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diff --git a/old/60773-0.txt b/old/60773-0.txt deleted file mode 100644 index 3230e29..0000000 --- a/old/60773-0.txt +++ /dev/null @@ -1,8879 +0,0 @@ -The Project Gutenberg EBook of The Philosophy of Health; Volume 1 (of 2), by -Thomas Southwood-Smith - -This eBook is for the use of anyone anywhere in the United States and most -other parts of the world 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. If you are not located in the United States, you'll have -to check the laws of the country where you are located before using this ebook. - -Title: The Philosophy of Health; Volume 1 (of 2) - or, an exposition of the physical and mental constitution of man - -Author: Thomas Southwood-Smith - -Release Date: November 23, 2019 [EBook #60773] - -Language: English - -Character set encoding: UTF-8 - -*** START OF THIS PROJECT GUTENBERG EBOOK PHILOSOPHY OF HEALTH, VOLUME 1 *** - - - - -Produced by Chris Curnow, Brian Wilsden and the Online -Distributed Proofreading Team at http://www.pgdp.net (This -file was produced from images generously made available -by The Internet Archive) - - - - - -TRANSCRIBER'S NOTE: Italic text is denoted by _underscores_ and bold -text by =equal signs=. - - - - - THE - - PHILOSOPHY OF HEALTH; - - OR, - - AN EXPOSITION - - OF THE - - PHYSICAL AND MENTAL CONSTITUTION - OF MAN, - - WITH A VIEW TO THE PROMOTION OF - - HUMAN LONGEVITY AND HAPPINESS. - - BY - - SOUTHWOOD SMITH, M.D., - - _Physician to the London Fever Hospital, to the Eastern Dispensary, - and to the Jews' Hospital._ - - IN TWO VOLUMES. VOL. I. - - _THIRD EDITION._ - - LONDON: - C. COX, 12, KING WILLIAM STREET, STRAND. - - 1847. - - - - -London: Printed by W. CLOWES and SONS, Stamford Street. - - - - -CONTENTS OF VOL. I. - - - INTRODUCTION Page 1 - - - CHAPTER I. - - Characters by which living beings are distinguished - from inorganic bodies—Characters by which - animals are distinguished from plants—Actions - common to plants and animals—Actions peculiar - to animals—Actions included in the ORGANIC - circle—Actions included in the ANIMAL - circle—Organs and functions defined—Action of - physical agents on organized structures—Processes - of supply, and processes of waste—Reasons why the - structure of the animal is more complex than that - of the plant 13 - - - CHAPTER II. - - Two distinct lives combined in the - animal—Characters of the apparatus of the organic - life—Characters of the apparatus of the animal - life—Characteristic differences in the action of - each—Progress of life—Progress of death 51 - - - CHAPTER III. - - Ultimate object of organization and life—Sources - of pleasure—Special provision by which the - organic organs influence consciousness and afford - pleasure—Point at which the organic organs cease - to affect consciousness and why—The animal - appetites: the senses: the intellectual faculties: - the selfish and sympathetic affections: the moral - faculty—Pleasure the direct, the ordinary, - and the gratuitous result of the action of the - organs—Pleasure conducive to the development - of the organs, and to the continuance of their - action—Progress of human knowledge—Progress of - human happiness 73 - - - CHAPTER IV. - - Relation between the physical condition - and happiness, and between happiness and - longevity—Longevity a good, and why—Epochs of - life—The age of maturity the only one that admits - of extension—Proof of this from physiology—Proof - from statistics—Explanation of terms—Life a - fluctuating quantity—Amount of it possessed in - ancient Rome: in modern Europe: at present in - England among the mass of the people and among the - higher classes 106 - - - CHAPTER V. - - Ultimate elements of which the body is composed— - Proximate principles—Fluids and solids—Primary tissues— - Combinations—Results—Organs, systems, apparatus— - Form of the body—Division into head, trunk, and - extremities—Structure and function of each—Regions— - Seats of the more important internal organs 148 - - - CHAPTER VI. - - Of the blood—Physical characters of the blood: - colour, fluidity, specific gravity, temperature; - quantity—Process of coagulation—Constituents of - the blood; proportions —Constituents of the body - contained in the blood—Vital properties of the - blood—Practical applications 334 - - - CHAPTER VII. - - Of the circulation—Vessels connected with the - heart; chambers of the heart—Position of the - heart—Pulmonic circle; systemic circle—Structure - of the heart, artery, and vein—Consequences - of the discovery of the circulation to the - discoverer—Action of the heart; sounds occasioned - by its different movements—Contraction; - dilatation—Disposition and action of the - valves—Powers that move the blood—Force of - the heart—Action of the arterial tubes; the - pulse; action of the capillaries; action of the - veins—Self-moving power of the blood—Vital - endowment of the capillaries; functions—Practical - applications 357 - - - FOOTNOTES. 408 - - - - -INTRODUCTION. - - -The object of the present work is to give a brief and plain account -of the structure and functions of the body, chiefly with reference -to health and disease. This is intended to be introductory to an -account of the constitution of the mind, chiefly with reference to -the development and direction of its powers. There is a natural -connexion between these subjects, and an advantage in studying them -in their natural order. Structure must be known before function can -be understood: hence the science of physiology is based on that of -anatomy. The mind is dependent on the body: hence an acquaintance with -the physiology of the body should precede the study of the physiology -of the mind. The constitution of the mind must be understood before its -powers and affections can be properly developed and directed: hence a -knowledge of the physiology of the mind is essential to a sound view of -education and morals. - -In the execution of the first part of this work, that which relates -to the organization of the body, a formidable difficulty presents -itself at the outset. The explanation of structure is easy when the -part described can be seen. The teacher of anatomy finds no difficulty -in communicating to the student a clear and exact knowledge of the -structure of an organ; because, by the aid of dissection, he resolves -the various complex substances, of which it is built up, into their -constituent parts, and demonstrates the relation of these elementary -parts to each other. But the case is different with him who attempts -to convey a knowledge of the structure of an organ merely by the -description of it. The best conceived and executed drawing is a -most inadequate substitute for the object itself. It is impossible -wholly to remove this difficulty: what can be done, by the aid of -plates, to lessen it, is here attempted. A time may come when the -objects themselves will be more generally accessible: meanwhile, the -description now given of the chief organs of the body may facilitate -the study of their structure to those who have an opportunity of -examining the organs themselves, and will, it is hoped, enable every -reader at once to understand much of their action. - -Physical science has become the subject of popular attention, and -men of the highest endowments, who have devoted their lives to the -cultivation of this department of knowledge, conceive that they can -make no better use of the treasures they have accumulated, than that of -diffusing them. Of this part of the great field of knowledge, to make -"the rough places plain, and the crooked places straight," is deemed a -labour second in importance only to that of extending the boundaries of -the field itself. But no attempt has hitherto been made to exhibit a -clear and comprehensive view of the phenomena of life; the organization -upon which those phenomena depend; the physical agents essential -to their production, and the laws, as far as they have yet been -discovered, according to which those agents act. The consequence is, -that people in general, not excepting the educated class, are wholly -ignorant of the structure and action of the organs of their own bodies, -the circumstances which are conducive to their own health, the agents -which ordinarily produce disease, and the means by which the operation -of such agents may be avoided or counteracted; and they can hardly be -said to possess more information relative to the connexion between the -organization of the body and the qualities of the mind, the physical -condition and the mental state; the laws which regulate the production, -combination, and succession of the trains of pleasurable and painful -thought, and the rules deducible from those laws, having for their -object such a determination of voluntary human conduct, as may secure -the pleasurable and avoid the painful. - -Yet nothing would seem a fitter study for man than the nature of man in -this sense of the term. A knowledge of the structure and functions of -the body is admitted to be indispensable to whoever undertakes, as the -business of his profession, to protect those organs from injury, and to -restore their action to a sound state when it has become disordered; -but surely some knowledge of this kind may be useful to those who -have no intention to practise physic, or to perform operations in -surgery; may be useful to every human being, to enable him to take a -rational care of his health, to make him observant of his own altered -sensations, as indications of approaching sickness; to give him the -power of communicating intelligibly with his medical adviser respecting -the seat and the succession of those signs of disordered function, and -to dispose and qualify him to co-operate with his physician in the use -of the means employed to avert impending danger, or to remove actual -disease. - -But if to every human being occasions must continually occur, when -knowledge of this kind would be useful, the possession of it seems -peculiarly necessary to those who have the exclusive care of infancy, -almost the entire care of childhood, a great part of the care of -the sick, and whose ignorance, not the less mischievous because its -activity is induced by affection, constantly endangers, and often -defeats, the best concerted measures of the physician. - -The bodily organization and the mental powers of the child depend -mainly on the management of the infant; and the intellectual and -moral aptitudes and qualities of the man have their origin in the -predominant states of sensation, at a period far earlier in the history -of the human being than is commonly imagined. The period of infancy is -divided by physiologists into two epochs; the first, commencing from -birth, extends to the seventh month: the second, commencing from the -seventh month, extends to the end of the second year, at which time -the period of infancy ceases, and that of childhood begins. The first -epoch of infancy is remarkable for the rapidity of the development -of the organs of the body: the processes of growth are in extreme -activity; the formative predominates over the sentient life, the chief -object of the action of the former being to prepare the apparatus -of the latter. The second epoch of infancy is remarkable for the -development of the perceptive powers. The physical organization of -the brain, which still advances with rapidity, is now capable of a -greater energy, and a wider range of function. Sensation becomes more -exact and varied; the intellectual faculties are in almost constant -operation; speech commences, the sign, and, to a certain extent, the -cause of the growing strength of the mental powers; the capacity of -voluntary locomotion is acquired, while passion, emotion, affection, -come into play with such constancy and energy, as to exert over the -whole economy of the now irritable and plastic creature a prodigious -influence for good or evil. If it be, indeed, possible to make correct -moral perception, feeling, and conduct, a part of human nature, as much -a part of it as any sensation or propensity—if this be possible for -every individual of the human race, without exception, to an extent -which would render _all_ more eminently and consistently virtuous than -_any_ are at present (and of the possibility of this, the conviction -is the strongest in the acutest minds which have studied this subject -the most profoundly), preparation for the accomplishment of this object -must be commenced at this epoch. But if preparation for this object -be really commenced, it implies, on the part of those who engage in -the undertaking, some degree of knowledge; knowledge of the physical -and mental constitution of the individual to be influenced; knowledge -of the mode, in which circumstances must be so modified in adaptation -to the nature of the individual being, as to produce upon it, with -uniformity and certainty, a given result. The theory of human society, -according to its present institutions, supposes that this knowledge is -possessed by the mother; and it supposes, further, that this adaptation -will actually take place in the domestic circle through her agency. -Hence the presumed advantage of having the eye of the mother always -upon the child; hence the apprehension of evil so general, I had almost -said instinctive, whenever it is proposed to take the infant, for the -purpose of systematic physical and mental discipline, from beyond the -sphere of maternal influence. But society, which thus presumes that -the mother will possess the power and the disposition to do this, what -expedients has it devised to endow her with the former, and to secure -the formation of the latter? I appeal to every woman whose eye may -rest on these pages. I ask of you, what has ever been done for you to -enable you to understand the physical and mental constitution of that -human nature, the care of which is imposed upon you? In what part of -the course of your education was instruction of this kind introduced? -Over how large a portion of your education did it extend? Who were -your teachers? What have you profited by their lessons? What progress -have you made in the acquisition of the requisite information? Were -you at this moment to undertake the guidance of a new-born infant to -health, knowledge, goodness, and happiness, how would you set about -the task? How would you regulate the influence of external agents upon -its delicate, tender, and highly-irritable organs, in such a manner -as to obtain from them healthful stimulation, and avoid destructive -excitement? What natural and moral objects would you select as the best -adapted to exercise and develope its opening faculties? What feelings -would you check, and what cherish? How would you excite aims; how would -you apply motives? How would you avail yourself of pleasure as a final -end, or as the means to some further end? And how would you deal with -the no less formidable instrument of pain? What is your own physical, -intellectual, and moral state, as specially fitting you for this -office? What is the measure of your own self-control, without a large -portion of which no human being ever yet exerted over the infant mind -any considerable influence for good? There is no philosopher, however -profound his knowledge, no instructor, however varied and extended his -experience, who would not enter upon this task with an apprehension -proportioned to his knowledge and experience; but knowledge which men -acquire only after years of study, habits which are generated in men -only as the result of long-continued discipline, are expected to come -to you spontaneously, to be born with you, to require on your part no -culture, and to need no sustaining influence. - -But, indeed, it is a most inadequate expression of the fact, to say -that the communication of the knowledge, and the formation of the -habits which are necessary to the due performance of the duties of -women, constitute no essential part of their education: the direct -tendency of a great part of their education is to produce and foster -opinions, feelings, and tastes, which positively disqualify them for -the performance of their duties. All would be well if the marriage -ceremony, which transforms the girl into the wife, conferred upon the -wife the qualities which should be possessed by the mother. But it is -rare to find a person capable of the least difficult part of education, -namely, that of communicating instruction, even after diligent study, -with a direct view to teaching; yet an ordinary girl, brought up in -the ordinary mode, in the ordinary domestic circle, is intrusted with -the direction and control of the first impressions that are made upon -the human being, and the momentous, physical, intellectual, and moral -results that arise out of those impressions! - -I am sensible of the total inadequacy of any remedy for this -evil, short of a modification of our domestic institutions. Mere -information, however complete the communication of it, can do little -beyond affording a clearer conception of the end in view, and of -the means fitted to secure it. Even this little, however, would be -something gained; and the hope of contributing, in some degree, to -the furtherance of this object, has supplied one of the main motives -for undertaking the present work. Meantime, women are the earliest -teachers; they must be nurses; they can be neither, without the risk -of doing incalculable mischief, unless they have some understanding -of the subjects about to be treated of. On these grounds I rest their -_obligation_ to study them; and I look upon that notion of delicacy, -which would exclude them from knowledge calculated, in an extraordinary -degree, to open, exalt, and purify their minds, and to fit them for the -performance of their duties, as alike degrading to those to whom it -affects to show respect, and debasing to the mind that entertains it. - -Though each part of this work will be made as complete in itself as -the author is capable of rendering it, and to that extent independent -of any other part, yet there will be found to be a strict connexion -between the several portions of the whole; and greatly as the topics -included in the latter differ from those which form the earlier -subjects, the advantage of having studied the former before the latter -are entered on, will be felt precisely as the word _study_ can be -justly applied to the operation of the mind on such matters. - -In the expository portion of the work I have not been anxious to -abstain from the employment of technical terms, when a decidedly useful -purpose was to be obtained by the introduction of them; but I have been -very careful to use no such term without assigning the exact meaning -of it. A technical term unexplained is a dark spot on the field of -knowledge; explained, it is a clear and steady light. - -In order really to understand the states of health and disease, -an acquaintance with the nature of organization, and of the vital -processes of which it is the seat and the instrument, is indispensable: -it is for this reason that the exposition of structure and function, -attempted in this first part of the work, is somewhat full; but there -cannot be a question that, if it accomplish its object, it will not -only enable the account of health and disease in the subsequent part of -it to be much more brief, but that it will, at the same time, render -that account more intelligible, exact, and practical. - - S. S. - - - - -THE - -PHILOSOPHY OF HEALTH. - - - - -CHAPTER I. - - Characters by which living beings are distinguished - from inorganic bodies—Characters by which animals are - distinguished from plants—Actions common to plants and - animals—Actions peculiar to animals—Actions included in the - organic circle—Actions included in the animal circle—Organs - and functions defined—Action of physical agents on - organized structures—Processes of supply, and processes - of waste—Reasons why the structure of the animal is more - complex than that of the plant. - - -The distinction between a living being and an inorganic body, -between a plant and a stone, is, that the plant carries on a number -of processes which are not performed by the stone. The plant absorbs -food, converts its food into its own proper substance, arranges this -substance into bark, wood, vessels, leaves, and other organized -structures; grows, arrives at maturity, and decays; generates and -maintains a certain degree of heat; derives from a parent the primary -structure and the first impulse upon which these varied actions depend; -gives origin to a new being similar to itself, and, after a certain -time, terminates its existence in death. - -No such phenomena are exhibited by the stone; it neither absorbs -food, nor arranges the matter of which it is composed into organized -structure; nor grows, nor decays, nor generates heat, nor derives its -existence from a parent, nor gives origin to a new being, nor dies. -Nothing analogous to the processes by which these results are produced, -is observable in any body that is destitute of life; all of them are -carried on by every living creature. These processes are, therefore, -denominated vital, and, being peculiar to the state of life, they -afford characters by which the living being is distinguished from the -inorganic body. - -In like manner the distinction between an animal and a plant is, that -the animal possesses properties of which the plant is destitute. It is -endowed with two new and superior powers, to which there is nothing -analogous in the plant; namely, the power of sensation, and the power -of voluntary motion; the capacity of feeling, and the capacity of -moving from place to place as its feeling prompts. The animal, like -the plant, receives food, transforms its food into its own proper -substance, builds this substance up into structure, generates, and -maintains a certain temperature, derives its existence from a parent, -produces an offspring like itself, and terminates its existence in -death. Up to this point the vital phenomena exhibited by both orders of -living creatures are alike: but at this point the vital processes of -the plant terminate, while those of the animal are extended and exalted -by the exercise of the distinct and superior endowments of sensation -and voluntary motion. To feel, and to move spontaneously, in accordance -with that feeling, are properties possessed by the animal, but not by -the plant; and therefore these properties afford characters by which -the animal is distinguished from the plant. - -The two great classes of living beings perform, then, two distinct -sets of actions: the first set is common to all living creatures; the -second is peculiar to one class: the first set is indispensable to -life; the second is necessary only to one kind of life, namely, the -animal. The actions included in the first set, being common to all -living or organized creatures, are called ORGANIC; the actions included -in the second class, belonging only to one part of living or organized -creatures, namely, animals, are called ANIMAL. The ORGANIC actions -consist of the processes by which the existence of the living being is -maintained, and the perpetuation of its species secured: the ANIMAL -actions consist of the processes by which the living being is rendered -percipient, and capable of spontaneous motion. The ORGANIC processes -comprehend those of nutrition, respiration, circulation, secretion, -excretion, and reproduction; the first five relate to the maintenance -of the life of the individual being; the last to the perpetuation of -its species. The ANIMAL processes comprehend those of sensation and -of voluntary motion, often denominated processes of relation, because -they put the individual being in communication with the external -world. There is no vital action performed by any living creature -which may not be included in one or other of these processes, or in -some modification of some one of them. There is no action performed -by any inorganic body which possesses even a remote analogy to either -of these vital processes. The line of demarcation between the organic -and the inorganic world is, therefore, clear and broad; and the line -of demarcation between the two great divisions of the organic world, -between the inanimate and the animate, that is, between plants and -animals, is no less decided: for, of the two sets of actions which have -been enumerated, the one, as has just been stated, is common to the -whole class of living beings, while the second set is peculiar to one -division of that class. The plant performs only the organic actions: -all the vital phenomena it exhibits are included in this single circle; -it is, therefore, said to possess only organic life: but the animal -performs both organic and animal actions, and is therefore said to -possess both organic and animal life. - -Both the organic and the animal actions are accomplished by means -of certain instruments, that is, organized bodies which possess a -definite structure, and which are moulded into a peculiar form. Such -an instrument is called an organ, and the action of an organ is called -its function. The leaf of the plant is an organ, and the conversion -of sap by the leaf into the proper juice of the plant, by the process -called respiration, is the function of this organ. The liver of the -animal is an organ; and the conversion of the blood that circulates -through it into bile, by the process of secretion, is its function. The -brain is an organ; the sentient nerve in communication with it is also -an organ. The extremity of the sentient nerve receives an impression -from an external object, and conveys it to the brain, where it becomes -a sensation. The transmission of the impression is the function of -the nerve; the conversion of the impression into a sensation is the -function of the brain. - -The living body consists of a congeries of these instruments or -organs: the constituent matter of these organs is always partly in a -fluid and partly in a solid state. Of the fluids and solids which thus -invariably enter in combination into the composition of the organs, the -fluids may be regarded as the primary and essential elements, for they -are the source and the support of the solids. There is no solid which -is not formed out of a fluid; no solid which does not always contain, -as a constituent part of it, some fluid, and none which is capable of -maintaining its integrity without a continual supply of fluids. - -Whatever be the intimate composition of the fluids out of which the -solids are formed, the investigation of which is more difficult than -that of the solids and the nature of which is therefore less clearly -ascertained, it is certain that all the matter which enters into -the composition of the solid is disposed in a definite order. It is -this disposition of the constituent matter of the living solid in a -definite order that constitutes the arrangement so characteristic of -all living substance. Definite arrangements are combined in definite -modes, and the result is what is termed organization. From varied -arrangements result different kinds of organized substances, each -endowed with different properties, and exhibiting peculiar characters. -By the recombination of these several kinds of organized substances, -in different proportions and different modes, are formed the special -instruments, or organs, of which we have just spoken; while it is the -combining, or the building up of these different organized substances -into organs, that constitutes structure. - -In the living body, not only is each distinct organ alive, but, with -exceptions so slight that they need not be noticed here, every solid -which enters into the composition of the organ is endowed with vital -properties. This is probably the case with the primary substances or -tissues which compose the several organs of the plant; but that the -animal solids are alive is indubitable; nay, the evidence is complete, -that many even of the animal fluids possess vitality. The blood in the -animal is as truly alive as the brain, and the bone as the flesh. The -organized body, considered as a whole, is the seat of life; but life -also resides in almost every component part of it. - -Yet the matter out of which these living substances is formed is not -alive. By processes of which we know nothing, or, at least, of which -we see only the first steps,—matter, wholly destitute of life, is -converted into living substance. The inorganic matter, which is the -subject of this wonderful transformation, is resolvable into a very -few elementary substances. In the plant, these substances consist of -three only, namely, oxygen, hydrogen, and carbon. The first two are -aëriform or gaseous bodies; the last is a solid substance, and it is of -this that the plant is chiefly composed: hence the basis of the plant -is a solid. The elementary bodies, into which all animal substance is -resolvable, are four, namely, azote, oxygen, hydrogen, and carbon. -Into every animal fluid and solid this new substance azote enters so -largely, that it may be considered as the fundamental and distinctive -element of the animal organization: hence the basis of the animal is -an aëriform or gaseous fluid. The animal is composed of air, the plant -of solid matter; and this difference in their elementary nature gives -origin to several distinctive characters between the plant and the -animal, in addition to those which have been already stated. - -Thus the characters of the plant are solidity, hardness, fixedness, and -durability; while the animal is comparatively fluid, soft, volatile, -and perishable; and the reason is now manifest. The basis of the animal -being an aëriform fluid, its consistence is softer than that of the -plant, the basis of which is a firm solid; and, at the same time, the -component elements of the animal being more numerous than those of the -plant, and the fluidity of these elements, and of the compounds they -form, greatly favouring their action and reaction on each other and on -external agents, the animal body is more volatile and perishable during -life, and more readily decomposed after death. - -It has been stated, that the object of every structure or organ -of the living body, is the performance of some special action or -function,—the ultimate object of the fluids being the production of -the solids; the ultimate object of the solids being the formation of -organs; the ultimate object of organs being the performance of actions -or functions; while it is in the performance of actions or functions -that life consists. Functions carried on by organs; organs in action; -special organs performing definite actions, this it is that constitutes -the state of life. Every particle of matter which enters into the -composition of the living body has thus its own place, forming, or -destined to form, a constituent part of some organ; every organ has -its own action; all the organs of the body form the body; and all -the actions of all the organs constitute the aggregate of the vital -phenomena. - -Every organ is excited to action, or its function is called into -operation by means of some external body. The external bodies capable -of exciting and maintaining the functions of living organs, consist -of a definite class. Because these bodies belong to that department -of science which is called physical, they are termed physical agents. -They are air, water, heat, cold, electricity, and light. Without the -living organ, the physical agent can excite no vital action: without -the physical agent, the living organ can carry on no vital process. -The plant cannot perform the vital process of respiration without the -leaf, nor, with the leaf, without air. The physical agent acts upon the -living organ; the living organ reacts upon the physical agent, and the -action between both is definite. In the lung of the animal a certain -principle of the air unites, in definite proportions, with a certain -principle of the blood; the oxygen of the air combines with the carbon -of the blood; the air is changed by the abstraction of its oxygen; -the blood is changed by the abstraction of its carbon. Atmospheric -air goes to the lung, but atmospheric air does not return from the -lung; it is converted into a new substance by the action of the organ: -it is changed into carbonic acid by the union of a given quantity of -oxygen, which it transmits to the organ, with a given quantity of -carbon which the organ conveys to it. Venous blood goes to the lung, -but venous blood does not return from the lung; it is converted, by -the instrumentality of the organ, into a new substance, into arterial -blood, by giving to the air carbon, and by receiving from the air -oxygen. In this manner the change in the physical agent is definite and -uniform; and the change in the living substance is equally definite and -uniform. - -It is this determinate interchange of action between the living organ -and the physical agent that constitutes what is termed a vital process. -All vital processes are carried on by living organs; the materials -employed in all vital processes are physical agents; the processes -themselves are vital functions. All the changes produced by all the -organs of the plant upon physical agents, and all the changes produced -by all physical agents upon the organs of the plant, constitute all -the vital processes of the plant—comprehend the whole sum of its -vital phenomena. The root, the trunk, the woody substance, the bark, -the ascending vessels bearing sap, the descending vessels bearing -secreted fluids, the leaves, the flowers, these are the living organs -of the plant. Air, water, heat, cold, electricity, light, these are the -physical agents which produce in these organs definite changes, and -which are themselves changed by them in definite modes; and the whole -of these changes, taken together, comprehend the circle of actions, or -the range of functions performed by this living being. - -In the state of life, during the interchange of action which thus -incessantly goes on between physical agents and vital organs, the -laws to which inorganic matter is subject are resisted, controlled, -and modified. Physical and chemical attractions are brought under the -influence of a new and superior agency, with the laws of which we are -imperfectly acquainted, but the operation of which we see, and which we -call the agency of life. Air, water, heat, electricity, are physical -agents, which subvert the most intimate combinations of inorganic -bodies, resolving them into their simple elements, and recombining -these elements in various modes, and thus forming new bodies, endowed -with totally different properties; but the physical and chemical -agencies by which these changes are wrought in the inorganic, are -resisted, controlled, and modified by the living body: resisted, for -these physical agents do not decompose the living body; controlled -and modified, for the living body converts these very agents into the -material for sustaining its own existence Of all the phenomena included -in that circle of actions which we designate by the general term life, -this power of resisting the effects universally produced by physical -agents on inorganic matter, and of bringing these very agents under -subjection to a new order of laws, is one of the most essential and -distinctive. - -All vital processes are processes of supply, or processes of waste. By -every vital action performed by the organized body, some portion of its -constituent matter is expended. Numerous vital actions are constantly -carried on for the sole purpose of compensating this expenditure. Every -moment old particles are carried out of the system; every moment new -particles are introduced into it. The matter of which the organized, -and more especially the animal, body is composed, is thus in a state -of perpetual flux; and in a certain space of time it is completely -changed, so that of all the matter that constitutes the animal body at -a given point of time, not a single particle remains at another point -of time at a given distance. - -All the wants of the economy of the plant are satisfied by a due -supply of air, water, heat, cold, electricity, and light. Some of -these physical agents constitute the crude aliment of the plant; -others produce in this aliment a series of changes, by which it is -converted from crude aliment into proper nutriment, while others act -as stimulants, by which movements are excited, the ultimate object of -which is the distribution of the nutriment to the various parts of the -economy of the plant. - -The same physical agents are indispensable to the support of the animal -body; but the animal cannot be sustained by these physical agents -alone; for the maintenance of animal life, in some shape or other, -vegetable or animal matter, or both in a certain state of combination, -must be superadded: hence another distinction between the plant and the -animal,—the necessity, on the part of the animal, of an elaborated -aliment to maintain its existence. By the vital processes of its -economy, the plant converts inorganic into organic matter; by the vital -processes of its economy, the animal converts matter, already rendered -organic, into its own proper substance. The plant is thus purveyor to -the animal: but it is more than purveyor to it; for while it provides, -it also prepares its food; it saves the animal one process, that of -the transmutation of inorganic into organic matter. The ultimate end, -or the final cause of the vital processes performed by the first class -of living beings, is thus the elaboration of aliment for the second: -the inferior life is spent in ministering, and the great object of its -being is to minister to the existence of the superior. - -At the point at which organization commences structure is so simple -that there is no manifest distinction of organs. Several functions are -performed apparently by one single organized substance. The lowest -plants and the lowest animals are equally without any separate organs, -as far as it is in our power to distinguish them, for carrying on the -vital actions they perform. An organized tissue, apparently of an -homogeneous nature, containing fluid matter, is all that can be made -out by which the most simply-constructed plant carries on its single -set, and by which the most simply-constructed animal carries on its -double set, of actions. But this simplicity of structure exists only -at the very commencement of the organized world. Every advancement in -the scale of organization is indicated by the construction of organs -manifestly separate for the performance of individual functions; -and, invariably, the higher the being, the more complete is this -separation of function from function, and, consequently, the greater -the multiplication of organs, and the more elaborate and complex the -structure;—and hence another distinction between the plant and the -animal. The simplicity of the structure of the plant is in striking -contrast to the complexity of the structure of the animal; and this -difference is not arbitrary; it is a matter of absolute necessity, and -the reason of this necessity it will be instructive to contemplate. - -The plant, as has been shown, performs only one set of functions, the -organic; while the animal performs two sets of functions, the organic -and the animal. The animal, then, performs more functions than the -plant, and functions of a higher order; it carries on its functions -with a greater degree of energy; its functions have a more extended -range, and all its functions bear a certain relation to each other, -maintaining an harmonious action. The number, the superiority, the -relation, the range, and the energy of the functions performed by -the animal are, then, so many conditions, which render it absolutely -indispensable that it should possess a greater complexity of structure -than the plant. - -1. To build up structure is to create, to arrange, and to connect -organs. Organs are the instruments by which functions are performed, -and without the instrument there can be no action. With as many -more organs than the plant possesses the animal must, therefore, be -provided, as are necessary to carry on the additional functions it -performs. Organs, for its organic functions, it must have as well as -the plant; but to these must be superadded organs of another class, for -which the plant has no need, namely, organs for its animal functions. -Two sets of organs must, therefore, be provided for the animal, while -the plant requires but one. - -2. Some functions performed by the animal are of a higher order than -any performed by the plant, and the superior function requires a higher -organization. The construction of an organ is complex as its action is -elevated; the instrument is elaborately prepared in proportion to the -nobleness of its office. - -[Illustration: Fig. I.] - -[Illustration: Fig. II.] - -[Illustration: Fig. III.] - -[Illustration: Fig. IV.] - -3. But this is not all; for the addition of a superior function -requires not only the addition of an organ having a corresponding -superiority of structure, but it requires, further, that a certain -elevation of structure should be communicated to all the organs of -all the inferior functions, on account of the relation which it is -necessary to establish between function and function. Unless the organ -of an inferior function be constructed with a perfection corresponding -to that of the organ of a superior function, the inferior will be -incapable of working in harmony with the superior. Take, for example, -the inferior function of nutrition: nutrition is an organic function -equally necessary to the plant and to the animal, and requiring in -both organs for performing it; but this function cannot be performed -in the animal by organs as simple as suffice for the plant. Nutrition, -in the plant, is carried on in the following mode:—The root of the -plant is divided, like the trunk, into numerous branches (fig. I. 1). -These branches divide and subdivide into smaller and smaller branches, -until at last they reach an extreme degree of minuteness (fig. I. 2 2). -The smallest of these divisions, called, from their hair-like tenuity, -_capillary_ (fig. I. 2 2), are provided with a peculiar structure, -which is endowed with a specific function. In most plants this peculiar -structure is found at the terminal point of the rootlet (fig. I. 2 2); -but in some plants the capillary branches of the rootlets are provided -with distinct bodies (fig. II. 1 2), scarcely to be discerned when -the root has been removed some time from the soil, and has become dry -(fig. II. 2 2); but which, in a few minutes after the root has been -plunged in water, provided the plant be still alive, become turgid with -fluid, and, consequently, distinctly visible (fig. II. 1 1 1). These -bodies, when they exist, or the terminal point of the rootlet when -these bodies are absent, are termed _spongeolæ_, or spongeoles; and the -structure and function of the organ, in both cases, are conceived to -be precisely the same. In both the organ consists of a minute cellular -structure. Fig. III. 1, shows this structure as it appears when the -object is magnified. The office of this organ is to absorb the aliment -of the plant from the soil; and so great is its absorbing power, that, -as is proved by direct experiment, it absorbs the colouring molecules -of liquids, though these molecules will not enter the ordinary pores, -which are of much greater magnitude. With the spongeoles are connected -vessels which pass through the substance of the stem or trunk to the -leaf. Fig. III. 2, shows these tubes springing from the cellular -structure of the spongeole, and passing up to the stem or trunk. Fig. -IV. 2, exhibits a magnified view of the appearance of the mouths of -these tubes on making an horizontal section of the spongeole. Fig. V. -1 1 1, exhibits a view of these tubes passing to the leaf. Figs. VI. -and VII. 1 1 1 1, show these vessels spread out upon, and ramifying -through, the leaf. The crude aliment, borne by these tubes to the leaf, -is there converted into proper nutriment; and from the leaf, when -duly elaborated, this proper nutriment is carried out by ducts to the -various organs of the plant, in order to supply them with the aliment -they need. - -[Illustration: Fig. V.] - -Now, for carrying on the process of nutrition in this mode, there -must be organs to absorb the crude aliment, organs to convey the crude -aliment to the laboratory, the leaf, in which it is converted into -proper nutriment; and, finally, organs for carrying out this proper -nutriment to the system. Complication of structure, to this extent, is -indispensable; and, accordingly, with spongeolæ, with sap-vessels, with -leaves, with distributive ducts, the plant is provided. Without all the -parts of this apparatus it could not carry on its function: any further -complication would be useless. - -[Illustration: Fig. VI.] - -But, suppose a new and superior function to be added to the plant; -suppose it to be endowed with the power of locomotion, what would be -the consequence of communicating to it this higher power? That its -former state of simplicity would no longer suffice for the inferior -function. Why? because the exercise of the superior would interrupt -the action of the inferior function. Nutrition by imbibition, and -the exercise of locomotion, cannot go on simultaneously in the same -being. The plant is fixed in the soil by its roots; and from this, its -state of immobility, results this most important consequence, that its -spongeolæ are always in contact with its food. - -[Illustration: Fig. VII.] - -[Illustration: Fig. VIII.] - -But we may imagine a plant not fixed to the soil; a plant so -constituted as to be capable of moving from place to place; such a -plant would not be always in contact with its food, and therefore, as -it exercised its faculty of locomotion, it could not but interrupt -or suspend its function of nutrition. In a being capable of carrying -on these two functions simultaneously, the entire apparatus of the -function of nutrition must then be modified. Instead of having -spongeolæ fixed immovably in the earth, and spread out in a soil -adapted to transmit to these organs nutrient matter in a state fitted -for absorption, it must be provided with a reservoir for containing -its food, in order that it may carry its aliment about with it in -all its changes of place. And such is the modification uniformly -found in all animals: an internal reservoir for containing its food -is provided, perhaps, for every animal without exception. Even the -simplest and minutest creatures with which the microscope has made -us acquainted, the lowest tribes of the Infusoria (fig. VIII.), the -sentient, self-moving cellules, placed at the very bottom of the -animal scale, possess this modification of structure. For a long -time it was conceived that these minute and simple creatures were -without distinction of parts, that they had no separate organs for the -reception and digestion of their food; that they absorbed their aliment -through the porous tissue of which their body is composed; that thus, -instead of having a separate stomach, their entire body is a stomach, -and instead of having even as much as a separate organ for absorption, -like the more perfect plant, the whole body might be considered as a -single spongeole. - -But, by a simple and beautiful experiment, a German physiologist -has shown the incorrectness of this opinion, and has established