Life_, 1874, pp. 96–106. - -[17] At the time this was written, I had some fish ova in the course -of development. Out of the same mass, and in the same vessel, all -those which were supported by weed at a depth of half an inch from -the surface, lived and developed; all those, without exception, that -were at a depth of two to four inches, perished. In ordinary parlance, -surely, nothing would be objected to in the phrase, “these ova were -all in the _same_ Medium”; the water was the same, the weed the same, -the vessel the same; yet some difference of temperature and carbonic -acid made all the difference between life and death. Another curious -fact was observed; I removed eight of these ova with active embryos, -and placed them in a large watch-glass containing a solution (one half -per cent) of bichromate of ammonia. In this acid the embryos lived -and were active fifty-seven hours, although other embryos placed in a -similar watch-glass containing pond-water, survived only forty hours. -The non-effect of the acid was probably due to the non-absorption -which nullifies the effect of certain virulent poisons when they are -swallowed; but why the fish should live longer in the acid than in the -simple water, I do not at all comprehend. - -[18] AGASSIZ, _Essay on Classification_, 1859, p. 15. - -[19] HAECKEL, _Generelle Morphologie_, II. 211. - -[20] See on this last point RANKE, _Die Lebensbedingungen der Nerven_, -1868, p. 34. - -[21] See WALDEYER, art. _Eierstock_, in STRICKER’S _Handbuch der Lehre -von den Geweben_, 1870, p. 570. “I found in a fœtus, which, in a case -of extra-uterine pregnancy, had lain thirty years in the body of its -mother, the structure of the muscles as intact as if it had been born -at its full time.”--VIRCHOW, _Cellular Pathologie_, Lect. XIV. - -[22] See BEALE, _The Structure of the Simple Tissues_, 1861; the -Introd. to his edition of _Todd and Bowman’s Physiological Anatomy_, -1866; and _How to Work with the Microscope_, 4th ed., 1868; also -_Bioplasm_, 1872. - -[23] “The physical property of the tissue does not depend upon this -matter, _nor is its function due to it_.”--Beale, _Introduction to Todd -and Bowman_, p. 11. That is to say, he regards even contractility and -neurility as physical, not vital facts. - -[24] In turning over the pages of a work which was celebrated some -half-century ago--RUDOLPHI’S _Grundriss der Physiologie_--I was -interested to find a clear recognition of this biological principle: -“Alle Theile aller Organismen,” he says, I. 233, “sie mögen noch so -verschieden in ihrem Bau, in ihrer Mischung, und in ihrer Thätigkeit -seyn, sind ohne Ausnahme _als organisch und mithin als lebend zu -betrachten_.” In a note he adds that physiologists have considered -certain solid parts--epidermis, nail, hair, and bones--to be dead; “but -all these are organically developed, and are in direct connection with -the other parts.” - -[25] VIRCHOW, _Die Cellular Pathologie_, 1860, Lect. I. - -[26] BEALE, _Bioplasm_, 104. - -[27] KÖLLIKER, _Gewebelehre_, 5th ed., 1867, p. 12. - -[28] Nevertheless there are some facts directly contradicting his -conclusions. For example, he considers the axis cylinder of the nerve -to be formed material, and agrees with MAX SCHULTZE and others as to -its fibrillated structure; yet according to LISTER and TURNER, GERLACH -and FREY, the axis cylinder is deeply stained by carmine, and in this -respect resembles the nucleus of protoplasm. - -[29] From the quite recent experiments M. BAILLON has submitted to the -_Académie des Sciences_ (15th February, 1875), it appears that although -cut flowers absorb colored fluids, the roots when intact only absorb -the fluid, and reject the coloring matters, by a veritable dialysis. - -[30] GERLACH cited by RANKE, _op. cit._, p. 76. - -[31] STEIN, _Der Organismus der Infusionsthierchen_, 1859, p. 76. - -[32] STAHL had a profound conviction of the radical difference, -though he was not able to point out the conditions involved. See his -_Disquisitio de mechanismi et organismi vera diversitate_. - -[33] M. FERNAND PAPILLON has shown that animals may be fed with food -deprived of phosphates of lime if its place is supplied with magnesia, -strontia, or alumina; they make their bones out of these as out of -lime. But no such substitution is possible in muscle, nerve, or gland; -we cannot replace the phosphate of magnesia in muscles by the phosphate -of iron, lime, or potash, as we can replace the iron of a wheel by -steel, copper, or brass. - -[34] Anatomy resolves the Tissues into Organites (cells, fibres, -tubes); here its province ends, and that of Chemistry begins by -pointing out the molecular composition of the Organites. - -[35] This luminous conception, though vaguely seized by PINEL, was -first definitely wrought out by BICHAT. See his _Recherches sur la Vie -et la Mort_--and especially his _Anatomie Générale_, 1812, I. p. lxx. -It was one of the most germinal conceptions of modern times. - -[36] Just as there go other materials besides canvas to make a sail, -and others besides iron to make a windlass, so there go other tissues -besides the muscular to form a muscle--there is the membranous -envelope, the nerve, the blood-vessels, the lymphatics, the tendon, and -the fat. Even in Contraction there is another property involved besides -the Contractility of the muscular element, namely, the Elasticity -of the fibrous wall of the muscular tube; but Contractility is the -dominant property, and determines the speciality of the function. - -[37] “L’élément musculaire peut être annexé à une foule de mécanismes -divers; tantôt à un os, tantôt à un intestin, tantôt à une vessie, -tantôt à un vaisseau, tantôt à un conduit excréteur, tantôt enfin à des -appareils tout à fait spéciaux à certaines espèces d’animaux.”--CLAUDE -BERNARD, _Rapport sur les Progrès de la Physiologie générale_, 1867, p. -38. - -[38] VULPIAN, _Leçons sur la Physiologie du Système Nerveux_, 1866, -p. 581. In a work just published I find M. LUYS hesitating at the -consistent application of this law. After pointing out the identity -of the tissue in cerebrum and spinal cord, he is only prepared -to say that we cannot deny that there is _no impossibility_ in -admitting physiological equivalence where there is morphological -equivalence.--LUYS, _Actions Reflexes du Cerveau_, 1874, p. 14. - -[39] It is because men converted the result into a principle, and -supposed that Life preceded the Organism, that they were led to puzzle -themselves over such facts as the continuance of vitality in divided -organisms. ARISTOTLE felt the force of the objection: “Plants when -divided are seen to live, and so are certain insects, as if still -possessing the same Vital Principle (ψυχή) considered specifically -(τῷ εἴδει) though not the same numerically (μὴ ἀριθμῷ). Each of these -parts has sensation and locomotion for a time; and there is no room for -surprise at their not continuing to manifest these properties, seeing -that the organs necessary for their preservation are absent.”--_De -Anima_, Lib. I. Ch. IV. Compare BASSO, _Philos. Naturalis adversus -Aristotelem_, Amsterdam, 1649, p. 260; and TAURELLUS, _Contra -Cæsalpinum_, 1650, p. 850; neither of them grappling with the -difficulty so firmly as ARISTOTLE. - -[40] SPENCER, _Principles of Biology_, 1864, I. 153. - -[41] Comp. LAMARCK, _Philos. Zool._, II. 114. - -[42] Comp. SPENCER, _op. cit._, II. 362, 363, for good illustrations of -this. - -[43] AGASSIZ, _Essay on Classification_, p. 91. - -[44] “Nulla in corpore animali para ante aliam facta est, et omnes -simul creatæ exiatunt.”--HALLER, _Elementa Physiologiæ_, VIII. 148. - -[45] QUATREFAGES, _Metamorphoses de l’Homme et des Animaux_, 1862, p. -42. - -[46] VON BAER, _Ueber Entwickelungageschichte_, 1828, I. 221. - -[47] Curiously enough, while the Nudibranch, which is without a shell, -possesses one during its embryonic life, there is another mollusc, -_Neritina fluviatilis_, which possessing a shell in its subsequent life -is without one during the early periods, and according to CLAPARÈDE -begins an independent existence, capable of feeding itself before it -acquires one. See his admirable memoir on the _Neritina_, in _Müller’s -Archiv_, 1857. - -[48] Has any advocate of the hypothesis that animals were created as -we see them now, fully formed and wondrously adapted in all their -parts to the conditions in which they live, ever considered the hind -legs of the seal, which he may have watched in the Zoölogial Gardens? -Here is an animal which habitually swims like a fish, and cannot use -his hind limbs except as a rudder to propel him through the water; but -instead of having a fish-like tail he has two legs flattened together, -and nails on the toes--toes and nails being obvious superfluities. Now -which is the more rational interpretation, that these limbs, in spite -of their non-adaptation, were retained in rigid adherence to a Plan, or -that the limbs were inherited from an ancestor who used them as legs, -and that these legs have gradually become modified by the fish-like -habits of the seal? - -[49] MILNE EDWARDS, _Intro. à la Zoologie Générale_, 1851, p. 9. - -[50] VON BAER, _op. cit._, I. 203. - -[51] WOLFF, _Theorie der Generation_, 1764, § 67. The reader will find -abundant and valuable corroboration of this biological principle in SIR -JAMES PAGET’S _Lectures on Surgical Pathology_. - -[52] VON BAER, _Selbstbiographie_, 1866, p. 319. - -[53] MILNE EDWARDS, _Intro. à la Zoologie Générale_, 176. - -[54] VON BAER, _Ueber Entwickelungsgeschichte_, I. 147. - -[55] LOTZE, art. _Lebenskraft_, in _Wagner’s Handwörterbuch der -Physiologie_, p. XXVI. - -[56] I had kept these tritons four years in the hope that they would -breed; but in spite of their being subjected to great varieties of -treatment--for months well supplied with food, and for months reduced -almost to starvation--they never showed the slightest tendency to -breed; another among the many illustrations of the readiness with which -the generative system is affected even in very hardy and not very -impressionable animals. CLAPARÈDE observed the still more surprising -fact that