the -fact, that the distinction between the plant and the animal, here -contended for, is found even at the very lowest point of the animal -scale. Like other physiologists, conceiving that the difficulty of -discovering the structure of the lower tribes of the animalculi -might be owing to the transparency or the tissues of which they are -composed, it struck Ehrenberg, that if he could feed them with coloured -substances, he might obtain some insight into their organization. -In his first endeavours to accomplish this object he failed, for he -employed the pigments in ordinary use; but either the animals would not -touch aliment thus adulterated, or those that did so were instantly -killed. It then occurred to him, that these colours are adulterated -with lead and other substances, in all probability noxious to the -little subjects of his experiment. "What I require," said he, "is some -vegetable or animal colouring matter perfectly pure." He then tried -perfectly pure indigo and perfectly pure carmine. His success was -now complete: in a minute or two, after mixing with their food pure -vegetable colouring matter, he observed in the interior of the body of -these creatures minute spots of a definite figure, and of the colour -of the pigment employed (fig. VIII. 1 1 1 1). The form and magnitude -of these spots were different in different tribes, but the same in the -same individual, and even in the same species (fig. IX. 1 1, fig. X. -1 1). No other parts of the body were tinged with the colour, though -the animals remained in the coloured fluid for days together. This was -decisive. This physiologist had now obtained an instrument capable of -revealing to him the interior organization of a class of beings, the -structure of which had heretofore been wholly unknown. On applying -it to the MONAS TERMO (fig. VIII.), the animated point, or cellule, -which stands at the bottom of the animal scale, he discovered, in the -posterior portion of its body, several coloured spots which constitute -its stomachs (fig. VIII. 1 1 1 1). The different situations and -different forms of the stomach in different tribes of these creatures, -are represented by the coloured portions (fig. VIII. 1, fig. IX. 1, -fig. X. 1), in which the currents of fluid flowing to their mouths -are seen (fig. IX. 2, fig. X. 2). These experiments go far towards -establishing the fact, that every animal, even the very lowest, has an -external mouth and an internal stomach, and that it takes its food by -an act of volition. - -[Illustration: Fig. IX.] - -[Illustration: Fig. X.] - -But if the proof of this must be admitted to be still imperfect -with regard to the lowest tribes of animals, it is certain that, as -we ascend in the scale of organization, the nutritive apparatus is -uniformly arranged in this mode. Every animal of every class large -enough to be distinctly visible, and the structure of which is not -rendered inappreciable by the transparency of its solids and fluids, is -manifestly provided with a distinct internal reservoir for containing -its food. On the internal surface of this reservoir open the mouths of -vessels, minute in size but countless in number, which absorb the food -from the stomach. - -Fig. XI. shows these vessels opening on the inner surface of the -stomach, the white points representing their mouths, turgid with the -food they have absorbed. Fig. XII. exhibits magnified views of the same -vessels, the points representing their open mouths, and the lines the -vessels themselves in continuation with their mouths. Fig. XIII. shows -the appearance of the inner surface of the intestine soon after the -animal has taken food; the smaller white lines (1 1 1 1) representing -the absorbent vessels full of digested food, and the larger lines (2 2 -2 2) the trunks of the absorbent vessels formed by the union of many of -the smaller. - -[Illustration: Fig. XI.] - -[Illustration: Fig. XII.] - -From this account, it is clear that the absorbing vessels of the -stomach perform an office precisely analogous to that of the spongeoles -of the root. What the soil is to the plant, the stomach is to the -animal. The absorbing vessels diffused through the stomach, as long -as the stomach contains food, are in exactly the same condition as -the spongeoles of the root spread out in the soil; and the absorbing -vessels of the stomach are as much and as constantly in contact with -the aliment, which it is their office to take into the system, as the -spongeoles of the root. Such, then, is the expedient adopted to render -the function of nutrition compatible with the function of locomotion. -A reservoir of food is placed in the interior of the animal, provided -with absorbent vessels which are always in contact with the aliment. In -this mode, contact with aliment is not disturbed by continual change of -place; the organic process is not interrupted by the exercise of the -animal function. - -[Illustration: Fig. XIII.] - -But the more elaborate organization which it is necessary to impart -to the apparatus of the inferior function, in consequence of the -communication of a superior faculty, is not completed simply by the -addition of this new organ, the stomach. Other complications are -indispensable; for if food be contained in an isolated organ, placed in -the interior of the body, means must be provided for conveying the food -into this organ; hence the necessity of an apparatus for deglutition. -Moreover, the food having been conveyed to the stomach, and having -undergone there the requisite changes, means must next be provided for -conveying it from the stomach to the other parts of the body; hence -the necessity of an apparatus for the circulation. But food, however -elaborately prepared by the stomach, is incapable of nourishing the -body, until it has been submitted to the action of atmospheric air; -hence the necessity of an additional apparatus, either for conveying -food to the air, or for transmitting air to the food, or for bringing -both the food and the air into contact in the same organ. And, when -structure after structure has been built up, in order to carry on this -extended series of processes, the number of provisions required is -not even yet complete; for of the most nutritious fond the whole mass -is not nutritive; and even the whole of that portion of it which is -actually applied to the purpose of nutrition, becomes, after a time, -worn out, and must be removed from the system; hence the necessity of a -further apparatus for excretion. - -That nutrition and locomotion may go on together, it is clear, then, -that there must be provided a distinct apparatus for containing -food, a distinct apparatus for deglutition, a distinct apparatus for -circulation, a distinct apparatus for respiration, a distinct apparatus -for excretion, and so on; and that, in this manner, the communication -of a single function of a superior order renders a modification not -merely of one but of many inferior functions absolutely indispensable, -in order to adjust the one to the other, and to enable them to act in -harmony. - -But the necessary complication of structure does not stop even here; -for the communication of one function of a superior order imposes -the necessity of communicating still another. Locomotion cannot be -exercised without perception; sensation is indispensable to volition, -and volition, of course, to voluntary motion. A being endowed with -the power of moving from place to place, without possessing the power -of perceiving external objects, must be speedily destroyed. The -communication of sensation to a creature fixed immovably to a single -spot, conscious of the approach of bodies, but incapable of avoiding -their contact, would be not only useless but pernicious, since it -would be to make a costly provision for the production of pain, and -nothing else; but the communication of locomotion without sensation -would be as unwisely defective, as the former would be perniciously -expensive; since it would be to endow a being with a faculty, the -exercise of which would be fatal to it for the want of a second faculty -to guide the first. Nor could the possession of locomotion, without the -further possession of sensation, be otherwise than fatal, for another -reason. Consciousness is not necessary to nutrition as performed by -the plant, but it is indispensable to nutrition as performed by the -animal: for if the food of the animal be not always on the same spot -with itself; if it be under the necessity of searching for it, and of -conveying it, when found, into the interior of its body, it must, of -course, possess the power of perceiving it when within its reach, and -of apprehending and appropriating it by an act of volition, of none of -which actions is it capable without the possession of sensation. Again, -then, we see that, in order to secure harmonious action, function must -be put in relation with function. In order to prevent jarring and -mutually-destructive action, function must be superadded to function, -and throughout the animal creation the complication of structure, which -is necessary for the accomplishment of these ends, is given without -parsimony, but without profusion: nothing is given which is not needed, -nothing is withheld which is required. - -4. As we ascend in the scale of organization, numerous functions being -carried on, and numerous organs constructed for performing them, it -is obvious that the range of each function must be proportionally -extended; the range necessarily increasing with the multiplication -of organ and function: and this is another cause of the unavoidable -complication of structure. Slight consideration will suffice to show -the necessary connexion between an extended range of action and -complication of structure. Take, as an example, the organic function -of respiration: respiration is the function by which air is brought -into contact with food; it is the completion of digestion. The sole -end of all the apparatus that belongs to this function is to bring the -air and the food into a certain degree of proximity. Now, when all the -substances that enter into the composition of the body of an animal are -slight, delicate, and permeable to air (as in fig. XIV.), and when the -body is always surrounded by air, air must at all times be in contact -with the particular organ that contains the food, no less than with -the general system to which the food is distributed. In this case, to -construct a separate apparatus for containing air would be useless, -because wherever food is, there air must be, since it constantly -permeates every part of the body. - -[Illustration: Fig. XIV.] - -When, on the other hand, the tissues are so firm and dense as to be -impermeable; when they are folded into bulky and complex organs, and -when these organs are placed in situations to which the external air -cannot reach, the construction of a separate apparatus for respiration -is indispensable. The respiratory apparatus consists either of organs -for carrying air to the food, or of organs for carrying food to the -air. The one or the other is adopted, according to the nature of the -body. If the size of the animal be small; if the tissues which form -the solid portion of its body be delicate in texture; if, at the same -time, the wants of its economy require that its food should be highly -aërated (for there is the closest connexion between energy of function -and perfect aëration of the food), an apparatus of sufficient magnitude -to aërate the food in a high degree would occupy the entire bulk of the -body. In such a case, it is easier to carry air to the food than food -to the air; it is better to make the entire body a respiratory organ, -than to construct a respiratory organ disproportioned to the magnitude -of the body. Air-tubes diffused through every part of the body, and -opening on its external surface, would obviously afford to every point -of the system an easy access of air. By an expedient of this kind the -system might be highly aërated, while the respiratory apparatus would -occupy but a comparatively small space; the function might be performed -on an extended scale, while there would be no necessity for encumbering -a minute body with a bulky organ. And this is the mode in which -respiration is carried on in large tribes of creatures, whose body -is small in size and delicate in texture, and the functions of whose -economy are performed with energy (fig. XV.). - -[Illustration: Fig. XV. - - The Achilles Butterfly of South America (_Papilio Achilles_), - showing the tracheæ on the upper and under side of the wings.] - -But this contrivance will not do when the animal is of large -magnitude; when its body is divided into numerous compartments; when -these compartments extend far beneath the external surface; when -important organs are placed in deeply-seated cavities; and when -the substances that compose the organs are dense, hard, thick, and -convoluted. To construct air-tubes of the requisite diameter and -length, always open, always in a condition to permit the ingress and -egress of an adequate current of air to and from the remotest nook and -corner of a body such as this, would be difficult, if not impossible. -At all events, it is easier, in such a case, to carry the food to the -air, than the air to the food. But, for the accomplishment of this -purpose, what is necessary? An organ for containing food; an organ -for containing air; vessels to carry food to and from the receptacle -of the aliment; vessels to carry air to and from the receptacle of -the air; expedients to expose a stream of food to a current of air; -and, finally, tubes to carry out to the system the product of this -complicated operation. Accordingly, a reservoir of food and a reservoir -of air; an apparatus by which both are conveyed to their respective -receptacles; and an apparatus by which both are brought into contact -sufficiently close to admit of their mutual action, are all combined -in the lung of the animal, and in the mechanism by which its movements -are effected. The object is accomplished, but the apparatus by which it -is effected is as complex in structure as it is efficient in action; -the result simple; the means by which the result is secured, highly -complicated. - -And if this be true of an inferior or organic function, it is still -more strikingly true of a superior or animal function. The relation is -still stricter between the complexity of the apparatus of sensation and -the range of feeling, than between the complexity of the apparatus of -respiration and the range of the respiratory process. The greater the -number of the senses, the greater the number of the organs of sense; -the more accurate and varied the impressions conveyed by each, the more -complex the structure of the instrument by which they are communicated; -the more extended the range of the intellectual operations, the larger -the bulk of the brain, the greater the number of its distinct parts, -and the more exquisite their organization. From the point of the animal -scale, at which the brain first becomes distinctly visible, up to man, -the basis of the organ is the same; but, as the range of its function -extends, part after part is superadded, and the structure of each part -becomes progressively more and more complex. The evidence of this, -afforded by comparative anatomy, is irresistible, and the interest -connected with the study of it can scarcely be exceeded. - -5. In the last place, structure is complex in proportion to the -energy of function. The greater the power with which voluntary motion -is capable of being exerted, the higher the organization of the -apparatus by which it is performed; the more compact and dense the -shell, the cartilage, the bone, the firmer the fibre of the muscle, -and, in general, the greater its comparative bulk. The wing of the -eagle is as much more developed than the wing of the wren, as its -flight is higher, and its speed swifter. The muscles which give to the -tiger the rapidity and strength of its spring possess a more intense -organization than those which slowly move on the tardigrade sloth. The -structure of the brain of man is more exquisite than that of the fish, -as his perceptions are more acute, and capable of greater combination, -comprehension, and continuity. - -Thus we see that the organization of the animal is more complex than -that of the plant, not from an arbitrary disposition, but from absolute -necessity. The few and simple functions performed by the plant require -only the few and simple organs with which it is provided: the numerous -and complicated functions performed by the animal require its numerous -and complicated organs: the plant, simple as it is in structure, is -destitute of no organ required by the nature of its economy; the -animal, complex as it is in structure, is in possession of no organ -which it could dispense with: from the one, nothing is withheld which -is needed; to the other, nothing is given which is superfluous: in the -one, there is economy without niggardliness; in the other, munificence -without waste. - - - - -CHAPTER II. - - Two distinct lives combined in the animal—Characters of the - apparatus of the organic life—Characters of the apparatus of - the animal life—Characteristic differences in the action of - each—Progress of life—Progress of death. - - -Of the two sets of functions carried on by living beings, it has been -shown, that the plant performs only one, while the animal exercises -both. The two lives thus in continual play in the animal differ from -each other as much as the process of vegetation differs from that of -thought, yet they are united so closely, and act so harmoniously, -that their existence as distinct states is not only not apparent to -ordinary observation, but the very discovery of the fact is of recent -date, and forms one among the splendid triumphs of modern physiology. -Their action is perfect, yet their separate identity is so distinctly -preserved, that each has its own apparatus and its own action, which -are not only not the same, but, in many interesting circumstances, are -in striking contrast to each other. - -1. In general the organs that belong to the apparatus of the organic -life are single, and not symmetrical; the organs that belong to the -apparatus of the animal life are either double, or symmetrical, or -both. As will be shown hereafter, the heart, the lungs, the stomach, -the intestines, the liver, the pancreas, the spleen, the instruments -by which the most important functions of the organic life are carried -on, are single organs. (Chap. 5.) The figure of each is more or less -irregular, so that if a line were carried through their centre, it -would not divide them into two equal and precisely corresponding -portions. On the contrary, the organs of the animal life are -symmetrical. The brain and the spinal cord are divisible into two -perfectly equal parts. (Chap. 5.) The nerves which go off from these -organs for the most part go off in pairs equal in size and similar -in distribution. (Ibid.) The trunk, so important an instrument of -voluntary motion, when well formed, is divisible into two perfectly -corresponding portions. (Ibid.) The muscular apparatus of one half -of the body is the exact counterpart of that of the other; while the -arms, the hands, and the lower extremities are not only double, but the -organization of the one is precisely similar to that of its fellow. - -2. In general, the apparatus of the organic life is placed in the -interior of the body, while that of the animal life is placed on the -external surface. The organic organs are the instruments by which -life is maintained. There is no action of any one of them that can -be suspended even for a short space of time without the inevitable -extinction of life. But the animal organs are not so much instruments -of life as means by which a certain relation is established between the -living being and external objects. And this difference in their office -is the reason of the difference in their position. Existence depending -on the action of the organic organs, they are placed in the interior of -the body; they are fixed firmly in their situation in order that they -may not be disturbed by the movements of locomotion; they are enveloped -in membranes, covered by muscles, placed under the shelter of bones, -and every possible care is taken to secure them from accident and to -shield them from violence. Existence not being immediately dependent -on the action of the organs of the animal life, they do not need to -be protected from the contact of external objects with extraordinary -care, but it is necessary to the performance of their functions that -they should be placed at the exterior of the body. And there they are -placed, and so placed as to afford an effectual defence to the organic -organs. Thus the groundwork of the animal is made the bulwark of the -organic life. The muscles, the immediate agents by which voluntary -motion is effected, and the bones, the fixed points and the levers by -which that motion acquires the nicest precision and the most prodigious -rapidity and power, are so disposed that, while the latter accomplish, -in the most perfect manner, their primary and essential office in -relation to the muscles, they serve a secondary but scarcely less -important office in relation to the internal viscera. As we advance -in our subject, we shall see that a beautiful illustration of this is -afforded in the structure and action of the trunk; that the trunk is -moveable; that it is composed of powerful muscles, and of firm and -compact bones; and that while its movements are effected by the action -of the muscles which are attached to the bones, these bones enclose -a cavity, in which are placed the lungs, the heart, the great trunks -of the venous system, the great trunks of the arterial system, and -the main trunk of the thoracic duct, the vessel by which the digested -aliment is carried into the blood. (Chap. 5.) Thus, by these strong and -firm bones, together with the thick and powerful muscles that rest upon -them, is formed a secure shelter for a main portion of the apparatus -of the organic functions of respiration, circulation, and digestion. -The bones and muscles of the thorax, themselves performing an important -part in the function of respiration, afford to the lungs the chief -organ of this function, composed of tender and delicate tissues, easily -injured, and the slightest injury perilling life, a free and secure -place to act in. The fragile part of the apparatus is defended by the -osseous portion of it, the play of the latter being equally essential -to the function as that of the former. In like manner the tender and -delicate substance of the brain and spinal cord, the central seat of -the animal life, with which all the senses are in intimate communion, -is protected by bones and muscles which perform important voluntary -movements while the organs of sense which put us in connexion with the -external world, which render us susceptible of pleasure, and which -give us notice of the approach of objects capable of exciting pain, -are placed where external bodies may be brought most conveniently -and completely into contact with them; and where alone they can be -efficient as the sentinels of the system. For this reason, with the -exception of the sense of touch, which, though placed especially at the -extremities of the fingers, is also diffused over the whole external -surface of the frame, all the senses have their several seats in the -head, the most elevated part of the body, of an ovoid figure, capable -of moving independently of the rest of the fabric, and which, being -supported on a pivot, is enabled to describe at least two-thirds of a -circle. - -Such is the difference in the structure and position of the apparatus -of the two lives, but the difference in their action is still more -striking. - -1. The action of the apparatus of the organic life when sound is -without consciousness; the object of the action of the apparatus of -the animal life is the production of consciousness. The final cause -of the action of the apparatus of the organic life is the maintenance -of existence; the final cause of the action of the apparatus of the -animal life is the production of conscious existence. What purpose -would be answered by connecting consciousness with the action of -the organic organs? Were we sensible of the organic processes; did -we know when the heart beats, and the lung plays, and the stomach -digests, and the excretory organ excretes, the consciousness could -not promote, but might disturb the due and orderly course of these -processes. Moreover they would so occupy and engross our minds that -we should have little inclination or time to attend to other objects. -Beneficently therefore are they placed equally beyond our observation -and control. Nevertheless, when our consciousness of these processes -may be of service; when they are going wrong; when their too feeble or -too intense action is in danger of destroying existence, the animal -life is made sensible of what is passing in the organic, in order that -the former may take beneficial cognizance of the latter, may do what -experience may have taught to be conducive to the restoration of the -diseased organ to a sound state, or avoid doing what may conduce to the -increase or maintenance of its morbid condition. - -But while the action of the organic organs is thus kept alike from our -view and feeling, the sole object of the action of the animal organs is -to produce and maintain a state of varied and extended consciousness. -We do not know when the heart dilates to receive the vital current, -nor when it contracts to propel it with renewed impetus through the -system; nor when the blood rushes to the lung to give out its useless -and noxious particles; nor when the air rushes to the blood to take -up those particles, to replace them by others, and thus to purify and -renovate the vital fluid. Many processes of this kind are continually -going on within us during every moment of our existence, but we are -no more conscious of them than we are of the motion of the fluids in -the blade of grass on which we tread. On the contrary when an external -object produces, in a sentient nerve, that change of state which we -denote by the words "an impression;" when the sentient nerve transmits -this impression to the brain; when the brain is thereby brought into -the state of perception, the animal life is in active operation, and -percipient or conscious existence takes place. Consciousness does not -belong to the organic, it _is_ the animal life. - -2. The functions of the organic life are performed with uninterrupted -continuity; to those of the animal life rest is indispensable. The -action of the heart is unceasing; it takes not and needs not rest. -On it goes, for the space of eighty or ninety years, at the rate of -a hundred thousand strokes every twenty-four hours, having at every -stroke a great resistance to overcome, yet it continues this action for -this length of time without intermission. Alike incessant is the action -of the lung, which is always receiving and always emitting air; and the -action of the skin, which is always transpiring and always absorbing; -and the action of the alimentary canal, which is always compensating -the loss which the system is always sustaining. - -But of this continuity of action the organs and functions of the -animal life are incapable. No voluntary muscle can maintain its action -beyond a given time; no effort of the will can keep it in a state of -uninterrupted contraction; relaxation must alternate with contraction; -and even this alternate action cannot go on long without rest. No organ -of sense can continue to receive impression after impression without -fatigue. By protracted exertion the ear loses its sensibility to sound, -the eye to light, the tongue to savour, and the touch to the qualities -of bodies about which it is conversant. The brain cannot carry on -its intellectual operations with vigour beyond a certain period; the -trains of ideas with which it works become, after a time, indistinct -and confused; nor is it capable of reacting with energy until it -has remained in a state of rest proportioned to the duration of its -preceding activity. - -And this rest is sleep. Sleep is the repose of the senses, the rest of -the muscles, their support and sustenance. What food is to the organic, -sleep is to the animal life. Nutrition can no more go on without -aliment, than sensation, thought, and motion without sleep. - -But it is the animal life only that sleeps: death would be the -consequence of the momentary slumber of the organic. If, when the brain -betook itself to repose, the engine that moves the blood ceased to -supply it with its vital fluid, never again would it awake. The animal -life is active only during a portion of its existence; the activity of -the organic life is never for a moment suspended; and in order to endow -its organs with the power of continuing this uninterrupted action, -they are rendered incapable of fatigue: fatigue, on the contrary, is -inseparable from the action of the organs of the animal life; fatigue -imposes the necessity of rest, rest is sleep, and sleep is renovation. - -3. Between all the functions of the organic life there is a close -relation and dependence. Without the circulation there can be no -secretion; without secretion, no digestion; without digestion, no -nutrition; without nutrition, no new supply of circulating matter, -and so through the entire circle. But the functions of the animal -life are not thus dependent on each other. One of the circle may be -disordered without much disturbance of the rest; and one may cease -altogether, while another continues in vigorous action. Sensation may -be lost, while motion continues; and the muscle may contract though it -cannot feel. One organ of sense may sleep while the rest are awake. -One intellectual faculty may be in operation while others slumber. The -muscle of volition may act, while there is no consciousness of will. -Even the organs of the voice and of progression may perform their -office while the sensorium is deeply locked in sleep. - -4. The two lives are born at different periods, and the one is in -active operation before the other is even in existence. The first -action observable in the embryo is a minute pulsating point. It is the -young heart propelling its infant stream. Before brain, or nerve, or -muscle can be distinguished, the heart is in existence and in action; -that is, the apparatus of the organic function of the circulation is -built up and is in operation before there is any trace of an animal -organ. Arteries and veins circulate blood, capillary vessels receive -the vital fluid, and out of it form brain and muscle, the organs of the -animal, no less than the various substances that compose the organs of -the organic life. The organic is not only anterior to the animal life, -but it is by the action of the organic that existence is given to the -animal life. The organic life is born at the first moment of existence; -the animal life not until a period comparatively distant; the epoch -emphatically called the period of birth, namely, the period when -the new being is detached from its mother; when it first comes into -contact with external objects; when it carries on all the functions -of its economy by its own organs, and consequently enjoys independent -existence. - -5. The functions of the organic life are perfect at once. The heart -contracts as well, the arteries secrete as well, the respiratory -organs work as well the first moment they begin to act as at any -subsequent period. They require no teaching from experience, and they -profit nothing from its lessons. On the contrary, the operations -of the brain, and the actions of the voluntary muscles, feeble and -uncertain at first, acquire strength by slow degrees, and attain -their ultimate perfection only at the adult age. How indistinct -and confused the first sensations of the infant! Before it acquire -accuracy, precision, and truth, how immense the labour spent upon -perception! Sensations are succeeded by ideas; sensations and ideas -coalesce with sensations and ideas; combinations thus formed suggest -other combinations previously formed, and these a third, and the third -a fourth, and so is constituted a continuous train of thought. But -the infantile associations between sensation and sensation, between -idea and idea, and between sensations and ideas, are, to a certain -extent, incorrect, and to a still greater extent inadequate; and the -misconception necessarily resulting from this early imperfection in the -intellectual operations is capable of correction only by subsequent and -more extended impressions. During its making hours, a large portion of -the time of the infant is spent in receiving impressions which come -to it every instant from all directions, and which it stores up in -its little treasury; but a large portion is also consumed in the far -more serious and difficult business of discrimination and correction. -Could any man, after having attained the age of manhood, reverse the -order of the course through which he has passed; could he, with the -power of observation, together with the experience that belong to -manhood, retrace with perfect exactness every step of his sentient -existence, from the age of forty to the moment that the air first came -into contact with his body at the moment of his leaving his maternal -dwelling, among the truths he would learn, the most interesting, if -not the most surprising, would be those which relate to the manner in -which he dealt with his earliest impressions; with the mode in which -he combined them, recalled them, laid them by for future use; made his -first general deduction; observed what subsequent experience taught to -be conformable, and what not conformable, to this general inference; -his emotions on detecting his first errors, and his contrasted feelings -on discovering those comprehensive truths, the certainty of which -became confirmed by every subsequent impression. Thus to live backwards -would be, in fact, to go through the analysis of the intellectual -combinations, and, consequently, to obtain a perfect insight into the -constitution of the mind; and among the curious results which would -then become manifest, perhaps few would appear more surprising than the -true action of the senses. The eye, when first impressed by light, does -not perceive the objects that reflect it; the ear, when first impressed -by sound, does not distinguish the sonorous body. When the operation -for cataract has been successfully performed in a person born blind, -the eye immediately becomes sensible to light, but the impression of -light does not immediately give information relative to the properties -of bodies. It is gradually, not instantaneously; it is even by slow -degrees that luminous objects are discerned with distinctness and -accuracy. To see, to hear, to smell, to taste, to touch, are processes -which appear to be performed instantaneously, and which actually are -performed with astonishing rapidity in a person who observes them -in himself; but they were not always performed thus rapidly: they -are processes acquired, businesses learnt; processes and businesses -acquired and learnt, not without the cost of many efforts and much -labour. But the senses afford merely the materials for the intellectual -operations of memory, combination, comparison, discrimination, -induction, operations the progress of which is so slow, that they -acquire precision, energy, and comprehensiveness only after the culture -of years. - -And the same is true of the muscles of volition. How many efforts are -made before the power of distinct articulation is acquired! how many -before the infant can stand! how many before the child can walk! The -organic life is born perfect; the animal life becomes perfect only by -servitude, and the aptitude which service gives. - -6. The organic life may exist after the animal life has perished. The -animal life is extinguished when sensation is abolished, and voluntary -motion can be performed no more. But disease may abolish sensation and -destroy the power of voluntary motion, while circulation, respiration, -secretion, excretion, in a word, the entire circle of the organic -functions continues to be performed. In a single instant apoplexy may -reduce to drivelling fatuity the most exalted intellect, and render -powerless and motionless muscles of gigantic strength; while the action -of the heart and the involuntary contractions of the muscles may not -only not be weakened, but may act with preternatural energy. In a -single instant, apoplexy may even completely extinguish the animal -life, and yet the organic may go on for hours, days, and even weeks; -while catalepsy, perhaps the most singular disease to which the human -frame is subject, may wholly abolish sensation and volition, while -it may impart to the voluntary muscles the power of contracting with -such unnatural energy and continuity, that the head, the trunk, the -limbs may become immoveably fixed in whatever attitude they happen -to be at the moment the paroxysm comes on. In this extraordinary -condition of the nervous system, however long the paroxysm last, and -however complete the abolition of consciousness, the heart continues -to beat, and the pulse to throb, and the lungs to respire, and all the -organic organs to perform their ordinary functions. Dr. Jebb gives the -following description of the condition of a young lady who was the -subject of this curious malady. - -"My patient was seized with an attack just as I was announced. At that -moment she was employed in netting; she was in the act of passing -the needle through the mesh; in that position she became immoveably -rigid, exhibiting, in a pleasing form, a figure of death-like sleep, -beyond the power of art to imitate, or the imagination to conceive. -Her forehead was serene, her features perfectly composed. The paleness -of her colour, and her breathing, which at a distance was scarcely -perceptible, operated in rendering the similitude to marble more exact -and striking. The position of her fingers, hands, and arms was altered -with difficulty, but preserved every form of flexure they acquired: -nor were the muscles of the neck exempted from this law, her head -maintaining every situation in which the hand could place it, as firmly -as her limbs." - -In this condition of the system the senses were in a state of profound -sleep; the voluntary muscles, on the contrary, were in a state of -violent action; but this action not being excited by volition, nor -under its control, the patient remained as motionless as she was -insensible. The brain was in a state of temporary death; the muscle -in a state of intense life. And the converse may happen: the muscle -may die, while the brain lives; contractility may be destroyed, while -sensibility is perfect; the power of motion may be lost, while that of -sensation may remain unaffected. A case is on record, which affords -an illustration of this condition of the system. A woman had been for -some time confined to her bed, labouring under severe indisposition. -On a sudden she was deprived of the power of moving a single muscle of -the body; she attempted to speak, but she had no power to articulate; -she endeavoured to stretch out her hand, but her muscles refused to -obey the commands of her will, yet her consciousness was perfect, and -she retained the complete possession of her intellectual faculties. -She perceived that her attendants thought her dead, and was conscious -of the performance upon her own person of the services usually paid to -the dead; she was laid out, her toes were bound together, her chin was -tied up; she heard the arrangements for her funeral discussed, and yet -she was unable to make the slightest sign that she was still in the -possession of sense, feeling, and life. - -In one form of disease, then, the animal life, both the sensitive and -the motive portions of it, may perish; and in another form of disease, -either the one or the other part of it may be suspended, while the -organic life continues in full operation: it follows that the two -lives, blended as they are, are distinct, since the one is capable of -perishing without immediately and inevitably involving the destruction -of the other. - -7. And, finally, as the organic life is the first born, so it is the -last to die; while the animal life, as it is the latest born, and -the last to attain its full development, so it is the earliest to -decline and the first to perish. In the process of natural death, the -extinction of the animal is always anterior to that of the organic -life. Real death is a later, and sometimes a much later event than -apparent death. An animal appears to be dead when, together with the -abolition of sensation and the loss of voluntary motion, respiration, -circulation, and the rest of the organic functions can no longer be -distinguished; but these functions go on some time after they have -ceased to afford external indications of their action. In man, and the -warmblooded animals in general, suspension or submersion extinguishes -the animal life, at the latest, within the space of four minutes from -the time that the atmospheric air is completely excluded from the -lung; but did the organic functions also cease at the same period, it -would be impossible to restore an animal to life after apparent death -from drowning and the like. But however complete and protracted the -abolition of the animal functions, re-animation is always possible as -long as the organic organs are capable of being restored to their usual -vigour. The cessation of the animal life is but the first stage of -death, from which recovery is possible; death is complete only when the -organic together with the animal functions have wholly ceased, and are -incapable of being re-established. - -In man, the process of death is seldom altogether natural. It is -generally rendered premature by the operation of circumstances which -destroy life otherwise than by that progressive and slow decay which is -the inevitable result of the action of organized structure. Death, when -natural, is the last event of an extended series, of which the first -that is appreciable is a change in the animal life and in the noblest -portion of that life. The higher faculties fail in the reverse order of -their development; the retrogression is the inverse of the progression, -and the noblest creature, in returning to the state of non-existence, -retraces step by step each successive stage by which it reached the -summit of life. - -In the advancing series, the animal is superadded to the organic -life; sensation, the lowest faculty of the animal life, precedes -ratiocination, the highest. The senses called into play at the moment -of birth soon acquire the utmost perfection of which they are capable; -but the intellectual faculties, later developed, are still later -perfected, and the highest the latest. - -In the descending series, the animal life fails before the organic, and -its nobler powers decay sooner and more rapidly than the subordinate. -First of all, the impressions which the organs of sense convey to -the brain become less numerous and distinct, and consequently the -material on which the mind operates is less abundant and perfect; but -at the same time, the power of working vigorously with the material it -possesses more than proportionally diminishes. Memory fails; analogous -phenomena are less readily and less completely recalled by the presence -of those which should suggest the entire train; the connecting links -are dimly seen or wholly lost; the train itself is less vivid and less -coherent; train succeeds train with preternatural slowness, and the -consequence of these growing imperfections is that, at last, induction -becomes unsound just as it was in early youth; and for the same -reason, namely, because there is not in the mental view an adequate -range of individual phenomena; the only difference being that the -range comprehended in the view of the old man is too narrow, because -that which he had learnt he has forgotten; while in the youth it is -too narrow, because that which it is necessary to learn has not been -acquired. - -And with the diminution of intellectual power the senses continue -progressively to fail: the eye grows more dim, the ear more dull, the -sense of smell less delicate, the sense of touch less acute, while -the sense of taste immediately subservient to the organic function of -nutrition is the last to diminish in intensity and correctness, and -wholly fails but with the extinction of the life it serves. - -But the senses are not the only servants of the brain; the voluntary -muscles are so equally; but these ministers to the master-power, no -longer kept in active service, the former no longer employed to convey -new, varied, and vivid impressions, the latter no longer employed -to execute the commands of new, varied, and intense desires, become -successively feebler, slower, and more uncertain in their action. -The hand trembles, the step totters, and every movement is tardy and -unsteady. And thus, by the loss of one intellectual faculty after -another, by the obliteration of sense after sense, by the progressive -failure of the power of voluntary motion; in a word, by the declining -energy and the ultimate extinction of the animal life, man, from the -state of maturity, passes a second time through the stage of childhood -back to that of infancy; lapses even into the condition of the embryo: -what the fœtus was, the man of extreme old age is: when he began to -exist, he possessed only organic life; and before he is ripe for the -tomb, he returns to the condition of the plant. - -And even this merely organic existence cannot be long maintained. Slow -may be the waste of the organic organs; but they do waste, and that -waste is not repaired, and consequently their functions languish, and -no amount of stimulus is capable of invigorating their failing action. -The arteries are rigid and cannot nourish; the veins are relaxed and -cannot carry on the mass of blood that oppresses them; the lungs, -partly choked up by the deposition of adventitious matter, and partly -incapable of expanding and collapsing by reason of the feeble action -of the respiratory apparatus, imperfectly aërate the small quantity -of blood that flows through them; the heart, deprived of its wonted -nutriment and stimulus, is unable to contract with the energy requisite -to propel the vital current; the various organs, no longer supplied -with the quantity and quality of material necessary for carrying on -their respective processes, cease to act; the machinery stops, and this -is death. - -And now the processes of life at an end, the body falls within the -dominion of the powers which preside universally over matter; the tie -that linked all its parts together, holding them in union and keeping -them in action, in direct opposition to those powers dissolved, it -feels and obeys the new attractions to which it has become subject; -particle after particle that stood in beautiful order fall from their -place; the wonderful structures they composed melt away; the very -substances of which those structures were built up are resolved into -their primitive elements; these elements, set at liberty, enter into -new combinations, and become constituent parts of new beings; those new -beings in their turn perish; from their death springs life, and so the -changes go on in an everlasting circle. - -As far as relates to the organized structures in which life has its -seat, and to the operations of life dependent on those structures, -such is its history; a history not merely curious, but abounding with -practical suggestions of the last importance. The usefulness of a -familiar acquaintance with the phenomena which have now been elucidated -will be apparent at every step as we proceed. - - - - -CHAPTER III. - - Ultimate object of organization and life—Sources of - pleasure—Special provision by which the organic organs - influence consciousness and afford pleasure—Point at which - the organic organs cease to affect consciousness, and - why—The animal appetites: the senses: the intellectual - faculties: the selfish and sympathetic affections: the - moral faculty—Pleasure the direct, the ordinary, and the - gratuitous result of the action of the organs—Pleasure - conducive to the development of the organs, and to - the continuance of their action—Progress of human - knowledge—Progress of human happiness. - - -The object of structure is the production of function. Of the two -functions combined in the living animal, one is wholly subservient -to the other. To build up the apparatus of the animal life, and to -maintain it in a condition fit for performing its functions, is the -sole object of the existence of the organic life. What then is the -object of the animal life? That object, whatever it be, must be the -ultimate end of organization, and of all the actions of which it is the -seat and the instrument. - -Two functions, sensation and voluntary motion, are combined in the -animal life. Of these two functions, the latter is subservient to the -former: voluntary motion is the servant of sensation, and exists only -to obey its commands. - -Is sensation, then, the ultimate object of organization? Simple -sensation cannot be an ultimate object, because it is invariably -attended with an ultimate result; for sensation is either pleasurable -or painful. Every sensation terminates in a pleasure or a pain. -Pleasure or pain, the last event in the series, must then be the final -end. - -Is the production of pain the ultimate object of organization? That -cannot be, for the production of pain is the indirect, not the -direct,—the extraordinary, not the ordinary, result of the actions -of life. It follows that pleasure must be the ultimate object, for -there is no other of which it is possible to conceive. The end of -organic existence is animal existence; the end of animal existence -is sentient existence; the end of sentient existence is pleasurable -existence; the end of life therefore is enjoyment. Life commences with -the organic processes; to the organic are superadded the animal; the -animal processes terminate in sensation; sensation ends in enjoyment; -it follows, that enjoyment is the final end. For this every organ is -constructed; to this every action of every organ is subservient; in -this every action ultimately terminates. - -And without a single exception in the entire range of the sentient -creation, the higher the organized structure the greater the enjoyment, -mediately or immediately, to which it is subservient. From its most -simple to its most complex state, every successive addition to -structure, by which function is rendered more elevated and perfect, -proportionally increases the exquisiteness of the pleasure to which the -function ministers, and in which it terminates. - -Pleasure is the result of the action of living organs, whether -organic or animal; pleasure is the direct, the ordinary, and the -gratuitous result of the action of both sets of organs; the pleasure -resulting from the action of the organs is conducive to their complete -development, and thereby to the increase of their capacity for -affording enjoyment; the pleasure resulting from the action of the -organs, and conducive to their development, is equally conducive to the -perpetuation of their action, and consequently to the maintenance of -life; it follows not only that enjoyment is the end of life, but that -it is the means by which life is prolonged. Of the truth of each of -these propositions, it will be interesting to contemplate the plenitude -of the proof. - -1. In the first place, pleasure is the result of the action of the -organic organs. It has indeed been shown that the very character by -which the action of these organs is distinguished is that they are -unattended with consciousness. Nevertheless, by a special provision, -consciousness is indirectly connected with the processes of this -class, limited in extent indeed, and uniformly terminating at a -certain point; but the extent and the limitation alike conducing to -the pleasurableness of its nature. And this is an adjustment in the -constitution of our frame which is well deserving of attention. - -Organic processes are dependent on a peculiar influence derived from -that portion of the nervous system distinguished by the term organic. -The organic nerves, distributed to the organic organs, take their -origin and have their chief seat in the cavities that contain the main -instruments of the organic life, namely, the chest and abdomen (see -chap. v.). As will be fully shown hereafter, these nerves encompass -the great trunks of the blood-vessels that convey arterial blood -to the organic organs. In all its ramifications through an organic -organ, an arterial vessel is accompanied by its organic nerve; so that -wherever the capillary arterial branch goes, secreting or nourishing, -there goes, inseparably united with it, an organic nerve, exciting and -governing. - -Among the peculiarities of this portion of the nervous system, one -of the most remarkable is, that it is wholly destitute of feeling. -Sensibility is inseparably associated with the idea commonly formed of -a nerve. But the nervous system consists of two portions, one presiding -over sensation and voluntary motion, hence called the sentient and -the motive portions; the other destitute of sensation, but presiding -over the organic processes, hence called the organic portion. If the -communication between the organic organ and the organic nerve be -interrupted, the function of the organ, whatever it be, is arrested. -Without its organic nerves, the stomach cannot secrete gastric juice; -the consequence is, that the aliment is undigested. Without its organic -nerves, the liver cannot secrete bile, the consequence is, that the -nutritive part of the aliment is incapable of being separated from its -excrementitious portion. The organic organ receives from its organic -nerve an influence, without which it cannot perform its function; -but the nerve belonging to this class neither feels nor communicates -feeling, and hence it imparts no consciousness of the operation of any -process dependent upon it. Yet there is not one of these processes that -does not exert a most important influence over consciousness. How? By a -special provision, as curious in its nature as it is important in its -result. - -Branches of sentient nerves are transmitted from the animal to the -organic system, and from the organic to the animal; and an intimate -communication is established between the two classes. The inspection -of fig. XVI. will illustrate the mode in which this communication is -effected. A B represents a portion of the spinal cord (one of the -central masses of the sentient system), covered with its membranes. The -part here represented is a front view of that portion of the spinal -cord which belongs to the back, and which is technically called the -dorsal portion. - -[Illustration: Fig. XVI.] - -1, 2, 3, 4, 5, 6, 7, 8, 9, the second, &c. ribs with the corresponding -dorsal (sentient) nerves, _a_, _b_, _c_, _d_, _e_, _f_, _g_, _h_, going -out to supply their respective organs with sensation. - -C D E, a portion of the main trunk of the organic (non-sentient) nerve, -commonly called the Great Sympathetic. - -F G H, the membrane of the spinal cord cut open and exposing I K, the -spinal cord itself, L, the anterior branch of one of the dorsal nerves, -arising from the anterior surface of the spinal cord by several bundles -of fibres. - -M, the posterior branch of the same nerve, arising in like manner from -the posterior surface of the spinal cord by several branches of fibres. - -The anterior and posterior branches uniting to form one trunk N. - -Two branches, P Q, sent off from the spinal (sentient) trunk to unite -with the organic (non-sentient) trunk. - -R S T U V W, other branches of the sentient, connected with the -branches of the non-sentient nervous trunks in the same mode. - -X Y, the main trunk of the sympathetic (non-sentient) nerve cut across -and turned aside, in order that the parts beneath it (P N) may be more -distinctly seen. - -From this description, it is apparent that each sentient nerve, -before it goes out to the animal organs, to which it is destined to -communicate sensation, sends off two branches to the organic or the -non-sentient. These sentient nerves mix and mingle with the insensible -nerves; accompany them in their course to the organic organs, and -ramify with them throughout their substance. It is manifest, then, -that sentient nerves, that nerves not necessary to the organic -processes, having, as far as is known, nothing whatever to do with -those processes, enter as constituent parts into the composition of the -organic organs. What is the result? That organic organs are rendered -sentient; that organic processes, in their own nature insensible, -become capable of affecting consciousness. What follows? What is the -consciousness excited? Not a consciousness of the organic process. -Of that we still remain wholly insensible. Not simple sensation. The -result uniformly produced, as long as the state of the system is that -of health, is pleasurable consciousness. The heart sends out to the -organs its vital current. Each organ, abstracting from the stream the -particles it needs, converts them into the peculiar fluid or solid -it is its office to form. The stomach, from the arterial streamlets -circulating through it, secretes gastric juice; the liver, from the -venous streamlets circulating through it, secretes bile. When these -digestive organs have duly prepared their respective fluids, they -employ them in the elaboration of the aliment. We are not conscious -of this elaboration, though it go on within us every moment; but is -consciousness not affected by the process? Most materially. Why? -Because sentient mingle with organic nerves; because the sentient -nerves are impressed by the actions of the organic organs. And how -impressed? As long as the actions of the organic organs are sound, -that is, as long as their processes are duly performed, the impression -communicated to the sentient nerves is in its nature agreeable; is, -in fact, THE PLEASURABLE CONSCIOUSNESS WHICH CONSTITUTES THE FEELING -OF HEALTH. The state of health is nothing but the result of the -due performance of the organic organs: it follows that the feeling -of health, the feeling which is ranked by every one among the most -pleasurable of existence, is the result of the action of organs of -whose direct operations we are unconscious. But the pleasurable -consciousness thus indirectly excited is really the consequence of a -special provision, established for the express purpose of producing -pleasure. Processes, in their own nature insensible, are rendered -sentient expressly for this purpose, that, over and above the special -object they serve, they may afford enjoyment. In this case, the -production of pleasure is not only altogether gratuitous, not only -communicated for its own sake, not only rested in as an ultimate -object, but it is made to commence at the very confines of life; it is -interwoven with the thread of existence: it is secured in and by the -actions that build up and that support the very framework, the material -instrument of our being. - -But if the communication of sensibility to processes in their own -nature incapable of exciting feeling, for the purpose of converting -them into sources of pleasurable consciousness, indicate an express -provision for the production of enjoyment, that provision is no less -exemplified in the point at which this superadded sensibility is made -to cease. - -Some of the consequences of a direct communication of consciousness -to an organic process have been already adverted to. Had the eye, -besides transmitting rays of light to the optic nerve, been rendered -sensible of the successive passage of each ray through its substance, -the impression excited by luminous bodies, which is indispensable to -vision, the ultimate object of the instrument, if not wholly lost, -must necessarily have become obscure, in direct proportion to the -acuteness of this sensibility. The hand of the musician could scarcely -have executed its varied and rapid movements upon his instrument, had -his mind been occupied at one and the same instant with the process -of muscular contraction in the finger, and the idea of music in the -brain. Had the communication of such a twofold consciousness been -possible, in no respect would it have been beneficial, in many it would -have been highly pernicious; and the least of the evils resulting -from it would have been, that the inferior would have interrupted the -superior faculty, and the means deteriorated the end. But in some -cases the evil would have been of a much more serious nature. Had we -been rendered sensible of the flow of the vital current through the -engine that propels it; were the distension of the delicate valves that -direct the current ever present to our view; by some inward feeling -were we reminded, minute by minute, of the progress of the aliment -through the digestive apparatus, and were the mysterious operations -of the organic nerves palpable to sight, the terror of the maniac, -who conceived that his body was composed of unannealed glass, would -be the ordinary feeling of life. Every movement would be a matter of -anxious deliberation; and the approach of every body to our own would -fill us with dismay. But adjusted as our consciousness actually is, -invariably the point at which the organic process begins is that at -which sensation ends. Had sensation been extended beyond this point, it -would have been productive of pain: at this point it uniformly stops. -Nevertheless, by the indirect connexion of sensation with the organic -processes, a vast amount of pleasure might be created: a special -apparatus is constructed for the express purpose of establishing the -communication. There is thus the twofold proof, the positive and the -negative, the evidence arising as well from what they do, as from -what they abstain from doing, that the organic processes are, and are -intended to be, sources of enjoyment. - -But the production of pleasure, commencing at this the lowest point -of conscious existence, increases with the progressive advancement of -organization and function. - -The appetite for food, and the voluntary actions dependent upon it, -may be considered as the first advancement beyond a process purely -organic. The function by which new matter is introduced into the -system and converted into nutriment, is partly an animal and partly an -organic operation. The animal part of it consists of the sensations of -hunger and thirst, by which we are taught when the wants of the system -require a fresh supply of aliment, together with the voluntary actions -by which the aliment is introduced into the system. The organic part -of the function consists of the changes which the aliment undergoes -after its introduction into the system, by which it is converted into -nutriment. Sensations always of a pleasurable nature arise indirectly -in the manner already explained, from the due performance of the -organic part of the function; but pleasure is also directly produced by -the performance of the animal part of it. Wholesome food is grateful; -the satisfaction of the appetite for food is pleasurable. Food is -necessary to the support of life; but it is not indispensable to the -maintenance of life that food should be agreeable. Appetite there -must be, that food may be eaten; but the act of eating might have -been secured without connecting it with pleasure. Pleasure, however, -is connected with it, first directly, by the gratefulness of food, -and secondly indirectly, by the due digestion of the food. And the -annexation of pleasure in this twofold mode to the performance of the -function of nutrition is another case of the gratuitous bestowment of -pleasure; another instance in which pleasure is communicated for its -own sake, and rested in as an ultimate object. Pleasures of this class -are sometimes called low; they are comparatively low; but they are not -the less pleasures, because they are exceeded in value by pleasures of -a nobler nature. Man may regard them with comparative indifference, -because he is endowed with faculties which afford him gratifications -superior in kind and larger in amount; but it is no mark of wisdom to -despise and neglect even these: for they are annexed to the exercise -of a function which is the first to exalt us above a merely organic -existence; they are the first pleasures of which, considered merely as -sentient creatures, we are susceptible; they amount in the aggregate to -an immense sum; and they mark the depth in our nature in which are laid -the fountains of enjoyment. - -Organs of sense, intellectual faculties, social affections, moral -powers, are superadded endowments of a successively higher order: -at the same time, they are the instruments of enjoyment of a nature -progressively more and more exquisite. - -An organ of sense is an instrument composed of a peculiar arrangement -of organized matter, by which it is adapted to receive from specific -agents definite impressions. Between the agent that produces and the -organ that receives the impression, the adaptation is such, that the -result of their mutual action is, in the first place, the production of -sensation, and, in the second place, the production of pleasure. The -pleasure is as much the result as the sensation. This is true of the -eye in seeing, the ear in hearing, the hand in touching, the organ of -smell in smelling, and the tongue in tasting. Pleasure is linked with -the sense; but there might have been the sense without the pleasure. -A slight difference in the construction of the organ, or in the -intensity of the agent, would not merely have changed, it would even -have reversed the result; would have rendered the habitual condition of -the eye, the ear, the skin, not such as it now is in health, but such -as it is in the state of inflammation. But the adjustment is such as -habitually to secure that condition of the system in which every action -that excites sensation produces pleasure as its ordinary concomitant; -and the amount of enjoyment which is thus secured to every man, and -which every man without exception actually experiences in the ordinary -course of an ordinary life, it would be beyond his power to estimate -were he always sensible of the boon; but the calculation is altogether -impossible, when, as is generally the case, he merely enjoys without -ever thinking of the provisions which enable him to do so. - -But if the pleasures that arise from the ordinary operations of sense -form, in the aggregate, an incalculable sum, how great is the accession -brought to this stock by the endowments next in order in the ascending -scale, namely, the intellectual faculties! - -There is one effect resulting from the operation of the intellectual -faculties on the senses that deserves particular attention. The higher -faculties elevate the subordinate in such a manner as to make them -altogether new endowments. In illustration of this, it will suffice -to notice the change wrought, as if in the very nature of sensation, -the moment it becomes combined with an intellectual operation, as -exemplified in the difference between the intellectual conception of -beauty, and the mere perception of sense. The grouping of the hills -that bound that magnificent valley which I behold at this moment spread -out before my view; the shadow of the trees at the base of some of -them, stretching its deep and varied outline up the sides of others; -the glancing light now brightening a hundred different hues of green -on the broad meadows, and now dancing on the upland fallows; the -ever-moving, ever-changing clouds; the scented air; the song of birds; -the still more touching music which the breeze awakens in the scarcely -trembling branches of those pine trees,—the elements of which this -scene is composed, the mere objects of sense, the sun, the sky, the -air, the hills, the woods, and the sounds poured out from them, impress -the senses of the animals that graze in the midst of them; but on their -senses they fall dull and without effect, exciting no perception of -their loveliness, and giving no taste of the pleasures they are capable -of affording. Nor even in the human being, whose intellectual faculties -have been uncultivated, do they awaken either emotions or ideas; the -clown sees them, hears them, feels them no more than the herds he -tends: yet in him whose mind has been cultivated and unfolded, how -numerous and varied the impressions, how manifold the combinations, how -exquisite the pleasures produced by objects such as these! - -And from the more purely intellectual operations, from memory, -comparison, analysis, combination, classification, induction, how -still nobler the pleasure! Not to speak of the happiness of him who, -by his study of natural phenomena, at length arrived at the stupendous -discovery that the earth and all the stars of the firmament move, and -that the feather falls to the ground, by the operation of one and the -same physical law; nor of the happiness of him who sent his kite into -the cloud, and brought down from its quiet bed the lightning which -he suspected was slumbering there; nor of the happiness of him who -concentrated, directed, and controlled that mighty power which has -enabled the feeble hand of man to accomplish works greater than have -been feigned of fabled giant; which has annihilated distance; created, -by economizing time; changed in the short space in which it has been in -operation the surface of the habitable globe; and is destined to work -upon it more and greater changes than have been effected by all other -causes combined; nor of the happiness of him who devoted a longer life -with equal success to a nobler labour, that of REARING THE FABRIC OF -FELICITY BY THE HAND OF REASON AND OF LAW. The intellectual pleasures -of such men as Newton, Franklin, Watt, and Bentham, can be _equalled_ -only by those who possess equal intellectual power, and who put forth -equal intellectual energy: to be greatly happy as they were, it were -necessary to be as highly endowed; but to be happy, it is not necessary -to be so endowed. In the ordinary intellectual operations of ordinary -men, in their ordinary occupations, there is happiness. Every human -being whose moments have passed with winged speed, whose day has been -short, whose year is gone almost as soon as it seemed commenced, has -derived from the exercise of his intellectual faculties pleasures -countless in number and inestimable in value. - -But the sympathetic pleasures, out of which grow the social, are of -a still higher order even than the intellectual. The pleasures that -result from the action of the organic organs, from the exercise of the -several senses, and from the operation of the intellectual faculties, -like the sensations in which they arise, belong exclusively to the -individual being that experiences them, and cannot be communicated -to another. Similar sensations and pleasures may be felt by beings -similarly constituted; but the actual sensations and pleasures afforded -by the exercise of a person's own organs and faculties are no more -capable of becoming another's than his existence. These, then, are -strictly the selfish pleasures; and the provision that has been made -for securing them has been shown. - -But there are pleasures of another class, pleasures having no relation -whatever to a person's own sensation or happiness; pleasures springing -from the perception of the enjoyment of others. The sight of pleasure -not its own affects the human heart, provided its state of feeling be -natural and sound, just as it would be affected were it its own. Not -more real is the pleasure arising from the gratification of appetite, -the exercise of sense, and the operation of intellect, than that -arising from the consciousness that another sentient being is happy. -Pleasures of this class are called sympathetic, in contradistinction to -those of the former class, which are termed selfish. - -There are then two principles in continual operation in the human -being, the selfish and the sympathetic. The selfish is productive of -pleasure of a certain kind; the sympathetic is productive of pleasure -of another kind. The selfish is primary and essential; the sympathetic, -arising out of the selfish, is superadded to it. And so precisely -what the animal life is to the organic, the sympathetic principle is -to the selfish; and just what the organic life gains by its union -with the animal, the mental constitution gains by the addition of -the sympathetic to the selfish affection. The analogy between the -combination in both cases is in every respect complete. As the organic -life produces and sustains the animal, so the sympathetic principle -is produced and sustained by the selfish. As the organic life is -conservative of the entire organization of the body, so the selfish -principle is conservative of the entire being. As the animal life is -superadded to the organic, extending, exalting, and perfecting it, -so the sympathetic principle is superadded to the selfish, equally -extending, exalting, and perfecting it. The animal life is nobler than -the organic, whence the organic is subservient to the animal; but there -is not only no opposition, hostility, or antagonism between them, but -the strictest possible connexion, dependence, and subservience. The -sympathetic principle is nobler than the selfish, whence the selfish is -subservient to the sympathetic; but there is not only no opposition, -hostility, or antagonism between them, but the strictest possible -connexion, dependence, and subservience. Whatever is conducive to the -perfection of the organic, is equally conducive to the perfection of -the animal life; and whatever is conducive to the attainment of the -true end of the selfish is equally conducive to the attainment of the -true end of the sympathetic principle. The perfection of the animal -life cannot be promoted at the expense of the organic, nor that of the -organic at the expense of the animal; neither can the ultimate end of -the selfish principle be secured by the sacrifice of the sympathetic, -nor that of the sympathetic by the sacrifice of the selfish. Any -attempt to exalt the animal life beyond what is compatible with the -healthy state of the organic, instead of accomplishing that end, only -produces bodily disease. Any attempt to extend the selfish principle -beyond what is compatible with the perfection of the sympathetic, -or the sympathetic beyond what is compatible with the perfection of -the selfish, instead of accomplishing the end in view, only produces -mental disease. Opposing and jarring actions, antagonizing and mutually -destructive powers, are combined in no other work of nature; and it -would be wonderful indeed were the only instance of it found in man, -the noblest of her works, and in the mind of man, the noblest part of -her noblest work. - -No one supposes that there is any such inharmonious combination in -the organization of his physical frame, and the notion that it exists -in his mental constitution, as it is founded in the grossest ignorance, -so it is productive of incalculable mischief. In both, indeed, are -manifest two great powers, each distinct; each having its own peculiar -operation; and the one being subservient to the other, but both -conducing alike to one common end. By the addition of the apparatus of -the animal to that of the organic life, a nobler structure is built -up than could have been framed by the organic alone: by the addition -of the sympathetic to the selfish part of the mental constitution, a -happier being is formed than could have been produced by the selfish -alone. And as the organic might have existed without the animal life, -but by the addition of the animal a new and superior being is formed, -so might the selfish part of the mental constitution, and the pleasures -that flow from it, have existed alone; but by the addition of the -sympathetic, a sum is added to enjoyment, of the amount of which some -conception may be formed by considering what human life would be, with -every selfish appetite and faculty gratified in the fullest conceivable -degree, but without any admixture whatever of sympathetic or social -pleasure. Selfish enjoyment is not common. If any one set himself to -examine what at first view might seem a purely selfish pleasure, he -will soon be sensible that, of the elements composing any given state -of mind to which he would be willing to affix the term pleasurable, -a vast preponderance consists of sympathetic associations. The more -accurately he examine, and the farther he carry his analysis, the -stronger will become his conviction, that a purely selfish enjoyment, -that is, a truly pleasurable state of mind, in no degree, mediately or -immediately, connected with the pleasurable state of another mind, is -exceedingly rare. - -But if the constitution of human nature and the structure of human -society alike render it difficult for the human heart to be affected -with a pleasure in no degree derived from—absolutely and totally -unconnected with sympathetic association, of that complex pleasure -which arises out of social intercourse, partly selfish and partly -sympathetic, how far sweeter the sympathetic than the selfish -part; and as the sympathetic preponderates over the selfish, how -vast the increase of the pleasure! And when matured, exalted into -affection—affection, that holy emotion which exerts a transforming -influence over the selfish part of human nature, turning it into the -sympathetic; affection, which renders the happiness of the beloved -object inexpressibly dearer to the heart than its own; affection, -among the benignant feelings of which as there is none sweeter so -there is none stronger than that of self-devotion, nay, sometimes even -of self-sacrifice; affection, which is sympathy pure, concentrated, -intense—Oh how beautiful is the constitution of this part of our -nature, by which the most transporting pleasures the heart receives are -the direct reflection of those it gives! - -Nor ought it to be overlooked, that, while nearly all the selfish, -like all the sensual pleasures, cannot be increased beyond a fixed -limit, cannot be protracted beyond a given time, are short-lived in -proportion as they are intense, and satiate the appetite they gratify, -the sympathetic pleasures are capable of indefinite augmentation; are -absolutely inexhaustible; no limit can be set to their number, and no -bound to their growth; they excite the appetite they gratify; they -multiply with and by participation, and the more is taken from the -fountain from which they flow, the deeper, the broader, and the fuller -the fountain itself becomes. - -But not only is the mental state of affection in all its forms and -degrees highly pleasurable, but the very consciousness of being the -object of affection is another pleasure perfectly distinct from that -arising immediately from the affection itself. It has been said of -charity, that it is twice blessed, that it blesses alike him that -gives and him that receives; but love has in it a threefold blessing: -first, in the mental state itself; secondly, in the like mental state -which the manifestation of it produces in another; and thirdly, in the -mental state inseparable from the consciousness of being the object of -affection. And this reflex happiness, this happiness arising from the -consciousness of being the object, is even sweeter than any connected -with being the subject of affection. - -In like manner there is pleasure in the performance of beneficent -actions; in energetic, constant, and therefore ultimately successful -exertions to advance the great interests of human kind, in art, in -science, in philosophy, in education, in morals, in legislation, -in government; whether those exertions are put forth in the study, -the school, the senate, or any less observed though perhaps not -less arduous nor less important field of labour. Exertions of this -kind beget in those for whom, towards those by whom, they are made, -benignant feelings—respect, veneration, gratitude, love. With -such feelings the philosopher, the instructor, the legislator, the -statesman, the philanthropist, knows that he is, or that, sooner or -later, he will be regarded by his fellow men; and in this consciousness -there is happiness: but this is another source of happiness perfectly -distinct from that arising from the performance of beneficent actions; -it is a new happiness superadded to the former, and, if possible, -still more exquisite. Thus manifold is the beneficent operation of the -sympathetic affection: thus admirable is the provision made in the -constitution of our nature for the excitement and extension of this -affection, and, through its instrumentality, for the multiplication and -exaltation of enjoyment! - -In affections and actions of the class just referred to, and in the -pleasures that result from them, there is much of the nature which is -commonly termed moral. And the power to which the moral affections and -actions are referred is usually and justly considered as the supreme -faculty of the mind; for it is the regulator and guide of all the -others; it is that by which they attain their proper and ultimate -object. Of whatever pleasure human nature is capable in sensation, in -idea, in appetite, in passion, in emotion, in affection, in action; -whatever is productive of real pleasure, in contradistinction to what -only cheats with the false hope of pleasure; whatever is productive -of pure pleasure, in contradistinction to what is productive partly -of pleasure and partly of pain, and consequently productive not of -pure, but of mixed pleasure; whatever is productive of a great degree -of pleasure in contradistinction to what is productive of a small -degree of pleasure; whatever is productive of lasting pleasure, in -contradistinction to what is productive of temporary pleasure; whatever -is productive of ultimate pleasure, in contradistinction to what is -productive of immediate pleasure, but ultimate pain; this greatest and -most perfect pleasure it is the part of the moral faculty to discover. -In the degree in which the operation of this faculty is correct and -complete, it enables the human being to derive from every faculty of -his nature the greatest, the purest, the most enduring pleasure; that -is, the maximum of felicity. This is the proper scope and aim of the -moral faculty; to this its right exercise is uniformly conducive; and -this, as it is better cultivated and directed, it will accomplish in -a higher degree, in a continual progression, to which no limit can -be assigned. But if the operation of this faculty be to render every -other in the highest degree conducive to happiness, conformity to -the course of conduct required by it, must of course be that highest -happiness. Conformity to the course of conduct pointed out by the -moral faculty as conducive in the highest degree to happiness is moral -excellence, or, in the definite and exact sense of the word, virtue. -And in this sense it is that virtue is happiness. It is because it -discriminates the true sources of happiness, that is, directs every -other faculty into its proper course, and guides it in that course to -the attainment of its ultimate object, that the moral faculty is ranked -as the highest faculty of the mind. Supposing the operation of this -faculty to be perfect, it is but an identical expression to say, that -to follow its guidance implicitly is to follow the road that leads to -the most perfect happiness. But, over and above the happiness thus -directly and necessarily resulting from yielding uniform and implicit -obedience to the moral faculty, there is, in the very consciousness of -such conformity, a new happiness, as pure as it is exalted. Thus, in -a twofold manner, is the moral the highest faculty of the mind, the -source of its highest happiness; and thus manifest it is, from every -view that can be taken of the constitution of human nature, that every -faculty with which it is endowed, from the highest to the lowest, not -only affords its own proper and peculiar pleasure, but that each, as -it successively rises in the scale, is proportionately the source of a -nobler kind, and a larger amount of enjoyment. - -And the pleasure afforded by the various faculties with which the human -being is endowed is the immediate and direct result of their exercise. -With the exception of the organic organs, and the reason for the -exception in regard to them has been assigned, the action of the organs -is directly pleasurable. From the exercise of the organs of sense, from -the operation of the intellectual faculties, from appetite, passion, -and affection, pleasure flows as directly as the object for which the -instrument is expressly framed. - -And pleasure is the ordinary result of the action of the organs; pain -is sometimes the result, but it is the extraordinary not the ordinary -result. Whatever may be the degree of pain occasionally produced, or -however protracted its duration, yet it is never the natural, that -is, the usual or permanent state, either of a single organ, or of an -apparatus, or of the system. The usual, the permanent, the natural -condition of each organ, and of the entire system, is pleasurable. -Abstracting, therefore, from the aggregate amount of pleasure, the -aggregate amount of pain, the balance in favour of pleasure is immense. -This is true of the ordinary experience of ordinary men, even taking -their physical and mental states such as they are at present; but the -ordinary physical and mental states, considered as sources of pleasure -of every human being, might be prodigiously improved; and some attempt -will be made, in a subsequent part of this work, to show in what manner -and to what extent. - -It has been already stated that there are cases in which pleasure is -manifestly given for its own sake; in which it is rested in as an -ultimate object: but the converse is never found: in no case is the -excitement of pain gratuitous. Among all the examples of secretion, -there is no instance of a fluid, the object of which is to irritate -and inflame: among all the actions of the economy, there is none, the -object of which is the production of pain. - -Moreover, all such action of the organs, as is productive of pleasure, -is conducive to their complete development, and consequently to the -increase of their capacity for producing pleasure; while all such -action of the organs as is productive of pain is preventive of their -complete development, and consequently diminishes their capacity -for producing pain. The natural tendency of pleasure is to its own -augmentation and perpetuity. Pain, on the contrary, is self-destructive. - -Special provision is made in the economy, for preventing pain -from passing beyond a certain limit, and from enduring beyond a -certain time. Pain, when it reaches a certain intensity, deadens the -sensibility of the sentient nerve; and when it lasts beyond a certain -time, it excites new actions in the organ affected, by which the organ -is either restored to a sound state, or so changed in structure that -its function is wholly abolished. But change of structure and abolition -of function, if extensive and permanent, are incompatible with the -continuance of life. If, then, the actions of the economy, excited by -pain, fail to put an end to suffering by restoring the diseased organ -to a healthy state, they succeed in putting an end to it by terminating -life. Pain, therefore, cannot be so severe and lasting as materially to -preponderate over pleasure, without soon proving destructive to life. - -But the very reverse is the case with pleasure. All such action of the -organs as is productive of pleasure is conducive to the perpetuation -of life. There is a close connexion between happiness and longevity. -Enjoyment is not only the end of life, but it is the only condition -of life which is compatible with a protracted term of existence. The -happier a human being is, the longer he lives; the more he suffers, -the sooner he dies; to add to enjoyment, is to lengthen life; to -inflict pain, is to shorten the duration of existence. As there is a -point of wretchedness beyond which life is not desirable, so there is -a point beyond which it is not maintainable. The man who has reached -an advanced age cannot have been, upon the whole, an unhappy being; -for the infirmity and suffering which embitter life cut it short. -Every document by which the rate of mortality among large numbers of -human beings can be correctly ascertained contains in it irresistible -evidence of this truth. In every country, the average duration of life, -whether for the whole people or for particular classes, is invariably -in the direct ratio of their means of felicity; while, on the other -hand, the number of years which large portions of the population -survive beyond the adult age may be taken as a certain test of the -happiness of the community. How clear must have been the perception of -this in the mind of the Jewish legislator when he made the promise, -THAT THY DAYS MAY BE LONG IN THE LAND WHICH THE LORD THY GOD HATH GIVEN -THEE—the sanction of every religious observance, and the motive to -every moral duty! - -Deeply then are laid the fountains of happiness in the constitution -of human nature. They spring from the depths of man's physical -organization; and from the wider range of his mental constitution -they flow in streams magnificent and glorious. It is conceivable that -from the first to the last moment of his existence, every human being -might drink of them to the full extent of his capacity. Why does he -not? The answer will be found in that to the following question. What -must happen before this be possible? The attainment of clear and just -conceptions on subjects, in relation to which the knowledge hitherto -acquired by the most enlightened men is imperfect. Physical nature, -every department of it, at least, which is capable of influencing -human existence and human sensation; human nature, both the physical -and the mental part of it; institutions so adapted to that nature -as to be capable of securing to every individual, and to the whole -community, the maximum of happiness with the minimum of suffering—this -must be known. But knowledge of this kind is of slow growth. To -expect the possession of it on the part of any man in such a stage of -civilization as the present, is to suppose a phenomenon to which there -is nothing analogous in the history of the human mind. The human mind -is equally incapable of making a violent discovery in any department of -knowledge, and of taking a violent bound in any path of improvement. -What we call discoveries and improvements are clear, decided, but -for the most part gentle, steps in advancement of the actual and -immediately-preceding state of knowledge. The human mind unravels the -great chain of knowledge, link by link; when it is no longer able to -trace the connecting link, it is at a stand; the discoverer, in common -with his contemporaries, seeing the last ascertained link, and from -that led on by analogies which are not perceived by, or which do not -impress, others, at length descries the next in succession; this brings -into view new analogies, and so prepares the way for the discernment -of another link; this again elicits other analogies which lead to the -detection of other links, and so the chain is lengthened. And no link, -once made out, is lost. - -Chemists tell us that the adjustment of the component elements of -water is such, that although they readily admit of separation and are -subservient to their most important uses in the economy of nature -by this very facility of decomposition, yet that their tendency to -recombination is equal, so that the quantity of water actually existing -at this present moment in the globe is just the same as on the first -day of the creation, neither the operations of nature, nor the purposes -to which it has been applied by man, having used up, in the sense of -destroying, a single particle of it. Alike indestructible are the -separate truths that make up the great mass of human knowledge. In -their ready divisibility and their manifold applications, some of -them may sometimes seem to be lost; but if they disappear, it is only -to enter into new combinations, many of which themselves become new -truths, and so ultimately extend the boundaries of knowledge. Whatever -may have been the case in time past, when the loss of an important -truth, satisfactorily and practically established, may be supposed -possible, such an event is inconceivable now when the art of printing -at once multiplies a thousand records of it, and, with astonishing -rapidity, makes it part and parcel of hundreds of thousands of minds. -A thought more full of encouragement to those who labour for the -improvement of their fellow beings there cannot be. No onward step is -lost; no onward step is final; every such step facilitates and secures -another. The savage state, that state in which gross selfishness seeks -its object simply and directly by violence, is past. The semi-savage or -barbarous state, in which the grossness of the selfishness is somewhat -abated, and the violence by which it seeks its object in some degree -mitigated, by the higher faculties and the gentler affections of our -nature, but in which war still predominates, is also past. To this has -succeeded the state in which we are at present, the so-called civilized -state—a state in which the selfish principle still predominates, in -which the justifiableness of seeking the accomplishment of selfish -purposes by means of violence, that of war among the rest, is still -recognized, but in which violence is not the ordinary instrument -employed by selfishness, its ends being commonly accomplished by the -more silent, steady, and permanent operation of institutions. This -state, like the preceding, will pass away. How soon, in what precise -mode, by what immediate agency, none can tell. But we are already -in possession of the principle which will destroy the present and -introduce a better social condition, namely, the principle at the basis -of the social union, THE MAXIMUM OF THE AGGREGATE OF HAPPINESS; THE -MAXIMUM OF THE AGGREGATE OF HAPPINESS SOUGHT BY THE PROMOTION OF THE -MAXIMUM OF INDIVIDUAL HAPPINESS! - - - - -CHAPTER IV. - - Relation between the physical condition and happiness, and - between happiness and longevity—Longevity a good, and - why—Epochs of life—The age of maturity the only one that - admits of extension—Proof of this from physiology—Proof - from statistics—Explanation of terms—Life