the _Neritina fluviatilis_ (a river snail) not only will not -lay eggs, but will not even feed in captivity. He attributes it to the -stillness of the water in the aquarium, so unlike that of the running -streams in which the mollusc lives. See _Müller’s Archiv_, 1857. - -[57] BRONN, _Morphologische Studien über die Gestaltungs-Gesetze_, -1858. Compare the note on § 11. - -[58] DARWIN, _On Domestication_, II. 340. In the _Annales des -Sciences_, 1862, p. 358, M. MALM describes a fish in his collection, -the tail of which had been broken, and the bone which grew out at the -injured spot had formed a second tail with terminal fin. - -[59] In the memoir on the _Anatomy and Physiology of the Nematoids_, -by Dr. CHARLTON BASTIAN, which appeared in the _Philosophical -Transactions_ for 1866, we read that even these lowly organized -worms have little power of repair. Speaking of the “paste eels” -(_Anguilulidæ_), he says, “I may state as the result of many -experiments with these that the power they possess of repairing -injuries seems very low. I have cut off portions of the posterior -extremity, and though I watched the animal for days after, could never -recognize any attempt at repair.” Perhaps, however, the season may have -some influence; and Dr. WILLIAMS’S denial respecting the Naïs may be -thus explained. [What is said above was written in 1868, and published -in the June number of the _Fortnightly Review_. In the August of that -year the question of reproduction of lost limbs was treated by Prof. -ROLLESTON in his _Address to the British Medical Association_, in which -he showed cogent evidence for the conclusion that the reproduction -of limbs only exists is animals that have feeble respiration, and -consequently slow vital processes.] - -[60] This beautiful and transparent larva reminds one in many respects -of the Pike as it poises itself in the water awaiting its prey. It is -enabled to do so without the slightest exertion by the air-bladders -which it possesses in the two kidney-shaped rudiments of tracheæ, and -which in the gnat become developed into the respiratory apparatus. The -resemblance to the air-bladder of fishes is not simply that it serves -a similar purpose of sustaining the body in the water, it is in both -cases a rudiment of the respiratory apparatus, which in the fish never -becomes developed. WEISMANN calls attention to an organ in the larvæ of -certain insects (the _Culicidæ_), which have what he calls a tracheal -_gill_, which gill has this striking analogy with the fish-gill that -it separates the air from the water, and not, as a trachea, direct -from the atmosphere. See his remarkable memoir _Die nachembryonale -Entwickelung des Muscidens_, in _Siebold und Kölliker’s Zeitschrift_, -1864, p. 223. - -[61] _The Variation of Animals and Plants_, 1868, II. p. 272. - -[62] _Origin of Species_, 5th ed. p. 96. - -[63] Mr. Darwin has himself, in the following passage, stated a -somewhat similar view, and rejected it: “In one sense the conditions of -life may be said not only to cause variability, but likewise to include -Natural Selection, for _the conditions determine whether this or that -variety shall survive_. But when man is the selecting agent, we clearly -see that the two elements of change are distinct; the conditions -cause the variability, the will of man acting either consciously or -unconsciously accumulates the variations in certain directions, and -this answers to the survival of the fittest under nature.” (p. 168.) - -[64] Even in the nerve-sheaths of some Annelids there are muscles. - -[65] SPENCER, _Principles of Biology_, II. 72 - -[66] FAIVRE, _Variabilité de l’Espèce_, p. 15. - -[67] These luminous organs would furnish an interesting digression -if space permitted it. The student is referred to the chapter in -MILNE EDWARDS’S _Leçons sur la Physiologie et l’Anatomie Comparée_, -1863, VIII. 94, sq. LEYDIG, _Histologie_, 1857, p. 343. KÖLLIKER, -_Microscopical Journal_, 1858, VIII. 166, and MAX SCHULTZE, _Archiv -für mikros. Anat._, 1865, p. 124. My friend SCHULTZE was kind enough -to show me some of his preparations of the organs of _Lempyris -splendidula_, from which the drawings in his memoir were made. -They reminded me of the electric organs in fishes by a certain -faint analogy, the trachea in the one holding the position of -nerves in the other. I may remark, in passing, that it is not every -phosphorescent animal that has distinct luminous organs. There is a -lizard (_Pterodactylus Gecko_) which occasionally becomes luminous. “A -singular circumstance occurred to the colonial surgeon, who related it -to me. He was lying awake in bed when a lizard fell from the ceiling -upon the top of his mosquito-curtain; at the moment of touching it the -lizard became brilliantly luminous, illuminating the objects in the -neighborhood, much to the astonishment of the doctor.” COLLINGWOOD, -_Rambles of a Naturalist_, 1868, p. 169. - -[68] MAX SCHULTZE, _Zur Kenntniss der electrischen Organe der Fische_, -1858–9. - -[69] LEYDIG, _Histologie_, 1857, p. 45. - -[70] OWEN, _Anatomy of The Vertebrates_, 1866, I. 358. - -[71] DAVY, _Researches, Physiological and Anatomical_, 139, I. 33. - -[72] “If it could be demonstrated that any complex organ existed -which could not possibly have been formed by numerous successive -slight modifications, my theory would absolutely break down.”--DARWIN, -_Origin of Species_, 5th ed. p. 227. In several passages insistence -is made on this. “Natura non facit saltum” may be perfectly true; but -without impugning the Law of Continuity we may urge that the Law of -Discontinuity is equally true. The one is an abstract ideal conception; -the other is a concrete ideal conception. According to the one, every -change from rest to motion, or from one state to another, must pass -through infinites; according to the other every change is abrupt. -In my First Series, Vol. I. p. 327, I have shown how, on mechanical -principles, every change in an organism must be abrupt. A glance at -the metamorphoses of the embryo, or the stages of insect-development, -will show very sudden and abrupt changes. Let me also cite Mr. Darwin -against himself: “When we remember such cases as the formation of -the more complex galls, and certain monstrosities, which cannot be -accounted for by reversion, cohesion, etc., and _sudden, strongly -marked deviations of structure_, such as the appearance of a moss-rose -on a common rose, we must admit that the organization of the individual -is capable through _its own laws of growth, under certain conditions_, -of undergoing great modifications, independent of the gradual -accumulation of slight inherited modifications.”--_Origin_, p. 151. See -also note to § 130, further on, p. 142. - -[73] On the Nutrition of Monads, see the remarkable memoir by -CIENKOWSKI, in the _Archiv für mikros. Anatomie_, I. 221, sq. - -[74] PAGET, _Lectures on Surgical Pathology_, edited by TURNER, 1865, -p. 19. - -[75] It has recently been shown that certain Crustacea vary not only -from species to species, but from genus to genus, when living in -water of different degrees of saltness. By continued dilution of the -salt water an _Artemia_ was developed into another species, and this -again into a _Branchipus_--a genus of large dimensions, with an extra -abdominal segment, and a different tail; a genus, moreover, which is -propagated sexually, whereas the _Artemia_ is parthenogenetic, as a -rule. See _Nature_, 1876, June 8, p. 133. - -The exceeding importance of this fact is, that it proves specific -and even generic differences to originate simply through the gradual -changes of the medium and the adaptation of the organism to these new -conditions. It also disproves the very common notion--adopted even -by Mr. DARWIN himself--that “organic beings must be exposed _during -several generations_ to new conditions to cause any appreciable amount -of variation.” Again, “Natural Selection, if it be a true principle, -will banish the belief of any great and sudden modification of -structure.”--Comp. note to § 121, p. 132. - -[76] Compare LEYDIG, _Vom Bau des thierischeu Körpers_, 1864, p. 27. - -[77] FERDINAND COHN, _Die contractile Gewebe im Pflanzenreich_, 1862. -By a series of numerous well-devised experiments, Cohn found that in -the stamen of the _centauria_ a tissue exists which is excitable by the -same stimula as muscle is, and which reacts like muscle, describing a -similar curve when excited, and, after reaching its maximum, relaxing. -Like the muscle it becomes fatigued by repeated contraction, and -recovers its powers by repose. Like the muscle it may be rendered -tetanic. (The researches of Dr. BURDON SANDERSON and Mr. DARWIN have -since placed beyond a doubt the Contractility and Sensibility of -certain plants.) - -[78] MIVART, _The Genesis of Species_, 1871, p. 23. - -[79] DOHRN, _Der Ursprung der Wirbelthiere und das Princip des -Functionswechsels_, 1875, p 74. - -[80] SIGMUND MAYER, _Die peripherische Nervenzelle und die sympathische -Nervensystem_, 1876. - -[81] On these cells see note to § 140. - -[82] These terms designate the surface aspect of a transverse section, -of what more correctly should be called the gray columna. See Figs. 3 -to 6. - -[83] But this only in the higher animals. In reptiles and amphibia the -medulla descends into the cervical region, as far as the second and -third cervical vertebræ. This should be remembered in experimenting. - -[84] FOSTER and BALFOUR, _Elements of Embryology_, Part I., 1874. Comp. -SCHWALBE, art. _Die Retina_, in the _Handbuch der Augenheilkunde_ of -GRAEFE _and_ SÄMISCH, 1874, I. 363. - -[85] The development of the olfactory lobe and bulb is similar; it need -not be followed here. - -[86] German anatomists divide this axis into trunk and crown -(_Hirnstamm_ and _Hirnmantel_). There is convenience in this division. -If we remove all the gray matter of the cerebrum, with all the white -matter radiating from it, until we again come upon gray matter--and -if we then cut the cerebellum from its descending strands of white -matter--we shall have removed the _crown_, and leave the _trunk_ -remaining. This trunk is constituted by the corpora striata, nucleus -lentiformis, optic thalami, corpora quadrigemina, crura cerebri, pons, -medulla oblongata, and medulla spinalis. From this trunk all the organs -of the body are directly innervated (except those innervated from the -sympathetic?). - -[87] “On s’est préoccupé du rôle spécial que pouvaient jouer les -ganglions périphériques situés dans le voisinage de certaines organes; -et on a prétendu que les nerfs ne jouissaient de leur propriété d’agir -sur ces organes qu’après avoir traversé ces ganglions. On avait admis -que l’excitation portée sur le filet nerveux avant son entré dans le -ganglion restait sans effet; que pour obtenir l’action excitatrice -des fonctions de l’organe il fallait exciter le nerf entre lui et le -ganglion voisin.”