a fluctuating - quantity—Amount of it possessed in ancient Rome: in modern - Europe: at present in England among the mass of the people - and among the higher classes. - - -Life depends on the action of the organic organs. The action of the -organic organs depends on certain physical agents. As each organic -organ is duly supplied with the physical agent by which it carries on -its respective process, and as it duly appropriates what it receives, -the perfection of the physical condition is attained; and, according to -the perfection or imperfection of the physical condition, supposing no -accident interrupt its regular course, is the length or the brevity of -life. - -It is conceivable that the physical condition might be brought to a -high degree of perfection, the mind remaining in a state but little -fitted for enjoyment; because it is necessary to enjoyment that there -be a certain development, occupation, and direction of the mental -powers and affections: and the mental state may be neglected, while -attention is paid to the physical processes. But the converse is not -possible. The mental energies cannot be fully called forth while the -physical condition is neglected. Happiness presupposes a certain degree -of excellence in the physical condition; and unless the physical -condition be brought to a high degree of excellence, there can be no -such development, occupation, and direction of the mental powers and -affections as is requisite to a high degree of enjoyment. - -That state of the system in which the physical condition is sound is -in itself conducive to enjoyment; while a permanent state of enjoyment -is in its turn conducive to the soundness of the physical condition. -It is impossible to maintain the physical processes in a natural and -vigorous condition if the mind be in a state of suffering. The bills -of mortality contain no column exhibiting the number of persons who -perish annually from bodily disease, produced by mental suffering; -but every one must occasionally have seen appalling examples of the -fact. Every one must have observed the altered appearance of persons -who have sustained calamity. A misfortune, that struck to the heart, -happened to a person a year ago; observe him some time afterwards; he -is wasted, worn, the miserable shadow of himself; inquire about him at -the distance of a few months, he is no more. - -It is stated by M. Villermé, that the ordinary rate of mortality in -the prisons of France, taking all together, is one in twenty-three—a -rate which corresponds to the age of sixty-five in the common course -of life. But in the vast majority of cases the unfortunate victims -of the law are no older than from twenty-five to forty-five years of -age. Taking them at the mean age of thirty-five, it follows that the -suffering from imprisonment, and from the causes that lead to it, is -equivalent to thirty years wear and tear of life. But this is not all; -for it is found that, during imprisonment, the ordinary chances of -death are exactly quadrupled. - -In regard to the whole population of a country, indigence may be -assumed to be a fair measure of unhappiness, and wealth of happiness. -If the rate of mortality in the indigent class be compared with that -of the wealthy, according to M. Villermé, it will be found in some -cases to be just double. Thus it is affirmed that, in some cases in -France, taking equal numbers, where there are one hundred deaths in a -poor arrondissement, there are only fifty in a rich; and that taking -together the whole of the French population, human life is protracted -twelve years and a half among the wealthy beyond its duration among -the poor: consequently, in the one class, a child, newly born, has a -probability of living forty-two and a half years; in the other only -thirty years. - -In the great life-insurance establishments in England, a vast -proportion of the persons who insure their lives are persons compelled -to do so by their creditors; while three-fourths of those who -voluntarily insure their lives are professional men, living in great -towns, and experiencing the anxieties and fatigues, the hopes and -disappointments of professional life. In one of these establishments in -London, out of 330 deaths that happened in twenty-six years preceding -the year 1831, it was found that eleven died by suicide, being one -in thirty, implying the existence of an appalling amount of mental -suffering. The number of persons belonging to an insurance office who -perish by suicide is sure to be accurately known, death by suicide -rendering the policy void. It would be most erroneous to suppose that -these persons put an end to their existence under the mere influence of -the mental states of disappointment and despondency. The mind reacted -upon the body: produced physical disease, probably inflammation of the -brain, and under the excitement of this physical disease, the acts of -suicide were committed. More than one case has come to my knowledge -in which inflammation of the brain having been excited by mental -suffering, suicide was committed by cutting the throat. During the flow -of blood, which was gradual, the brain was relieved; the mind became -perfectly rational; and the patient might have been saved had a surgeon -been upon the spot, or had the persons about the patient known where -and how to apply the pressure of the finger to staunch the flow of -blood, until surgical aid could be procured. - -By a certain amount and intensity of misery life may be suddenly -destroyed; by a smaller amount and intensity, it may be slowly worn out -and exhausted. The state of the mind affects the physical condition; -but the continuance of life is wholly dependent on the physical -condition: it follows that in the degree in which the state of the -mind is capable of affecting the physical condition, it is capable of -influencing the duration of life. - -Were the physical condition always perfect, and the mental state always -that of enjoyment, the duration of life would always be extended to -the utmost limit compatible with that of the organization of the -body. But as this fortunate concurrence seldom or never happens, -human life seldom or never numbers the full measure of its days. -Uniform experience shows, however, that, provided no accident occur to -interrupt the usual course, in proportion as body and mind approximate -to this state, life is long; and as they recede from it, it is short. -Improvement of the physical condition affords a foundation for the -improvement of the mental state; improvement of the mental state -improves up to a certain point the physical condition; and in the ratio -in which this twofold improvement is effected, the duration of life -increases. - -Longevity then is a good, in the first place, because it is a sign -and a consequence of the possession of a certain amount of enjoyment; -and in the second place, because this being the case, of course in -proportion as the term of life is extended, the sum of enjoyment must -be augmented. And this view of longevity assigns the cause, and shows -the reasonableness of that desire for long life which is so universal -and constant as to be commonly considered instinctive. Longevity and -happiness, if not invariably, are generally, co-incident. - -If there may be happiness without longevity, the converse is not -possible: there cannot be longevity without happiness. Unless the state -of the body be that of tolerable health, and the state of the mind -that of tolerable enjoyment, long life is unattainable: these physical -and mental conditions no longer existing, nor capable of existing, the -desire of life and the power of retaining it cease together. - -An advanced term of life and decrepitude are commonly conceived to -be synonymous: the extension of life is vulgarly supposed to be the -protraction of the period of infirmity and suffering, that period which -is characterized by a progressive diminution of the power of sensation, -and a consequent and proportionate loss of the power of enjoyment, the -"sans teeth, sans eyes, sans taste, sans every thing." But this is so -far from being true, that it is not within the compass of human power -to protract in any sensible degree the period of old age properly so -called, that is, the stage of decrepitude. In this stage of existence, -the physical changes that successively take place clog, day by day, the -vital machinery, until it can no longer play. In a space of time, fixed -within narrow limits, the flame of life must then inevitably expire, -for the processes that feed it fail. But though, when fully come, the -term of old age cannot be extended, the coming of the term may be -postponed. To the preceding stage, an indefinite number of years may be -added. And this is a fact of the deepest interest to human nature. - -The division of human life into periods or epochs is not an arbitrary -distinction, but is founded on constitutional differences in the -system, dependent on different physiological conditions. The periods -of infancy, childhood, boyhood, adolescence, manhood, and old age, are -distinguished from each other by external characters, which are but -the outward signs of internal states. In physiological condition, the -infant differs from the child, the child from the boy, the boy from the -man, and the adult from the old man, as much in physical strength as in -mental power. There is an appointed order in which these several states -succeed each other; there is a fixed time at which one passes into -another. That order cannot be inverted: no considerable anticipation -or postponement of that fixed time can be effected. In all places and -under all circumstances, at a given time, though not precisely at the -same time in all climates and under all modes of life, infancy passes -into childhood, childhood into boyhood, boyhood into adolescence, and -adolescence into manhood. In the space of two years from its birth, -every infant has ceased to be an infant, and has become a child; in the -space of six years from this period, every male child will have become -a boy; add eight years to this time, and every boy will have become a -young man; in eight years more, every young man will have become an -adult man; and in the subsequent ten years, every adult man will have -acquired his highest state of physical perfection. But at what period -will this state of physical perfection decline? What is the maximum -time during which it can retain its full vigour? Is that maximum fixed? -Is there a certain number of years in which, by an inevitable law, -every adult man necessarily becomes an old man? Is precisely the same -number of years appointed for this transition to every human being? -Can no care add to that number? Can no imprudence take from it? Does -the physiological condition or the constitutional age of any two -individuals ever advance to precisely the same point in precisely the -same number of years? Physically and mentally, are not some persons -older at fifty than others are at seventy? And do not instances -occasionally occur in which an old man, who reaches even his hundredth -year, retains as great a degree of juvenility as the majority of those -who attain to eighty? - -If this be so, what follows? One of the most interesting consequences -that can be presented to the human mind. The duration of the periods of -infancy, childhood, boyhood, and adolescence, is fixed by a determinate -number of years. Nothing can stay, nothing retard, the succession of -each. Alike incapable of any material protraction is the period of old -age. It follows that every year by which the term of human existence is -extended is really added to the period of mature age; the period when -the organs of the body have attained their full growth and put forth -their full strength; when the physical organization has acquired its -utmost perfection; when the senses, the feelings, the emotions, the -passions, the affections, are in the highest degree acute, intense, -and varied; when the intellectual faculties, completely unfolded -and developed, carry on their operations with the greatest vigour, -soundness, and continuity; in a word, when the individual is capable of -receiving and of communicating the largest amount of the highest kind -of enjoyment. - -A consideration more full of encouragement, more animating, there -cannot be. The extension of human life, in whatever mode and degree it -may be possible to extend it, is the protraction of that portion of it, -and only of that portion of it, in which the human being is capable of -RECEIVING AND OF COMMUNICATING THE LARGEST MEASURE OF THE NOBLEST KIND -OF ENJOYMENT. - -Considerations, purely physiological, establish this indubitably; but -it is curious that a class of facts, totally different from those of a -physiological nature, equally prove it; namely, the results obtained -from the observation of the actual numbers that die at different ages, -and the knowledge consequently acquired of the progressive decrement -of life. Mortality is subject to a law, the operation of which is as -regular as that of gravitation. The labours of my valued friend Mr. -Finlaison, the actuary of the National Debt, have not only determined -what that law is in relation to different nations at different periods -of their history, but this celebrated calculator has also invented a -striking mode of expressing and representing the fact. He constructed -a chart on which 100 perpendicular lines, answering to the respective -ages of human life, are laid down and numbered in succession. These -are crossed at right angles by 500 horizontal lines; so that, in the -manner of musical notation, a point may be laid down either on the -horizontal line, or on the space between any two of them: and thus, -1000 points may be laid down on each of the perpendicular lines. The -horizontal lines are in like manner numbered from 1 to 1000, ascending -from the base. Taking any observation which shows the number of living -persons that commence, and in like manner the number that die in each -particular year of human life, the calculator reduced by the rule of -three every such actual number of living persons for every separate -year to 10,000: he next showed the corresponding proportion of deaths -out of such 10,000. These proportions he represented on the chart by -a point inserted on the horizontal line or space for the number of -deaths, and on the perpendicular line for the particular age. He then -connected all the points so laid down, and the result is a curve, -representing the track of death through an equal number of human beings -existing at each age of life. As the curve rises on the perpendicular -line, at any given age, it indicates by so much an increase of the -mortality at that age; and as the curve falls, the reverse is denoted. - -Now, it is a highly interesting fact, that the curves on this chart -drawn upon it before the physiological phenomena were known to the -operator, placed there because such he found to be the actual path -along which death marshals his course, exactly correspond to the epochs -which physiology teaches to be determinate stages of human existence. -The infant, the child, the boy, the adolescent, the man, the old man, -are not exposed to the same danger. The liability of each to death -is not merely different; it is widely different; the liability of -each class is uniformly the same, the circumstances influencing life -remaining the same; and under no known change of circumstances does -the relative liability of the class vary; under no change does the -liability of the adolescent become that of the infant, or the liability -of the adult that of the aged. Take from any statistical document any -number of persons; observe out of this number the proportion that -dies at the different stages just enumerated; and the period of human -life which admits of extension will be strikingly manifest. Take with -this view the Prussian statistical tables, the general correctness of -which is admitted. From these tables it appears, and the correctness -of the result is confirmed by a multitude of other tables, that out -of a million living male births, there will die in the first year of -life 180,492 infants, and out of the like number of living female -births, there will die 154,705 infants. Let us follow up the decrement -of life through the different epochs of human existence, confining -our observations to the male sex, in which the development is more -emphatically marked. - -In Mr. Finlaison's report, printed by the House of Commons on the 30th -of March, 1829, there are six original observations on the mortality of -as many separate sets of annuitants of the male sex. - -From an examination and comparison of these observations, it -appears—1st. That the rate of mortality falls to a minimum at -the close of the period of childhood. 2d. That from this point -the mortality rises until the termination of adolescence or the -commencement of adult age. 3d. That from the commencement of adult age -the mortality again declines, and continues to decline to the period of -perfect maturity. And 4th. That from the period of perfect maturity, -the mortality rises, and uniformly, without a single exception, -returns, at the age of forty-eight, to the point at which it stood at -the termination of adolescence. These results clearly indicate that -certain fixed periods are marked by nature as epochs of human life; -and that at the date of the recorded facts which furnish the data -for these observations, and as far as regards the class of persons -to which they relate, the age of forty-eight was the exact point at -which the meridian of life was just passed, and a new epoch began. The -following table exhibits at one view the exact results of each of the -observations. For example, - - According to The mortality From whence From this And from this - the is at a it rises point it age it again - observation, minimum at the until declines rises, but is not - No. age of the age of to the equal to the - age of mortality in - the 2d column - until the age of - - 15 — 13 — 23 — 34 — 48 - - 16 — 13 — 23 — 35 — 48 - - 17 — 14 — 22 — 33 — 48 - - 18 — 13 — 23 — 33 — 48 - - 19 — 13 — 24 — 34 — 48 - - 20 — 13 — 24 — 34 — 48 - -The observation, No. 15, is founded on the large mass of 9,347 lives -and 4,870 deaths. From this observation, it appears that, at the age of -thirteen, the mortality out of a million is 5,742, being 174,750 less -than in the first year of infancy At the age of twenty-three, it is -15,074, being 9,332 more than at the close of childhood. At the age of -thirty-four, the period of complete manhood, it falls to 11,707, being -3,367 less than at the close of adolescence. At the age of forty-eight, -the mortality returns to 14,870, all but identically the same as at -twenty-three, the adult age. From the age of forty-eight, when, as -has been stated, life just begins to decline from its meridian, the -mortality advances slowly, but in a steady and regular progression. -Thus, at the age of fifty-eight it is 29,185, being 14,315 more than -at the preceding decade, or almost exactly double. At the age of -sixty-eight, it is 61,741, being 32,556 more than at the preceding -decade, or more than double. At the age of seventy-eight, it is -114,255, being 52,514 more than at the preceding decade. At the age of -eighty-eight, it is 246,803, being 132,548 more than at the preceding -decade. - -During the first year of infancy, as has been shown, the mortality -out of a million is 180,492. At the extreme age of eighty-four, it -is 178,130, very nearly the same as in the first year of infancy. -Greatly as the mortality of all the other epochs of life is affected -by country, by station, by a multitude of influences arising out of -these and similar circumstances; yet the concurrent evidence of all -observation shows that at this and the like advanced ages the mean term -of existence is nearly the same in all countries, at all periods, and -among all classes of society. Thus, among the nobility and gentry of -England, the expectation of life at eighty-four is four years; among -the poor fishermen of Ostend, it is precisely the same. M. De Parcieux, -who wrote just ninety years ago, establishes the expectation of life -at that time in France, at the same age, to have been three and a half -years; and Halley, who wrote 120 years ago, and whose observations are -derived from documents which go back to the end of the seventeenth -century, states the expectation of life at eighty-four to be two years -and nine months. - -From these statements, then, it is obvious, that from the termination -of infancy at three years of age, a decade of years brings childhood to -a close, during which the mortality, steadily decreasing, comes to its -minimum. Another decade terminates the period of adolescence, during -which the mortality as steadily advances. A third decade changes the -young adult into a perfect man, and during this period, the golden -decade of human life, the mortality again diminishes; while, during -another decade and a half, the mortality slowly rises, and returns -at the close of the period to the precise point at which it stood at -adult age. Thus the interval between the period of birth and that of -adult age includes a term of twenty-three years. The interval between -the period of adult age and that when life just begins to decline from -its meridian, includes a term of twenty-four years: consequently, a -period more than equal to all the other epochs of life from birth -to adult age is enjoyed, during which mortality makes no advance -whatever. Now the term of years included in the several epochs that -intervene between birth and adult age is rigidly fixed. Thus the -period of infancy includes precisely three years, that of childhood -ten years, and that of adolescence ten years. Within the space of time -comprehended in these intervals, physiological changes take place, -on which depend every thing that is peculiar to the epochs. These -changes cannot be anticipated, cannot be retarded, except in a very -slight degree. In all countries, among all classes, they take place in -the same order and nearly in the same space of time. In like manner, -in extreme old age, or the age of decrepitude, which may be safely -assumed to commence at the period when the mortality equals that of the -first year of infancy, namely, the age of eighty-four, physiological -changes take place, which, within a given space of time, inevitably -bring life to a close. That space of time, in all countries, in all -ranks, in all ages, or rather as far back as any records enable us to -trace the facts, appears to be the same. As within a given time the -boy must ripen into manhood, so within a given time the man of extreme -old age must be the victim of death. Consequently, it is the interval -between the adult age and the age of decrepitude, and only this, that -is capable of extension. During the interval between adult age and the -perfect meridian of life, comprehending at present, as we have seen, -a period of twenty-four years, the constitution remains stationary, -mortality making no sensible inroad upon it. But there is no known -reason why this stationary or mature period of life should, like -the determinate epochs, be limited to a fixed term of years. On the -contrary, we do in fact know that it is not fixed; for we know that the -physiological changes on which age depends are, in some cases, greatly -anticipated, and in others, proportionately postponed; so that some -persons are younger at sixty, and even at seventy, than others are at -fifty; whereas, an analogous anticipation or postponement of the other -epochs of life is never witnessed. So complete is the proof, that the -extension of human life can consist in the protraction neither of the -period of juvenility, nor in that of senility, but only in that of -maturity. - -Were it necessary to adduce further evidence of this most interesting -fact, it would be found equally in the statistics of disease as -in those of mortality. Indeed, the evidence derived from both -these sources must be analogous, because mortality is invariably -proportionate to the causes of mortality, of which causes, sickness, in -all its forms, may be taken as the general or collective expression. - -We do not possess the same means of illustrating the prevalence -of disease through all the epochs of life as we do of showing the -intensity of mortality; yet the report of Mr. Finlaison, already -referred to, enables us to show its comparative prevalence at several -of those stages. Thus, from this document, it appears, that among -the industrious poor of London, members of benefit societies, out -of a million of males, the proportion constantly sick at the age of -twenty-three, is 19,410; at the age of twenty-eight, it is 19,670; at -the age of thirty-three, it is 19,400; at the age of thirty-eight, -it is 23,870; at the age of forty-three, it is 26,260; at the age of -forty-eight, it is 26,140; at the age of fifty-three, it is 27,060; -at the age of fifty-eight, it is 36,980; at the age of sixty-three, -it is 57,000; at the age of sixty-eight, it is 108,040; at the age of -seventy-three and upwards, it is 317,230. The prevalence of sickness -is not an exact and invariable measure of the intensity of mortality; -but there is a close connexion between them, as is manifest from -the progressively increasing amount of sickness, as age advances. -Thus, in the first ten years from the age of twenty-three to that of -thirty-three, there is no increase of sickness, its prevalence is -all but identically the same; in the next ten years from the age of -thirty-three to that of forty-three, the increase of sickness, as -compared with that of the preceding decade, is 6,860; in the next ten -years from the age of forty-three to that of fifty-three, the increase -is only 800; in the next ten years from the age of fifty-three to -that of sixty-three, the increase is 29,940, while from the age of -sixty-three to seventy-three, it is 260,230. - -Such are the results derived from the experience of disease considered -in the aggregate, all its varied forms taken together. I am enabled -further to present an exact and most instructive proof, that one -particular disease which, in this point of view, may be considered -as more important than any other, because it is the grand agent of -death, namely fever, carries on its ravages in a ratio which steadily -and uniformly increases as the age of its victim advances. Having -submitted the experience of the London Fever Hospital for the ten -years preceding January 1834, an observation including nearly 6,000 -patients affected with this malady, to Mr. Finlaison, it was subjected -by him to calculation. Among other curious and instructive results to -be stated hereafter, it was found that the mortality of fever resolves -itself into the following remarkable progression. Thus suppose 100,000 -patients to be attacked with this disease between the ages of 5 and -16, of these there would die - 8,266 and of an equal number - - between 15 and 26 there would die 11,494 - 25 and 36 " " " 17,071 - 35 and 46 " " " 21,960 - 45 and 56 " " " 30,493 - 55 and 66 " " " 40,708 - 65 and upwards " " " 44,643 - -Thus the risk of life from this malady is twice as great at the age -of thirty-one as it is at eleven. It is also nearly twice as great -at forty-one as it is at twenty-one. It is five times as great at -sixty-one as it is at eleven, and nearly four times as great above -sixty-five as it is at twenty-one. - -From the whole of the foregoing statements, it is manifest that life is -a fluctuating quantity. In order to compare this fluctuating quantity -under different circumstances, writers on this branch of statistics use -several terms, the exact meaning of which it is desirable to explain. -It is, for example, very important to have a clear understanding of -what is meant by such expressions as the following: the expectation, -the probability, the value, the decrement of life, and the law of -mortality. - -1. THE EXPECTATION OF LIFE. It is important to bear in mind that -several expressions in common use have a signification perfectly -synonymous with this: namely, _share of existence_; _mean duration of -life_; _la vie moyenne_. - -By these terms is expressed the total number of years, including also -the fractional parts of a year, ordinarily attained by human beings -from and after any given age. Suppose, for example, that one thousand -persons enter on the eighty-sixth year of their age: suppose the -number of years and days which each one of them lives afterwards be -observed and recorded; suppose the number ultimately attained by each -be formed into a sum total; suppose this total be divided equally among -the thousand, the quotient of this division is said to be each one's -share of existence, or his mean duration of life, or his expectation -of life. Thus, of the thousand persons in the present case supposed -to commence the age of eighty-five, suppose the number of years they -collectively attain amount to 3,500 years: the one-thousandth part of -3,500 is three and a half: three years and a half then is said to be -the expectation of life at the age of eighty-five, because, of all the -persons originally starting, this is the equal share of existence that -falls to the lot of each. - -2. PROBABILITY OF LIFE; or _the probable duration of life_, _la vie -probable_. These are synonymous terms, in use chiefly among continental -writers as an expression of the comparative duration of life. The -tabular methods of setting forth the duration of life consist, for the -most part, in assuming that 10,000 infants are born; and that at the -age of one, two, three, and each successive year of life, there are -so many still remaining in existence. Fix on any age; observe what -number remain alive to commence that age; note at what age this number -decreases to one-half; the age at which they so come to one-half is -called the probable term of life; because, say the continental writers, -it is an equal wager whether a person shall or shall not be alive at -that period. Thus, suppose one thousand males commence together the age -of eighty-four; suppose the table indicate that there will be alive -at the age of eighty-five, 817; at the age of eighty-six, 648; at the -age of eighty-seven, 493; at the age of eighty-eight, 357, and so on. -In the present case, the probable duration of life at eighty-four is -said to be very nearly three years, because, at the age of eighty-seven -there are left alive 493, very nearly one-half of the thousand that -originally started together. - -3. VALUE OF LIFE. This term, when used accurately, expresses the -duration of life as measured by one or other of the methods already -expounded. But it is sometimes popularly used in a loose and singularly -inaccurate sense. Thus it is very commonly said—"Such a man's life -is not worth ten years' purchase," which is the same thing as to say, -that an annuity, suppose a hundred pounds a year, payable during the -life of the person in question, is not worth ten times its magnitude, -that is one thousand pounds. If a thousand pounds be put into a bank -at some rate of interest to be agreed upon, and if a hundred pounds be -drawn every year from the stock, the expression under consideration -affirms that the person in question will be dead before the principal -and interest are exhausted. For instance, at four per cent., the value -of an annuity of one hundred pounds to a man of the age of twenty-five -is 1694_l._, which is 16-9/10 years' purchase; whereas, his expectation -of life at that age is 35-9/10 years. - -4. LAW OF MORTALITY. By this term is expressed the proportion out of -any determinate number of human beings who enter on a given year of -age, that will die in that year. Every observation on the duration of -life presents certain numbers, which, by recorded facts, are found to -pass through each year of age, and also shows how many have died or -failed to pass through every year of age. Those numbers, by the rule -of three, are converted into the proportions who would die at each -age out of one million of persons, if such a number had commenced it. -Suppose, then, a million of persons to be in existence at the first -year of age; suppose a million to be in existence at the second year -of age; suppose a million to be in existence at the third year of -age; and in this manner suppose an equal number to be in existence at -the commencement of each and every year to the extreme term of human -life. Now, the proportions that by actual observation are found to -die at each and every year out of the million that were alive at the -commencement of it, form separately the law of mortality for each year, -and collectively for the whole of life. - -5. DECREMENT OF LIFE. Assuming, as before, that a million of male -children are born alive (for the still-born must be excluded from -the calculation) if it be found that 180,492 would die in the first -year, it follows that the difference, namely, 819,508, will enter upon -the age of one year. Suppose the law of mortality indicate that the -proportion that will die, out of a million, between the age of one -and two, is 30,000; it is plain that the number who would die out of -819,508 will by the rule of three be 27,863, and consequently that the -residue, namely, 791,615, will remain alive, and so enter on the age -of two years. This method being pursued through each and every age to -the extreme term of life, when none of the original million survive, -the result is a table of mortality in the form in which it is commonly -presented in the works of writers on this branch of science. In the -table thus constructed there is a column containing the number of -living persons who, out of the original million, lived to enter upon -each and every year. Of this rank of numbers the difference between -each term and its next succeeding one, is the number who die in that -particular interval: that number is the measure of what is technically -called the decrement of life for that particular year, and the whole -of the decrements for each and every year taken collectively is termed -the decrement of life. The decrement of life, then, is not only not -the same as the law of mortality, but is carefully to be distinguished -from it. The law of mortality is derived from observing the number -who die out of one and the same number which is always supposed to -enter on each and every year. The decrement of life constitutes a -rank of numbers arising out of the successive deaths; that is, out of -the original million in the first year; out of the survivors of that -million in the second year; out of the survivors of those survivors in -the third year, and so on. In the first case the number of the living -is always the same; the number that die is the variable quantity: in -the second case the number of the living is the variable quantity, -while the number that die may remain pretty much the same for a -succession of years; and on casting the eye on the tables constructed -in the ordinary mode, it will be seen that the number often does remain -the same for a considerable series of years. - -We have said that life is a fluctuating quantity. It fluctuates -in different countries at the same period; in the same country at -different periods; in the same country, at the same period, in -different places; in the same country, at the same period, in the -same place, among different classes; in the same country, at the same -period, in the same place, among the same class, at the different -determinate stages of life. Some few of these fluctuations, and -more especially the last, depend on the primary constitution of the -organization in which life itself has its seat, over which man has -little or no control. The greater part of them depend on external -and adventitious agencies over which man has complete control. Human -ignorance, apathy, and indolence, may render the duration of life, in -regard to large classes and entire countries, short; human knowledge, -energy and perseverance, may extend the duration of life far beyond -what is commonly imagined. It will be interesting and instructive to -select a few of the more striking examples of this from the records we -possess, few and imperfect as they are, in relation to this subject. - -Of the duration of life in the earlier periods of the history of the -human race we know nothing with exactness, though there are incidental -statements which afford the means of deducing with some probability -the rate of mortality in particular situations. There has come down to -us one document through Domitius Ulpianus, a judge, who flourished in -the reign of Alexander Severus, which enables us to form a probable -conjecture at least of the opinion of the Roman people of the value -of life among the citizens of Rome in that age. It happened at Rome -as in other countries, that when an estate came into the possession -of an individual it was burthened with a provision for another person -during the life of the latter, a younger brother, for example. This -provision was called by the Romans an aliment. No estate, burthened -with such a provision, could be sold by the heir in possession, unless -the purchaser retained in his hands so much of the price as was deemed -adequate to secure the regular and continuous payment of the aliment. -This imposed upon the Romans the necessity of considering what the term -of life would probably be from and after any given age. What they did -conceive that term to be is stated in a document of Ulpianus, recorded -by Justinian, and given in the note below.[1] This document imports -that from infancy up to the age of - - 20 there should be allowed 30 years - From 20 to 25 " " " " 28 " - 25 to 30 " " " " 25 " - 30 to 35 " " " " 22 " - 35 to 40 " " " " 20 " - ———— - From 50 to 55 " " " " 9 " - 55 to 60 " " " " 7 " - And at all ages above 60 " " " " 5 " - -But between 40 and 50, as many years were to be allowed as the age of -the party fell short of 60, deducting one year. - -No clue has hitherto been obtained to the discovery of the real -meaning of this document. It is, however, highly probable that the -Romans had fallen on one of the two methods of measuring the value of -life already explained; namely, that termed the Probability of Life. -Of the two modes of determining the value of life, the probability was -more likely to occur to a Roman judge than the expectation. He had -no tables, no registers to guide him. What course, then, would he be -likely to take? Probably he would form a list of his own school-fellows -and others within his own knowledge, of the age, say, of twenty. By -prevailing on persons of his own age, on whose correctness he could -rely, to draw out similar lists, he might accumulate some thousand -names. In this list it is probable that the male sex alone would be -included, on account of the greater ease of ascertaining both their -exact age and the exact date of their death. For the same reason, -it is probable that the list would consist only of the nobility and -the inhabitants of towns. Having thus completed his list, the next -step would be to frame another list of all who died at the age of -twenty-one; and next, another list of all who died at the age of -twenty-two, and so on through each and every year of life. Now by -subtracting the number in the list, No. 1, that is, those who died -between twenty and twenty-one, from the number who originally started -at twenty, which, in other words, would be to find the decrement of -life, in the mode already explained, he would see how many lived to -commence the age of twenty-one, and so on, through each year of life. -But this would be to construct a table, showing the probable duration -of life; that is, a table from which he could observe at what advanced -age the number originally starting at twenty, and so on, came to -diminish to one-half, when it would naturally occur to him that it -is an equal wager whether such younger life would or would not be in -existence at the advanced age so ascertained. If we suppose this to -have been the method actually adopted by the Roman judge, and apply -it to the table of Ulpianus, the result obtained is consistent in an -extraordinary degree, and is highly interesting. - -There is reason to believe that the mortality at present throughout -Europe, taking all countries together, including towns and villages, -and combining all classes into one aggregate, is one in thirty-six. -Süssmilch, a celebrated German writer, who flourished about the middle -of the last century, estimated it at this average at that period. The -result of all Mr. Finlaison's investigations is a conviction that the -average for the whole of Europe does not materially differ at the -present time. He has ascertained by an actual observation, that in the -year 1832 it was precisely this in the town of Ostend. Taking this -town, then, as the subject of comparison, it is found that the probable -duration of life among the male sex at Ostend exceeds the Roman -allowance by the following number of years; namely, - - At the age of 17, the excess in round - numbers is 5 years. - 22 " " 5 - 27 " " 5 - 32 " " 5 - 37 " " 3 - 42 " " 3 - 47 " " 5 - 52 " " 5 - 57 " " 4 - 62 " " 4 - 67 " " 2 - 72 " " 1 - 77 " " 0 - -But it is not improbable that the Romans made some deduction from -what they knew to be the real value of life among the citizens of -Rome, on account of the use of the money appropriated to the aliment, -which the purchaser of the estate retained in his own hands. It has -been shown that the average mortality at present at Ostend is one -in thirty-six; which is the same thing as to assert that a new-born -child at Ostend has an expectation of thirty-five and a half years -of life. The Roman allowance from birth, _à primâ ætate_, was thirty -years. If we suppose the Romans deducted from the real value of life -five and a half years for the interest of money, it would bring the -Roman allowance and the duration of life at Ostend to the same. The -like deduction at the age of seventeen would likewise bring the -probability of life in both cases to the same. It is not likely that -the Romans, without any record of the individual facts, and acting -only on a general principle of utility, the best they could find, -would make any variation for the intermediate years of childhood and -youth: consequently the presumption is, that the duration of life at -Rome, 1300 years ago, was very much the same as it is throughout Europe -at the present day. This estimate, however, for the reasons already -assigned, includes only the resident citizens of Rome, the male sex, -and the higher classes. What the mortality was at Rome among the lower -class, including the slaves—what it was in the Roman provinces, and in -the less civilized countries of that age—we have no means of forming -even a conjecture. What it was in Europe during the succeeding ages -of barbarism we do not know. In civilized Rome, the value of life -had probably reached a very high point; in barbarian Europe we may -be sure it fell to an exceedingly low point. From that low point, in -civilized Europe, it has been slowly but gradually rising, until, in -modern times, the whole mass of the European population has, to say -the very least, reached the highest point attained by the select class -in ancient Rome. But in some favoured spots in Europe, the whole mass -has advanced considerably beyond the select class in ancient Rome. In -England, for example, the expectation of life, at the present day, for -the mass of the people, as compared with that of the mass at Ostend, -which, as has been shown, is the same as that of the whole of Europe, -is as follows:— - - At birth 41½ years. - At 12 46¾ - 17 41½ - 22 38⅜ - 27 35¼ - 32 32 - 37 28¾ - 42 25½ - 47 22¼ - 52 19 - 57 16 - 62 13 - 67 10½ - 72 8 - 77 6 - -It should be borne in mind that the females of the mass exceed in -duration the lives of the males at every age by two or three years. - -The earliest statistical document bearing on the rate of mortality, in -any European nation, emerging from the state of barbarism, appears to -be a manuscript of the fourteenth century, relating to the mortality -of Paris, from which M. Villermé has calculated that the mortality -of Paris at that period was one in sixteen. How the individual facts -contained in this manuscript were collected, from which M. Villermé's -calculation is made, does not appear; and it makes the mortality so -excessive as to be altogether incredible. Yet a statement scarcely -less extraordinary is made with regard to Stockholm, in the middle of -the last century. From a table given by Dr. Price, vol. ii., p. 411, -it appears that, for all Sweden, between the years 1756 and 1763, the -expectation of life - - Of males at birth, was Females, - 33¼ years. 35¾ years. - -while at the same time it was at Stockholm, - - For males at birth, Females, - 14¼ years. 