--CLAUDE BERNARD, _Systéme Nerveux_, II. 169. But on -proceeding to verify these statements by experiment, BERNARD is led to -the conclusion, “que le ganglion n’a pas d’influence propre sur le mode -de l’excitation transmise à l’organe.” - -I was delighted to find my opposition to the current teaching -respecting the central functions of ganglionic cells thoroughly -borne out by the elaborate researches of SIGMUND MAYER (_Archiv für -Psychiatrie_, Bd. VI. Heft 2). Having artificially produced such cells, -he pertinently asks, How can we attribute central functions to cells -which appear in the process of regeneration of a divided nerve! The -error has its origin in the confusion of functions with properties. - -[88] It is often, though incorrectly, stated that every segment of an -annulose animal has its separate ganglion. The fact is, that while the -ganglia are usually fewer than the segments, they are sometimes more -numerous. - -[89] It has been proved that the cells of the cornea and the pigment -cells of the skin contract under nervous excitation. We cannot suppose -that although these are the only cells which have hitherto been brought -under experimental observation, they are the only cells subject to -nerve-influence. We may safely assume that wherever a nerve-fibre -terminates, its action will be transformed into an excitation of the -part. Habitually, however, motor-nerves are spoken of as muscle-nerves. - -[90] On Deduction, see _Problems: First Series_, Vol. II. p. 159 - -[91] I do not here touch upon the question as to whether these actions -of the senses are _sensations_, because that question demands that -we should first settle what is _Sensation_. I may at once, however, -say that what is ordinarily understood as a sensation of _color_, -or a sensation of _sound_, is, in my opinion, not possible without -the cerebrum. But the sensibility of the eye and ear is manifestly -preserved. - -[92] It has been observed that removal of the cerebellum affects the -pigment cells of the skin. No doubt other parts are also affected, but -the changes have hitherto escaped observation. - -[93] OWSJANNIKOW describes the results of removing carefully the -cranial ganglia of the crayfish; and these effects MEYER observes to -be identical with those which follow removal of the large claw of -the crayfish! A. B. MEYER, _Das Hemmungsnerven-system des Herzens_, -1869, p. 23. Let me add that the phenomena described by M. FAIVRE -as following the destruction of one subœsophageal ganglion in the -_Dytiscus_, are so little to be referred to the mere absence of the -ganglion, that I find them not to occur when the whole head is removed. - -[94] PFLÜGER, _Die Sensorischen Funktionen des Rückenmarks_,1858. -AUERBACH, _Günzburg’s Zeitschrift_. Jahrgang IV. p. 486. LEWES, _Leeds -Meeting of British Association_, 1858, and _Physiology of Common Life_, -1860. - -This recognition of sensation, and even of volition, in spinal actions -may be found in the writings of WHYTT, UNZER, PROCHASKA, LEGALLOIS, and -MAYO; but the establishment of the Reflex Theory had displaced it, and -its revival dates from PFLÜGER. - -[95] FRIEDLÄNDER (_Versuch über die innern Sinne_, 1826, I. -77) declares it to be a rational necessity: “Die Annahme eines -Nervenfluidums ist Nothwendigkeit der Vernunft.” - -[96] These terms and the conception they embody were proposed by me in -1859 in a paper “On the necessity of a reform in Nerve-physiology,” -read at the Aberdeen meeting of the British Association, and were -reproduced in the _Physiology of Common Life_. (Prof. OWEN, probably -in forgetfulness of my suggestion, proposed “neuricity.” _Lectures -on the Comp. Anat. of Vertebrates_, 1866, I. p. 318.) The terms were -fortunate enough to meet with acceptance from some physiologists -both in England and France; and the conception has been more widely -accepted than the terms. The most distinguished approver was Prof. -VULPIAN. “Faute d’une meilleure détermination on peut, avec M. Lewes, -donner à la propriété physiologique des fibres nerveuses le nom de -_neurilité_; c’est là ce qui correspondra à la oontractilitè des fibres -musculaires.” _Leçons sur la physiologie du système nerveux_, 1866, p. -220. He also adopted my suggestion (since modified) of Sensibility as -the property of ganglionic cells. Compare also GAVARRET, _Phénomènes -physiques de la Vie_, 1869, pp. 213 and 222. TAULE, _Notions sur la -nature de la matière organisée_, 1866, p. 131. CHARLES ROBIN, _Anatomie -et physiologie cellulaires_, 1873, p. 166. - -By these channels, and by the German, Italian, Russian, Polish, and -Hungarian translations of my work, the suggestions were carried over -Europe, crept into scientific journals, and became known to writers who -never heard of me. I only mention these facts lest the reader should -suppose that my views had been anticipated by certain continental -writers. - -[97] “La force nerveuse n’existe pas comme puissance independant des -propriétés de tissu. Elle consiste en l’action des parties excités, sur -les parties excitables, l’état de l’excitation des premières agissant -comme impression ou stimulation sur les secondes.”--LANDRY, _Traité des -Paralysies_, 1859, I. 142. - -[98] “Le système nerveux est tout à la fois l’origine des sensations -et l’origine des mouvements. Mais est-ce par une propriété unique, ou -par deux propriétés diverses qu’il détermine deux phénomènes aussi -distincts!” FLOURENS, _Recherches sur les propriétés et les fonctions -du Système Nerveux_, 1824, p. 1. He concludes that “la puissance -nerveuse n’est pas unique; il n’y a pas une seule propriété, il y en a -deux,” p. 24. In this he has been generally followed. - -[99] “I have raised and stretched the thick orbital nerve of horses -on the handle of a scalpel, like a string on the bridge of a violin, -without exciting the least sensation; but as soon as mechanical or -chemical irritation had given rise to inflammation of the nerve a -gentle touch caused violent pain.”--ROMBERG, _Nervous Diseases_ -(translated for the Sydenham Society), I. 10. - -[100] The experiments of HALLER, _Sur la nature sensible et irritable -des parties_, I. 245; and the remarks of PROCHASKA, DE FUNCTIONIBUS -SYSTEMATIS NERVOSI (translated by LAYCOCK in the volume published by -the _Sydenham Society_, p. 396), ought to have sufficed. See further -on, Chap. V. - -[101] In mammals about three days, in birds four days, in frogs -fourteen to twenty days. - -[102] RUTHERFORD, in _Journal of Anatomy_, 1873, No. VIII. p. 331. -(FLEISCHL denies that the nerve _in situ_ has different degrees of -reaction. _Sitzungsberichte der Wiener Akad._, December, 1876.) - -[103] MUNK, in the _Archiv für Anat._, 1860, p. 798. - -[104] HALLER, _Mémoires sur la nature sensible et irritable des -parties_. - -[105] _Comptes Rendus_, 1862, LIV. p. 965. - -[106] “J’espère vous convaincre que tous les éléments anatomiques -des nerfs sensitifs, moteurs, vasomoteurs, et autres, ont les -mêmes propriétés, et ne sont distincts que par leurs fonctions. -Cette question est de la plus haute importance pour la physiologie -générale. C’est celle qui domine toute la physiologie des fibres -nerveuses.”--VULPIAN, _Leçons sur la Physiologie du Système Nerveux_, -p. 11. - -[107] Mr. JAMES ANDREWS. - -[108] In the second number of _La Revue Philosophique_, Paris, 1876, I -have treated this question of specific energies more at length than I -could find space for in the present volume. - -[109] In 1859 I mentioned that if the nerves of a frog’s back be -exposed by raising the skin, they may be pricked or even cut without -sensible effect, although a slight prick on the skin will excite the -nerves, and cause a reflex action. In 1870, Prof. FICK expressed his -astonishment at finding that after he had cut out a piece of the -skin, leaving it attached to the body by a single nerve, electrical -stimulation of this excised skin caused the frog to make the reflex -movement of rubbing the irritated surface; whereas electrical -stimulation of the nerve-trunk itself produced no reflex effect, only a -twitching of a muscle. _Pflüger’s Archiv_, 1870, p. 327. BROWN SÉQUARD -tries to establish a distinct species of nerves as _conductors_ of -sensitive impressions, from those which are _impressionable_. The -facts on which he founds these two properties simply show that nerves -are so disposed that the stimulus which excites them in one place -fails in another. He could hardly maintain that a skin nerve contained -impressionable fibres at its periphery, and only conducting fibres in -its trunk! See his communication to the Royal Society, _Proceedings_, -1856; and _Lectures_ in the _Lancet_, 10th July, 1858. - -[110] In consequence of this observation some physiologists have -maintained that Feeling or Consciousness never arises in cerebral -activity, unless the thalami and the connected tracts are at the -same time in action. I go further, and maintain that there is no -Consciousness (in the restricted meaning of the term) _unless the whole -organism is involved_. Cerebral or spinal activity will be activity of -Sensibility; but this is only the basis of Consciousness. - -[111] “An unconscious sensation, which Lewes distinguishes -from perception, is to me an inconceivable (ist für mich -ein Unding).”