18 years. - -Whereas, for the twenty years preceding 1800, it was, for all Sweden, -at birth, - - Males, Females, - 34¾. 37½. - -Hitherto, in all places which man has made his abode, noxious agents -have been present which act injuriously upon his body, tending to -disturb the actions of its economy, and ultimately to extinguish life. -All these noxious agents, of whatever name or quality, may be included -under the term Causes of Mortality. Inherent in the constitution of the -body are conservative powers, the tendency of which is to resist the -influence of these causes of mortality. The actual mortality at all -times will of course be according to the relative strength of these -destructive agents, and the relative weakness of these conservative -powers. There are states of the system tending to enfeeble these -conservative powers. Such states become tests, often exceedingly -delicate, of the presence and power of the destructive agents to which -the body is exposed; and such, more especially, are, the states of -parturition, infancy, and sickness. During the prevalence of these -states, in which the conservative powers of the body are weak, life -is destroyed by causes which do not prove mortal in other conditions -of the system. Accordingly, in every age and country, the rate of -mortality among its lying-in women, its infants and its sick, may -be taken as a measure of the degree in which the state of the whole -population is favourable or unfavourable to life. - -The change that has taken place in the condition of lying-in women -during the last century in all the nations of Europe cannot be -contemplated without astonishment. The mortality of lying-in women in -France, at the Hôtel Dieu of Paris, in 1780, is stated to have been -one in 15. In 1817, for the whole kingdom of Prussia, including all -ranks, it was one in 112. In England, in the year 1750, at the British -Lying-in Hospital of London, it was one in 42; in 1780, it diminished -to one in 60; in the years between 1789 and 1798, it further decreased -to one in 288; in 1822, at the Lying-in Hospital of Dublin, it was no -more than one in 223; while during the last fifteen years at Lewes, a -healthy provincial town, out of 2410 cases there have been only two -deaths, that is, one in 1205. There is no reason to suppose that the -mortality in the state of parturition is less at Lewes than in any -other equally healthy country-town in England. - -Equally striking is the proof of the diminished violence of the -prevalent causes of disease and death derived from the diminished -mortality of children, the vital power of resistance being always -comparatively weak in the human infant, and consequently, the agents -that prove destructive to life exerting their main force on the new -born, and on those of tender age. From mortuary tables, preserved with -considerable accuracy at Geneva since the year 1566, it appears that at -the time of the Reformation one-half of the children born died within -the sixth year; in the seventeenth century, not till within the twelfth -year; in the eighteenth century, not until the twenty-seventh year; -consequently, in the space of about three centuries, the probability -that a child born in Geneva would arrive at maturity has increased -fivefold. In the present day, at Ostend, only half of the new-born -children attain the age of thirty; whereas, in England, they attain the -age of forty-five. - -No less remarkable is the progressive diminution of mortality among -the sick of all ages. Hippocrates has left a statement, which has come -down to our times, of the history and fate of forty-two cases of acute -disease. Out of this number, thirty-seven were cases of continued -fever; of these thirty-seven febrile cases twenty-one died, above half -of the whole. The remaining five were cases of local inflammation, -and of these four were fatal; thus, of the whole number of the sick -(forty-two), twenty-five were lost. Now, even in the Fever Hospital of -London, to which, for the most part, only the worst cases that occur -in the metropolis are sent, and even of these many not until so late -a period of the disease that all hope of recovery is extinct, the -mortality ranges in different years from one in six to one in twelve; -and for a period of ten consecutive years, it is no more than one in -seven; while, in the Dublin Fever Hospital, where most of the cases are -sent very early, the average mortality from 1804 to 1812 was one in -twelve. At the Imperial Hospital at Petersburg, the average mortality -for fourteen years, ending in 1817, was one in four and a half. In the -Charité of Berlin, on an average of twenty years, from 1796 to 1817, -it was one in six. At Dresden, it was one in seven; at Munich, it was -one in nine, the lowest of any hospital of equal size in Germany. In -the year 1685, the average mortality at St. Bartholomew's and St. -Thomas's Hospitals was from one in seven to one in ten. During the ten -years from 1773 to 1783, it decreased to one in fourteen. From 1803 to -1813, it was one in sixteen. The average for fifty years from 1764 to -1813, was one in fifteen. In the smaller towns, the mortality is still -less. It is less in Edinburgh and Dublin than in London; while in the -hospital at Bath during 1827, even among the physician's patients, the -mortality was only one in twenty. In the German provincial towns, the -diminution is still more remarkable. In the hospital at Gottingen, for -example, it is only one in twenty-one. - -If the accuracy of these statements could be relied on, they -would not only afford striking illustrations of the well-known fact -that extraordinary differences prevail in the rate of mortality -in different places, at different periods, and under different -circumstances; but they would further prove that, during the last -century, a steady and progressive diminution of mortality has taken -place in all the countries of Europe. But of the truth of this there -is much more certain evidence than can be derived from calculations, -the trustworthiness of the data of which is not established, and -the correctness of the calculators not known. Both the fluctuations -of mortality and the increase in the value of life in the different -countries of Europe, from the earliest period when statistical facts -began to be collected and compared, are exhibited in a striking -point of view in the following table, drawn up by Mr. Finlaison. The -facts relating to selected lives and to the mass of the people are -distinguished from each other, in order that they may be contrasted. -The data are derived from the most authentic sources, and the -calculations are made by men of the highest authority. - - -Let it be conceived, that at each 50 55 60 65 70 75 80 85 -of the following ages, viz. Yrs.Yrs.Yrs.Yrs.Yrs.Yrs.Yrs.Yrs. - -The average duration of Human -Life of both sexes collectively -may thenceforward be assumed at -a maximum of[2] 23 19 16 13 11 8 6 3 - -By how many weeks does the -average duration which results -from the most authentic Tables -at present known fall short of -the maximum Term thus assumed? - - Among the higher classes of people exclusively. - - Answer. Name of the - Observer. Wks. Wks. Wks. Wks. Wks. Wks. Wks. Wks. -In England— -Among the Government -Annuitants, between -1775 and 1822 - John Finlaison. 35 1 7 10 47 11 14 53 - -Among the Lives assured -at the Equitable Office, -between 1760 and 1834 - Arthur Morgan. 119 83 87 81 96 33 10 27 - -Among the Nominees of -the Tontine of 1693-- -between that year -and 1775 - John Finlaison. 269 195 170 141 157 110 90 89 - -In France-- -Among the Nominees of -the Tontine of 1693-- -between that year and -1745 M. de Parcieux. 133 88 87 86 118 70 55 65 - -In Holland-- -Among the Public -Annuitants, between -1615 and 1740 - M. Kersseboom. 186 118 104 75 96 61 48 84 - -In regard to the mass of the people. - -In Breslau in Silesia, -between 1700 and 1725, - Dr. Halley. 275 211 181 150 166 100 36 137 - -In Sweden, -between 1775 -and 1795, M. Nicander, - and Mr. Milne. 207 161 164 146 156 94 60 60 - -In Northampton, -in England, between -1735 and 1780, - Dr. Price. 209 178 145 110 125 76 65 85 - -In Carlisle, -in England, between -1779 and 1787, Dr. Heysham, - and Mr. Milne. 98 74 86 63 94 52 26 46 - -In all England and -Wales, between -1811 and 1831, - John Finlaison. 100 59 65 58 87 48 37 49 - -In the town of Ostend, -in Flanders, between -1805 and 1832, - John Finlaison. 276 210 184 146 143 76 50 75 - -In all Belgium, between -1725 and 1832, - M. Quetelet. 183 133 133 117 112 84 50 61 - - -Let us trace from this table the differences that have taken place, in -different countries at different periods, in the duration of life at -a given age. Let us take the age given in the first column, namely, -fifty. Assuming, then, the highest degree of longevity hitherto -attained at the age of fifty to be twenty-three years, it appears that, -between the years 1700 and 1725, the mass of the people in Breslau, -in Silesia, fell short of reaching this period by 275 weeks; the -inhabitants of the town of Ostend in Flanders, between 1805 and 1832, -by 276 weeks; the nominees of the tontine of England, between the years -1693 and 1775, by 269 weeks; the inhabitants of the town of Northampton -in England, between 1735 and 1780, by 209 weeks; the mass of the people -in Sweden, between 1775 and 1795, by 207 weeks; the public annuitants -of Holland, between 1615 and 1740, by 186 weeks; the inhabitants of -all Belgium, between 1725 and 1832, by 183 weeks; the persons assured -at the Equitable Office, between 1760 and 1834, by 119 weeks; the -inhabitants of all England and Wales, between 1811 and 1831, by 100 -weeks; the English government annuitants, between 1775 and 1832, only -by 35 weeks. - -From these statements, it appears that, towards the close of the -seventeenth century, the duration of life in England was considerably -less than in France: less even than in Holland nearly a century -earlier. Thus, the nominees of the tontine of France, between the years -1693 and 1745, at the age of fifty, according to M. De Parcieux, fell -short of the maximum longevity by 133 weeks; the public annuitants of -Holland, seventy-eight years before, namely, between the years 1615 and -1740, according to M. Kersseboom, fell short of the maximum longevity -by 186 weeks; whereas, the nominees of the tontine of England, between -the years 1693 and 1775, according to Mr. Finlaison, fell short of it -by 269 weeks; a difference nearly double that of Holland, and quite -double that of France in persons of the corresponding rank in society. - -Since that period, surprising changes have taken place in all the -nations of Europe; but in none has the change been so great as in -England. From that period, when its mortality exceeded that of any -great and prosperous European country, its mortality has been steadily -diminishing, and at the present time the value of life is greater in -England than in any other country in the world. Not only has the value -of life been regularly increasing until it has advanced beyond that of -any country of which there is any record; but the remarkable fact is -established, that the whole mass of its people now live considerably -longer than its higher classes did in the seventeenth and eighteenth -centuries. Thus, by inspecting the preceding table, it will be seen -that between the years 1693 and 1715, the nominees of the tontine of -England, at the age of fifty, fell short of the maximum longevity -by 269 weeks; whereas, the mass of the people in all England and -Wales, between the years 1811 and 1831, fell short of it only by 100 -weeks; the entire mass having not only reached the select class, but -absolutely advanced beyond it by 169 weeks. - -There cannot be a more interesting and instructive thing than to -connect these facts with their causes. This will be attempted in a -subsequent part of this work; but the reader will be incomparably -better prepared for the investigation when the processes of life have -been explained, and the influence of physical and moral agents upon -them traced. And with this exposition we now proceed. - - - - -CHAPTER V. - - Ultimate elements of which the body is composed—Proximate - principles—Fluids and solids—Primary - tissues—Combinations—Results—Organs, systems, - apparatus—Form of the body—Division into head, trunk, and - extremities—Structure and function of each—Regions—Seats - of the more important internal organs. - - -1. The ultimate elements of which the human body is composed are -azote, oxygen, and hydrogen (gaseous fluids); and carbon, phosphorus, -calcium, sulphur, sodium, potassium, magnesium, and iron (solid -substances). These bodies are called elementary and ultimate, because -they are capable of being resolved by no known process into more simple -substances. - -2. These elementary bodies unite with each other in different -proportions, and thus form compound substances. A certain proportion -of azote uniting with a certain proportion of oxygen, hydrogen, and -carbon, forms a compound substance possessing certain properties. -Another proportion of azote uniting with a different proportion -of oxygen, hydrogen, and carbon, forms another compound substance -possessing properties different from the former. Oxygen, hydrogen, and -carbon, uniting in still different proportions without any admixture -of azote, form a third compound possessing properties different from -either of the preceding. The compounds thus formed by the primary -combinations of the elementary substances with each other are called -PROXIMATE PRINCIPLES. - -3. Each proximate principle constitutes a distinct form of animal -matter, of which the most important are named gelatin, albumen, fibrin, -oily or fatty matter, mucus, urea, pichromel, osmazome, resin, and -sugar. - -4. By chemical analysis it is ascertained that all the proximate -principles of the body, however they may differ from each other in -appearance and in properties, are composed of the same ultimate -elements. Gelatin, for example, consists (in 100 parts) of azote -16-988/1000, oxygen 27-207/1000, hydrogen 7-914/1000, carbon -47-881/1000 parts. The elementary bodies uniting in the above -proportions form an animal substance, soft, tremulous, solid, soluble -in water, especially when heated, and on cooling, which may be -considered as its distinctive property, separating from its solution in -water into the same solid substance, without undergoing any change in -its chemical constitution. - -5. Again, albumen consists of azote 15-705/1000, oxygen 23-872/1000, -hydrogen 7-540/1000, carbon 52-888/1000, parts. The elementary bodies -uniting in these different proportions, there results a second -proximate principle, an adhesive fluid, transparent, destitute of smell -and taste, miscible in water, but when subjected to a temperature of -about 165°, converted into a solid substance no longer capable of being -dissolved in water. This conversion of albumen from a fluid, which is -its natural state, into a solid, by the application of heat, is called -coagulation. It is a process familiar to every one. The white of egg is -nearly pure albumen, naturally a glary and adhesive fluid: by boiling, -it is coagulated into a white and firm solid. - -6. In like manner, fibrin consists of azote 19-934/1000, oxygen -19-685/1000, hydrogen 7-021/1000, carbon 53-360/1000 parts, forming -a solid substance of a pale whitish colour and firm consistence, the -peculiar character of which is its disposition to arrange itself into -minute threads or fibres. - -7. On the other hand, fat or oil, which is a fluid substance of a -whitish yellow colour, inodorous, nearly insipid, unctuous, insoluble -in water and burning with rapidity, consists of a larger proportion of -hydrogen, a small proportion of oxygen, and a still smaller proportion -of carbon, without any admixture of azote. - -8. From this account of the composition of the proximate principles, -which it is not necessary to extend further, it is manifest that all of -them consist of the same ultimate elements, and that they derive their -different properties from the different proportions in which their -elements are combined. - -9. The ultimate elements that compose the body are never found in a -separate or gaseous state, but always in combination in the form of one -or other of the proximate principles. - -10. In like manner, the proximate principles never exist in a distinct -and pure state, but each is combined with one or more of the others. No -part consists wholly of pure albumen, gelatin, or mucus, but albumen is -mixed with gelatin, or both with mucus. - -11. Simple or combined, every proximate principle assumes the form -either of a fluid or of a solid, and hence the most general and obvious -division of the body is into fluids and solids. But the terms fluid -and solid are relative, not positive; they merely express the fact -that some of the substances in the body are soft and liquid compared -with others which are fixed and hard; for there is no fluid, however -thin, which does not hold in solution some solid matter, and no solid, -however dense, which does not contain some fluid. - -12. Fluids and solids are essentially the same in nature; they -differ merely in their mode of aggregation; hence the easy and rapid -transition from the one to the other which incessantly takes place in -the living body, in which no fluid long remains a fluid, and no solid a -solid, but the fluid is constantly passing into the solid and the solid -into the fluid. - -13. The relative proportion of the fluids in the human body is always -much greater than that of the solids; hence its soft consistence and -rounded form. The excess, according to the lowest estimate, is as 6 -to 1, and according to the highest, as 10 to 1. But the proportion is -never constant; it varies according to age and to the state of the -health. The younger the age, the greater the preponderance of the -fluids. The human embryo, when first perceptible, is almost wholly -fluid: solid substances are gradually but slowly superadded, and even -after birth the preponderance is strictly according to age; for in -the infant, the fluids abound more than in the child; in the child, -more than in the youth; in the youth, more than in the adolescent; in -the adolescent, more than in the adult; and in the adult, more than -in the aged. Thus, among the changes that take place in the physical -constitution of the body in the progress of life, one of the most -remarkable is the successive increase in the proportion of its solid -matter: hence the softness and roundness of the body in youth; its -hard, unequal, and angular surface in advanced life; its progressively -increasing fixedness and immobility in old age, and ultimate inevitable -death. - -14. The fluids are not only more abundant than the solids, but they -are also more important, as they afford the immediate material of the -organization of the body; the media by which both its composition and -its decomposition are effected. They bear nourishment to every part, -and by them are carried out of the system its noxious and useless -matter. In the brain they lay down the soft and delicate cerebral -substance; in the bone, the hard and compact osseous matter; and the -worn-out particles of both are removed by their instrumentality. Every -part of the body is a laboratory in which complicated and transforming -changes go on every instant; the fluids are the materials on which -these changes are wrought; chemistry is the agent by which they are -effected, and life is the governing power under whose control they take -place. - -15. The fluids, composed principally of water holding solid matter in -solution, or in a state of mechanical division, either contribute to -the formation of the blood, or constitute the blood, or are derived -from the blood; and after having served some special office in a -particular part of the system, are returned to the blood; and according -to the nature and proportion of the substances they contain, are -either aqueous, albuminous, mucous, gelatinous, fibrinous, oleaginous, -resinous, or saline. - -16. When the analysis of the different kinds of animal matter that -enter into the composition of the body has been carried to its ultimate -point, it appears to be resolvable into two primitive forms: first, a -substance capable of coagulation, but possessing no determinate figure; -and secondly, a substance having a determinate figure and consisting of -rounded particles. The coagulable substance is capable of existing by -itself; the rounded particles are never found alone, but are invariably -combined with coagulated or coagulable matter. Alone or combined with -the rounded particles, the coagulable matter forms, when liquid, the -fluids, when coagulated, the solids. - -17. When solid, the coagulable substance is disposed in one of two -forms, either in that of minute threads or fibres, or in that of minute -plates or laminæ; hence every solid of the body is said to be either -fibrous or laminated. The fibres or laminæ are variously interwoven -and interlaced, so as to form a net-work or mesh; and the interspaces -between the fibres or laminæ are commonly denominated areolæ or cells -(fig. XVII). - -18. This concrete substance, fibrous or laminated, is variously -modified either alone or in combination with the rounded particles. -These different modifications and combinations constitute different -kinds of organic substance. When so distinct as obviously to possess a -peculiar structure and peculiar properties, each of these modifications -is considered as a separate form of organized matter, and is called a -PRIMARY TISSUE. Anatomists and physiologists have been at great pains -to discriminate and classify these primary tissues; for it is found -that when employed in the composition of the body, each preserves its -peculiar structure and properties wherever placed, however combined, -and to whatever purpose applied, undergoing only such modification -as its local connexions and specific uses render indispensable. -Considering every substance employed in the construction of the body, -not very obviously alike, as a distinct form of organized matter, these -primary tissues may be said to consist of five, namely, the membranous, -the cartilaginous, the osseous, the muscular, and the nervous. - -19. The first primary tissue is the peculiar substance termed MEMBRANE. -It has been already stated (16) that one of the ultimate forms of -animal matter is a coagulable substance, becoming concrete or solid -under the process of coagulation. The commencement of organization -seems to be the arrangement of this concrete matter into straight -thready lines, at first so small as to be imperceptible to the naked -eye. Vast numbers of these threads successively uniting, at length -form a single thread of sufficient magnitude to be visible, but still -smaller than the finest thread of the silkworm. If the length of these -threads be greater than their breadth, they are called fibres; if, -on the contrary, their breadth exceed their length, they are termed -plates or laminæ. By the approximation of these fibres or plates in -every possible direction, and by their accumulation, combination, and -condensation, is constituted the simplest form of organized substance, -the primary tissue called membrane. - -20. Membrane once formed is extensively employed in the composition -of the body: it is indeed the material principally used in producing, -covering, containing, protecting, and fixing every other component -part of it. It forms the main bulk of the cartilaginous tissue; it -receives into its cells the earthy matter on which depend the strength -and hardness of the osseous tissue; it composes the canals or sheaths -in which are deposited the delicate substance of the muscular, and the -still more tender pulp of the nervous tissue; it gives an external -covering to the entire body; it lines all its internal surfaces; it -envelopes all internal organs; it enters largely as a component element -into the substance of every organ of every kind; it almost wholly -constitutes all the internal pouches and sacs, such as the stomach, the -intestines, the bladder; and all tubes and vessels, such as arteries, -veins, and lymphatics; it furnishes the common substance in which -all the parts of the body are, as it were, packed; it fills up the -interstices between them; it fixes them in their several situations; it -connects them all together; in a word, it forms the basis upon which -the other parts are superinduced; or rather the mould into which their -particles are deposited; so that were it possible to remove every other -kind of matter, and to leave this primary tissue unaltered in figure -and undiminished in bulk, the general form and outline of the body, as -well as the form and outline of all its individual parts, would remain -unchanged. - -21. The properties which belong to membrane are cohesion, flexibility, -extensibility, and elasticity. By its property of cohesion, the several -parts of the body are held together; by its combined properties of -cohesion, flexibility, and extensibility, the body in general is -rendered strong, light, and yielding, while particular parts of it -are made capable of free motion. But elasticity, that property by -which parts removed from their situation in the necessary actions of -life are restored to their natural position, may be regarded as its -specific property. The varied purposes accomplished in the economy -by the property of elasticity will be apparent as we advance in our -subject. Meantime, it will suffice to observe that it is indispensable -to the action of the artery in the function of the circulation; to the -action of the thorax in the function of respiration; to the action of -the joints in the function of locomotion: in a word, to the working -of the entire mechanism by which motion of every kind and degree -is effected. All these properties are physical, not vital; vital -properties do belong even to this primary form of animal matter; but -they are comparatively obscure. In the tissue with which organization -commences, and which is the least removed from an inorganic substance, -the properties that are prominent and essential are merely physical. - -22. By chemical analysis, membrane is found to contain but a small -proportion of azote, the peculiar element of animal matter. Its -proximate principles are gelatin, albumen, and mucus. In infancy and -youth, gelatin is the most abundant ingredient; at a more advanced -period, albumen predominates[3]. Gelatin differs from albumen in -containing a less proportion of azote and a greater proportion of -oxygen; on both accounts it must be regarded as less animalized. Thus -animalization bears a certain relation to organization. The simplest -animal tissue is the least animalized, and the least of all at the -earliest period of life. Not only are the physical and mental powers -less developed in the young than in the adult, but the very chemical -composition of the primary tissue of which the body is constructed is -less characteristic of the perfect animal. - -23. Membrane exists under several distinct forms; a knowledge of the -peculiarities of which will materially assist us in understanding the -composition of the body. The simplest form of membrane, and that which -is conceived to constitute the original structure from which all the -others art produced, is termed the _cellular_. When in thin slices, -_cellular membrane_ appears as a semi-transparent and colourless -substance; when examined in thicker masses, it is of a whitish or -greyish colour. It consists of minute threads, which cross each other -in every possible direction, leaving spaces between them, and thus -forming a mesh or net-work (fig. XVII.), not unlike the spider's web. -The term cells, given to these interspaces, is employed rather in a -figurative sense than as the expression of the fact; for there are no -such distinct partitions as the term cell implies. The best conception -that can be formed of the arrangement of the component parts of -this structure is, to suppose a substance consisting of an infinite -number of slender thready lines crossing each other in every possible -direction (fig. XVII.). The interspaces between these lines during -life, and in the state of health, are filled with a thin exhalation of -an aqueous nature, a vapour rather than a fluid, rendering and keeping -the tissue always moist. This vapour consists of the thinner part of -the blood, poured into these interstitial spaces by a process hereafter -to be described, termed secretion. When occupying those spaces, it -makes no long abode within them, but is speedily removed by the process -of absorption. In health, these two operations exactly equal each -other; but if any cause arise to disturb the equilibrium, the vapour -accumulates, condenses and forms an aqueous fluid, which distends the -cells and gravitates to the most depending parts. Slightly organized -as this tissue is, and indistinct as its vita functions may be, it -is obvious that it must be the seat of at least two vital functions, -secretion and absorption. - -[Illustration: Fig. XVII. - -A single film of the cellular tissue lifted up and slightly distended.] - -24. It is certain that the interspaces or cells of this membrane have -no determinate form or size, that they communicate freely with each -other, and that this communication extends over the whole body; for if -a limb which has been infiltrated be frozen, a thousand small icicles -will be formed, assuming the shape of the containing cells, some of -which are found to be circular and others cylindrical, and so on. If -air or water escape into any particular part of the body, it is often -effused over the whole extent of it, and butchers are observed to -inflate animals by making a puncture in some part where the cellular -tissue is loose, and from this one aperture the air is forced to the -most distant parts of the body. - -25. Cellular membrane, variously modified and disposed, forms the -main bulk of all the other solid parts of the body, constituting -their common envelope and bond of union, and filling up all their -interstices. It is dense or loose, coarse or fine, according to its -situation and office. Wherever it is subject to pressure, it is dense -and firm, as in the palm of the hand and the sole of the foot; around -the internal organs it is more loose and delicate, and it becomes finer -and finer as it divides and subdivides, in order to envelope the soft -and tender structures of the body. - -[Illustration: Fig. XVIII. - -A portion of cellular tissue, very highly magnified, showing the -strings of globules of which its ultimate fibres are by some supposed -to consist.] - -26. According to some who have carefully examined with the microscope -its component threads, they consist of minute particles of a globular -figure (fig. XVIII.); other microscopical observers regard the cellular -threads as coagulated or condensed animal substance, perfectly -amorphous (without form). - -27. Every part of this tissue is penetrated by arteries, veins, -absorbents, and nerves, endowing it with properties truly vital, though -in a less degree than any of the other primary tissues; and varied and -important as the uses are which it serves in the economy, the most -manifest, though certainly not the only ones, are those which depend -upon its physical properties of cohesion, flexibility, extensibility, -and elasticity. - -[Illustration: Fig. XIX. 1, A portion of adipose tissue; 2, minute bags -containing the fat; 3, a cluster of the bags, separated and suspended.] - -28. The tissue which contains the fat, termed the _adipose_, is -the second form of membrane; it is obviously a modification of the -cellular, from which it differs both in the magnitude of its fibres, -whence it constitutes a tougher and coarser web, and in their -arrangement; for it is so disposed as to form distinct bags in which -the fat is contained. Adipose tissue consists of rounded packets, -separated from each other by furrows (fig. XIX. 2, 2); each packet -is composed of small spheroidal particles (fig. XIX. 2, 2); each -particle is again divisible into still smaller grains, which, on minute -inspection, present the appearance of vesicles filled with the adipose -matter (fig. XIX. 3). - -29. The cells of the cellular tissue, as has been shown (24), are -continuous over the whole body; but each adipose vesicle is a distinct -bag, having no communication whatever with any other (fig. XIX. 2, 2). -The cellular tissue is universally diffused; but the adipose is placed -only in particular parts of the body; principally beneath the skin, and -more especially between the skin and the abdominal muscles, and around -some of the organs contained in the chest and abdomen, as the heart, -the kidneys, the mesentery, and the omenta. In most of these situations -some portion of it is generally found, whatever be the degree of -leanness to which the body may be reduced; while in the cranium, the -brain, the eye, the ear, the nose, and several other organs, there is -none, whatever be the degree of corpulency. The uses of the fat, which -are various, will be stated hereafter. - -30. The third form of membrane is termed the - -_serous_. Like the adipose, _serous membrane_ is a modification of -the cellular, and, like it also, it is limited in its situation to -particular parts of the body, that is, to its three great cavities, -namely, the head, the chest, and the abdomen. To the two latter it -affords an internal lining, and to all the organs contained in all -the three cavities, it affords a covering. By its external surface it -is united to the wall of the cavity or the substance of the organ it -invests; by its internal surface it is free and unattached; whence this -surface is in contact only with itself, forming a close cavity or shut -sac, having no communication with the external air. Smooth and polished -(fig. XX.), it is rendered moist by a fluid which is supposed to be -exhaled in a gaseous state from the serum of the blood; and from this -serous fluid the membrane derives its name. - -[Illustration: Fig. XX. - -A portion of intestine, showing its external surface or serous coat.] - -31. Though thin, serous membrane is dense, compact, and of great -strength in proportion to its bulk: it is extensible and elastic; -extensible, for it expands with the dilatation of the chest in -inspiration; elastic, for it contracts with the diminished size -of the chest in expiration. In like manner, it stretches with the -enlargement of the stomach during a hearty meal, and contracts as -the stomach gradually diminishes on emptying itself of its contents. -It is furnished with no blood-vessels large enough to admit the -colouring matter of the blood; but it is supplied with a great number -of the colourless vessels termed exhalents, with the vessels termed -absorbents, and with a few nerves. It indicates no vital properties, -but those which are common to the simple form of the primary tissue. -Its specific uses are to afford a lining to the internal cavities; to -furnish a covering to the internal organs; by its polished and smooth -surface, to allow a free motion of those organs on each other, and by -the moisture with which it is lubricated, to prevent them from adhering -together, however closely, or for however long a period they may be in -contact. - -32. The fourth form of membrane, the _fibrous_, named from the obvious -arrangement of its component parts, consists of longitudinal fibres, -large enough to be visible to the naked eye, placed parallel to each -other, and closely united. Sometimes these fibres are combined in such -a manner as to form a continuous and extended surface, constituting -a thin, smooth, dense, and strong membrane, such as that which lines -the external surface of bones termed PERIOSTEUM, or the internal -surface of the skull (dura mater). At other times, they form a firm and -tough expansion (aponeurosis) which descends between certain muscles, -separating them from each other, and affording a fixed point for the -origin or insertion of neighbouring muscles; or which is stretched -over muscles, and sometimes over even an entire limb, in order to -confine the muscles firmly in their situation, and to aid and direct -their action (fig. XXVII.). Fibrous membrane also constitutes the -compact, strong, tough, and flexible bands used for tying parts firmly -together, termed LIGAMENTS, principally employed in connecting the -bones with each other, and particularly about the joints; and lastly, -fibrous membrane forms the rounded white cords in which muscles often -terminate, called TENDONS (fig. XXV., XXVI.), the principal use of -which is to connect the muscles with the bones, and to serve as cords -or ropes to transmit the action of the muscle to a distant point, in -the accomplishment of which purposes their operation appears to be -entirely mechanical. - -33. The fifth form of membrane, the _mucous_ (fig. XXI.), derives its -name from the peculiar fluid with which its surface is covered, called -mucus, and which is secreted by numerous minute glands, imbedded in -the substance of the membrane. As serous membrane forms a shut sac, -completely excluding the air, mucous membrane, on the contrary, lines -the various cavities which are exposed to the air, such as the mouth, -the nostrils, the wind-pipe, the gullet, the stomach, the intestines, -the urinary organs, and the uterine system. Its internal surface, or -that by which it is attached to the passages it lines, is smooth and -dense; its external surface, or that which is exposed to the contact -of the air, is soft and pulpy, like the pile of velvet (fig. XXI.). It -bears a considerable resemblance to the external surface of the rind of -the ripe peach. - -[Illustration: Fig. XXI. - -A portion of the stomach, showing its internal surface or mucous coat.] - -Unlike all the other tissues of this class, the mucous membranes are -the immediate seat of some of the most important functions of the -economy; in the lung, of respiration; in the stomach, of digestion; in -one part of the intestine, of chylification; in another, of excretion; -while in the mouth and nose, they are the seat of the animal functions -of taste and smell; and they are highly organized in accordance with -the importance of the functions they perform. - -34. The last form of membrane which it is necessary to our present -purpose to particularize, is that which constitutes the external -covering of the body, and which is called the _skin_. The skin is -everywhere directly continuous with the mucous membranes that line the -internal passages, and its structure is perfectly analogous. Both the -external and the internal surface of the body may be said therefore to -be covered by a continuous membrane, possessing essentially the same -organization, and almost identically the same chemical composition. -The skin is an organ which performs exceedingly varied and important -functions in the economy, to the understanding of which it is necessary -to have a clear conception of its structure; some further account of it -will therefore be required; but this will be more advantageously given -when the offices it serves are explained. - -[Illustration: Fig. XXII. Portions of cartilage, seen in section.] - -35. Such is the structure, and such are the properties, of the -first distinct form of organized matter. The second primary tissue, -termed the CARTILAGINOUS (fig. XXII.), is a substance intermediate -between membrane and bone. The nature of its organization is not -clearly ascertained. By some anatomists, it is regarded as a uniform -and homogeneous substance, like firm jelly, without fibres, plates, -or cells; others state that they have been able to detect in it -longitudinal fibres, interlaced by other fibres in an oblique and -transverse direction, but without determinate order. All are agreed -that it is without visible vessels or nerves: not that it is supposed -to be destitute of them, but that they are so minute as to elude -observation. Its manifest properties are wholly mechanical. It is -dense, strong, inextensible, flexible, and highly elastic. It is -chiefly by its property of elasticity that it accomplishes the various -purposes it serves in the economy. It is placed at the extremities of -bones, especially about the joints, where, by its smooth surface, it -facilitates motion, and, by its yielding nature, prevents the shock or -jar which would be produced were the same kind and degree of motion -effected by a rigid and inflexible substance. Where a certain degree -of strength with a considerable degree of flexibility are required, it -supplies the place of bone, as in the spinal column, the ribs and the -larynx. - -[Illustration: Fig. XXIII. - -Membranous portion of bone; the osseous portion being so completely -removed, that the bone is capable of being tied in a knot.] - -36. The third distinct form of organized matter is termed the -OSSEOUS tissue. Bone is composed of two distinct substances, an animal -and an earthy matter: the former organic, the latter inorganic. The -animal or organic matter is analogous both in its nature and in its -arrangement to cellular tissue; the earthy or inorganic matter consists -of phosphoric acid combined with lime, forming phosphate of lime. The -cellular tissue is aggregated into plates or laminæ, which are placed -one upon another, leaving between them interspaces or cells, in which -is deposited the earthy matter (phosphate of lime). If a bone, for -example, the bone called the radius, one of the bones of the fore-arm, -be immersed in diluted sulphuric, nitric, muriatic, or acetic acid, it -retains its original bulk and shape; it loses, however, a considerable -portion of its weight, while it becomes so soft and pliable, that it -may be tied in a knot (fig. XXIII.). In this case, its earthy matter -is removed by the agency of the acid, and is held in solution in the -fluid; what remains is membranous matter (cellular tissue). If the -same bone be placed in a charcoal fire, and the heat be gradually -raised to whiteness, it appears on cooling as white as chalk; it is -extremely brittle; it has lost much of its weight, yet its bulk and -shape continue but little changed. In this case, the membraneous matter -is wholly consumed by the fire, while the earth is left unchanged (fig. -XXIV.). Every constituent atom of bone consists, then, essentially -of animal and earthy matter intimately combined. A little more than -one-third part consists of animal matter (albumen), the remaining -two-thirds consist of earthy matter (phosphate of lime); other saline -substances, as the fluate of lime and the phosphate of magnesia, are -also found in minute quantity, but they are not peculiar to bone. - -[Illustration: Fig. XXIV. - -Earthy portion of bone.] - -37. In general, the osseous tissue is placed in the interior of the -body. Even when bone approaches the surface, it is always covered -by soft parts. It is supplied with but few blood-vessels, with -still fewer nerves, with no absorbents large enough to be visible, -so that though it be truly alive, yet its vital properties are not -greatly developed. The arrangement of its component particles is -highly curious; the structure, the disposition, and the connexion of -individual bones afford striking examples of mechanism, and accomplish -most important uses in the economy; but those uses are dependent -rather upon mechanical than vital properties. The chief uses of bone -are— 1. By its hardness and firmness to afford a support to the soft -parts, forming pillars to which the more delicate and flexible organs -are attached and kept in their relative positions. 2. To defend the -soft and tender organs by forming a case in which they are lodged and -protected, as that formed by the bones of the cranium for the lodgment -and protection of the brain (fig. XLVII.); by the bones of the spinal -column for the lodgment and protection of the spinal cord (fig. -XLVIII.); by the bones of the thorax (fig. LIX.), for the lodgment and -protection of the lungs, the heart, and the great vessels connected -with it (fig. LIX.). 