--SCHRÖDER VAN DER KOLK, _Die Pathologie des -Geistes-Krankheiten_, p. 22. - -[112] By selective adaptation is meant the varying combination of motor -impulses to suit the varying requirements of the effect to be produced. -Physical mechanisms are limited to the performance of definite actions; -sensitive mechanisms employ fluctuating combinations of elements in -response to fluctuations of stimuli. The wheels, levers, springs, and -valves of a machine cannot be differently combined according to varying -degrees of the motor-force, as the nerves and muscles of an organism -are differently combined by varying sensations. An automaton may be -constructed to play on the violin, but it will only play the air to -which it is _set_; it cannot vary the performance,--cannot play a false -note, or throw in a _crescendo_ here, a _largo_ there, according to a -caprice of feeling. We must admit that violinist has his delicate and -changing movements guided by sensations, auditory and muscular; any -interruption in the sensations would arrest the movements, which in -truth _incorporate_ them. And yet it is well known that the violinist -may perform while completely “unconscious.” I do not simply refer to -the fact that his thoughts and attention may be elsewhere; I refer to -such facts as are recorded in Pathology. TROUSSEAU, for example, had an -epileptic patient who was occasionally seized with attacks of complete -unconsciousness while he was performing in the orchestra; yet, on -reawakening to consciousness, he found that he had continued to play, -had kept proper time, and played the proper notes. - -[113] CLAUDE BERNARD, _Système Nerveux_, 1858, I. 349. - -[114] WORDSWORTH, _The Prelude_. - -[115] “On peut dire que toujours un phénomène de mouvement reconnait -pour point de départ une impression sensitive.”--CLAUDE BERNARD, I. 267. - -[116] Since this was written Prof. MICHAEL FOSTER and Mr. DEW SMITH -have published their very important researches on the motions of the -heart, which establish beyond a doubt that, in the molluscs at least, -there is no co-operation of either centre or nerve.--_Proceedings of -the Royal Society_, 18th March, 1875. (_See also Studies from the -Physiological Laboratory of Cambridge_, Part II., 1876.) Mr. Foster -knows that I had independently, and from a totally different line -of research, arrived at the same conclusion respecting the heart’s -movement. - -[117] _Comptes Rendus de la Socíété de Biologie_, 1847, I. 40. In -1856 he showed that not only were the muscles of the iris directly -stimulated by light (and this not by its calorific or chemical rays), -but that sixteen days after removal of the eye from the orbit, this -effect was observable in the eel. Yet a very few days after extirpation -of the eye the nerves are disintegrated.--_Proceedings of the Royal -Society_, 1856, p. 234. - -DONDERS has the following observations: “The movements of the iris -are of two kinds--reflex and voluntary. Reflex action is exhibited as -constriction of the pupil in consequence of the stimulus of incident -light upon the retina. Fontana has shown that the light falling upon -the iris produces no remarkable contraction. We have confirmed this -result by causing the image of a small distant light to fall, by means -of a convex lens, upon the iris, whereby, during slight perception of -light, a doubtful contraction occurred, which gave way to a strong -contraction so soon as the light entering the pupil excited a vivid -perception. Nevertheless, the experiments of Harless and Budge have -shown that even after death, so long as irritability remains, the pupil -still contracts upon the continued action of light. Of the correctness -of this we have satisfied ourselves. In a dog killed by loss of blood -the one eye was closed, the other opened and turned to the light: after -the lapse of an hour, the pupil of the opened eye was perceptibly -smaller than that of the closed eye. The latter now remained also -exposed to the light, and on the following day the diameter of both -eyes was equal. The upper jaw, alone with the eyes, was taken out of -some frogs; one eye was exposed to the light, while the other was -covered with a closely folded piece of black paper: after the lapse of -half an hour the pupil turned to the light was narrow, the other wide. -But the latter also contracted almost immediately after the removal of -the paper.”--DONDERS, _On the Anomalies of Accommodation and Refraction -of the Eye_. Trans. of the New Sydenham Society, p. 572. - -[118] The experiment often fails, but I have seen it several times -succeed. - -[119] _Pflüger’s Archiv_, 1872, p. 618. - -[120] See his Researches in _Pflüger’s Archiv, Bde._ II. and IV. - -[121] D’ORBIGNY, _Des Mollusques Vívants et fossils_, p. 113. - -[122] _Seaside Studies_, 2d ed., p. 101. - -[123] Cited by BROWN SÉQUARD, _Journal de la Physiologie_, 1858, p. 359. - -[124] Dr. NORRIS has recorded some striking observations in his paper -on “Muscular Irritability” in the _Journal of Anatomy_, 1867, No. II. -p. 217. Here is the only one I can find room for: “On taking up the -_dead_ frog and touching the limb (which during life had been paralysed -by section of its nerve) with my finger, _it was suddenly shot out -as if alive_. I placed the body down, and one or two _apparently -spontaneous movements_ of small extent afterwards occurred. On touching -the skin gently with the point of a needle, by the slight pressure upon -the muscle beneath, movements of the limb were also induced, but this -high degree of exaltation very rapidly disappeared.” - -[125] See their papers in the _Archiv für Psychiatrie_, 1875, Bd. V. -Heft 3. - -[126] This latter statement will be justified when I come to expound -the Triple Process, which I have named the _Psychological Spectrum_. - -[127] FOSTER and BALFOUR, _Elements of Embryology_, 1874, Part I. p. -52. HIS, _Untersuchungen über die erste Anlage des Wirbelthierleibes_, -1868, p. 197. - -[128] They state that the cells of the epiblast are the results -of direct segmentation, whereas the cells of the other layers are -formed at a subsequent period, and are only indirectly results of -segmentation. But if the observations of KOWALEWSKY are exact, this is -not the case with the hypoblast of the Amphioxus, which is from the -first identical with the epiblast. - -[129] KÖLLIKER, _Entwicklungsgeschichte des Menschen und der höheren -Thiere_, 1861, p. 71. - -[130] [According to BALFOUR’S recent observations, a large part of the -muscular tissue is derived from the layer of the mesoblast belonging to -the hypoblast.] - -[131] HIS, _Untersuchungen_, pp. 39, 40. - -[132] Quite recently OWSJANNIKOW has pointed out the termination of -fibres in the phosphorescent cells of the _Lampyris Noctiluca_. See his -paper in the _Mémoires de l’Acad. de St. Petersbourg_, 1868, XI. 17. -These phosphorescent cells are said to be ganglion-cells by PANCERI, -_Intorno della luce che emana dalle celleule nervose_ (Rendiconto della -Accad. delle Scienze, April, 1872); and by EIMER, _Archiv für mikros. -Anatomie_, 1872, p. 653. KÖLLIKER also calls the phosphorescent organ a -nervous organ. This is not to be interpreted as meaning that neurility -is phosphorescence, but simply that in some nerve-cells there is -phosphorescent matter, which is called into activity by stimulus of the -nerves. - -[133] BIDDER und KUPFFER, _Textur des Rückenmarks_, 1857, p. 108. -[What is said in the text has been rendered doubtful by the recent -researches of Mr. F. BALFOUR, _On the Development of the Spinal Nerves -in Elasmobranch Fishes_ (_Philos. Trans._, Vol. CLXVI. Part I.), which -show that in these fishes the ganglion has its origin in the spinal -cord.] - -[134] Comp. PROBLEM I. § 130, with the remarks of CHARLES ROBIN, -_Anatomie et Physiologie Cellulaires_, 1873, p. 20. - -[135] KLEINENBERG, _Hydra; Eine Anatomisch-Entwickelungs-Untersuchung_, -1872, p. 11. EIMER, _Zoologische Studien auf Capri_, 1873, p. 66. - -A similar formation is described by Dr. ALLMAN in the _Myriothela_; he -says, however, that he has never been able to trace a direct continuity -of the caudal processes of the cells with muscular fibrils. He believes -that the processes make their way to the muscular layer through -undifferentiated protoplasm.--_Philos. Transactions_, Vol. CLXV. Part -II. p. 554. - -An intermediate stage between this neuro-muscular tissue and the two -differentiated tissues seems presented in the Nematoid worms which -have muscles that send off processes into which the nerves pass. -GEGENBAUR declares his inability to decide whether these processes are -muscles or nerves. BÜTSCHLI thinks the nerve-process blends with the -muscle-process.--_Archiv für mikros. Anatomie_, 1873, p. 89. - -[136] “The gray matter of the cord seems undoubtedly to be formed by a -metamorphosis of the external cells of the epiblast of the neural tube, -and is directly continuous with the epithelium; there being no strong -line of demarcation between them.”--_Op. cit._, p. 185. - -[137] ROBIN, _Anat. et Physiol. Cellulaires_, p. 332. - -[138] STILLING, _Bau der Nervenprimitiv-Fasern_, 1856, p. 16. - -[139] “There was a time,” says KÖLLIKER, “when I confidently believed -that an hypothetical explanation of the arrangement of elements in -the spinal cord could be grounded on a basis of fact; but the deeper -my insight into the minute anatomy, the less my confidence became; -and now I am persuaded that the time is not yet come to frame such an -hypothesis.”--_Gewebelehre_, 5te Auf. 1867. - -[140] In the Gasteropoda the cells range from 220 μ to 3 μ (μ = 0,001 -millimètre). - -[141] HAECKEL, _Müller’s Archiv_, 1857. LEYDIG, _Vom Bau des -thierischen Körpers_, 1864, I. 84. ROBIN, _Anat. et Physiol. -Cellulaires_, p. 89. Should the observations of HEITZMANN be -confirmed, there would be ground for believing that neurine is -normally fibrillated. He says that the living protoplasm in the -Amœba, white blood-corpuscle, etc., is an excessively fine network, -which condenses into granules at each contraction. (Cited in the -_Jahresberichte über Anat. und Physiol._, 1873, Bd. II.) WALTHER, who -examined frozen brains, describes the cells as quite transparent at -first, with very rare granules, but gradually while under observation -the granules became more numerous. _Centralblatt_, 1868, p. 459. -According to MAUTHNER, _Beiträge zur Kenntniss der morphologischen -Elemente des Nervensystems_, 1862, p. 41, neurine has three cardinal -forms--transparent, finely granular, and coarsely granular. - -[142] TRINCHESE, _Struttura del sistema nervoso dei Cefalopodi_, -Florence, 1868, p. 7. - -[143] An eminent friend of mine was one day insisting to me that the -physiological postulate made it _impossible_ for a nerve-cell to be -without its ingoing and outgoing fibres; and he was not a little -astounded when I replied, “Come into my workroom and I will show you a -thousand.” - -[144] EICHHORST in _Virchow’s Archiv_, 1875, LXIV. p. 432. - -[145] AUERBACH (_Ueber einen Plexus Myentericus_, 1862) describes -the ganglia as filled with apolar cells, among which only a few are -unipolar. STIEDA (_Centralnervensystem der Vögel_, 1868) finds both -apolar and unipolar cells in the spinal ganglia of birds. AXMANN (_De -Gangliorum Systematis Structura penitiori_, 1847) says the spinal cells -are all unipolar. SCHWALBE (_Archiv für mikros. Anat._, 1868) and -COURVOISIER (_ibid._, 1869) say the same. So also RANVIER, _Comptes -Rendus_, 1875. KÖLLIKER (_Gewebelehre_) speaks decidedly in favor of -both apolar and unipolar cells, but thinks the apolar are embryonic. -PAGLIANI (_Saggio sullo Stato attuale delle Cognizioni della Fisiologia -intorno al Sistema nervoso_, 1873), who represents the views of -MOLESCHOTT, admits the existence of apolar and unipolar cells. The -authors just cited are those I happen to have before me during the -rewriting of this chapter, and the list might easily be extended if -needful. AUERBACH, BIDDER, and SCHWEIGGER-SEIDEL describe unipolar -cells which in some places present the aspect of bipolar cells simply -because two cells lie together, their single poles having opposite -directions. I will add that the bipolar cells do not really render the -physiological interpretation a whit more easy than the unipolar, for -they are simply cells which form enlargements in the course of the -nerve-fibres. - -[146] When Dr. BEALE says “that it is probable no nerve-cell exists -which has only _one single fibre_ connected with it” (_Bioplasm_, p. -186), he has no doubt this in his mind; since he would not, I presume, -deny that there are cells each with a single _process_. - -[147] DEITERS, _Untersuchungen über Gehirn und Rückenmark_, 1865. - -[148] _Archiv für mikros. Anat._, 1869, p. 217. Compere also BUTZKE, -_Archiv für Psychiatrie_, 1872, p. 584. - -[149] HENLE, _Nervenlehre_, 1871, p. 58, Fig. 21. - -[150] When men of such experience and skill as KÖLLIKER, BIDDER, GOLL, -and LOCKHART CLARKE declare that they have never seen a cell-process -pass directly into a dark-bordered fibre in the anterior root, what -are we to say to such figures and descriptions as those given in the -works of SCHRÖDER VAN DER KOLK, GRATIOLET, and LUYS? Even did such -arrangements exist, no transverse nor longitudinal section could -display them, owing to the different planes at which the fibres enter, -and the length and irregularity of their course. - -[151] Long after the text was written, WILLIGK published in _Virchow’s -Archiv_, 1875, LXIV. p. 163, observations of anastomoses which even -KÖLLIKER admitted to be undeniable. Yet out of sixty-four preparations, -amid hundreds of cells, he could only reckon seven cases of conjunction. - -[152] See the history given in STILLING’S learned work, _Ueber den Bau -der Nervenprimitiv-Faser_, p. 34; and compare MAX SHULTZE, _De Retinæ -Structura_, p. 8, and _Bau der Nasenschleimhaut_, p. 66; WALDEYER, in -the _Zeitschrift für rat. Med._, 1863; LISTER and TURNER, _Observations -on the Structure of Nerve-Fibres_, in _Quarterly Micros. Journal_, -1859; RANVIER, in the _Archives de Physiologie_, 1872. - -[153] _Virchow’s Archiv_, Bd. LXXII. p. 193. - -[154] _Monthly Journal of Micros. Science_, 1874, XI. p. 214. - -[155] BABUCHIN, _Centralblatt_, 1868, p. 756. - -[156] Even so eminent an authority as W. KRAUSE holds this both with -regard to the varicose aspect and the double contour: _Handbuch der -menschlichen Anatomie_, 1876, I. 367. BUTSCHLI, however, describes the -nerves in a living Nematode as varicose: _Archiv für Anat._, 1873, p. -78; and I have somewhere met with an observation of the double contour -being visible in the living animal. - -[157] BUTZKE, _Archiv für Psychiatrie_, 1872, p. 594, states that the -granular substance has the chemical composition of myeline. If this -be so, we may suppose the “fibrils of crystallization” to represent -the coagulation of the substance which is in solution amid the myeline -granules, and corresponds with the axis cylinder of a fibre. I may -remark that in almost every good preparation nerve-cells will be found -in which, while one process is distinctly granular, another is striated -or even fibrillated. - -[158] BOLL, _Die Histiologie und Histiogenese der nervösen -Centralorgane_, in the _Archiv für Psychiatrie_, 1873, p. 47. - -[159] STIEDA, _Studien über das Centralnervensystem der Vögel_, 1868, -p. 65. MAUTHNER, _Op. cit._, p. 4. - -[160] TURNER and LISTER, _Op. cit._, p. 8. - -[161] BLESSIG, _De Retinæ Structura_, 1857. - -[162] LUYS, _Recherches sur le Système nerveux_, 1865, p. 267. In a -recent and remarkable treatise the student is informed that “plus -une cellule est chargée d’un rôle purement mécanique plus elle est -volumineuse; plus l’acte qu’elle produit tend à revêtir un caractère -psychique plus elle est petite”; to move a limb the _agitation_ of -the cerebral cells must _materialize itself_ more and more, “Il a -besoin de passer par des cellules, de moins en moins spirituelles et -de plus en plus matérielles.... De même pour les cellules sensitives. -L’impression extérieure va en se modifiant, en se spiritualisant, de la -périphérie au centre.... Un phénomène de l’ordre spirituel ne sanrait -devenir sans transition un phénomène d’ordre physique.” And what is -this marvellous transition between spiritual and physical? It is the -action of medium-sized cells which “travaillent la vibration reçue, la -modifient de façon à lui ôter de son spiritualisme et à la rapprocher -davantage des ébranlements physiques.” I will not name the estimable -author, because he is simply restating what many others implicitly or -explicitly teach; but I will only ask the reader to try and realize in -thought the process thus described. - -[163] SCHRÖDER VAN DER KOLK, _Pathologie der Geisteskrankheiten_, 1863, -p. 69. - -[164] WUNDT, _Physiologische Psychologie_, p. 261. In his _Mechanik -der Nerven, 2 Abth._ (published just as this sheet is going to press), -he shows that a stimulus is both retarded and weakened in its passage -through a ganglion. - -[165] TRINCHESE also says that the fibres “provengono dalle cellule e -_non son altro che i loro prolungamenti o poli_.”--_Op. cit._, p. 13. -An unequivocal example is seen in the _Torpedo_, where the large cells -have each their prolongation continuing without interruption into the -electrical organ. See the figure given by REICHENHEIM in the _Archiv -für Anat._, 1873, Heft VI. - -[166] GOLGI, _Sulla struttura della sostanza grizia del Cervello_. -ARNDT, _Archiv für mikros. Anat._ 1870, p. 176. RINDFLEISCH also traces -these processes into the neuroglia (_ibid._, 1872, p. 453). “Deiters, -Boddaert, and other observers have stated that one dark-bordered -nerve-fibre enters each cell.... My own observations lead me to -conclude that _all_ the fibres are composed of the same material, but -that one fibre does not divide until it has passed some distance from -the cell, while others give off branches much closer to it.”--BEALE, -_Bioplasm_, p. 189. - -[167] BEALE, _Bioplasm_, p. 177. MAX SCHULTZE, in _Stricker’s -Handbuch_, p. 134. Comp. STILLING, _Nervenprimitiv-Faser_, p. 133. -ARNDT, _Archiv_ _für mikros. Anat._, 1868, p. 512; and 1869, p. 237. -Weighty as these authorities are, their view is questionable--firstly, -because the forms of these cells are too constant and definite in -particular places to result from the union of fibrils coming from -various origins; but secondly, and mainly, because the teaching of -Development is opposed to it. - -[168] ROBIN, _Anat. et Physiol. Cellulaires_, p. 335. - -[169] _Archives de Physiologie_, 1872, p. 268. - -[170] The fact of the existence of cells in the white substance is one -which is very difficult of interpretation on the current hypotheses. -The cells are found in regular columns and irregularly scattered. -BOLL thinks that while in the white substance of both cerebrum and -cerebellum there are true nerve-cells as well as connective corpuscles, -in the cord there are only the latter. But hitherto there has been -no decisive test by which a nerve-cell can be distinguished from a -connective corpuscle. - -[171] _Monthly Journal of Micros. Science_, XI. 219. This accords -with what KUPFFER says respecting the entire absence of cells -in the earliest stages observed by him in the sheep. The white -substance of the spinal cord he describes as soft, transparent, and -gelatinous, in which dark points are visible; these dark points are -seen in longitudinal sections to arise from the fibrillation of the -substance.--BIDDER und KUPFFER, _Op. cit._, p. 111. - -[172] WEISMANN, _Die nachembryonale Entwick. der Musciden_, in the -_Zeitschrift für Wissen. Zoologie_, 1864, Bd. XIV. Heft III. - -[173] The suggestion in the text has since received a striking -confirmation in the observations of SIGMUND MAYER on the regeneration -of nerves. The nerve when divided rapidly undergoes fatty degeneration, -which is succeeded by a transformation of the myeline and axis cylinder -into a homogeneous mass; in this resolved pulp new longitudinal -lines of division appear, which subsequently become new fibres, -and new nuclei are developed in the remains of the untransformed -substance.