3. By affording fixed points for the action of the -muscles, and by assisting in the formation of joints to aid the muscles -in accomplishing the function of locomotion. - -38. All the primary tissues which have now been considered consist of -precisely the same proximate principles. Albumen is the basis of them -all; with the albumen is always mixed more or less gelatin, together -with a minute quantity of saline substance: to the osseous tissue is -superadded a large proportion of earthy matter. With the exception -of the mucous, the organization of all these tissues is simple; -their vital properties are low in kind and in degree; their decided -properties are physical, and the uses they serve in the economy are -almost wholly mechanical. - -[Illustration: Fig. XXV. - -Portion of a muscle; showing (_a_) the muscular fibres and their -parallel direction; and (_b_) the termination of the fibres in tendon.] - -39. But we next come to a tissue widely different in every one of -those circumstances, a tissue consisting of a new kind of animal -matter, and endowed with a property not only peculiar to itself, -but proper to living substance, and characteristic of a high degree -of vital power. MUSCULAR TISSUE, the fourth distinct form of animal -matter, commonly known under the name of flesh, is a substance -resembling no other in nature. It consists of a soft and pulpy -substance, having little cohesive power, arranged into fibres which -are distinctly visible to the naked eye, and which are disposed in a -regular and uniform manner, being placed close and parallel to each -other (fig. XXV.). These fibres are every where pretty uniformly the -same in shape, size, and general appearance, being delicate, soft, -flattened, and though consisting only of a tender pulp, still solid -(fig. XXV.). When examined under the microscope, fibres, which to the -naked eye appear to be single threads, are seen to divide successively -into smaller threads, the minutest or the ultimate division not -exceeding, as is supposed, the 40,000th part of an inch in diameter. On -the other hand, the fibres which are large enough to be visible to the -naked eye, are obviously aggregated into bundles of different magnitude -in different muscles, but always of the same uniform size in the same -muscle (fig. XXV.). - -[Illustration: Fig. XXVI. - -Two portions of muscle; one of which, _a_, is covered with membrane; -the other, _b_, is uncovered; _c_, the muscular fibres terminating in -tendon.] - -40. The ultimate thread, or the minutest division of which the -muscular fibre is susceptible, is called a filament; the smallest -thread which can be distinguished by the naked eye is termed a fibre -(fig. XXVI.); and the bundle which is formed by the union of fibres -is denominated a fasciculus. The proper muscular substance is thus -arranged into three distinct forms progressively increasing in -size,—the filament, the fibre, and the fasciculus. The filament, the -fibre, the fasciculus, as well as the muscle itself, formed by the -aggregation of fasciculi, is each inclosed in its own distinct sheath -of cellular membrane (fig. XXVI. _a_). - -[Illustration: Fig. XXVII. - -Portion of a muscle enclosed in a sheath of fascia or aponeurosis.] - -41. The composition of the ultimate filament has been very carefully -examined by many distinguished physiologists with microscopes of high -magnifying power. Under some of these microscopes the filament appears -to consist of a series of rounded particles or globules of the same -size as the particles of the blood when deprived of their colouring -matter, so that it looks like a string of pearls (fig. XXVIII.), each -globule being commonly stated to be about the 2000th part of an inch -in diameter. But it is now pretty generally agreed that this globular -appearance of the ultimate muscular fibre vanishes under the more -improved microscopes of the present day, and, as viewed by the latter, -appears as a peculiar pulpy substance arranged into threads of extreme -minuteness, placed close and parallel to each other, intersected by a -great number of delicate lines passing transversely across the muscular -threads (fig. XXIX.), - -[Illustration: Fig. XXVIII. - -Ultimate fibres of muscle, very greatly magnified; showing the strings -of globules of which they are supposed by some to consist.] - -42. With the exception of the organs of sense, the muscular tissue is -more abundantly supplied with arteries, veins, and nerves, than any -other substance of the body. Every ultimate thread or filament appears -to be provided with the ultimate branch of an artery, vein, and nerve. -These vessels are seen ramifying on the surface of the delicate web of -membrane that incloses the pulp, but cannot be traced into it. - -[Illustration: Fig. XXIX. - -The appearance of the ultimate muscular fibres and of their transverse -lines, as seen under the microscope of Mr. Lister, when the object is -magnified 500 diameters.] - -43. The proximate principle of which the muscular pulp is composed -is fibrin. From the pulp, when inclosed in its sheath of membrane, -albumen, jelly, various salts, and a peculiar animal extract called -osmazome, are also obtained; but these substances are probably derived -from the membranous, not the muscular, matter. Fibrin contains a larger -proportion of azote, the element peculiar to the animal body, and by -the possession of which its chemical composition is distinguished from -that of the vegetable, than any other animal substance. - -[Illustration: Fig. XXX. - -Portion of the trunk of a nerve; dividing into branches.] - -44. Muscular tissue possesses a slight degree of cohesion, a high -degree of flexibility and extensibility, but no degree of elasticity; -for although muscle, considered as a compound of muscular substance and -membrane, be highly elastic, yet this property is probably altogether -owing to the membranous matter in which it is enveloped. Its peculiar -and distinctive property is vital, not physical, and consists in the -power of diminishing its length, or of contracting or shortening itself -on the application of a stimulus. This property, which is termed -contractility, is the great, if not the sole source of motion in the -body. Without doubt, elasticity and gravity, under the generating and -controlling powder of contractility, aid in accomplishing various -kinds of motion. Thus membranes, tendons, ligaments, cartilages, and -bones, by their physical and mechanical properties, modify, economize, -facilitate, concentrate and direct the motive power generated by the -pure muscular substance; but still the only real source of motion in -the body is muscular tissue, and the only mode in which motion is -generated is by contractility. This will be more fully understood -hereafter. - -[Illustration: Fig. XXXI. - -Ultimate fibres of nerve, very highly magnified; showing the strings of -globules of which they consist.] - -45. The last primary tissue, termed the NERVOUS, is equally distinct -in nature and peculiar in property. It consists of a soft and pulpy -matter, of a brownish white colour (fig. XXX.). According to some, -the nervous, like the muscular pulp, is composed of minute globules, -arranged in the same manner like a string of pearls (fig. XXXI.); -according to others, it consists of solid elongated threads, of a -cylindrical form, differing in thickness from that of a hair to the -finest fibre of silk. The pulp, whatever its form of aggregation, is -inclosed in a sheath of delicate cellular tissue. This external or -containing membrane is called the neurilema, or the nerve-coat; the -internal or contained substance, the proper nervous matter, is termed -the nerve-string. The nerve-string, enveloped in its nerve-coat, -constitutes the nervous filament. As in the muscle, so in the nerve, -many filaments unite to form a fibre, many fibres to form a fasciculus, -and many fasciculi to form the large cord termed a nerve. Moreover, -as in the muscle, so in the nerve, the filament, the fibre, the -fasciculus, the nervous cord itself, are each enveloped in its own -distinct sheath of cellular membrane; but the arrangement of the -nervous fibres differs from that of the muscular in this, that though -the nervous fibres are placed in juxtaposition, yet they do not, -like the muscular, maintain through their entire course a parallel -disposition, but cross and penetrate each other, so as to form an -intimate interlacement (fig. XXXII.). - -[Illustration: Fig. XXXII. - -Nervous fibres, deprived of their neurilema and unravelled, showing the -smaller threads, or filaments, of which the fibres consist.] - -46. The nervous pulp is at least as liberally supplied with -blood-vessels as the muscular; the vessels are spread out upon the -nerve-coat, in which they divide into innumerable branches of extreme -minuteness, the distribution of which is so perfect, that there is -not a particle of nervous matter which is not supplied both with an -arterial and a venous vessel. Hence the neurilema is not merely a -sheath containing and protecting the nervous pulp, but it affords an -extended mechanical surface for sustaining the arterial vessels, from -which the pulp is probably secreted, and certainly nourished. - -47. Albumen, in conjunction with a peculiar fatty matter, constitutes -the chief proximate principles of which the nervous tissue is composed. -To these are added a small proportion of the animal substance termed -osmazome, a minute quantity of phosphorus, some salts, and a very large -proportion of water; for out of one hundred parts of nervous substance, -water constitutes as much as eighty. Its peculiar vital property is -sensibility; and as all motion depends on the contractility of the -muscular fibre, so all sensation depends on the sensibility of the -nervous substance. - -48. Such are the primary tissues, or the several kinds of organized -matter of which the body is composed; and from this account it is -obvious that they consist of three only—namely, the concrete matter -forming the basis of membrane, the pulpy matter forming the proper -muscular substance, and the pulpy matter forming the proper nervous -substance. Of these three kinds of animal matter the component parts of -the body consist. In combining to form the different structures, these -primary substances are intermixed and arranged in a great variety of -modes; and from these combinations and arrangements result either an -organ, a system, or an apparatus. - -49. As filaments unite to form fibres, and fibres to form tissues, so -tissues unite to form organs: that is, bodies having a determinate -size and figure, and capable of performing specific actions. The -cellular, the muscular, and the nervous tissues are not organs; -membranes, muscles, and nerves are organs. The tissue, the simple -animal substance, is merely one of the elements of which the organ -is composed; the organ is compounded of several of those simple -substances, arranged in a determinate manner, and moulded into a given -shape, and so constituting a specific instrument. The basis of the -muscle is muscular tissue; but to this are added, invariably, membrane, -often tendon, and always vessels and nerves. It is this combination -that forms the specific instrument called a muscle, and that renders it -capable of performing its specific action. And every such combination, -with its appropriate endowment, constitutes an organ. - -50. Organs are arranged into groups or classes, according as they -possess an analogous structure, and perform an analogous function; and -this assemblage constitutes a SYSTEM. All the muscles of the body, -for example, whatever their size, form, situation, or use, have an -analogous structure, and perform an analogous function, and hence are -classed together under the name of the muscular system. All the bones, -whatever their figure, magnitude, density, position, or office, are -analogous in structure and function; and hence are classed together -under the name of the osseous system. For the same reason, all the -cartilages, ligaments, vessels and nerves, form respectively the -cartilaginous, ligamentous, vascular and nervous systems. - -51. An APPARATUS, on the contrary, is an assemblage of organs, it -may be differing widely from each other in structure, and exercising -various and even opposite functions; but all nevertheless concurring -in the production of some common object. The apparatus of nutrition -consists of the organs of mastication, deglutition, digestion, -absorption, and assimilation. Among the individual organs which concur -in carrying on these functions may be reckoned the lips, the teeth, -the tongue, the muscles connected with the jaws, the gullet, the -stomach, the duodenum, the small intestines, the pancreas, the liver, -the lacteal vessels, the mesenteric glands, and the lungs. Many of -these organs have no similarity in structure, and few have any thing -analogous in function; yet all concur, each in its appropriate mode and -measure, to the conversion of the aliment into blood. In the apparatus -of respiration, in that of circulation, of secretion, of excretion; -in the apparatus of locomotion, in the apparatus of sensation, and -more especially in the apparatus of the specific sensations,—vision, -hearing, smell, taste, touch, organs are combined which have nothing -in common but their concurrence in the production of a common end: -but this concurrence is the principle of their combination; and the -individual organs having this conjoint operation, taken together, -constitute an apparatus. - -52. A clear idea may now be affixed to the terms structure and -organization. Structure may be considered as synonymous with -arrangement; the disposition of parts in a determinate order; that -which is constructed or built up in a definite mode, according to a -determinate plan. The arrangement of the threads of the cellular web -into areolæ or cells; the combination of the primary threads into -fibres or laminæ; the disposition of the muscular pulp into filaments, -placed parallel to each other; the investment of the filaments in -membraneous sheaths; the combination of the filaments, included in -their sheaths, into fibres; the aggregation of fibres into fasciculi; -and the analogous arrangement and combination of the nervous pulp, -are examples of structure. But when those structures are applied to -particular uses; when they are so combined and disposed as to form -a peculiar instrument, endowed with a specific function; when the -cellular fibres, for example, are so arranged as to make a thin, dense, -and expanded tissue; when to this tissue are added blood-vessels, -absorbents, and nerves; when, in a word, a membrane is constructed, -an organ is formed; when, in like manner, to the muscular and the -nervous fibres, arranged and moulded in the requisite mode, are added -blood-vessels, absorbents, and nerves, other organs are constructed -capable of performing specific functions: and this is organization—the -building up of organs—the combination of definite structures -into special instruments. Structure is the preparatory process of -organization; the one is the mere arrangement of the material; the -other is the appropriation of the prepared material to a specific use. - -53. The term organization is employed in reference both to the -component parts of the body, and to the body considered as a whole. We -speak of an organized substance and of an organized body. An organized -substance is one in which there is not only a definite arrangement -of its component parts (structure), but in which the particular -arrangement is such as to fit it for accomplishing some special -use. Every organized substance is therefore essentially a special -organ; limited in its object it may be, and perhaps only conducive -to some further object; but still its distinctive character is, that -it has a peculiar structure, fitting it for the accomplishment of -some appropriate purpose. On the other hand, an organized body is a -congeries of organs—the aggregate of the individual organs. Attention -was directed in the early part of this work to one peculiar and -essential character, by which such an organized is distinguished from -an unorganized body. Between the individual parts of the organized body -there is so close a relation, that no one of them can be removed or -injured, or in any manner affected without a corresponding affection of -the whole. The action of the heart cannot cease without the cessation -of the action of the lung; nor that of the lung without that of the -brain; nor that of the brain without that of the stomach; in a word, -there is no organ in whatever distant nook of the system it be placed, -or however apparently insignificant its function, that is not necessary -to the perfection of the whole. But into whatever number of portions an -unorganized body may be divided, each portion retains the properties of -the mass, and constitutes in itself a perfect existence; there being -no relation between its individual parts, excepting that of physical -attraction: on the contrary, each component part of an organized body, -being endowed with some appropriate and specific power, on the exercise -of which the powers of all the other parts are more or less dependent, -the whole must necessarily suffer if but one part fail. - -54. From the whole, then, we see that the human body is a congeries of -organs; that those organs are constructed of a few simple tissues; and -that all its parts, numerous, diversified, and complex as they are, are -composed of but three primary forms of animal matter variously modified -and combined. - -[Illustration: Fig. XXXIII. - -Muscles of the back and shoulders; showing their symmetrical -disposition.] - -55. But though by the analysis of its component parts, this machine, -so complex in its construction, and so wonderfully endowed, may be -reduced to this state of simplicity; and although this analytical view -of it be highly useful in enabling us to form a clear conception of the -nature of its composition; yet it is only by considering its individual -parts such as they actually are, and by studying their situation, -connexion, structure, and action, that we can understand it as a whole, -and apply our knowledge of it to any practical use. - -56. Viewing then the human body as a complicated whole, as a congeries -of organs made up of various combinations of simple tissues, it may -be observed, in reference to its external configuration, that it is -rounded. This rounded form is principally owing to the large proportion -of fluids which enter into its composition. The roundness of the face, -limbs, and entire surface of the child, are in striking contrast to -the unequal and irregular surface of the old man, whose humours are -comparatively very much smaller in quantity. - -57. The length of the human body exceeds its breadth and thickness; -the degree of the excess varying at different periods of life, and -according to the peculiar constitution of the individual. In the -extremities, the bones, muscles, vessels, and nerves, are especially -distinguished by their length. - -[Illustration: Fig. XXXIV. - -Front view of the skeleton. 1. the head; 2. the trunk; 3. the superior -extremities; 4. the inferior extremities.] - -[Illustration: Fig. XXXV. - -Back view of the skeleton. 1. the head; 2. the trunk; 3. the superior -extremities; 4. the inferior extremities.] - -58. The form of the human body is symmetrical, that is, it is -capable of being divided into two lateral and corresponding halves. -Suppose a median line to pass from the vertex of the head through the -centre of the spinal column (fig. XXXIV. 1, 2); if the body be well -formed, it will be divided by this line into two exactly equal and -corresponding portions (fig. XXXV. 1). This symmetrical disposition -of the body is not confined to its external configuration. It is -true of many of the internal organs; but principally, as has been -already stated, of those that belong to the animal life. The brain and -the spinal cord are divisible into two exactly equal halves (figs. -XLVIII. _d_, and XLIX. 1, 2, 3); the organs of sense are double and -symmetrical: the muscles of one side of the body exactly correspond to -those of the other (fig. XXXIII.); the two hands and arms and the two -lower extremities are alike (figs. XXXIV., XXXV.); but for the most -part, the organs of the organic life, the stomach, the intestines, the -liver, the spleen, for example, are single, and not symmetrical. - -59. The human body is divided into three great portions, the head, the -trunk, and the extremities (figs. XXXIV. and XXXV. 1, 2, 3, 4). - -60. By the HEAD is meant all that part of the body which is placed -above the first bone of the neck (fig. XXXIV. 1). It is of a spheroidal -figure, broader and deeper behind than before, somewhat like an egg in -shape, with the broad end behind; it is flattened at its sides (figs. -XXXV. 1, and XXXVI. 2, 4). Its peculiar figure renders it at once -stronger and more capacious than it could have been had it possessed -any other form. It is supported by its base on the spinal column, to -which it is attached by the peculiar structure termed a joint (fig. -XXXIV.), and fastened by ligaments of exceeding strength. - -61. The head contains the central organ of the nervous system; the -organs of the senses, with the exception of that of touch; and the -organs of mastication. It comprehends the cranium and the face. Both -are composed partly of soft parts, as the teguments, namely, skin, fat, -&c., and muscles; and partly of bones. - -[Illustration: Fig. XXXVI. - -1. Frontal bone; 2. parietal bone; 3. occipital bone; 4. temporal bone; -5. nasal bone; 6. malar bone; 7. superior maxillary bone; 8. inferior -maxillary bone.] - -[Illustration: Fig. XXXVII. - -Bones of the skull, separated; front view. 1. Frontal bone; 2. portions -of the parietal bones; 3. malar or cheek bones; 4. nasal bones; 5. -superior maxillary or bones of the upper jaw; 6. the vomer; 7. the -inferior maxillary or bone of the lower jaw.] - -[Illustration: Fig. XXXVIII. - -Bones of the skull separated; side view. 1. Frontal bone; 2. parietal -bone; 3. occipital bone; 4. temporal bone; 5. nasal bone; 6. malar -bone; 7. superior maxillary bone; 8. the unguis; 9. the inferior -maxillary bone.] - -[Illustration: Fig. XXXIX. - -Bones forming the base of the skull; viewed from the inside. 1. -Occipital bone; 2. temporal bones; 3. sphenoid bone; 4. ethmoid bone; -5. superior maxillary bones, or bones of the upper jaw; 6. malar or -cheek bones; 7. foramen magnum.] - -62. The bones of the cranium are eight in number, six of which are -proper to the cranium, and two are common to it and to the face. The -six bones proper to the cranium are the frontal (fig. XXXVII. 1), the -two parietal (fig. XXXVI. 2), the two temporal (fig. XXXVIII. 4), and -the occipital (fig. XXXVIII. 3); the two common to the cranium and face -are the ethmoidal (fig. XXXIX. 4), and the sphenoidal (fig. XXXIX. -3). The frontal bone forms the entire forepart of the vault (fig. -XXXVII. 1); the two parietal form the upper and middle part of it (fig. -XXXVIII. 2); the two temporal form the lower part of the sides (fig. -XXXVIII. 4); the occipital forms the whole hinder part, together with a -portion of the base (figs. XXXVIII. 3, XXXVI. 3, XXXIX. 1); while the -ethmoidal forms the forepart, and the sphenoidal the middle part of the -base (fig. XXXIX. 3, 4). - -[Illustration: Fig. XL. - -2 1 - -Portions of the bones of the cranium; showing the corresponding -inequalities in their margins: which margins, when in apposition, -constitute the mode of union termed suture. 1. External surface of the -bone; 2. internal surface.] - -[Illustration: Fig. XLI. - -1 - -Fig. XLII. - -2 - -1. Side view of the adult skull, showing the several bones united by -suture; 2. side view of the fœtal skull, showing the bones imperfectly -ossified, separated to some extent from each other, the interspace -being occupied by membrane. The small size of the face compared with -that of the cranium is strikingly apparent.] - -63. These bones are firmly united together. The union of bones is -technically called an _articulation_ or _joint_. All joints are either -immoveable or moveable. The union of the bones of the cranium affords -an example of an immoveable articulation. Prominences and indentations, -like the teeth of a saw, are formed in the margins of the contiguous -bones (figs. XXXVIII. and XL.). At these inequalities of surface, which -are exactly adapted to each other (figs. XXXVIII. and XL.), the two -bones are in immediate apposition in such a manner as to preclude the -possibility of motion, and even to render the separation extremely -difficult. This mode of articulation is termed a _suture_. There are -certain advantages in constructing the cranium of several distinct -bones, and in uniting them in this peculiar mode. 1. The walls of the -vault are stronger than they could have been had they been formed of a -single piece. 2. In the fœtus, the bones are at some distance from each -other (fig. XLII.); at birth, they yield and overlap one another; and -in this manner they conduce to the security and ease of that event. 3. -Minute vessels pass abundantly and securely through the interstices of -the sutures to and from the interior of the cranium; in this manner, -a free communication is established between the vessels within and -without this cavity. 4. It is probable that the shock produced by -external violence is diminished in consequence of the interruption of -the vibration occasioned by the suture; it is certain that fracture is -prevented by it from extending as far as it would do in one continued -bony substance. - -[Illustration: Fig. XLIII. - -Section of the skull. 1. Cavity of the cranium occupied by the brain; -2. cut edge of the bones of the cranium, showing the two tables of -compact bone and the intervening spongy texture called diploë.] - -64. The vault of the cranium forms a cavity which contains the -brain (fig. XLIII. and XLVIII.) The size of this cavity is invariably -proportioned to that of the organ it lodges and protects. The form and -magnitude of the cavity, and consequently the shape and size of the -cranium, depend upon the brain, and not of the brain upon the cranium. -The soft parts model and adapt to themselves the hard, and not the hard -the soft. The formation of the brain in the fœtus is anterior to that -of the case which ultimately contains it; and the hard bone is moulded -upon the soft pulp, not the pulp upon the bone. At every period of -life, on the inner surface of the cranium there are visible impressions -made by the convolutions of the brain, and the ramifications of the -arteries (figs. XXXIX. 1, 2, and XL. 2), and on its external surface -are depressions occasioned by the action of the external muscles. Nor -does the modifying power of the brain over the bones of the cranium -terminate at birth. The formation of bone, always a slow process, -is never completed until the child has attained its third or fourth -year, and often not until a much later period. At this tender age, the -bones, which in advanced life are hard and rigid, are comparatively -soft and yielding, and consequently more readily receive and retain -the impression of the convolutions and of the other projecting parts -of the brain, by which they are sometimes so deeply marked, that an -attentive examination of the inner surface of the cranium is of itself -sufficient to determine not only that some part, but to indicate the -very part of the brain which has been preternaturally active. At this -tender age, pressure, internal or external, general or partial, may -readily change the form of the cranium. If, by a particular posture, -the head of a child be unequally balanced on the spine, the brain will -press more on that side of the cranium than on the other; the organ -will expand in the direction to which it inclines; that portion of it -will become preternaturally developed, and consequently the balance of -its functions will be disturbed. An awkward way of standing or sitting, -perhaps contracted inadvertently and kept up by habit; a wry neck; any -cause that keeps the head constantly inclined to one side, may produce -this result, examples of which and of its consequences will be given -hereafter. - -65. Tracing them from without inwards we see, then, that the various -coverings afforded to the brain, the central organ of the animal life, -seated in its vaulted cavity, are: 1. The tegument, consisting of the -skin and of cellular and adipose membrane. 2. Beneath the tegument, -muscles, in the forepart and at the vertex, comparatively slender and -delicate; at the sides and posteriorly, thick, strong, and powerful -(fig. XLIV.). 3. Beneath the muscles, a thin but dense membrane, termed -the pericranium, lining the external surface of the cranial bones. 4. -Beneath the pericranium, the bony substance of the cranium, consisting -of two firm and hard bony plates, with a spongy, bony structure, called -diploë, interposed between them (fig. XLIII. 2). 5. Immediately in -contact with the inner surface of the bony substance of the cranium, -and forming its internal lining, the dense and strong membrane, called -the _dura mater_, not only affording a general covering to the brain, -but sending firm partitions between individual portions of it (fig. -XLVIII. _c._). 6. A serous membrane lining the internal surface of -the dura mater, and reflected over the entire surface of the brain, -termed the arachnoid tunic. 7. A thin and delicate membrane in -immediate contact with the substance of the brain, descending between -all its convolutions, lining all its cavities and enveloping all its -fibres, called the pia mater. 8. An aqueous fluid, contained between -the arachnoid membrane and the pia mater. Skin, muscle, pericranium, -bone, dura mater, arachnoid membrane, pia mater, and aqueous fluid, -superimposed one upon another, form, then, the covering and defence of -the brain; so great is the care taken to protect this soft and tender -substance. - -66. The bones of the _face_ consist of fourteen, namely, the two -superior maxillary or jaw-bones (fig. XXXVII. 5), the two malar or -cheek bones (fig. XXXVII. 3), the two nasal bones (fig. XXXVII. 4), -the two palate bones, the two ossa unguis (fig. XXXVIII. 8), the two -inferior turbinated bones, the vomer (fig. XXXVII. 6), and the inferior -maxilla or the lower jaw (fig. XXXVII. 7.) This irregular pile of bones -is divided into the superior and inferior maxilla or jaws; the superior -maxilla being the upper and immoveable portion of the face; the -inferior maxilla being the lower and moveable portion of it. Besides -these bones, the face contains thirty-two teeth, sixteen in each -jaw. The bones of the upper jaw are united together by sutures, and -the union is so firm, that they have no motion but what they possess -in common with the cranium. The lower jaw is united by a distinct -articulation with the cranium (figs. XXXIV. and XXXV.). - -67. Besides the bones and the teguments, the face contains a number of -muscles, which for the most part are small and delicate (fig. XLIV.), -together with a considerable portion of adipose matter; while, as has -been stated, the face and head together contain all the senses, with -the exception of that of touch, which is diffused, more or less, over -the entire surface of the body. - -[Illustration: Fig. XLIV. - -Muscles of the face.] - -68. The second great division of the body, termed the TRUNK, extends -from the first bone of the neck to that called the pubis in front, and -to the lower end of the coccyx behind (fig. XXXIV. 2). It is subdivided -into the thorax, the abdomen, and the pelvis (fig. XLV.). - -69. The _thorax_ or _chest_ extends above from the first bone of -the neck, by which it is connected with the head, to the diaphragm -below, by which it is divided from the abdomen (figs. XLV. and LXI.). -It consists partly of muscles and partly of bones; the muscular and -the osseous portions being in nearly equal proportions. Both together -form the walls of a cavity in which are placed the central organs of -circulation and respiration (fig. LX. 2, 5). The chief boundaries of -the cavity of the thorax before, behind, and at the sides, are osseous -(fig. XLV.); being formed before, by the sternum or breast-bone (fig. -XLV. 6); behind, by the spinal column or back bone (fig. XLV. 2, 4); -and at the sides, by the ribs (fig. XLV. 7). Below, the boundary is -muscular, being formed by the diaphragm (fig. LXI. 2), while above the -thorax is so much contracted (fig. XLV.), that there is merely a space -left for the passage of certain parts which will be noticed immediately. - -70. The figure of the thorax is that of a cone, the apex being above -(fig. XLV.), through the aperture of which pass the tubes that lead -to the lungs and stomach, and the great blood-vessels that go to and -from the heart (fig. LX.). The base of the cone is slanting, and is -considerably shorter before than behind, like an oblique section of the -cone (fig. XLV.). - -71. The osseous portion of the walls of the thorax is formed behind by -the spinal column, a range of bones common indeed to all the divisions -of the trunk; for it constitutes alike the posterior boundary of the -thorax, abdomen, and pelvis (fig. XLV. 2, 4, 6). It is composed of -thirty distinct bones, twenty-four of which are separate and moveable -on one another, and on this account are called true vertebræ (fig. XLV. -2, 4); the other five, though separate at an early period of life, are -subsequently united into a single solid piece, called the sacrum (fig. -XLV. 5). The bones composing this solid piece, as they admit of no -motion on each other, are called false vertebræ (fig. XLV. 5). To the -extremity of the sacrum is attached the last bone of the series, termed -the coccyx (fig. XXXV.). - -72. From above downwards, that is, from the first bone of the neck to -the first bone of the sacrum, the separate bones forming the column -progressively increase in size; for this column is the chief support -of the weight of the head and trunk, and this weight is progressively -augmenting to this point (fig. XLV. 2, 4). From the sacrum to the -coccyx, the bones successively diminish in size, until, at the -extremity of the coccyx, they come to a point (fig. XXXV.). The spinal -column may therefore be said to consist of two pyramids united at their -base (fig. XLV. 4, 5). The superior pyramid is equal in length to about -one third of the height of the body, and it is this portion of the -column only that is moveable. - -73. The two surfaces of the spinal column, the anterior and the -posterior, present a striking contrast (figs. XXXIV. and XXXV.). The -anterior surface, which in its whole extent is rounded and smooth, is -broad in the region of the neck, narrow in the region of the back, and -again broad in the region of the loins (fig. XLV. 2, 4.). It presents -three curvatures (fig. XLV. 2, 4); the convexity of that of the neck -being forwards, that of the back backwards, and that of the loins again -forwards (fig. XLV. 2, 4). - -74. From the posterior surface of the column, which is every where -irregular and rough, spring, along the median line, in regular series, -strong, sharp, and pointed projections of bone (fig. XXXV.), which -from being sharp and pointed, like elongated spines, are called -spinous processes, and have given name to the whole chain of bones. -These processes afford fixed points for the action of powerful -muscles. Extending the whole length of the column, from the base of -the skull to the sacrum, on each side of the spinous processes, are -deep excavations, which are filled up with the powerful muscles that -maintain the trunk of the body erect. - -75. From the lateral surfaces of the column likewise spring short but -strong projections of bone, termed transverse processes, which also -give attachment to powerful muscles (fig. XLVI.). - -[Illustration: Fig. XLV. - -Bones of the trunk. 1. Spinal column; 2. the seven cervical vertebræ; -3. the twelve dorsal vertebræ; 4. the five lumbar vertebræ; 5. the -sacrum; 6. the sternum; 7. the true ribs; 8. the false ribs; 9. the -clavicle; 10. the scapula; 11. the ilium; 12. the ischium; 13. the -pubes; 14. the acetabulum; 15. the brim of the pelvis.] - -76. The separate bones of the series have a kind of turning motion on -each other; hence each is called a vertebra, and the name of vertebral -column is often given to the entire series, as well as that of spinal -column. That portion of the column which forms the neck consists of -seven distinct bones, called cervical vertebræ (fig. XLV. 2); that -portion which forms the back consists of twelve, called dorsal vertebræ -(fig. XLV. 3); that portion which forms the loins consists of five, -called lumbar vertebræ (fig. XLV. 4). Between each of these classes of -vertebræ there are specific differences, but they need not be described -here: all that is necessary to the present purpose is an account of the -structure which is common to every vertebra. - -77. By inspecting fig. XLVI. 1, it will be seen that the upper and -under edges of each vertebra consist of a ring of bone, of a firm -and compact texture, rendering what may be called the body of the -vertebra exceedingly strong (fig. XLVI. 3). This ring of bone forms a -superficial depression (fig. XLVI. 2), for the reception of a peculiar -substance, immediately to be described, which is interposed between -each vertebra (fig. XLVII. 2). - -78. The anterior surface of the body of the vertebra is convex (fig. -XLVI. 3); its posterior surface is concave (fig. XLVI. 4); from the -posterior surface springs a bony arch (figs. XLVI. 5 and LIII. 1), -which, together with the posterior concavity, forms an aperture of -considerable magnitude (fig. XLVI. 6), a portion of the canal for the -passage of the spinal cord (figs. XLVII. 3, and XLIX. 3). - -[Illustration: Fig. XLVI. - -View of some of the vertebræ, which by their union form the spinal -column. - -_a._ A vertebra of the neck; _b._ a vertebra of the back; a vertebra of -the loins. - -1. Ring of compact bone forming, 3, the body of the vertebra; 2. -superficial depression for the reception of the intervertebral -cartilage; 3. anterior surface of the body of the vertebra; 4. -posterior surface; 5. bony arch; 6. opening for the passage of the -spinal cord; 7. opening for the passage of the spinal nerves; 8. -articulating processes by which the vertebræ are joined to each other; -9. two dorsal vertebræ united, showing the arrangement of, 10, the -spinous processes; 11. a portion of a rib articulated with the side of -the vertebra.] - -79. Both the upper and under edges of the arch form a notch (fig. XLVI. -7.), which, together with a corresponding notch in the contiguous -vertebra, completes another aperture rounder and smaller than the -former, but still of considerable size (fig. XLVI. 7.), the passage of -the spinal nerves (fig. XLVII. 3). - -80. From both the upper and under sides of the arch proceed two short -but strong projections of bone (fig. XLVI. 8.), termed the articulating -processes, because it is chiefly by these processes that the vertebræ -are connected together. From the beginning to the end of the series, -the two upper processes of the one vertebra are united with the two -lower processes of the vertebra immediately above it (fig. XLVI. 9), -and around the edges of all the articulating processes are visible -rough lines, which mark the places to which the articulating ligaments -are attached. - -81. No vertebra, except the first, rests immediately upon its -contiguous vertebra (fig. XLV. 2, 4). Each is separated from its fellow -by a substance of a peculiar nature interposed between them, termed the -intervertebral substance (figs. XLVII. 2, and L. 2). This substance -partakes partly of the nature of cartilage, and partly of that of -ligament. It is composed of concentric plates, formed of oblique fibres -which intersect each other in every direction. This substance, for -about a quarter of an inch from its circumference towards its centre, -is tough, strong, and unyielding; then it becomes softer, and is -manifestly elastic; and so it continues until it approaches the centre, -when it becomes pulpy, and is again inelastic. The exterior tough and -unyielding matter is for the firmness of the connexion of the several -vertebræ with each other; the interior softer and elastic matter is for -the easy play of the vertebræ upon each other; the one for security, -the other for pliancy. And the adjustment of the one to the other is -such as to combine these properties in a perfect, manner. The quantity -of the unyielding substance is not so great as to produce rigidity; -the quantity of the elastic substance is not so great as to occasion -insecurity. The firm union of its solid matter renders the entire -column strong; the aggregate elasticity of its softer substance renders -it springy. - -[Illustration: Fig. XLVII. - -1. One of the Lumbar vertebræ. 2. Intervertebral substance. 3. A -portion of the spinal cord in its canal.] - -82. The column is not constructed in such a manner as to admit of an -equal degree of motion in every part of it. Every thing is contrived -to give to that portion which belongs to the neck freedom of motion, -and, on the contrary, to render that portion which belongs to the back -comparatively fixed. In the neck the mechanism of the articulating -processes is such as to admit of an equal degree of sliding motion -forwards, backwards, and from side to side, together with a turning -motion of one bone upon another; at the same time, the intervertebral -substance between the several vertebræ is thick. In consequence of this -mechanism, we can touch the breast with the chin, the back with the -hind head, and the shoulders with the ear, while we can make the head -describe more than a semicircle. But, in the back, the articulating -processes are so connected as to prevent the possibility of any motion, -either forwards or backwards, or any turning of one vertebra upon -another, while the intervertebral substance is comparatively thin (fig. -XLV. 2, 4). That portion of the column which belongs to the back is -intended to afford a fixed support for the ribs, a support which is -indispensable to their action in the function of respiration. In the -loins, the articulating processes are so connected as to admit of a -considerable degree of motion in the horizontal direction, and from -side to side, and the intervertebral substance here progressively -increases in thickness to the point at which the upper portion of the -column is united to the sacrum (fig. XLV. 2, 4), where the degree of -motion is extensive. - -83. The canal for the spinal cord, formed partly by the concavity in -the posterior surface of the vertebra, and partly by the arch that -springs from it (fig. XLVI. 6.), is lined by a continuation of the -dense and strong membrane that constitutes the internal periosteum -of the cranium, the dura mater (fig. XLVIII. _c_), which, passing -out of the opening in the occipital bone, called the foramen magnum -(figs. XXXIX. 7, and XLIX. 3), affords a smooth covering to the canal -throughout its whole extent. - -[Illustration: Fig. XLVIII. - -_a._ The scalp, turned down. - -_b._ The cut edge of the bones of the skull. - -_c._ The external strong membrane of the brain (Dura Mater) suspended -by a hook. - -_d._ The left hemisphere of the brain, showing its convolutions. - -_e._ The superior edge of the right hemisphere. - -_f._ The fissure between the two hemispheres.] - - -[Illustration: Fig. XLIX. - -1. Hemispheres of the brain proper, or cerebrum; 2. hemispheres of the -smaller brain, or cerebellum; 3. spinal cord continuous with the brain, -and the spinal nerves proceeding from it on each side.] - -84. The spinal cord itself, continuous with the substance of the -brain, passes also out of the cranium through the foramen magnum into -the spinal canal (fig. XLIX. 3), enveloped in the delicate membranes -that cover it, and surrounded by the aqueous fluid contained between -those membranes. The size of the spinal canal, accurately adapted -to that of the spinal cord, which it lodges and protects, is of -considerable size, and of a triangular shape in its cervical portion -(fig. XLIX. 3), smaller and rounded in its dorsal portion (fig. XLIX. -3), and again large and triangular in its lumbar portion (fig. XLIX. 3). - -85. The spinal column performs several different, and apparently -incompatible, offices. - -First, it affords a support and buttress to other bones. It sustains -the head (fig. XXXIV. 1); it is a buttress to the ribs (fig. XLVI. 7); -through the sternum and ribs it is also a buttress to the superior, and -through the pelvis, to the lower, extremities (fig. XXXIV. 2, 3, 4). - -Secondly, it affords a support to powerful muscles, partly to those -that maintain the trunk of the body in the erect posture against the -force of gravitation, and partly to those that act upon the superior -and inferior extremities in the varied, energetic, and sometimes -long-continued movements they execute. - -Thirdly, it forms one of the boundaries of the great cavities that -contain the chief organs of the organic life. To the support and -protection of those organs it is specially adapted; hence the surface -in immediate contact with them is even and smooth; hence its different -curvatures, convexities, and concavities, have all reference to their -accommodation; hence in the neck it is convex (fig. XLV. 2), in order -to afford a firm support to the esophagus, the wind-pipe, the aorta, -and the great trunks of the venous system (fig. LX. 3, 4); in the back -it is concave, in order to enlarge the space for the dilatation of -the lung in the act of inspiration (figs. XLV. 3, and LX. 5); in the -loins it is convex, in order to sustain and fix the loose and floating -viscera of the abdomen (figs. XLV. 4, and LX. 6, 7, 8, 9); in the -pelvis it is concave, in order to enlarge the space for lodging the -numerous delicate and highly-important organs contained in that cavity -(fig. XLV. 5). - -Fourthly, it forms the osseous walls of a canal (figs. XLVI. 6, and -XLVII. 3) for the lodgment and protection of the soft and tender -substance of the spinal cord, one of the great central masses of the -nervous system, the seat of the animal life (fig. XLIX. 3). - -Fifthly, it affords in its osseous walls secure apertures for the -passage of the spinal nerves (figs. XLVI. 7, and XLIX. 3), by which -impressions are transmitted from the organs to the spinal cord and -brain, in the function of sensation; and from the spinal cord and brain -to the organs in the function of volition. - -86. For the due performance of these offices, it is indispensable that -it should be firm, rigid, strong, and yet to a certain extent readily -flexible in every direction. By what mechanism is it endowed with these -apparently incompatible properties? - -87. By means of the ring of compact bone, which forms so large a part -of its body (fig. XLVI. 1) it is rendered firm, rigid, and strong. By -means of its numerous separate pieces, exactly adjusted to each other, -and dove-tailed into one another, an increase of strength is gained, -such as it would not have been possible to communicate to a single -solid piece. By the same mechanism, some degree of flexibility is also -obtained; each separate bone yielding to some extent, which, though -slight in a single bone, becomes considerable in the twenty-four. - -88. But the flexibility required is much greater than could be -obtained by this expedient alone. A rigid and immoveable pile of bones, -in the position of the spinal column, on which all the other parts of -the body rest, and to which they are directly or indirectly attached, -would necessarily have rendered all its movements stiff and mechanical; -and every movement of every kind impossible, but in a given direction. -That the movements of the body may be easy, free, and varied; that it -may be possible to bring into play new and complex combinations of -motion at any instant, with the rapidity of the changes of thought, -at the command of the impulses of feeling, it is indispensable that -the spinal column be flexible in every direction, forwards, backwards, -and at the sides: it is equally indispensable that it be thus capable -of yielding, without injuring the spinal cord; without injuring the -spinal nerves; without injuring the thoracic and abdominal viscera; and -without injuring the muscles of the trunk and extremities. The degree -in which it possesses this power of flexibility, and the extent to -which, by the cultivation of it, it is sometimes actually brought, is -exemplified in the positions and contortions of the posture-master and -the tumbler. It is acquired by means of the intervertebral substance, -the compressible and elastic matter interposed between the several -vertebræ. So compressible is this substance, that the human body is -half an inch shorter in the evening than in the morning, having lost -by the exertions of the day so much of its stature; yet, so elastic is -this matter, that the stature lost during the day is regained by the -repose of the night. The weight of the body pressing in all directions -upon the spinal column; muscles, bones, cartilages, ligaments, -membranes, with all their vessels and all the fluids contained in -them; the weight of all these component parts of the head, trunk, and -extremities, pressing, without the cessation of an instant, during all -the hours of vigilance, upon the intervertebral substance, compresses -it; but this weight, being taken off during the night, by the recumbent -posture of the body, the intervertebral substance, in consequence of -its elasticity, regains its original bulk, and of course the spinal -column its original length. - -89. But the flexibility acquired through the combined properties of -compressibility and elasticity is exceedingly increased by the action -of the pulpy and inelastic matter in the centre of the intervertebral -substance; this matter serving as a pivot to the vertebræ, facilitating -their motion on each other. Its effect has been compared to that of -a bladder partly filled with water, placed between two trenchers; in -this case, the approximation of the circumference of the two trenchers -on one side, would instantly displace a portion of the water on that -side, which would occupy the increasing space on the other, with the -effect of facilitating the change, in every possible direction, of -the position of the two trenchers in relation to each other. To this -effect, however, it is indispensable that the matter immediately around -this central pivot should be, not like itself, rigid and unyielding, -but compressible and elastic. It is an interesting fact, that since -this illustration was suggested, it has been discovered that this -very arrangement is actually adopted in the animal body. In certain -animals, in the very centre of their intervertebral substance, there -has been actually found a bag of water, with a substance immediately -surrounding the bag, so exceedingly elastic, that when the bag is cut, -the fluid contained in it is projected to the height of several feet in -a perpendicular stream. - -90. But besides securing freedom and extent of motion, the -intervertebral substance serves still another purpose, which well -deserves attention. - -Firmness and strength are indispensable to the fundamental offices -performed by the column; and to endow it with these properties, we -have seen that the external concentric layers of the intervertebral -substance are exceedingly tough and that they are attached to the -bodies of the vertebræ, which are composed of dense and compact bone. -But than dense and compact bone, nothing can be conceived better -calculated to receive and transmit a shock or jar on the application -of any degree of force to the column. Yet such force must necessarily -be applied to it in every direction, from many points of the body, -during almost every moment of the day; and did it actually produce a -corresponding shock, the consequence would be fatal: the spinal cord -and brain would be inevitably killed; for the death of these tender and -delicate substances may be produced by a violent jar, although not a -particle of the substances themselves be touched. A blow on the head -may destroy life instantaneously, by what is termed concussion; that -is, by the communication of a shock to the brain through the bones of -the cranium. The brain is killed; but on careful examination of the -cerebral substance after death, not the slightest morbid appearance -can be detected: death is occasioned merely by the jar. A special -provision is made against this evil, in the structure of the bones -of the cranium, by the interposition between its two compact plates -of the spongy substance called diploë (fig. XLIII. 