--_Archiv für Psychiatrie_, Bd. VI. Heft II. - -[174] Strong confirmation of various statements in the text, since -they were written, has been furnished by the researches of EICHHORST, -published in _Virchow’s Archiv_, LXIV. Our knowledge of the development -of nerve-tissue in human embryos is so scanty that these researches -have a great value. EICHHORST describes the striation of the cells in -the cord to begin only at the fourth month; up to this time they are, -what I find most invertebrate cells to be, granular, not fibrillar. -There is very slight branching of the cell processes until the ninth or -tenth month, when the multipolar aspect first appears; the cells are -unipolar up to the end of the fourth month. The connection between the -white columns and the gray columns is very loose up to the fifth month; -and the two are easily separated. Subsequently the union is closer. -The substance of the white columns readily separates into bundles and -fibres, but that of the gray columns falls into a granular detritus if -attempted to be teased out with needles. But after the fifth month this -is no longer so. Instead of a granular detritus there appears a network -of fine fibres and fibrils. Although the white posterior columns are -developed before the fifth month, not a single cell can be seen in -the posterior gray columns until the second half of the ninth month. -(Yet the fibres are imagined to arise in the cells!) The passage from -the granular to the fibrillar state is the same in the cell substance -and the neuroglia. The nerve-fibre, as distinguished from a naked -axis cylinder, does not appear till the fourth month. It is at first -a bipolar prolongation of the nucleus. As it elongates, the nucleus -seems to sit _on_ it, and so loosely that it is easily shifted away by -pressure on the covering glass. Finally the fibre separates entirely -from the nucleus, and _then_ begins to clothe itself with the medullary -sheath. Very curious is the observation that so long as the axis -cylinder is naked it is never varicose, but with the development of the -medulla the primitive axis becomes fluid. - -[175] MAYER, _Op. cit._, 393. I cannot, however, agree with MAYER when -he says that the continuity of a nerve-fibre with a cell has _never_ -been distinctly shown (p. 395); in the Invertebrata and in the Electric -fishes such a continuity is undeniable; and it has occasionally been -seen in Vertebrata. - -[176] RANVIER, in the _Comptes Rendus_, 1875, Vol. LXXXI. p. 1276. This -observation throws light on the fact that cell processes are sometimes -seen entering nerve-roots (§ 124). - -The very remarkable observations of Mr. F. BALFOUR, _On the Development -of the Spinal Nerves in Elasmobranch Fishes_ (_Philos. Trans._, Vol. -CLXVI. p. 1), show that the spinal root, ganglion, and nerve-trunk -arise from histological changes in a mass of cells at first all alike; -_not_ that ganglion-cells are formed and from their processes elongate -into fibres. The nerve, he says, forms a continuation of its root -rather than of its ganglion (p. 181); which accords with RANVIER’S view. - -[177] In the _Handbuch der menschlichen Anatomie_ of W. KRAUSE, which -has just appeared, I am pleased to find a similar view, p. 376. - -[178] On this point consult AXEL KEY and RETZIUS, in the _Archiv für -mikros. Anat._, 1873, p. 308, where the nutritive disturbance is -assigned to the fact that the lymph can no longer take its normal -course. WALLER’S observations on the degeneration of the optic nerves, -with preservation of the integrity of the retina, after division of the -nerves (_Proceedings of Royal Society_, 1856, p. 10), cannot be urged -in support of his view, because BERLIN and LEBERT’S observations are -directly contradictory of his. SAEMISCH _und_ GRAEFE, _Handbuch der -Augenheilkunde_, II. 346. It is said by KRENCHEL that if the nerves -be divided, so as to prevent disturbances in the circulation, no -peripheral degeneration takes place (cited by ENGELMANN in _Pflüger’s -Archiv_, 1875, p. 477). - -[179] SCHIFF, _Lehrbuch der Physiologie_, pp. 120, 121. - -[180] KÖLLIKER, _Gewebelehre_, 317. SCHWALBE, _Archiv für mikros. -Anat._, 1868, p. 51. - -[181] I was first shown this in 1858 by the late Prof. HARLESS in -Munich, who at the same time showed me that the nerve thus bared of -its sheath, if left some hours in gastric juice, split up into regular -discs, like the sarcous elements of muscles. - -[182] STIEDA, _Bau des centralen Nervensystem der Amphibien und -Reptilien_, 1875, p. 41. - -[183] BUTZKE, in _Archiv für mikroskopische Anatomie_, Bd. III. Heft 3, -p. 596. - -[184] Except in the rare cases where there is anastomosis of the -muscle-fibres; as, for example, in the heart. [According to ENGELMANN’S -remarkable researches, the muscles of the heart form a continuum, -so that irritation is propagated from one to the other: _Pflüger’s -Archiv_, 1875, p. 465. This is indubitably the case in the embryonic -heart, as ECKHARD pointed out.] This I hold to be the main cause of -its rhythmic pulsation after removal from the body. Whatever influence -the ganglia may have in exciting this pulsation, such influence would -be powerless were not the muscles so connected; as may be seen in the -other organs which are richly supplied with ganglia, yet do not move -spontaneously; and in organs (such as the ureter or the embryonic -heart, and the hearts of invertebrata) which move spontaneously, yet -have no ganglia. - -[185] SCHRÖDER VAN DER KOLK, _Bau und Funktionen der Med. Spinalis_, p. -67. - -[186] It is very instructive to learn that for some six months or so -the rat is quite incapable of correctly _localizing_ the pain. - -[187] VULPIAN, _Leçons sur le Système Nerveux_, p. 288. The experiment -has been confirmed by ROSENTHAL, and by BIDDER (_Archiv für Anatomie_, -1865, p. 246), who first (in 1842) attempted this union of different -nerves, but arrived at negative results; as did SCHIFF (_Lehrbuch -der Physiol_, 1859, p. 134) and GLUGE _et_ THIERNESSE (_Annales des -Sciences Naturelles_, 1859, p. 181). - -[188] SACHS, in the _Archiv für Anat._, 1874, pp. 195, _sq._ - -[189] LAPLACE, _Essai Philos. sur les Probabilités_, p. 239. - -[190] The mode of termination of nerves in muscles is still a point -on which histologists disagree; probably because there is no abrupt -termination, but a blending of the one tissue with the other. In the -Tardigrades, for example, there is actually no appreciable distinction -between nerve and muscle at the point of insertion of the nerve; and -if in the higher animals there is an appreciable difference between -nerve and muscle, there is an inseparable blending of undifferentiated -substance at their point of junction. [According to ENGELMANN’S -recent researches, there seems good reason to suppose that muscles -are composed of contractile substance and a substance which is a -modification of axis-cylinder substance; the first being doubly -refracting, the second isotropic: _Pflüger’s Archiv_, 1875, p. 432.] - -[191] SCHIFF, _Lehrbuch_, p. 73. - -[192] FREUSBERG observed that the reflex movements in the legs of a -dog whose spine had been divided were considerably lessened after -food or drink. They fell from 95 to 46 pendulum-beats in a minute -after a _litre_ of water had been drunk. See his instructive memoir, -_Reflex-Lähmungen beim Hunde_, in _Pflüger’s Archiv_, 1874, p. 369. - -[193] M. HERZEN thus describes the effects of stimulating the vagus -with varying intensities: “Si l’on se sert de l’appareil de Dubois -Raymond, on commence par appliquer une irritation tellement faible -qu’elle ne produit aucun effet; on rapproche alors peu à peu lea -deux bobines de l’appareil avec le plus grand soin, par fractions de -centimètres, par _millimètres_ s’il le faut, et l’on trouve ainsi -le degré d’irritation qui accelère les battements du cœur et qui -produit le maximum de pulsations dans l’unité de temps admise pour -l’expérience. Quand on est là il suffit _d’un millimètre_ de plus pour -faire disparaître l’augmentation, un autre millimètre peut produire une -diminution, et un _troisième_ peut arrêter le cœur complètement. En -reculant alors, en éloignant peu à peu les deux bobines, _on rètourne -à la force qui produit l’augmentation des battements_.” HERZEN, -_Expériences sur les Centres Modérateurs de l’Action Réflexe_, 1864, -p. 68. There have been serious doubts thrown on these experiments; but -several experimenters have confirmed their exactness. Quite recently -they have been confirmed by BULGHERI, _Il Morgagni_, VIII.; and by -ARLOING and TRIPIER, _Archives de Physiologie_, 1872, IV. p. 418. It -must be confessed, however, that the whole subject of the heart’s -innervation is at present very imperfectly understood. - -[194] CAYRADE, _Recherches sur les Mouvements Réflexes_, 1864, p. 58. - -[195] A frog’s brain is removed, and the body then suspended by the -lower jaw, the legs are allowed to dip into a slightly acidulated -liquid, the chemical action of which stimulates the skin. - -[196] I saw a patient in the Berlin _Charité_ whose face and left hand -were in a constant state of convulsive twitching, but no sooner was a -scar on the left hand (where the nerve had been divided) firmly pressed -than the twitchings ceased, and _pain_ was felt; on removal of the -pressure, pain ceased and the twitchings returned. - -[197] _Pflüger’s Archiv_, 1875. No one interested in the Reflex Theory -should omit a careful study of the papers by FREUSBERG and GOLTZ. I -have drawn freely from them. - -[198] Sir JAMES PAGET has an interesting collection of facts which -illustrate this Law of Arrest, in his paper on “Stammering with other -Organs than those of Speech,” _British Medical Journal_, 1868, Vol. II. -p. 437, reprinted in his _Clinical Lectures and Essays_, 1875, p. 77. - -[199] _Archives de Physiol._, 1868, p. 157. - -[200] _West Riding Lunatic Asylum Reports_, 1874, p. 200. - -[201] CLAUDE BERNARD, _Système Nerveux_, I. 383. - -[202] See the excellent remarks of Dr. LAUDER BRUNTON on this point in -his paper on Inhibition in the _West Riding Lunatic Asylum Reports_, -1874, p. 180. - -[203] The interesting question of interference has been experimentally -treated by WUNDT in his recently published _Mechanik der Nerven_, 1876, -and theoretically as wave-movement by MEDEM, _Grundzüge einer exakten -Psychologie_, 1876. - -[204] On the distinction between first notions and theoretic -conceptions, see _Problems of Life and Mind_, Vol. II. p. 277. - -[205] Not transcendental and _a priori_, as Kant teaches; but immanent -in Feeling. - -[206] The reader will understand that although mechanical relations -are modes of Feeling, as all other relations are, yet their aspect -is exclusively objective, referring to objects ideally detached from -subjects. - -[207] ANTOINE CROS, _Les Fonctions supérieures du Système nerveux_, -1875, p. 85. - -[208] The solution offered in the present chapter was first offered -in _Problems of Life and Mind_, 1875, II. 465, _sq._ I mention -this because since the publication of that volume other writers -have expressed the same ideas, sometimes using my language and -illustrations: e. g. M. TAINE in the _Revue Philosophique_, January, -1877, art., _Les Vibrations cérébrales et la Pensée_. - -[209] _Problems of Life and Mind_, Vol. II. pp. 443 and 482. - -[210] “The retinal image is the last effect known of the action -of objects on us; what happens beyond the retina we know not; -our knowledge of the objective process has at present here its -limit.”