2); and this is -sufficient to prevent mischief in ordinary cases. A great degree of -violence applied directly to the head is not common: when it occurs -it is accidental: thousands of people pass through life without ever -having suffered from it on a single occasion: but every hour, in the -ordinary movements of the body, and much more in the violent movements -which it occasionally makes, a degree of force is applied to the spinal -column, and through it transmitted to the head, such as, did it produce -a proportionate shock, would inevitably and instantly destroy both -spinal cord and brain. The evil is obviated partly by the elastic, and -partly by the non elastic properties of the matter interposed between -the several layers of compact bone. By means of the elastic property -of this matter, the head rides upon the summit of the column as upon a -pliant spring, while the canal of the spinal cord remains secure and -uninvaded. By means of the soft and pulpy portion of this matter, the -vibrations excited in the compact bone are absorbed point by point as -they are produced: as many layers of this soft and pulpy substance, so -many points of absorption of the tremors excited in the compact bone; -so many barriers against the possibility of the transmission of a shock -to the delicate nervous substance. - -91. Alike admirable is the mechanism by which the separate pieces -of the column are joined together. If but one of the bones were to -slip off its corresponding bone, or to be displaced in any degree, -incurable paralysis, followed ultimately by death, or instantaneous -death, would happen; for pressure on the spinal cord in a certain part -of its course is incompatible with the power of voluntary motion, and -with the continuance of life for any protracted term; and in another -part of its course, with the maintenance of life beyond a few moments. -To prevent such consequences, so great is the strength, so perfect the -attachment, so unconquerable the resistance of that portion of the -intervertebral substance which surrounds the edge of the bodies of the -vertebræ, that it will allow the bone itself to give way rather than -yield. Yet such is the importance of security to this portion of the -frame, that it is not trusted to one expedient alone, adequate as that -might seem. Besides the intervertebral substance, there is another -distinct provision for the articulation of the bodies of the vertebræ. -Commencing at the second cervical vertebra, in its fore part, and -extending the whole length of the column to the sacrum, is a powerful -ligament, composed of numerous distinct longitudinal fibres (fig. L.), -which are particularly expanded over the intervals between the bones -occupied by the intervertebral substance (figs. L. 1, and LI. 2, 2). -This ligament is termed the _common anterior vertebral_, beneath which, -if it be raised from the intervertebral substance, may be seen small -_decussating_ fibres, passing from the lower edge of the vertebra -above, to the upper edge of the vertebra below (fig. L. 3), from which -circumstance these fibres are termed _crucial_. - -[Illustration: Fig. L. - -1. Common anterior ligament; 2. intervertebral substance. The anterior -ligament is removed to exhibit (3.) the crucial fibres passing over it.] - -[Illustration: Fig. LI. - -1. Portion of the occipital bone; 2. common anterior ligament.] - -92. Corresponding with the ligament on the anterior, is another on -the posterior part of the spine (fig. LII. 1), which takes its origin -from the foramen magnum (fig. LII. 1); descends from thence, within the -vertebral canal, on the posterior surface of the bodies of the vertebra -(fig. LII. 1), and extends to the sacrum. This ligament is termed the -_common posterior vertebral_, which, besides adding to the strength of -the union of the bodies of the vertebræ, prevents the column itself -from being bent too much forward. - -[Illustration: Fig. LII. - -1. Posterior vertebral ligament.] - -93. Moreover, the bony arches of the vertebræ (fig. LIII. 1) are -connected by means of a substance partly ligamentous, and partly -cartilaginous (fig. LIII. 2), which, while it is extremely elastic, is -capable of resisting an extraordinary degree of force. - -[Illustration: Fig. LIII. - -1. Arches of the vertebræ seen from within; 2. ligaments connecting -them.] - -94. And in the last place, the articular processes form so many -distinct joints, each being furnished with all the apparatus of a -moveable joint, and thus possessing the ordinary provision for the -articulation of bones, in addition to the whole of the foregoing -securities. - -95. "In the most extensive motion of which the spinal column is -capable, that of flexion, the common anterior ligament is relaxed; the -fore part of the intervertebral substance is compressed, and its back -part stretched; while the common posterior ligament is in a state of -extension. In the _extension_ of the column the state of the ligaments -is reversed; those which were extended being in their turn relaxed, -while the common anterior vertebral is now put upon the stretch. In the -_lateral inclination_ of the column, the intervertebral substance is -compressed on that side to which the body is bent. In the _rotatory_ -motion of the column, which is very limited in all the vertebræ, but -more particularly in the dorsal, in consequence of their attachment to -the ribs, the intervertebral substance is contorted, as are likewise -all the ligaments. All the motions of the column are capable of being -aided to a great extent by the motion of the pelvis upon the thighs." - -96. "The number and breadth of the attachments of these bones," -says an accomplished anatomist and surgeon,[4] "their firm union by -ligament, the strength of their muscles, the very inconsiderable -degree of motion which exists between any two of them, and lastly, the -obliquity of their articular processes, especially in the dorsal and -lumbar vertebræ, render dislocation of them, at least in those regions, -impossible without fracture; and I much doubt whether dislocation even -of the cervical vertebræ ever occurs without fracture, either through -their bodies or their articular processes. The effects of each of these -accidents would produce precisely the same injury to the spinal marrow, -and symptoms of greater or less importance, according to the part of -the spinal column that is injured. Death is the immediate consequence -if the injury be above the third cervical vertebra, the necessary -paralysis of the parts to which the phrenic and intercostal nerves -are distributed causing respiration instantly to cease. If the injury -be sustained below the fourth cervical vertebra, the diaphragm is -still capable of action, and dissolution is protracted. The symptoms, -in fact, are less violent in proportion as the injury to the spinal -marrow is further removed from the brain; but death is the inevitable -consequence, and that in every case at no very distant period." - -97. So the object of the construction of the spinal column being -to combine extent and freedom of motion with strength, and it being -necessary to the accomplishment of this object to build up the column -of separate pieces of bone, the connecting substances by which the -different bones are united are constituted and disposed in such a -manner as to prove absolutely stronger than the bones themselves. Such -is the structure of this important portion of the human body considered -as a piece of mere mechanism; but our conception of its beauty and -perfection would be most inadequate if we did not bear in mind, that -while the spinal column performs offices so varied and apparently so -incompatible, it forms an integrant portion of a living machine: it is -itself alive: every instant, blood-vessels, absorbents and nerves, are -nourishing, removing, renewing, and animating every part and particle -of it. - -98. The anterior boundary of the thorax is formed by the bone called -the sternum, or the breast-bone, which is broad and thick at its upper, -and thin and elongated at its lower extremity (figs. XLV. 6, and -LIV.), where it gives attachment to a cartilaginous appendix, which -being pointed and somewhat like a broadsword, is called the ensiform -cartilage. - -[Illustration: Fig. LIV. - -Anterior view of the sternum.] - -99. Its position is oblique, being near the vertebral column at the -top, and distant from it at the bottom (fig. XLV. 6). Its margins -are thick, and marked by seven depressions, for the reception of the -cartilages of the seven true ribs (fig. LIV). Its anterior surface is -immediately subjacent to the skin, and gives attachment to powerful -muscles, which act on the superior extremities: its posterior surface -is slightly hollowed in order to enlarge the cavity of the thorax (fig. -LV.). - -[Illustration: Fig. LV. - -Posterior view of the sternum.] - -100. The thorax is bounded at the sides by the ribs, which extend like -so many arches between the spinal column and the sternum (fig. XLV. 7, -8). They are in number twenty-four, twelve on each side, of which the -seven upper are united to the sternum by cartilage, and are called true -ribs (fig. XLV. 7); the cartilages of the remaining five are united -with each other and are not attached to the sternum; these are called -false ribs (fig. XLV. 8): all of them are connected behind to the -spinal column (fig. XXXV.). - -101. The ribs successively and considerably increase in length as far -as the seventh, by which the cavity they encompass is enlarged; from -the seventh they successively diminish in length, and the capacity of -the corresponding part of the cavity is lessened. The direction of the -ribs from above downwards is oblique (fig. XLV. 7, 8). Their external -or anterior surface is convex (fig. XLV. 7, 8); their internal or -posterior surface is concave: by the first their strength is increased; -by the second the general cavity of the thorax is enlarged (fig. XLV. -7, 8). Their upper margin is smooth and rounded, and gives attachment -to a double layer of muscles, called the intercostal, placed in the -intervals that separate the ribs from each other (fig. LIX.). Along -the lower margin is excavated a deep groove, for the lodgment and -protection of the intercostal vessels. - -102. The ribs are connected with the spinal column chiefly by what is -termed the _anterior ligament_ (fig. LVI. 1), which is attached to the -head of the rib (fig. LVI.), and which, dividing into three portions -(fig. LVI. 1), firmly unites every rib to two of the vertebræ, and -to the intervertebral substance (fig. LVI. 1). This articulation is -fortified by a second ligament (fig. LVI. 2), also attached to a head -of the rib, termed the _interarticular_ (fig. LVI. 2), and by three -others, one of which is attached on the fore part, and the two others -in the back part, to the neck of the rib (fig. LVII. 1). - -[Illustration: Fig. LVI. - -Ligaments connecting the ribs to the spinal column. 1. anterior -ligaments; 2. interarticular ligament; 3. ligaments of the necks of the -ribs.] - -The cartilages of the seven superior ribs are attached to the sternum -by a double layer of ligamentous fibres, termed the _anterior and the -posterior ligaments of the sternum_ (fig. LVIII.). So strong are the -bands which thus attach the ribs to the spinal column and the sternum, -that the ribs cannot be dislocated without fracture. "Such at least is -the case in experiments upon the dead body, where, though the rib be -subjected to the application of force by means of an instrument best -calculated to detach its head from the articulation, yet it is always -broken." - -[Illustration: Fig. LVII. - -1, &c. Ligaments connecting the ribs to the vertebræ behind.] - -While thus firmly attached to their points of support, the ligaments, -which fix them, are so disposed as to render the ribs capable of being -readily moved upwards and downwards: upwards in inspiration; downwards -in expiration; and it is by this alternate action that they enlarge and -diminish the cavity of the thorax in the function of respiration. - -[Illustration: Fig. LVIII. - -Ligaments joining the cartilages of the ribs to the sternum.] - -103. Such are the boundaries of the cavity of the thorax as far as -its walls are solid. The interspaces between these solid portions at -the sides are filled up by muscles, principally by those termed the -intercostal (fig. LIX.); below, the boundary is formed by the diaphragm -(fig. LXI. 2); while above, as has been already stated (69), the cavity -is so contracted as only to leave an opening for the passage of certain -parts to and from the chest. - -[Illustration: Fig. LIX. - -A view of the muscles called _Intercostals_, filling up the spaces -between the ribs.] - -104. The inner surface of the walls of the thorax, in its whole -extent, is lined by a serous membrane, exceedingly thin and delicate, -but still firm, called the pleura. The same membrane is reflected over -the organs of respiration contained in the cavity, so as to give them -an external coat. The membrane itself is every where continuous, and -every where the same, whether it line the containing or the contained -parts; but it receives a different name as it covers the one or the -other: that portion of it which lines the walls of the cavity being -called the costal pleura (fig. LXI. _a_), while that which covers the -organs contained in the cavity is termed the pulmonary pleura (fig. LX. -5, 1). - -105. A fold of each pleura passes directly across the central part -of the cavity of the thorax; extending from the spinal column to the -sternum, and dividing the general cavity into two. This portion of the -pleura is called the mediastinum, from its situation in the centre -of the thorax, and it so completely divides the thoracic cavity into -two, that the organs on one side of the chest have no communication -with those of the other; so that there may be extensive disease in one -cavity (for example, a large accumulation of water,) while the other -may be perfectly sound. - -106. The main organs contained in the cavity of the thorax are the -lungs with their air tube; the heart with its great vessels; and the -tube passing from the mouth to the stomach (fig. LX.). - -107. The two lungs occupy the sides of the chest (fig. LX. 5). They -are completely separated from each other by the membranous partition -just described, the mediastinum. Between the two folds of the -mediastinum, namely, in the middle of the chest, but inclining somewhat -to the left side, is placed the heart, enveloped in another serous -membrane, the pericardium (fig. LX. 2, 1). - -108. The lungs are moulded to the cavities they fill; whence their -figure is conical, the base of the cone being downwards, resting on the -diaphragm (fig. LX. 5, _b_); and the apex upwards, towards the neck -(fig. LX. 5). - -109. That surface of each lung which corresponds to the walls of the -chest is convex in its whole extent (fig. LX. 5); on the contrary, that -surface which corresponds to the mediastinum is flattened (fig. LX. -5). The basis of the lung is concave, adapted to the convexity of the -diaphragm on which it rests (fig. LX. 5). - -110. The air-vessel of the lungs, termed the bronchus, together with -the blood-vessels and nerves, enter the organ at its flattened side, -not exactly in the middle, but rather towards the upper and back part. -This portion is termed the root of the lung. - -111. The lungs are attached to the neck by the trachea (fig. LX. 4), -the continuation of which forms the bronchus; to the spinal column by -the pleura, and to the heart by the pulmonary vessels (fig. LX. 3, -_d_): their remaining portion is free and unattached. - -112. In the living body, the lungs on each side completely fill the -cavity of the chest, following passively the movements of its walls, -and accurately adapting themselves to its size, whether its capacity -enlarge in inspiration, or diminish in expiration, so that the external -surface of the lung (the pulmonary pleura) is always in immediate -contact with the lining membrane of the walls of the cavity (the costal -pleura); consequently, during life, there is no cavity, the chest being -always completely full. - -[Illustration: Fig. LX. - -_a._ The cut edges of the ribs, forming the lateral boundaries of the -cavity of the thorax. - -_b._ The diaphragm, forming the inferior boundary of the thorax, and -the division between the thorax and the abdomen. - -_c._ The cut edges of the abdominal muscles, turned aside, exposing the -general cavity of the abdomen. - -1. The cut edge of the pericardium turned aside. - -2. The heart. - -3. The great vessels in immediate connexion with the heart. - -4. The trachea, or wind-pipe. - -5. The lungs. - -6. The liver. - -7. The stomach. - -8. The large intestine. - -9. The small intestines. - -10. The urinary bladder.] - -113. The anterior surface of the pericardium, the bag which envelopes -the heart, lies immediately behind the sternum, and the cartilages of -the second, third, fourth, and fifth ribs, covered at its sides by the -pleura, and firmly attached below to the diaphragm (fig. LX. 1). - -114. Surrounded by its pericardium, within the mediastinum, the heart -is placed nearly in the centre of the chest, but its direction is -somewhat oblique, its apex being directly opposite to the interval -between the fifth and sixth ribs on the left side (fig. LX. 2); while -its basis is directed upwards, backwards, and towards the right (fig. -LX. 2). That portion of its surface which is presented to view on -opening the pericardium is convex (fig. LX. 2); but its opposite -surface, namely, that which rests upon the part of the pericardium -which is attached to the diaphragm, is flattened (fig. LX. 1). It is -fixed in its situation partly by the pericardium and partly by the -great vessels that go to and from it. But under the different states -of expiration and inspiration, it accompanies, in some degree, the -movements of the diaphragm; and in the varied postures of the body, -the heart deviates to a certain extent from the exact position here -described. - -115. The second division of the trunk, the _abdomen_, is bounded above -by the diaphragm (fig. LXI. 2), below by the pelvis (fig. LXI. 3), -behind and at the sides by the vertebræ and muscles of the loins (fig. -LXIII.), and before by the abdominal muscles (fig. LXIII. 9). - -116. The organ which forms the superior boundary of the abdomen, the -diaphragm (midriff), is a circular muscle, placed transversely across -the trunk, nearly at its centre (fig. LXI. 2). It forms a vaulted -partition between the thorax and the abdomen (fig. LXI. 2). All around -its border it is fleshy (fig. LXI. 2); towards its centre it is -tendinous (fig. LXI. 2); the surface towards the abdomen is concave -(fig. LXI. 2); that towards the thorax convex (fig. LXI. 2); while its -middle tendinous portion ascends into the thorax as high as the fourth -rib (fig. LXI. 2). - -[Illustration: Fig. LXI. - -View of the diaphragm. 1. Cavity of the thorax; 2. diaphragm separating -the cavity of the thorax from that of the abdomen; 3. cavity of the -pelvis.] - -117. The diaphragm is perforated by several apertures, for the -transmission of tubes and vessels, which pass reciprocally between the -thorax and abdomen (fig. LXII.). - -1. A separate aperture is formed to afford an exit from the thorax -of the aorta, the common source of the arteries (fig. LXII. 2), and -an entrance into the thorax of the thoracic duct, the tube that bears -the digested aliment to the heart. 2. A little to the left of the -former, there is another aperture, through which passes the esophagus -or gullet (fig. LXII. 3), the tube that conveys the food from the mouth -to the stomach. 3. On the right side, in the tendinous portion of the -diaphragm, very carefully constructed, is a third aperture for the -passage of the vena cava (fig. LXII. 4), the great vessel that returns -the blood to the heart from the lower parts of the body. - -[Illustration: Fig. LXII. - -View of the diaphragm with the tubes that pass through it. 1. Arch -of the diaphragm; 2. the trunk of the aorta passing from the chest -into the abdomen; 3. the esophagus passing from the chest through the -diaphragm to the stomach; 4. the vena cava, the great vein that returns -the blood to the heart from the lower parts of the body, passing from -the abdomen, into the chest, in its way to the right side of the heart; -5. 6. muscles that arise in the interior of the trunk and that act upon -the thigh; 5. the muscle called psoas; 6. the muscle called iliacus.] - -118. The partition formed by the diaphragm between the thorax and -abdomen, though complete, is moveable; for as the diaphragm descends in -inspiration and ascends in expiration, it proportionally enlarges or -diminishes the cavities between which it is placed; consequently, the -actual magnitude of these cavities varies every moment, and the size of -the one is always in the inverse ratio of that of the other. - -119. Between the abdomen and the pelvis there is no separation; one -cavity is directly continuous with the other (fig. LXI. 3); but along -the inner surface of the expanded bones, which form a part of the -lateral boundary of the abdomen, there is a prominent line, termed -the brim of the pelvis (fig. XLV. 15), marking the point at which the -abdomen is supposed to terminate and the pelvis to commence. - -120. Behind and at the sides the walls of the abdomen are completed -partly by the lumbar portion of the spinal column and partly by the -lumbar muscles (fig. XLV. 4), and before by the abdominal muscles (fig. -LXIII. 9). - -121. The inner surface of the walls of the abdomen is lined throughout -by a serous membrane, termed the peritoneum (fig. LXIII.). From the -walls of the abdomen, the peritoneum is reflected upon the organs -contained in the cavity, and is continued over them so as to form their -external coat. The peritoneum also descends between the several organs, -connecting them together, and holding them firmly in their situation; -and it likewise forms numerous folds, in which are embedded the vessels -and nerves that supply the organs. It secretes a serous fluid, by -which its own surface and that of the organs it covers is rendered -moist, polished, and glistening, and by means of which the organs -glide smoothly over it, and over one another in the various movements -of the body, and are in constant contact without growing together. In -structure, distribution, and function, the peritoneum is thus perfectly -analogous to the pleura. - -122. Like the thorax, the abdomen is always completely full. When -the diaphragm is in action, it contracts. When the diaphragm is -in the state of contraction, the abdominal and lumbar muscles are -in the state of relaxation. By the contraction of the diaphragm, -the organs contained in the abdomen are pushed downwards, and the -anterior and lateral walls of the cavity being at this moment in -a state of relaxation, they readily yield, and, consequently, the -viscera are protruded forwards and at the sides. But the abdominal -and lumbar muscles in their turn contract, the diaphragm relaxing; -and, consequently, the viscera, forced from the front and sides of the -abdomen, are pushed upwards, together with the diaphragm, into the -cavity of the thorax. A firm and uniform pressure is thus at all times -maintained upon the whole contents of the abdomen: there is an exact -adaptation of the containing to the contained parts, and of one organ -to another. No space intervenes either between the walls of the abdomen -and the organs they enclose, or between one organ and another: so that -the term cavity does not denote a void or empty space, but merely the -extent of the boundary within which the viscera are contained. - -123. The contents of the abdomen consist of the organs which belong to -the apparatus of digestion, and of those which belong to the apparatus -of excretion. - -124. The organs which belong to the apparatus of digestion are—1. The -stomach (fig. LXIII. 2) 2. The duodenum (fig. LXIII. 4). 3. The jejunum -(fig. LXIII. 5). 4. The ilium (fig. LXIII. 5). The three last organs -are called the small intestines, and their office is partly to carry on -the digestion of the aliment commenced in the stomach, and partly to -afford an extended surface for the absorption of the nutriment as it is -prepared from the aliment. 5. The pancreas (fig. LXIV. 5). 6. The liver -(fig. LXIV. 2). 7. The spleen (fig. LXIV. 4). The three last organs -truly belong to the apparatus of digestion, and their office is to -co-operate with the stomach and the small intestines in the conversion -of the aliment into nutriment. - -[Illustration: Fig. LXIII. - -1. Esophagus; 2. stomach; 3. liver raised, showing its under surface; -4. duodenum; 5. small intestines; 6. cæcum; 7. colon; 8. urinary -bladder; 9. gall bladder; 10. abdominal muscles divided and reflected.] - -125. The organs which belong to the apparatus of excretion are—1. The -large intestines consisting of the cæcum (fig. LXIII. 6). 2. The colon -(fig. LXIII. 7). 3. The rectum (fig. LXIV. 10). It is the office of -these organs, which are called the large intestines, to carry out of -the system that portion of the alimentary mass which is not converted -into nourishment. 4. The kidneys (fig. LXIV. 6), the organs which -separate in the form of the urine an excrementitious matter from the -blood, in order that it may be conveyed out of the system. - -[Illustration: Fig. LXIV. - -General view of the viscera of the abdomen. 1. Stomach raised; 2. under -surface of liver; 3. gall bladder; 4. spleen; 5. pancreas; 6. kidneys; -7. ureters; 8. urinary bladder; 9. portion of the intestine called -duodenum; 10. portion of the intestine called rectum; 11. the aorta.] - -126. The last division of the trunk, called the pelvis (fig. LXI. 3), -consists of a circle of large and firm bones, interposed between the -lower portion of the trunk and the inferior extremities (fig. XLV.). -The bones that compose the circle, distinct in the child, are firmly -united in the adult into a single piece; but as the original separation -between each remains manifest, they are always described as separate -bones. They are the sacrum (fig. XLV. 5), the coccyx (fig. XXXV.), the -ilium (fig. XLV. 11), the ischium (fig. XLV. 12), and the pubis (fig. -XLV. 13). - -127. The sacrum, placed like a wedge between the moveable portion -of the spinal column and the lower extremities, forms the posterior -boundary of the pelvis. The figure of this bone is triangular (fig. -XLV. 5); its anterior surface is concave and smooth, for enlarging the -cavity of the pelvis and sustaining the organs contained in it (fig. -XLV. 5); its posterior surface is convex, irregular, and rough (fig. -XXXV.), giving origin to the great muscles that form the contour of the -hip, and to the strong muscles of the back and loins that raise the -spine and maintain the trunk of the body erect. - -128. The base or upper part of the sacrum receives the last vertebra -of the loins on a large and broad surface (fig. XLV. 4), forming a -moveable joint; and the degree of motion at this point is greater than -it is at the higher points of the spinal column. Firmly united at its -sides with the haunch bones, it admits there of no degree of motion. - -129. The coccyx, so named from its resemblance to the beak of the -cuckoo, when elongated by a succession of additional bones, forms the -tail in quadrupeds; but in man it is turned inwards to support the -parts contained in the pelvis, and to contract the lower opening of -the cavity. By means of a layer of cartilage, the medium by which this -bone is connected with the sacrum, it forms a moveable articulation, -continuing moveable in men until the age of twenty-five, and in women -until the age of forty-five; continuing moveable in women thus long, in -order that by yielding to the force which tends to push it backwards -during the period of labour, it may enlarge the lower aperture of the -pelvis, and so facilitate the process of parturition and diminish its -suffering. - -130. The lateral boundaries of the pelvis are formed by the ilium, -the haunch bone (fig. XLV. 11), and by the ischium, the hip bone (fig. -XLV. 12). The ilium forms the lower part of the abdomen and the upper -part of the pelvis (fig. XLV. 11); its broad expanded wing supports the -contents of the abdomen, and gives attachment to the muscles that form -the anterior portion of its walls (figs. XLV. 11, and LXIII. 9); its -external convex surface sustains the powerful muscles that extend the -thigh; and along its internal surface is the prominent line which marks -the brim of the pelvis (fig. XLV. 15), and which divides this cavity -from that of the abdomen. - -131. The ischium or hip bone is the lower part of the pelvis (fig. -XLV. 12); at its undermost portion is a rounded prominence called -the tuberosity (fig. XLV. 12), in its natural condition covered with -cartilage, upon which is superimposed a cushion of fat. It is this part -on which the body is supported in a sitting posture. - -132. The pubis or share bone forms the upper and fore part of the -pelvis (fig. XLV. 13), and together with the two former bones, -completes the large and deep socket, termed the acetabulum (fig. XLV. -14), into which is received the head of the thigh-bone (fig. XXXIV. -4). The margin of the acetabulum and the greater part of its internal -surface is lined with cartilage, so that in its natural condition it is -much deeper than it appears to be when the bones alone remain. - -133. The lower aperture of the pelvis, which appears large when all -the soft parts are removed, is not really large, for in its natural -state it is filled up partly by muscles and partly by ligaments, which -sustain and protect the pelvic organs, leaving only just space enough -for the passage to and from those which have their opening on the -external surface. - -134. The cavity of the pelvis, together with all the organs contained -in it, are lined by a continuation of the membrane that invests the -abdomen and its contents. - -135. The organs contained in the pelvis are the rectum (fig. LXIV. 9), -which is merely the termination of the large intestines, the urinary -bladder (fig. LXIV. 8), and the internal part of the apparatus of -reproduction. - -136. The large and strong bones of the pelvis not only afford lodgment -and protection to the tender organs contained in its cavity, but -sustain the entire weight of the body, the trunk resting on the sacrum -as on a solid basis (fig. XLV. 5), and the lower extremities being -supported in the sockets in which the heads of the thigh-bones play, in -the varied movements of locomotion (fig. XXXIV. 4). - -137. The last division of the body comprehends the superior and the -inferior extremities. - -138. The superior extremities consist of the shoulder, arm, fore-arm, -and hand. - -139. The soft parts of the SHOULDER are composed chiefly of muscles; -its bones are two, the scapula or the _blade bone_, and the clavicle or -the _collar bone_ (fig. LXV. 2, 4). - -[Illustration: Fig. LXV. - -1. Sternum; 2. clavicle; 3. ribs; 4. anterior surface of scapula; 5. -coracoid process of scapula; 6. acromion process of scapula; 7. margin -of glenoid cavity of scapula; 8. body of the humerus or bone of the -arm; 9. head of the humerus.] - -140. The SCAPULA is placed upon the upper and back part of the thorax, -and occupies the space from the second to the seventh ribs (fig. LXV. 4) - -[Illustration: Fig. LXVI. - -1. Posterior surface of scapula; 2. margin of scapula; 3. acromion -process; 4. margin of glenoid cavity; 5. clavicle; 6. body of humerus; -7. head of humerus.] - -Unlike that of any other bone of the body, it is embedded in muscles, -without being attached to any bone of the trunk, excepting at a single -point. From the bones of the thorax it is separated by a double layer -of muscles, on which it is placed as upon a cushion, and over the -smooth surface of which it glides. Originally, like the bones of the -skull, it consisted of two tables of compact bone, with an intermediate -layer of spongy bony substance (diploë); but, by the pressure of the -muscles that act upon it, it gradually grows thinner and thinner, -until, as age advances, it becomes in some parts quite transparent and -as thin as a sheet of paper. - -141. The figure of the scapula is that of an irregular triangle (fig. -LXVI.). Its anterior surface is concave (fig. LXV. 4), corresponding to -the convexity of the ribs (fig. XLV. 7); its posterior surface is very -irregular (fig. LXVI. 1), being in some parts concave and in others -convex, giving origin especially to two large processes (figs. LXV. 5, -and LXVI. 3); one of which is termed the _acromion_ (fig. LXVI. 3), -and the other the _coracoid_ process of the scapula (fig. LXV. 5). The -margins of the bone, whatever the thinness of some portions of it, are -always comparatively thick and strong (fig. LXVI. 2), affording points -of origin or of insertion to powerful muscles. At what is called the -anterior angle of the bone there is a shallow oval depression covered -with cartilage and deepened by a cartilaginous margin, called the -_glenoid_ cavity of the scapula (figs. LXV. 7, and LXVI. 4), which -receives the head of the humerus or bone of the arm (figs. LXV. 9, and -LXVI. 7, 6). - -142. The clavicle, the second bone of the shoulder, is a long and -slender bone, of the form of an italic [Illustration], projecting -a little forwards towards its middle, so as to give a slight convexity -of outline to the top of the chest and the bottom of the neck (fig. -LXV. 2). It is attached by one extremity to the sternum (fig. LXV. 2) -and by the other to the scapula (fig. LXV. 2), by moveable joints. The -nature of an immoveable joint has been explained (63). In the connexion -of the bones of the trunk, while the main object is to secure firmness -of attachment, some degree of motion is at the same time obtained (81 -et seq.): but the mode in which the several bones of the extremities -are connected with each other and with the trunk, admits of so great a -degree of motion, that these articulations are pre-eminently entitled -to the name of moveable joints. The component parts of all moveable -joints are bone, cartilage, synovial membrane, and ligament. The great -character of a moveable joint is the approximation of two or more -bones; yet these bony surfaces are never in actual contact, but are -invariably separated from each other by cartilage. The cartilage either -covers the entire extent of the articulating surface of the bones, -as in the shoulder-joint, where both the head of the humerus and the -cavity of the scapula that receives it are enveloped in this substance -(fig. LXV. 7. 9), or a portion of it is placed between the articulating -surfaces of the bones, as in the joint between the clavicle and sternum -(fig. LXVII. _a_); which, when so placed, is termed an interarticular -cartilage (fig. LXVII. _a_). By its smooth surface cartilage lessens -friction; while by its elasticity it facilitates motion and prevents -concussion. Slightly organized cartilage is provided with comparatively -few blood-vessels and nerves. Had it been vascular and sensible like -the skin and the muscle, the force applied in the movements of the -joint would have stimulated the blood-vessels to inordinate action, and -the sensibility of the nerves would have been the source of constant -pain: every motion of every joint would have been productive of -suffering, and have laid the foundation of disease. The facility and -ease of motion obtained by the smoothness, elasticity, and comparative -insensibility of cartilage are still further promoted by the fluid -which lubricates it, termed synovia, secreted by a membrane called -synovial, which lines the internal surface of the joint, and which -bears a close resemblance to the serous (30). Synovia is a viscid -fluid of the consistence of albumen (5). It is to the joint what oil -is to the wheel, preventing abrasion and facilitating motion; but it -is formed by the joint itself, at the moment when needed, and in the -quantity required. The motion of the joint stimulates the synovial -membrane to secretion, and hence the greater the degree of motion, the -larger the quantity of lubricating fluid that is supplied. The several -parts of the apparatus of moveable joints are retained in their proper -position by ligamentous substance, which, as has been shown (96 and -97), is oftentimes so strong that it is easier to fracture the bone -than to tear the ligament, and in every case the kind and extent of -motion possessed by the joint are dependent mainly on the form of -the articulatory surfaces of the bones and on the disposition of the -ligaments. - -143. In the joint formed by the clavicle and the sternum (fig. LXVII. -_a_) an interarticular cartilage is placed between the two bones which -are united, first by a strong fibrous ligament, which envelops them -as in a capsule (fig. LXVII. 1); by a second ligament, which extends -from the cartilage of the first rib to the clavicle (fig. LXVII. 4), -by which the attachment of the clavicle to the sternum is materially -strengthened; and by a third ligament which passes transversely from -the head of one clavicle to that of the other (fig. LXVII. 3). The -joint thus formed, though so strong and firm that the dislocation of -it is exceedingly rare, yet admits of some degree of motion in every -direction, upwards, downwards, forwards, and backwards; and this -articulation is the sole point by which the scapula is connected with -the trunk, and consequently by which the upper extremity can act, or be -acted upon, by the rest of the body. - -[Illustration: Fig. LXVII. - -1. The fibrous capsule of the sternum and clavicle; 2. the same laid -open, showing _a_, the interarticular cartilage; 3. the ligament -connecting the two clavicles; 4. the ligament joining the clavicle to -the first rib; 5. ligaments passing down in front of the sternum.] - -144. The scapular extremity of the clavicle (fig. LXVIII. 6) is -attached to the processes of the scapula (fig. LXVIII. 4. 3) by several -ligaments of great strength (fig. LXVIII. 7, 8, 9). First by very -strong fasciculi which pass from the upper surface of the clavicle -to the acromion of the scapula (fig. LXVIII. 6); and secondly by two -ligaments which unite the clavicle with the coracoid process of the -scapula (fig. LXVIII. 8, 9). These ligaments are so powerful that they -resist a force capable of fracturing the clavicle; and they need to be -thus strong, for the clavicle is a shaft which sustains the scapula, -and through the scapula the whole of the upper extremity; and the main -object of the joint by which these bones are united, is to afford a -firm attachment of the scapula to its point of support. - -[Illustration: Fig. LXVIII. - -1. The clavicle; 2. the anterior part of the scapula; 3. the coracoid -process; 4. the acromion process; 5. the humerus; 6. ligaments binding -the scapular end of the clavicle to the acromion; 7. 8. 9. ligaments -passing from one process of the scapula to the other; 10. the fibrous -capsule of the shoulder-joint.] - -145. The clavicle serves the following uses: it sustains the upper -extremity; it connects the upper extremity with the thorax; it prevents -the upper extremity from falling forwards upon the thorax; and it -affords a fixed point for steadying the extremity in the performance of -its various actions. - -146. The glenoid cavity of the scapula (fig. LXV. 7) receives the head -of the humerus, the bone of the arm (fig. LXV. 9), and the two bones -being united by ligament form the shoulder-joint (fig. LXVIII.). This -joint is what is termed a ball and socket joint, the peculiarities -of which are two: first, beyond all others this mode of articulation -admits of free and extensive motion; in the present case, there is -the utmost freedom of motion in every direction, upwards, downwards, -backwards, and forwards. In the second place, this mode of articulation -admits of the motion of the limb without that of the body, or of the -motion of the body without that of the limb. When at rest, the arm may -be moved in almost any direction without disturbing the position of any -other part of the frame; the manifold advantages of which are obvious. -On the other hand, by careful management, very considerable variations -in the posture of the body may be effected without the communication -of any degree of motion to the limb; an unspeakable advantage when the -limb has sustained injury, or is suffering from disease. - -147. It does not seem possible to construct a joint of great strength, -capable, at the same time, of the degree of motion possessed by the -joint of the shoulder. So shallow is the socket of the scapula, and -so large the head of the humerus, that it seems as if the slightest -movement must dislodge it from its cavity (fig. LXVI. 4. 7). For -sustaining heavy weights or resisting a great amount of pressure, -applied to it suddenly and in various directions, the arm is obviously -unfitted. But this is not its office. The superior extremities are the -organs of apprehension—the instruments by which the mind executes -the commands of the will. They do not need the strength required by -the organs that sustain the weight of the body and that perform the -function of locomotion; but they do need freedom and extent of motion: -to this strength may be sacrificed, and so it is; yet what can be -done to combine strength with mobility is effected. Large and strong -processes of bone, proceeding as has been shown (141), from the convex -surface of the scapula (figs. LXV. and LXVI.), overhang, and to a -considerable extent surround, the head of the arm-bone, especially -resisting the force that would dislodge it from its socket and drive -it upwards, inwards, and backwards (fig. LXV.), the directions in -which force is most commonly applied to it. By these processes of bone -the joint is greatly strengthened, especially in those directions. -Moreover, a strong ligament, termed the fibrous capsule (fig. LXVIII. -10) envelops the joint. This ligament, arising from the neck of -the scapula (fig. LXVIII. 10), expands itself in such a manner as -completely to surround the head of the humerus (fig. LXVIII. 10); and -then again contracts in order to be inserted into the neck of the bone -(fig. LXVIII. 10). This ligament is strengthened by the tendons of no -less than four muscles which are expanded over it, as well as by the -powerful substance termed fascia which is reflected upon it from both -the processes and ligaments of the scapula. In addition to all these -expedients for fortifying the joint, it receives a further security -in the position of the scapula, which is loose and unattached; which -slides easily over the ribs upon its cushion of flesh; which thus -obtains, by its facility of yielding, some compensation for its want of -strength, eluding the force which it cannot resist. - -148. The arm consists of numerous and powerful muscles, and of a -single bone, the humerus, which belongs to the class of bones termed -cylindrical (185). - -149. The upper end of the humerus terminates in a circular head -(fig. LXV. 9), which is received into the socket of the scapula (fig. -LXV. 9. 7) termed, as has been stated (141), its glenoid cavity. The -middle portion of the bone, or what is termed its shaft (fig. LXV. 8), -diminishes considerably in magnitude, and becomes somewhat rounded -(fig. LXV. 8), while its lower end again enlarges, and is spread out -into a flattened surface of great extent (fig. LXIX. 1, 3, 2, 4). Of -this broad flattened surface, the middle portion is grooved (fig. LXIX. -2): it is covered with cartilage; it forms the articulating surface -by which the arm is connected with the fore-arm. On each side of this -groove there is a projection of bone or tubercle, termed condyle (fig. -LXIX. 3, 4), the inner (fig. LXIX. 3) being much larger than the outer -(fig. LXIX. 4). The inner condyle gives origin to the muscles that -bend, the outer to those that extend the fore-arm and the fingers -(figs. LXXXIV. 1, 2, and LXXXV. 1). - -[Illustration: Fig. LXIX. - -1. Lower extremity of the humerus; 2. grooved surface; 3. internal -condyle; 4. external condyle; 5. the upper part of the ulna; 6. the -head; 7. the neck; 8. the tubercle of the radius.] - -150. The muscles that act upon the arm arise from the back (fig. -LXXII. 2), the chest (fig. LXXI. 1), the clavicle (fig. LXXI. 1), and -the scapula (fig. LXXI. 3); and they move the arm with freedom and -power upwards, downwards, forwards, backwards, inwards, and outwards. -The chief muscle that raises the arm is the deltoid (fig. LXXI. 3), -which arises partly from the clavicle and partly from the scapula -(fig. LXXI. 3). It has the appearance of three muscles proceeding in -different directions, the different portions being separated by slight -fissures (figs. LXXI. 3, and LXXII. 3). The fibres converging unite -and form a powerful muscle which covers the joint of the humerus (fig. -LXXI. 3). It is implanted by a short and strong tendon into the middle -of the humerus (fig. LXXI. 4). Its manifest action is to pull the arm -directly upwards. Its action is assisted by the muscles that cover -the back of the scapula, which are in like manner inserted into the -humerus, and which, at the same time that they elevate the arm, support -it when raised. - -[Illustration: Fig. LXXI. - -View of the muscles on the fore part of the chest that act upon the -arm. 1. The muscle called the great pectoral; 2. the small pectoral; 3. -the deltoid; 4. the humerus.] - -151. The principal muscle that carries the arm downwards is the -latissimus dorsi (fig. LXXII. 2), the broadest muscle of the body, -which, after having covered all the lower part of the back and loins, -terminates in a thin but strong tendon which stretches to the arm, and -is implanted into the humerus (fig. LXXII. 2), near the tendon of a -muscle immediately to be described,—the great pectoral. When the arm -is raised by the deltoid and its assistant muscles, the latissimus -dorsi carries it downwards with force, and its powerful action is -increased by that of other muscles which arise from the scapula and are -inserted into the arm. - -152. The principal muscle that carries the arm forwards towards the -chest, is the great pectoral (fig. LXXI. 1), which, arising partly from -the clavicle (fig. LXXI. 1), partly from the sternum (fig. LXXI. 1), -and partly from the cartilages of the second, third, fourth, fifth, and -sixth ribs (fig. LXXI. 1), covers the greater part of the breast (fig. -LXXI. 1). Its fibres, converging, terminate in a strong tendon, which -is inserted near the tendon of the longissimus dorsi into the humerus, -about four inches below its head (fig. LXXI. 1). These two muscles form -the axilla or armpit, the anterior border of the axilla consisting of -the pectoral muscle. Though each of these muscles has its own peculiar -office, yet they often act in concert, thereby greatly increasing their -power, and the result of their combined action is to carry the arm -either directly downwards or to the side of the chest. - -[Illustration: Fig. LXXII. - -View of the muscles seated on the back part of the trunk that act -upon the shoulder and arm. 1. The muscle called the trapezius; 2. the -latissimus dorsi; 3. the deltoid.] - -153. Some of the muscles that elevate the arm carry it inwards, and -others outwards; the muscles that carry it forwards likewise carry it -inwards; while of the muscles that pull it downwards, some direct it -forwards and inwards, and others backwards and outwards (151 and 152). - -154. It has been already stated that the shoulder-joint is completely -surrounded by the muscular fibres or the tendinous expansions of -several of these powerful muscles, which have a far greater effect in -maintaining the head of the humerus in its socket than the fibrous -capsule of the joint; the latter being necessarily loose, in order -to allow of the extended and varied motions of the arm, whereas the -muscles that encompass the joint adhere closely and firmly to it. -Moreover, by virtue of their vital power these muscles act with an -efficiency which a mere ligamentous band is incapable of exerting; for -they apportion the strength of resistance to the separating force, and -react with an energy proportioned to the violence applied. - -155. The bones of the fore-arm are two, the ulna and the radius (figs. -LXIX. and LXXIII.). The ulna is essentially the bone of the elbow -(figs. LXIX. 5, and LXXIII. 