--EWALD HERING, _Beiträge zur Physiologie_, 1862, p. 166. That -is to say, we have a definite translation of the process in geometric -terms as far as the retina, and thence onwards Geometry fails us, and -Neurology and Psychology are invoked. - -[211] Compare PROBLEM II. Chap. IV. - -[212] “Das Bewusstwerden ist nichts Anderes als ein weiter -fortgeschrittenes Erinnern oder Neuwerden des von aussen aufgenommenen -Wissens, ein innerliches Wissen dieses Wissens oder ein in sich -reflectirtes Wissen.”--JESSEN, _Versuch einer Wissenschaftlichen -Begründung der Psychologie_, 1855, p. 477. - -[213] In common language a stone or a tree is said to be unconscious; -but this is an anthropomorphic extension of the term. In strictness we -should no more speak of unconsciousness outside the sphere of Sentience -than of darkness outside the sphere of Vision. - -[214] The contraction may be effected in the eye out of the organism. -See p. 229. It is then no reflex. - -[215] _Glasgow Medical Journal_, 1857, p. 451. See also further on, -note to p. 426. - -[216] MAYER, _Die Elementarorganisation des Seelenorgans_, p. 12, is -the authority for the last statement. - -[217] _Allgemeine Zeitschrift für Psychiatrie_, Bd. 31, p. 711. - -[218] AUBERT, _Grundrüge der physiol. Optik_, 1876, p. 633. “The -accommodative movement of the eye is to be considered voluntary. It is -true we contract the pupil without being conscious of the contraction -of muscular fibres, _but this holds good for every voluntary movement_. -When a person raises the tone of his voice he is not conscious that -by muscular contraction he makes his chordæ vocales more tense; he -attains his object without being aware of the means by which he does -so. The same is applicable to accommodation for near objects and to -the contraction of the pupil accompanying it. The fact that _this last -is only an associated movement does not deprive it of its voluntary -character_, for there is perhaps no single muscle which can contract -entirely by itself.” DONDERS, _On the Anomalies of Accommodation_, -1864, p. 574. Professor BEER of Bonn has the rare power of contracting -or dilating the pupils of his eye at will; here ideas act as motors. -When he thinks of a very dark space the pupil dilates, when of a very -bright spot the pupil contracts. (NOBLE, _The Human Mind_, 1858, p. -124.) I believe this to be only an exaggerated form of the normal -tendency. In all of us the mechanism is so disposed that the feelings -of dilatation are associated with feelings (and consequently ideas) of -darkness; and by this association a reversal of the process obtains, so -that the idea of darkness calls up the feeling it symbolizes. - -[219] SPENCER, _Principles of Psychology_, I. 499. - -[220] DESCARTES expressly calls them sensitive machines. He refuses -them Thought, but neither “la vie ou le sentiment.” He adds, “Mon -opinion n’est pas que les bêtes voient comme nous lorsque nous sentons -que nous voyons.”--_Œuvres_, IV. p. 339. This example is cited by him -in proof of human automatism: “Que ce n’est point par l’entremise de -notre âme que les yeux se ferment, puisque c’est contre notre volonté, -laquelle est sa seule ou du moins sa principale action; mais c’est -à cause que la machine de notre corps est tellement composée que le -mouvement de cette main vers nos yeux excite un autre mouvement en -notre cerveau qui conduit les esprits animaux dans les muscles qui font -abaisser les paupières.” All indeed that we assign to Sensibility, he -assigns to these hypothetical animal spirits, and thence he concludes, -“Qu’il ne reste rien en nous que nous devions attribuer à notre âme -sinon nos pensées.”--_Les Passions de l’Âme_, art. 13 and 17. Comp. -_Discours de la Méthode_, partie iv. - -[221] DESCARTES compares the animal mechanism to that of the grottos -and fountains at Versailles, the nerves to the water-tubes:--“Les -objets extérieurs qui par leur seul présence, agissent contre les -organes des sens, et qui par ce moyen, la déterminent à se mouvoir -en plusieurs diverses façons, selon comme les parties du cerveau -sont disposées, sont comme les étrangers, qui entrant dans quelques -unes des grottes de ces fontaines causent euxmêmes sans y penser les -mouvements qui s’y font en leur présence: car ils n’y peuvent entrer -qu’en marchant sur certains carreaux tellement disposés, que s’ils -approchent d’une Diane qui se baigne, ils la font cacher dans les -roseaux; et s’ils passent outre pour la poursuivre, ils feront venir -vers eux un Neptune qui les menacera de son trident; ou s’ils vont de -quelque autre costé, ils en feront sortir un monstre marin qui leur -vomira de l’eau contre la face.”--_Traité de l’Homme_, 1664, p. 12. -Ingenious as the comparison is, it only illustrates how machines may -be constructed to imitate animal actions. Diana always hides herself -when a certain spot is trodden upon; and Neptune always appears when -another spot is trodden upon. There is no fluctuation, no sensibility -discerning differences and determining variations. Compare the -following experiment: A monkey was placed on the table and a shrill -whistle made close to its ear: “Immediately the ear was pricked and -the animal turned with an air of intense surprise, with eyes widely -opened and pupils dilated, to the direction whence the sound proceeded. -On repetition of the experiment several times, though the pricking -of the ear and the turning of the head and eyes constantly occurred, -the look of surprise and dilatation of the pupils ceased to be -manifested.”--FERRIER, _The Functions of the Brain_, 1876, p. 171. A -mechanical monkey would always have reacted in precisely the same way -on each stimulus. - -[222] Printed in the _Fortnightly Review_, November, 1874, from which -all my citations are made. - -[223] SCHIFF, _Lehrbuch der Physiol._, 1858, p. 212. HERMANN, -_Physiology_, translated by GAMGEE, 1875, p. 511. - -[224] Meanwhile the reader is referred to SCHRÖDER VAN DER KOLK, -_Pathologie der Geisteskrankheiten_, 1863, p. 51; or JESSEN, -_Physiologie des menschlichen Denkens_, 1872, p. 66. - -[225] GRIESINGER, _Les Maladies Mentales_, p. 96. - -[226] M. LUYS cites the case of a patient who conversed quite -rationally with a visitor “sans en avoir conscience, et ne se -souvenait de rien”; and he draws the extraordinary conclusion that -the conversation “s’opérait en vertu des forces réflexes.”--_Études -de Physiologie et de Pathologie Cérébrales_, 1874, p. 117. Is it -not obvious that the patient must have been conscious at the time, -though the consciousness vanished like that in a dream? The persistent -consciousness is the continuous linking on of one state with previous -states--the apperception of the past. - -[227] ABERCROMBIE, _Inquiries concerning the Intellectual Powers_, -1840, p. 151. WIGAN, _The Duality of the Mind_, 1844, p. 270. DESPINE, -_La Psychologie Naturelle_, 1868, I. 54. - -[228] Dr. HUGHLINGS JACKSON has quite recently cited some curious -examples in his own practice. See _West Riding Lunatic Asylum Reports -for 1875_. - -[229] PROBLEMS, Vol. II. p. 478, _sq._ - -[230] “Le sentiment fait naître le mouvement, et le mouvement donne -naissance au sentiment.”--VAN DEEN, _Traités et Découvertes sur la -Moëlle Épinière_, 1841, p. 102. - -[231] Dr. CARPENTER tells a similar story of Admiral CODRINGTON, who, -when a midshipman, could always be awakened from the profoundest -slumber if the word “signal” were uttered; whereas no other word -disturbed him. - -[232] Compare an interesting personal example given by JOUFFROY, quoted -in Sir W. HAMILTON’S _Lectures_, I. 331. - -[233] _Lancet_, 10th July, 1858. - -[234] MARSHALL HALL in _Philos. Trans._, 1833. _Lectures on the Nervous -System and its Diseases_, 1836. _New Memoir on the Nervous System_, -1843. - -[235] MÜLLER, _Physiology_, I. 721. - -[236] It is better simply to remove the brain, than to remove the whole -head, which causes a serious loss of blood. An etherized animal may be -operated on with ease and accuracy. For many experiments, mere division -of the spinal cord is better than decapitation. Great variations in the -results must be expected, because the condition of the animal, its age -and sex--whether fasting or digesting--whether the season be spring or -summer--and a hundred other causes, complicate the experiment. - -[237] VOLKMANN, quoted by PFLÜGER. - -[238] UNZER, _The Principles of Physiology_ (translated for the -Sydenham Society), p. 235. - -[239] Even so eminent an investigator as GOLTZ has fallen into this -confusion. He introduces an experiment to prove that the brainless -frog is insensible to pain by the words “when an animal, placed under -circumstances which would be very painful, makes no movement, although -quite capable of moving, the least we can say is that it is improbable -that the animal has sensation” (_Nervencentren des Frosches_, p. -127). I need not discuss the proof itself, having already done so in -_Nature_, Vol. IX. p. 84. The point to which I wish to call attention -is the confusion of insensibility in general with insensibility to pain. - -[240] See DUCHENNE, _De Électrisation localisée_, p. 398. GRIESINGER -cites various examples of insane patients who have burned the flesh off -their bones while manifesting a total indifference to these injuries. -_Maladies Mentales_, p. 94. FALRET says, “Nous avons vu plusieurs -fois des aliénés s’inciser, s’amputer eux-mêmes diverses parties du -corps sans paraître ressentir aucune souffrance.” _Leçons cliniques -de Médicine Mentale_, 1854, I. 189. Patients incapable of feeling the -contact of a hot iron with their skin have felt subjective burnings in -the skin thus objectively insensible. - -[241] CROS, _Les Fonctions supérieures du Syst. nerveux_, 1875, p. 27. - -[242] _Virchow’s Archiv_, Bd. XXVIII. p. 30. - -[243] The idea of a _fixed anatomical mechanism_ for reflexion, such -as that of an excito-motory system, is completely refuted by the fact -that the gray substance may anywhere be cut sway, and yet so long -as a small bridge of gray substance remains the stimulation will be -propagated through it. The idea of a _fixed pathway_ is also refuted by -the fact of the variations in the reflex responses, and the necessary -irradiation even for very simple reflexes. Take, for example, that of -breathing. An irritation of the bronchial filaments is transmitted by -the pneumogastric to its centre in the medulla oblongata; from this, -however, it is immediately irradiated _downwards_ to the cervical and -dorsal regions, which innervate the muscles of chest and diaphragm, and -_upwards_ to the brain, whether the stimulation awaken consciousness or -not. One may say, indeed, that inasmuch as under normal conditions the -bronchial irritation always causes a movement of a particular group of -muscles, there is to this extent a fixed pathway of discharge; but, as -I have formerly explained, this is only an expression of the particular -tension of particular centres, and is variable with that tension; the -other centres are also affected, even when they are not excited to -discharge. - -[244] LALLEMAND, _Recherches sur L’Encéphale_, III. 310. - -[245] _West Riding Lunatic Asylum Reports_, 1875, Vol. V. pp. 252, _sq._ - -[246] GALL _et_ SPURZHEIM, _Anat. et Physiol. du Système Nerveux_, I. -83. - -[247] Printed in the _British and Foreign Medical Review_, Jan. 1845. - -[248] GRIESINGER, _Abhandlungen_, 1872. The first volume contains a -reprint of this memoir. - -[249] LANDRY, _Traité des Paralysies_, I. 55. Conf. ZIEMSSEN, _Chorea_ -in the _Handbuch der speciellen Pathologie_, Bd. XII. 2, p. 408. And -LUYS, _Études de physiol. et pathol. cérébrales_, 1874, pp. 89–94. - -[250] SUE, _Recherches Philosophiques sur la Vitalité et le -Galvanisme_, p. 9. He was not consistent, however, but adopted Bichat’s -opinion respecting the sensibility of the viscera, p. 68. - -[251] LEGALLOIS, _Expériences sur le principe de la vie_. Published, -I conclude, in 1811; the edition I use is the one printed in the -_Encyclopédie des Sciences Medicales_, IV. - -[252] WILSON PHILIP, _Experimental Inquiry into the Laws of the Vital -Functions_, pp. 209, 210. - -[253] LONGET, _Traité de Physiologie_, II. 105. - -[254] He cites Cuvier, Majendie, Deamoulins, and Mayo as maintaining -this error. - -[255] GRAINGER, _Structure and Functions of the Spinal Cord_, p. 66. - -[256] NASSE, _Unters. zur Physiologie und Pathologie_, Vol. II. Part 2. - -[257] CARUS, _System der Physiologie_, III. 101. - -[258] J. W. ARNOLD, _Die Lehre von der Reflex-Function_, 86. - -[259] PFLÜGER, _Die sensorischen Functionen des Rückenmarks der -Wirbelthiere_. - -[260] Except AUERBACH, who repeated and varied the experiments; and -FUNKE, who partially adopted the conclusions in his systematic treatise -on Physiology. - -[261] SCHIFF, _Lehrbuch der Physiologie_, 208. - -[262] LANDRY, _Traité des Paralysies_, 1859, maintains that the cord is -a centre of sensation, and that there is in it a faculty _analogous_ -to the perception and judgment of the brain. Compare pp. 163 _et sq._ -and 305. He also cites an essay by Dr. PATON of Edinburgh (_Edinburgh -Medical Journal_, 1846), in which the sensational and volitional claims -of the spinal cord are advanced. - -[263] GOLTZ, _Beiträge zur Lehre von den Functionen der Nervencentren -des Froeches_, 1869. - -[264] _Pflüger’s Archiv_, Bd. XIV. p. 158. - -[265] See Prob. II. § 183. - -[266] “Il y a donc une mémoire par le cerveau et une mémoire par -l’automate. Tous les organes ont une mémoire propre, c’est à dire _une -tendance à_ reproduire les séries d’actes qu’ils ont plusieurs fois -executés.”--GRATIOLET, _Anat. du Système Nerveux_, 1857, p. 464. - -[267] To obviate misunderstanding let me say that, unless the contrary -is specified, I use the term Brain throughout this argument as -equivalent to the cerebral hemispheres, because it is in these that -sensation, volition, and consciousness are localized by the generality -of writers, many of whom, indeed, regard the cells of the gray matter -of the convolutions as the exclusive seat of these phenomena, dividing -these cells into sensational, emotional, and intellectual. There -are physiologists who extend sensation to the cerebral ganglia and -gray masses of the medulla oblongata; but the medulla spinalis is so -clearly continuous with the medulla oblongata that there is a glaring -inconsistency in excluding sensation from the one if it is accorded to -the other; and the grounds on which sensitive phenomena are admitted in -the absence of the hemispheres, force us to admit analogous phenomena -in the absence of the ganglia and medulla oblongata: in each case the -phenomena are less complex and varied as the mechanisms become less -complex. - -[268] Compare LUSSANA e LEMOIGNE, _Fisiologia dei centri encefalici_, -1871, II. 239, 240, 330. - -[269] See a very interesting case of this special loss of memory -in a priest who still occupied himself reading classic authors and -performing his official duties many months after an injury to the -brain. LUSSANA e LEMOIGNE, _Fisiologia dei centri encefalici_, I. 201. - -[270] BOUILLAUD, _Recherches Expérimentales sur les Fonctions du -Cerveau en général_, 1830, p. 5, _sq._ - -[271] LONGET, _Traité de Physiologie_, II. 240. - -[272] DALTON, _Human Physiology_, Philadelphia, 1859, p. 362. - -[273] DALTON, p. 362. - -[274] DALTON, p. 363. - -[275] FLOURENS, p. 89. - -[276] LEYDEN in the _Berliner klinische Wochenschrift_, 1867, No. 7. -MEISSNER, _Jahresbericht über Physiol._, 1867, p. 410. - -[277] VOIT in the _Sitzungsberichte der Münchener Academie_, 1868, p. -105. Comp. also GOLTZ in _Pflüger’s Archiv_, Bd. XIV. 435. - -[278] VULPIAN, _Système Nerveux_, 542–48. - -[279] For other examples see GINTRAC, _Pathologie Interne_, 1868, VI. -51–57. - -[280] If the water is perfectly still the fish sinks to the bottom and -remains motionless until the water be stirred. Mere _contact_ does not -suffice; there must be intermittent pulses from the moving water. - -[281] LUSSANA e LEMOIGNE, _Op. cit._, I. 15. - -[282] _Archives de Physiologie_, 1869, p. 539. - -[283] BRÜCKE, _Physiologie_, II. p. 53. While these sheets are passing -through the press, GOLTZ has published his second series of experiments -on the brain. The following detail is a good illustration of what is -said in the text: A dog deprived of a portion of both hemispheres -displayed a marked imperfection in the execution of ordinary instincts. -Although sight was impaired he could see, and recognize men and certain -objects: the sight of a whip made him cower, but the sight of meat -did not suffice to set the feeding mechanism in action. When meat -was suspended above his head, the scent caused him to sniff about in -search, but he failed to find it, and even when he was so placed that -he could see the suspended meat, the _unusual_ impression failed to -guide him. If the meat were held towards him, or placed before him in -a dish, he took it at once--this being the customary stimulation. So -also, if the hand were held up, in the usual way when dogs are made -to leap for food, this dog sprang vigorously up and caught the food; -but he would spring up in the same way when the hand was held empty, -and continue fruitlessly springing, whereas an uninjured dog ceases to -spring when he sees the hand is empty.--_Pflüger’s Archiv_, Bd. XIV. p. -419. - -[284] GRATIOLET, _Anat. Comparée du Système Nerveux_, 1857, p. 459. - -[285] LUSSANA e LEMOIGNE, _Op. cit._, I. 363. - -[286] _Virchow’s Archiv_, Bd. LX. pp. 130–33. Yet there are many -physiologists who persist in placing the _motorium commune_ in the -_corpora strata_! And they place the _sensorium commune_ in the optic -thalami, although, not to mention the ambiguous evidence of Pathology, -the experiments of NOTHENGEL and VEYSSIÈRE show that destruction of -the thalami does not destroy sensation. See VEYSSIÈRE, _Recherches -sur l’hémianesthésie de cause cérébrale_, 1874, pp. 83, 84. I may -observe, in passing, that the notion of the _corpora striata_ being -the necessary channel for volitional impulses, and the _optic thalami_ -for reflex actions, is utterly disproved by the experimental evidence -recorded in the text, as well as in § 66. - -[287] _Pflüger’s Archiv_, Bde. VIII. and IX. - - - - -Transcriber’s Notes - - -Punctuation, hyphenation, and spelling were made consistent when a -predominant preference was found in the original book; otherwise they -were not changed. - -Simple typographical errors were corrected; unbalanced quotation -marks were remedied when the change was obvious, and otherwise left -unbalanced. - -Illustrations in this eBook have been positioned between paragraphs and -nearer to the text that references them. - -Footnotes in this eBook have been collected and moved to the end of the -book. - -The Table of Contents entry for Problem II, Chapter II, referenced the -wrong page; corrected here. - - - - - -End of the Project Gutenberg EBook of Problems of Life and Mind. 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