3); the radius that of the hand (fig. -LXXV.). Supposing the arm to hang by the side of the body, and the palm -of the hand to be turned forwards, the ulna, in apposition with the -little finger, occupies the inner; and the radius, in apposition with -the thumb, occupies the outer part of the fore-arm (fig. XXXIV. 3). - -[Illustration: Fig. LXXIII. - - 1. The internal condyle of the humerus; 2. the external - condyle of the humerus; 3. the olecranon process of the ulna; - 4. the head of the radius.] - -156. The upper end of the ulna belonging to the elbow is large (figs. -LXIX. 5, and LXXIII. 3). It sends backwards the large projection -commonly named the elbow or _olecranon_ (fig. LXXII. 3), in the centre -of which there is a smooth and somewhat triangular surface (fig. -LXXIII. 3) which is always covered by skin of a coarse texture, like -that placed over the lower part of the knee-pan, as if nature intended -this for a part on which we may occasionally lean and rest. Large at -the elbow, the ulna gradually grows smaller and smaller as it descends -towards the wrist, where it ends in a small round head (fig. LXXXII. -2), beyond which, on the inner side, or that corresponding to the -little finger, it projects downwards a small rounded point, termed -the styloid process (fig. LXXXII. 3). As the styloid process and the -olecranon, the two extremities of the ulna (figs. LXXIII. 3, and -LXXII. 3), are easily and distinctly felt, the length of this bone was -primitively used as a measure, called a cubit, which was the ancient -name of the bone. - -157. The radius, the second bone of the fore-arm, placed along its -outer part next the thumb, is small at its upper end (figs. LXIX. 6, -and LXXIII. 4); but its body is larger than that of the ulna; while its -lower end, next the wrist to which it properly belongs, is very bulky -(fig. LXXXII. 1). Its upper end is formed into a small circular head, -which is united by distinct joints both to the humerus and to the ulna -(fig. LXIX. 6). The top of its rounded head is excavated into a shallow -cup (figs. LXIX. 6, and LXXIII. 4) which receives a corresponding -convexity of the humerus (fig. LXIX. 2), and its lower extremity is -excavated into an oblong cavity, which receives two of the bones of the -wrist (fig. LXXXIII. 1. 4). - -158. The joint of the elbow is composed above of the condyles of the -humerus (fig. LXIX. 3. 2), and below by the heads of the ulna and -radius (fig. LXIX. 5. 6). - -159. The upper surface of the ulna is so accurately adapted to the -lower surface of the humerus that the one seems to be moulded on -the other (figs. LXIX. 5, and LXXIII. 3), and the form of these -corresponding surfaces, which are everywhere covered with cartilage, -is such as to admit of free motion backwards and forwards, that is, -of extension and flexion; but to prevent any degree of motion in any -other direction. The joint is therefore a hinge-joint, of which the two -motions of flexion and extension are the proper motions. This hinge is -formed on the part of the humerus by a grooved surface, with lateral -projections (fig. LXIX. 2, 3, 4), and on the part of the ulna by a -middle projection with lateral depressions (fig. LXIX. 5): the middle -projection of the ulna turning readily on the grooved surface of the -humerus (fig. LXIX. 2). - -160. The bones are held in their proper situation, first, by a -ligament on the fore part of the arm, called the anterior (fig. LXXIV. -6), which arises from the lower extremity of the humerus, and is -inserted into the upper part of the ulna and the coronary ligament of -the radius (fig. LXXIV. 6. 8); secondly, by another ligament on the -back part of the arm, called the posterior ligament (fig. LXXV. 8), -placed in the cavity of the humerus that receives the olecranon of the -ulna (fig. LXXV. 8); and thirdly, by two other ligaments at the sides -of the ulna (fig. LXXV. 6, 7). The ulna and radius are united, first, -by a ligament called the coronary, which, arising from the ulna, passes -completely around the head of the radius (fig. LXXVI. 3), and the -attachment of which, while sufficiently close to prevent the separation -of the two bones, is yet not adherent to the radius, for a reason -immediately to be assigned; secondly, by another ligament which passes -in an oblique direction from one bone to the other (fig. LXXVI. 4); -and thirdly, by a dense and broad ligament, termed the _interosseous_ -(figs. LXXIV. 10, and LXXVI. 5), which fills up the space between the -two bones nearly in their whole extent. This ligament serves other -offices besides that of forming a bond of union, affording, more -especially, a greater extent of surface for the attachment of muscles, -and separating the muscles on the anterior from those on the posterior -part of the limb. - -[Illustration: Fig. LXXIV. - - Anterior view of the ligaments of the elbow-joint. 1. The - lower portion of the humerus; 2. the upper portion of the - radius; 3. the upper portion of the ulna; 4. the internal - condyle; 5. the external condyle; 6. the anterior ligament; - 7. portion of the internal lateral ligament; 8. portion of - the coronary ligament; 9. the oblique ligament; 10. upper - portion of the interosseous ligament.] - -[Illustration: Fig. LXXV. - - Posterior view of the ligaments of the elbow-joint. 1. Lower - end of the humerus; 2. internal condyle; 3. external condyle; - 4. the olecranon process of the ulna; 5. the upper portion of - the radius; 6. the internal lateral ligament; 7. the external - lateral ligament; 8. the posterior ligament.] - -[Illustration: Fig. LXXVI. - -View of the ligaments connecting the ulna and radius at their upper -part. 1. The radius; 2. the ulna; 3. the coronary ligament surrounding -the head of the radius; 4. the oblique ligament passing from the ulna -to the tubercle of the radius; 5 the upper portion of the interosseous -ligament.] - -161. At their inferior extremities the ulna and radius are united -partly by the interosseous ligament (fig. LXXVII. 1) and partly by -ligamentous fibres which pass transversely from one bone to the other -(fig. LXXVII. 2) on the anterior and the posterior surface of the -fore-arm. - -[Illustration: Fig. LXXVII. - -1. Interosseous ligament; 2. transverse fibres passing between the -radius and ulna, and uniting the two bones; 3. 4. 5. posterior and -lateral ligaments of the wrist joint; 6. ligaments uniting the bones of -the wrist with one another; 7. 8. ligaments which attach the metacarpal -to the carpal bones; 9. transverse ligaments for the attachment of the -phalanges of the fingers; 10. lateral ligaments for the attachment of -the phalanges of the fingers 11. ligaments of the thumb.] - -162. The lower extremity of the radius is also united to the wrist; -and the hand being attached to the wrist, the junction of the hand and -the fore-arm is effected by the articulation of the wrist with the -radius (fig. LXXVII.). The ligaments which connect the bones of the -wrist with the radius are bands of exceeding strength (fig. LXXVII. 3). - -163. The muscles that act upon the fore-arm are placed upon the arm -(fig. LXXVIII.). The joint of the elbow being a hinge-joint, the -fore-arm can admit only of two motions, namely, flexion and extension. -The muscles by which these motions are effected are four, two for each; -the two flexors being placed on the fore part (fig. LXXVIII. 2. 4), and -the two extensors on the back part of the arm (fig. LXXIX. 5). - -164. The two flexor muscles of the fore-arm are termed the biceps and -the brachialis (fig. LXXVIII. 2, 4). The biceps is so called because -it has two distinct heads or points of origin (fig. LXXVIII. 2), both -of which arise from the scapula (fig. LXXVIII. 2). About a third part -down the humerus the two heads meet, unite and form a bulky muscle -(fig. LXXVIII. 2), which, when it contracts, may be felt like a firm -ball on the fore part of the arm, the upper part of the ball marking -the point of union of the two heads (fig. LXXVIII. 2). The muscle -gradually becoming smaller, at length terminates in a rounded tendon -(fig. LXXVIII. 3), which is implanted into the tubercle of the radius -a little below its neck (fig. LXXVIII. 3). It is an exceedingly thick -and powerful muscle, and its manifest action is to bend the fore-arm -with great strength. But since its tendon is inserted into the radius, -besides bending the fore-arm, it assists other muscles that also act -upon the radius in the performance of a function to be described -immediately (168). - -[Illustration: Fig. LXXVIII. - -View of the flexor muscles of the fore-arm. 1. The anterior surface -of the scapula; 2. the muscle called biceps; 3. tendon of the biceps -passing to the tubercle of the radius; 4. the muscle called brachialis.] - -165. The second flexor of the fore-arm, termed the brachialis, is -placed immediately under the biceps, and is concealed by it for a -considerable part of its course (fig. LXXVIII. 4). Arising from the -humerus, on each side of the insertion of the deltoid, it continues its -attachment to the bone all the way down the fore part of the humerus, -to within inch of the joint; it then passes over the joint, adhering -firmly to the anterior ligament (fig. LXXVIII. 4), and is inserted by a -strong tendon into the ulna (fig. LXXVIII. 4). It is a thick and fleshy -muscle, powerfully assisting the action of the biceps. - -166. The two extensor muscles are named the triceps and the anconeous -(fig. LXXIX.). The triceps, seated on the back part of the arm, derives -its name from having three distinct points of origin, or three separate -heads (fig. LXXIX. 5); one of which arises from the scapula and two -from the humerus (fig. LXXIX. 5). All these heads adhere firmly to the -humerus, as the brachialis does on the fore part of the arm, down to -within an inch of the joint (fig. LXXIX. 5), where they form a strong -tendon, which is implanted into the olecranon of the ulna (fig. LXXIX. -3); the projection of which affords a lever for increasing the action -of the muscle. In all animals that leap and bound, this process of the -ulna is increased in length in proportion to their power of performing -these movements. The triceps forms an exceedingly thick and strong -muscle, which envelops the whole of the back part of the arm (fig. -LXXIX.); its action is simple and obvious; it powerfully extends the -fore-arm. The anconeous, a small muscle of a triangular form, arising -from the external condyle of the humerus, and inserted into the ulna a -little below the olecranon, assists the action of the triceps. - -[Illustration: Fig. LXXIX. - -View of the extensor muscles of the fore-arm. 1. The scapula; 2. the -upper part of the humerus; 3. upper end of the ulna; 4. upper end -of the radius; 5. the muscle called _triceps_, the extensor of the -fore-arm.] - -167. Such are the motive powers which act upon the fore-arm, and -which produce all the motions of which the hinge-joint of the elbow -renders it capable. But besides flexion and extension, the fore-arm is -capable of the motion of rotation, which is accomplished by means of -the radius. It has been shown (157) that the top of the rounded head of -the radius is excavated into a shallow cup (figs. LXIX. 6, and LXXIII. -4) which receives a corresponding convexity of the humerus (figs. -LXIX. 2, and LXXIII. 2). In consequence of this articulation with the -humerus, the radius, like the ulna, can move backwards and forwards -in flexion and extension, the proper movements of the hinge-joint; -but that portion of the margin of the hinge of the radius which is in -apposition with the ulna is convex (fig. LXIX. 6), and is received into -a semilunar cavity hollowed out in the ulna (fig. LXIX. 5). In this -cavity the rounded head of the radius revolves, the two bones being -held together by the ligament already described (160), which surrounds -the head of the radius (fig. LXXVI. 3), and which holds it firmly -without being adherent to it, and without impeding in any degree the -rotatory motion of the radius. Below, the surface of the radius next -the ulna is hollowed out into a semilunar cavity (fig. LXXXII. 1), -which receives a corresponding convex surface of the ulna (fig. LXXXII. -2), upon which convex surface the radius rolls (fig. LXXXII. 1). Thus, -by the mode in which it is articulated with the ulna above, the radius -turns upon its own axis. By the mode in which it is articulated with -the ulna below, the radius revolves upon the head of the ulna; and, in -consequence of both articulations, is capable of performing the motion -of rotation. Moreover, the hand being attached to the radius through -the medium of the wrist (figs. LXXXII. 1. 4. and LXXXIII. 1. 4) must -necessarily follow every movement of the radius; the rotation of which -brings the hand into two opposite positions. In the one, the palm of -the hand is directed upwards (fig. LXXXII.); in the other, it is turned -downwards (fig. LXXXIII.). When the hand is turned upwards, it is said -to be in the state of _supination_ (fig. LXXXII.); when downwards, in -that of _pronation_ (fig. LXXXIII.). A distinct apparatus of muscles -is provided for effecting the rotation of the radius, in order to -bring the hand into these opposite states: one set for producing its -supination, and another its pronation. - -168. The principal supinators arise from the external condyle of the -humerus (fig. LXXX.), and are called long and short (fig. LXXX. 4, 5). -The long supinator extends as far as the lower end of the radius, into -which it is inserted (fig. LXXX. 4): the short supinator surrounds the -upper part of the radius, and is attached to it in this situation (fig. -LXXX. 5.). Moreover, the triceps, being inserted into the radius (164), -often cooperates with the supinators and powerfully assists their -action. - -169. The principal pronators are also two, called the round and the -square (figs. LXXXI. and LXXXVI. 1). The round pronator arises from the -internal condyle, and passing downwards, is inserted into the middle -of the radius (fig. LXXXI. 4); the square pronator is a small muscle -between the radius and ulna, at their lower extremities being attached -to each (fig. LXXXVI. 1). - -[Illustration: Fig. LXXX. - -View of the supinators of the radius and hand. 1. The humerus; 2. the -ulna; 3. the radius; 4. the muscle called the long supinator passing to -be inserted into the lower portion of the radius; 5. the muscle, called -the short supinator, surrounding the upper part of the radius.] - -170. The action of these muscles in producing the rotation of the -radius, and so rendering the hand supine or prone, is sufficiently -manifest from the mere inspection of the diagrams (fig. LXXXI. 4). - -[Illustration: Fig. LXXXI. - -View of the pronators of the hand. 1. Lower end of the humerus; 2. the -radius; 3. the ulna; 4. the muscle called the round _pronator_, one of -the powerful pronators of the hand.] - -171. The hand is composed of the carpus, metacarpus, and fingers. - -172. The carpus (fig. LXXXII. 4) consists of eight small wedge-shaped -bones, placed in a double row, each row containing an equal number, and -the whole disposed like stones in an arch (fig. LXXXII. 4). They do in -fact form an arch, the convexity of which is upwards, on the dorsal -surface (fig. LXXXIII. 4); and the concavity downwards, on the palmar -surface (fig. LXXXII. 4). But they differ from the stones of an arch -in this, that each bone is joined to its fellow by a distinct moveable -joint, each being covered with a smooth articulating cartilage. At the -same time all of them are tied together by ligaments of prodigious -strength, which cross each other in every direction (fig. LXXVII. 6), -so that the several separate joints are consolidated into one great -joint. The consequence of this mechanism is that some degree of motion -is capable of taking place between the several bones, which, when -multiplied together, gives to the two rows of bones such an extent of -motion, that when the wrist is bent the arch of the carpus forms a kind -of knuckle. By this construction a facility and ease of motion, and -a power of accommodation to motion and force, are obtained, such as -belong to no arch contrived by human ingenuity. - -[Illustration: Fig. LXXXII. - -1. Lower extremity of the radius; 2. lower extremity of the ulna; -3. styloid process of the ulna; 4. bones of the carpus or wrist; -5. metacarpal bones; 6. first phalanges of the fingers; 7. second -phalanges of the fingers; 8. third phalanges of the fingers.] - -173. The metacarpus (fig. LXXXII. 5), the middle portion of the hand, -interposed between the wrist and the fingers, is composed of five -bones, which are placed parallel to each other (fig. LXXXII. 5). They -are convex outwardly, forming the back (fig. LXXXIII. 5), and concave -inwardly, forming the hollow of the hand (fig. LXXXII. 5). They are -large at each end, to form the joints by which they are connected with -the wrist and fingers (figs. LXXXII. and LXXXIII.): they are small in -the middle, in order to afford room for the lodgment and arrangement -of the muscles, that move the fingers from side to side (fig. LXXXVI. -2). Their ends, which are joined to the carpus, are connected by nearly -plane surfaces (figs. LXXXII. and LXXXIII.): their ends, which support -the fingers, are formed into rounded heads, which are received into -corresponding cup-shaped cavities, excavated in the top of the first -bones of the fingers (fig. LXXXII. 5.). The powerful ligaments that -unite these bones pass, both on the dorsal and the palmar surface, from -the inferior extremity of the second row of the carpal to the bases of -the metacarpal bones (fig. LXXVII, 7, 8). The ligaments are arranged in -such a manner as to limit the motions of the joints chiefly to those -of flexion and extension, allowing, however, a slight degree of motion -from side to side. - -174. Each of the fingers is composed of three separate pieces of bone, -called phalanges; the thumb has only two (fig. LXXXII. 6, 7, 8): the -phalanges are convex outwardly (fig. LXXXII. 6, 7, 8) for increasing -their strength, and flattened inwardly (fig. LXXXIII. 6, 7, 8) for -the convenience of grasping. The last bones of the fingers, which are -small, terminate at their under ends, in a somewhat rounded and rough -surface (fig. LXXXIII. 8), on which rests the vascular, pulpy, and -nervous substance, constituting the special organ of touch, placed at -the points of the fingers, and guarded on the upper surface by the nail -(fig. LXXXII. 8). - -[Illustration: Fig. LXXXIII. - -1. Lower extremity of the radius; 2. lower extremity of the ulna; 3. -styloid process of the ulna; 4. bones of the carpus; 5. metacarpal -bones; 6. 7. 8. first, second, and third phalanges of the fingers.] - -175. The round inferior extremity of the metacarpus is admitted into -the cavity of the superior extremity of the first phalanx of the five -fingers (figs. LXXXII. and LXXXIII.), and their joints are connected by -lateral and transverse ligaments of great strength (fig. LXXVII. 9). -The situation and direction of the ligaments which unite the several -phalanges of the fingers (fig. LXXVII. 9) are precisely the same as -those of the articulation of the phalanges with the metacarpus (fig. -LXXVII. 7, 8); and the articulation of these bones with one another is -such as to admit only of the motions of flexion and extension. - -176. The muscles which perform these motions are seated for the most -part on the fore-arm. Independently of the supinators and pronators -which have been already described (167 et seq.), there are distinct -sets of muscles for bending and extending the wrist and the fingers. -The flexors arise from the internal, and the extensors from the -external, condyle of the humerus (fig. LXIX. 3, 4). The internal -condyle is larger and longer than the external (fig. LXIX. 3, 4); for -the flexors require a larger point of origin and a longer fulcrum -than the extensor muscles; because to the actions of flexion, such as -grasping, bending, pulling, more power is necessary than to the action -of extension, which consists merely in the unfolding or the opening of -the hand previously to the renewal of the grasp. - -177. For the same reason, two muscles are provided for flexing, -while only one is provided for extending the fingers. The flexors, -bulky, thick, and strong, are placed on the fore part of the fore-arm -(fig. LXXXIV.). The first, named the superficial flexor (fig. LXXXIV. -1), about the middle of the arm, divides into four fleshy portions, -each of which ends in a slender tendon (fig. LXXXIV. 1). As these -tendons approach the fingers they expand (fig. LXXXIV. 1), and when -in apposition with the first phalanx, split and form distinct sheaths -for the reception of the tendons of the second flexor (fig. LXXXIV. -3). After completing the sheath, the tendons proceed forward along the -second phalanx, into the fore part of which they are implanted, and -the chief office of this powerful muscle is to bend the second joint -of the fingers upon the first, and the first upon the metacarpal bone. -Its action is assisted by a second muscle, called the deep or profound -flexor (fig. LXXXIV. 2), because it lies beneath the former; or the -perforans, because it pierces it. Bulky and fleshy, this second flexor, -like the first, about the middle of the arm, divides into four tendons, -which, entering the sheaths prepared for them in the former muscle -(where the tendons are small and rounded for their easy transmission -and play), pass to the root of the third phalanx of the fingers into -which they are implanted (fig. LXXXIV. 3). - -[Illustration: Fig. LXXXIV. - -View of the flexor muscles of the fingers. 1. The superficial flexor, -divided and turned aside, to show, 2. the deep flexor; 3. sheaths for -the tendons of the deep flexor, formed by the splitting of the tendons -of the superficial flexor; 4. the anterior annular ligament, divided -and turned aside.] - -118. The muscle that extends the fingers, called the common extensor, -is placed on the back part of the fore-arm (fig. LXXXV.), about the -middle of which it divides into four portions which terminate in -so many tendons (fig. LXXXV. 2). When they reach the back of the -metacarpal bones, these tendons become broad and flat, and send -tendinous expansions to each other, forming a strong tendinous sheath -which surrounds the back of the fingers (fig. LXXXV. 2). These -tendinous expansions are inserted into the posterior part of the bones -of the four fingers (fig. LXXXV. 2); and their office is powerfully to -extend all the joints of all the fingers (fig. LXXXV. 2). - -179. On both the palmar and dorsal regions of the wrist are placed -ligaments for tying down these tendons, and preventing them from -starting from their situation during the action of the muscles (figs. -LXXXIV. and LXXXV.). On the palmar region an exceedingly strong -ligament passes anteriorly to the concave arch of the carpus (fig. -LXXXIV. 4) for the purpose of tying down the tendons of the flexor -muscles. On the dorsal surface (fig. LXXXV.), a similar ligament, -passing in an oblique direction from the styloid process of the radius -to the styloid process of the ulna (fig. LXXXV. 3), performs the same -office in tying down the tendons of the extensor muscle. Both these -ligaments are called annular. - -[Illustration: Fig. LXXXV. - -View of the extensor muscles of the fingers. 1. The common extensor, -sending (2 2 2 2) tendons to each finger; 3. the posterior annular -ligament.] - -180. In the palm of the hand are placed additional muscles which -assist the flexors of the fingers (fig. LXXXVI. 2), being chiefly -useful in enabling the fingers to perform with strength and precision -short and quick motions. There are especially four small and rounded -muscles (fig. LXXXVI. 2), resembling the earth worm in form and size, -and hence called lumbricales; but as their chief use is to assist the -fingers in executing short and rapid motions, they have also received -the better name of the musculi fidicinales. - -[Illustration: Fig. LXXXVI. - -1. The muscle called the square pronator; 2. muscles seated in the palm -of the hand, by which, chiefly, the fingers execute short and rapid -motions.] - -181. The thumb, in consequence of the comparative looseness of its -ligaments, is capable of a much greater extent of motion than the -fingers, and can be applied to any part of each of the fingers, to -different parts of the hand, and in direct opposition to the power -exerted by the whole of the fingers and hand, in the act of grasping. -The muscles which enable it to perform these varied motions, and which -act powerfully in almost every thing we do with the hand, form a mass -of flesh at the ball of the thumb (fig. LXXXVII. 1), almost entirely -surrounding it. The little finger is also provided with a distinct -apparatus of muscles (fig. LXXXVII. 2), which surrounds its root, just -as those of the thumb surround its ball, in order to keep it firm in -opposition to the power of the thumb in the act of grasping, and in -various other motions. - -[Illustration: Fig. LXXXVII. - -1. The mass of muscles forming the ball of the thumb; 2. the mass of -muscles forming the ball of the little finger; 3. tendons of one of the -flexor muscles of the fingers; 4. sheaths formed by the tendons of the -superficial flexor for the reception of the tendons of the deep flexor.] - -182. The upper extremity is covered by a tendinous expansion or fascia -which envelopes the whole arm, encloses its muscles as in a sheath, -and affords them, in their strong actions, "that kind of support which -workmen feel in binding their arms with thongs." This fascia likewise -descends between many of the muscles, forming strong partitions between -them, and affording points of origin to many of their fibres, scarcely -less fixed than bone itself. - -183. From the whole, it appears, that the first joint of the upper -extremities, that of the shoulder, is a ball and socket joint, a joint -admitting of motion in every direction; that the second joint, that of -the elbow, is partly a hinge-joint, admitting of flexion and extension, -and partly a rotation joint, admitting of a turning or rotatory motion; -and that the joints of the wrist and of the fingers are likewise -hinge-joints, admitting at the same time of some degree of lateral -motion. When these various motions are combined, the result is that -the hand can apply itself to bodies in almost every direction, in any -part of the area described by the arm, when all the joints are moved to -their utmost extent. There is thus formed an instrument of considerable -strength, capable of a surprising variety and complexity of movements, -capable of seizing, holding, pulling, pushing and striking with great -power, yet at the same time capable of apprehending the minutest -objects, and of guiding them with the utmost gentleness, precision, and -accuracy, so that there are few conceptions of the designing mind which -cannot be executed by the skilful hand. - -184. The lower extremities consist of the thigh, leg, and foot. - -185. The osseous part of the thigh consists of a single bone, called -the femur (fig. XXXIV. 4), the longest, thickest, and strongest bone in -the body. It sustains the entire weight of the trunk, and occasionally -much heavier loads superimposed upon it. It is constructed in such -a manner as to combine strength with lightness. This is effected by -rendering the bone what is technically called cylindrical; that is, a -bone in which the osseous fibres are arranged around a hollow cylinder. -There are two varieties of osseous matter,—the compact, in which the -fibres are dense and solid (fig. LXXXVIII. 1), and the spongy, in which -the fibres are comparatively tender and delicate (fig. LXXXVIII. 2). -Both varieties are, indeed, combined, more or less, in every bone, -the compact substance being always external, and the spongy internal; -but in the cylindrical bones the arrangement is peculiar. Every long -or cylindrical bone consists of a body or shaft (fig. LXXXVIII. 4.), -and of two extremities (fig. LXXXVIII. 5). The body is composed -principally of compact substance, which on the external surface is so -dense and solid, that scarcely any distinct arrangement is visible; -but towards the interior this density diminishes; the fibres become -distinct (fig. LXXXVIII. 5), and form an expanded tissue of a cellular -appearance (fig. LXXXVIII. 5), the cells being called cancelli, and -the structure cancellated. In the centre of the bone even the cancelli -disappear; the osseous fibres terminate; and a hollow space is left -filled up, in the natural state, by an infinite number of minute -membranous bags which contain the marrow (fig. LXXXVIII. 3). In the -body of the bone, to which strength is requisite, that part being the -most exposed to external violence, the compact matter is arranged -around a central cavity. By this means strength is secured without -any addition of weight; for the resisting power of a cylindrical body -increases in proportion to its diameter; consequently the same number -of osseous fibres placed around the circumference of a circle produce -a stronger bone than could have been constructed had the fibres been -consolidated in the centre, and had the diameter been proportionally -diminished. The hollow space thus gained in its centre, renders the -bone lighter by the subtraction of the weight of as many fibres as -would have gone to fill up that space; while its strength is not only -not diminished by this arrangement, but positively increased. On the -other hand, at the extremities of the bone, space, not strength, is -required; required for the attachment and arrangement of the tendons -of the muscles that act upon it, and for the formation of joints (fig. -LXXXVIII. 5). Accordingly, at its extremities the bone swells out into -bulky surfaces; but these surfaces are composed, not of dense and solid -substance, but of spongy tissue, covered by an exceedingly thin crust -of compact matter, and so, as by the former expedient strength is -secured without increase of weight, by this, space is obtained without -increase of weight. - -[Illustration: Fig. LXXXVIII. - -A section of the femur, showing, 1. the compact bony substance; 2. the -spongy or cancellated structure; 3. the internal cavity containing the -marrow; 4. body; 5, extremities of the bone.] - -186. The thigh-bone, placed at the under and outer part of the pelvis, -has an oblique direction, the under being considerably nearer its -fellow than the upper end (fig. XXXIV. 4), in order to afford space for -the passages at the bottom of the pelvis, and also to favour the action -of walking. The body of the bone, which is of a rounded form (fig. -XXXIV. 4), is smooth on its anterior surface (fig. XXXIV. 4), where it -is always slightly convex, the convexity being forwards (fig. XXXIV. -4), while its posterior surface is irregular and rough, and forms a -sharp prominent line, termed the linea aspera (fig. XXXV. 4), giving -attachment to numerous muscles. - -187. The superior extremity of the femur terminates in a large ball or -head, which forms nearly two-thirds of a sphere (fig. LXXXIX. 4.). It -is smooth, covered with cartilage, and received into the socket of the -ilium called the acetabulum, which, deep as it is, is still further -deepened by the cartilage which borders the brim (fig. LXXXIX. 3). The -brim is particularly high in the upper and outer part, because it is in -this direction that the reaction of the ground against the descending -weight of the trunk tends to dislodge the ball from its socket. - -188. Passing obliquely downwards and outwards from the ball, is that -part of the femur which is called the neck (fig. LXXXIX. 5). It spreads -out archlike between the head and the body of the bone, and is more -than an inch in length (fig. LXXXIX. 5). It is thus long in order -that the head of the bone may be set deep in its socket, and that its -motions may be wide, free, and unembarrassed. - -[Illustration: Fig. LXXXIX. - -1. Lower portion of the ilium; 2. tuberosity of the ischium: 3. socket -for the head of the femur, or thigh-bone; 4. head of the femur; 5. neck -of the femur; 6. the great process of the femur called the trochanter -major; 7. the body of the femur.] - -189. From the external surface of the femur, nearly in a line with -its axis, proceeds the largest and strongest bony process of the body -which gives insertion to its most powerful muscles, namely, those that -extend the thigh and that turn it upon its axis (fig. LXXXIX. 6). -Because, from its oblique direction, it rotates the thigh, this process -is called the trochanter, and, from its size, the trochanter major. At -the under and inner part of the neck on the posterior surface of the -bone, is a similar process, but much smaller, called the trochanter -minor (fig. XXXV. 4), into which are inserted the muscles that bend the -thigh. - -190. The inferior extremity of the femur, much broader and thicker -than the superior (fig. XC. 1), is terminated by two eminences, with -smooth surfaces, termed condyles (fig. XC. 2), which, articulated with -the tibia, and the patella, form the joint of the knee (figs. XC. 2, 4, -5, and XCI. 1, 2, 3). - -[Illustration: Fig. XC. - -1. Lower end of the femur; 2. condyles of the femur; 3. upper end of -the tibia; 4. articular surfaces on the head of the tibia on which the -thigh-bone plays; 5. the patella, or knee-pan; 6. upper end of the -fibula, not entering into the knee-joint.] - -[Illustration: Fig. XCI. - -Posterior view of the bones forming the knee-joint. 1. Lower end of the -femur; 2. upper end of the tibia; 3. articular surfaces on the head of -the tibia, on which the thigh-bone plays; 4. upper end of the fibula, -not entering into the knee joint.] - -191. The bones of the leg, two in number, consist of the tibia (fig. -XC. 3) and fibula (fig. XC. 6). The tibia, next to the femur, the -longest bone in the body, is situated at the inner side of the leg -(fig. XC. 3). Its superior extremity is bulky and thick (fig. XC. 3). -The top of it forms two smooth and slightly concave surfaces, adapted -to the convex surfaces of the condyles of the femur (fig. XC. 4, 2). -On its outer side there is a smooth surface, to which the head of the -fibula is attached (fig. XC. 6). Its lower extremity, which is small, -forms a concavity adapted to the convexity of the bone of the tarsus, -called the astragalus, with which it is articulated (fig. XCII. 4.) -Its inner part is produced so as to form the inner ankle (figs. XCII. -2, and XCIII. 3): its outer side is excavated into a semilunar cavity, -for receiving the under end of the fibula, which forms the outer ankle -(figs. XCII. 3, and XCIII. 4). - -192. The fibula, in proportion to its length the most slender bone of -the body, is situated at the outer side of the tibia (fig. XC. 6). Its -upper end formed into a head, with a flat surface on its inner side -(figs. XC. 6, and XCI. 4), is firmly united to the tibia (fig. XC. 4). -Its lower end forms the outer ankle, which is lower and farther back -than the inner (fig. XCII. 3, 2). - -[Illustration: Fig. XCII. - -Anterior view of the bones forming the ankle-joint. 1. Lower end of -the tibia; 2. production of the tibia, forming the inner ankle; 3. -lower end of the fibula, forming the outer ankle; 4. upper part of the -astragalus: these three bones form the ankle-joint; 5 5 5, other bones -of the tarsus; 6 6 6 6 6 metatarsal bones.] - -[Illustration: Fig. XCIII. - -Posterior view of the bones forming the ankle-joint. 1. Lower end of -the tibia; 2. lower end of the fibula; 3. internal malleolus or ankle; -4. external malleolus or ankle; 5. one of the tarsal bones, called the -astragalus, with which the tibia and fibula are articulated; 6. the os -calcis or heel.] - -193. The patella, or knee-pan (fig. XC. 5), is a light but strong -bone, of the figure of the heart as painted on playing-cards, placed -at the fore part of the joint of the knee, and attached by a strong -ligament to the tibia, the motions of which it follows (fig. XC. 5). It -is lodged, when the knee is extended, in a cavity formed for it in the -femur (fig. XC.); when bent, in a cavity formed for it at the fore part -of the knee (fig. XC. 5). - -194. The foot consists of the tarsus, metatarsus, and toes. - -195. The tarsus, or instep, is composed of seven strong, -irregular-shaped bones, disposed like those of the carpus, in a double -row (fig. XCII. 4, 5). The arrangement of the tarsal bones is such as -to form an arch, the convexity of which above, constitutes the upper -surface of the instep (fig. XCII. 4, 5): in the concavity below are -lodged the muscles, vessels, and nerves that belong to the sole. - -196. The metatarsus consists of five bones, which are placed parallel -to each other (fig. XCII. 6), and which extend between the tarsus -and the proper bones of the toes (fig. XCII. 6). Their extremities, -especially next the tarsus, are large, in order that they may form -secure articulations with the tarsal bones (fig. XCII. 6). Their -bodies are arched upwards (fig. XCII. 6), slightly concave below, and -terminate forwards in small, neat, round heads, which receive the -first bones of the toes, and with which they form joints, admitting -of a much greater degree of rotation than is ever actually exercised, -in consequence of the practice of wearing shoes. The natural, free, -wide-spreading form of the toes, and the consequent security with -which they grasp the ground, is greatly impaired by this custom. Taken -together, the bones of the metatarsus form a second arch corresponding -to that of the tarsus (fig. XCVIII. 2). - -197. Each toe consists of three distinct bones, called, like those -of the fingers, phalanges (fig. XCVIII.), but the great toe, like -the thumb, has only two (fig. XCVIII.). That extremity of the first -phalanges which is next the metatarsal bones is hollowed into a socket -for the head of the metatarsal bones. - -198. Besides the bones already described, there are other small bones, -of the size and figure of flattened peas, found in certain parts of -the extremities, never in the trunk, called sesamoid, from their -resemblance to the seed of the sesamum. They belong rather to the -tendons of the muscles than to the bones of the skeleton. They are -embedded within the substance of tendons, are found especially at the -roots of the thumb and of the great toe, and are always placed in the -direction of flexion. Their office, like that of the patella, which is, -in truth, a bone of this class, is to increase the power of the flexor -muscles by altering the line of their direction, that is, by removing -them farther from the axis of the bone on which they are intended to -act. - -199. The ligaments which connect the bones of the lower extremities -are the firmest and strongest in the body. Of these, the fibrous -capsule of the hip-joint (fig. XCIV. 1), which secures the head of the -femur in the cavity of the acetabulum (fig. XCIV.), is the thickest and -strongest. It completely surrounds the joint (fig. XCIV. 1). It arises -from the whole circumference of the acetabulum, and, proceeding in a -direction outwards and backwards, is attached below to the neck of the -femur (fig. XCIV. 1). It is thicker, stronger, and much more closely -attached to the bones than the fibrous capsule of the shoulder-joint -(144), because the hip-joint is formed, not like the shoulder-joint, -for extent of motion, but for strength. Its internal surface is -lined by synovial membrane, and its external surface is covered and -strengthened by the insertion of muscles that move the thigh-bone. -The joint is strengthened by another ligament, which passes from the -inner and fore part of the cavity of the acetabulum (fig. XCV.) to be -inserted into the head of the femur (fig. XCIV.), called the round -ligament, the office of which obviously is to hold the head of the -femur firmly in its socket. - -[Illustration: Fig. XCIV. - -1. The fibrous capsule of the hip-joint, laid open and turned aside to -show, 2. the round ligament in its natural position.] - -[Illustration: Fig. XCV. - -A view of the head of the femur drawn out of its socket, and suspended -by the round ligament, to show more clearly the action of the ligament -in retaining the head of the femur in its socket.] - -200. Numerous and complicated ligaments connect the bones that form -the knee-joint (fig. XCVI.), and the strength of these powerful bands -is greatly increased by the tendons that move the leg (fig. XCVI. 5), -which pass over, and more or less surround, the joint. - -[Illustration: Fig. XCVI. - -General view of the ligaments of the knee-joint. 1. Lower end of the -femur; 2. upper end of the tibia; 3. upper end of the fibula; 4. the -patella; 5. united tendons of the extensor muscles; 6. ligaments of -the patella; 7. the capsular investment of the knee; 8. the internal -lateral ligament; 9. the external lateral ligaments; 10. the posterior -ligament; 11. the ligament connecting the tibia and fibula; 12. a -portion of the interosseous ligament.] - -201. Strong ligaments maintain in their proper position the bones that -form the ankle-joint (fig. XCVII.), connect the bones of the tarsus -and metatarsus with one another (fig. XCVIII. 1), and articulate the -several phalanges of the toes (fig. XCVIII. 2). - -[Illustration: Fig. XCVII. - -General view of the posterior ligaments of the ankle-joint. 1. Lower -end of the tibia; 2. lower end of the fibula; 3. astragalus; 4. os -calcis; 5. ligament between the tibia and fibula; 6. ligament passing -from the fibula to the astragalus; 7. ligament passing from the fibula -to the os calcis; 8. ligament passing from the tibia to the astragalus.] - -[Illustration: Fig. XCVIII. - -General view of the ligaments of the sole of the foot. 1. Ligaments -connecting the bones of the tarsus; 2. ligaments connecting the bones -of the toes.] - -202. The joint of the hip, like that of the shoulder, is capable of -flexion, extension, and rotation; but its rotatory motions are to a -much less extent, on account of the greater depth of the acetabulum and -the stronger and shorter fibrous capsule. When the femur is flexed, the -thigh is bent upon the pelvis, and its inferior extremity is carried -forwards. When it is extended, the thigh is carried backwards. The -two thighs may be separated from each other laterally (abduction), or -brought near to each other (adduction), or the one may be made to cross -the other, and they may be rotated outwards or inwards. - -203. The apparatus of muscles that produces these varied motions is -seated partly on the trunk and partly on the pelvis. Thus, the powerful -muscle that flexes the thigh, or that carries it forwards, termed -the psoas (fig. XCIX. 1), arises from the last vertebra of the back, -and successively from each vertebra of the loins (fig. XCIX. 1), and -is inserted into the lesser trochanter of the femur (fig. XCIX. 3). -Its action is assisted first by a large and strong muscle named the -iliacus (fig. XCIX. 2), which occupies the whole concavity of the ilium -(fig. XCIX. 2), and which, like the psoas, is inserted into the lesser -trochanter of the femur (fig. XCIX. 3). - -[Illustration: Fig. XCIX. - -View of the muscles that bend the thigh. 1. The muscle called psoas; -2. the muscle called iliacus; 3. tendons of these muscles, going to be -inserted into the trochanter minor of the femur.] - -204. The muscles that extend the thigh, or that carry it backwards, -named the glutæi, the most powerful muscles of the body, are placed -in successive layers, one upon the other, on the back part of the -ilium (fig. C. 1, 2, 3), and are inserted into the linea aspera of the -femur. They constitute the mass of flesh which forms the hip, and their -powerful action in drawing the thigh backwards is assisted by several -other muscles (fig. C. 4, 5, 6). Their action is never perfectly simple -and direct; for those which move the thigh forwards sometimes carry it -inwards, and sometimes outwards; and in like manner, those which move -it backwards, at one time carry it inwards and at another outwards, -according to the direction of the fibres of the muscle and the position -of the limb when those fibres act; while some of them, and more -especially those which carry it backwards, at the same time rotate it, -or roll it upon its axis. - -[Illustration: Fig. C. - -View of the muscles that extend the thigh. 1. The muscle called glutæus -maximus, removed from its origin, 2, 2, to show the muscles which lie -beneath it; 2. cut edge showing the origin of the same muscle; 3. the -muscle called glutæus medius; 4, 5, 6. smaller muscles, assisting the -action of the glutæi.] - -205. The knee is a hinge-joint, admitting only of flexion and -extension, and is therefore provided only with two sets of muscles, one -for bending and the other for extending the leg. The flexors of the leg -arise from the under and back part of the pelvis, are seated on the -back part of the thigh, and are inserted into the upper part either of -the tibia or of the fibula (fig. CI). They consist for the most part of -three muscles, named the semi-tendinosus, the semi-membranosus (fig. -CI. 3), and the biceps of the leg (fig. CI. 1). The tendons of the two -former muscles, in passing to be inserted into the leg, form the inner, -and that of the latter the outer, hamstrings (fig. CI. 4, 5). - -[Illustration: Fig. CII. - -View of the flexor and extensor muscles of the leg. 1. The biceps of -the leg; 2. tendon of the biceps, inserted into the head of the fibula; -3. the semi-membranosus, passing to be inserted into the head of the -fibula; 4. tendon of the semi-membranosus forming the inner, and 5. -tendon of the biceps forming the outer, hamstring; 6. upper part of the -gastrocnemius muscle; 7. the four large muscles which unite to form the -great extensor muscle of the leg, inserted into 8. the patella; 9. a -portion of the glutæus maximus concealing the other muscles of the hip.] - -206. Four large muscles, blended together in such a manner as to form -one muscle of prodigious size, termed the quadriceps cruris (fig. CI. -7), occupying nearly all the forepart and the sides, and a considerable -portion of the back part of the thigh, constitute the great flexor of -the thigh. This enormous mass of muscle arises partly from the ischium, -and partly from the upper part of the femur (fig. CI. 7), and is all -inserted into the patella (fig. CI. 8), which constitutes a pulley for -the purpose of assisting the action of these powerful muscles. - -207. The muscles which bend the toes and extend the foot, termed the -gastrocnemii (fig. CII. 1, 2), are placed on the back part of the leg, -and form the mass of muscle which constitutes the calf of the leg (fig. -CII. 1, 2). They arise partly from the lower extremity of the femur -(fig. CII.) and partly from the upper and back part of the fibula and -tibia; and they form the largest and strongest tendon in the body, -termed the tendo achillis (fig. CII. 3), which is implanted into the -heel (fig. CII. 4). - -[Illustration: Fig. CII. - -View of the muscles which bend the toes, and which, by lifting the -heel, extend the foot. 1. The muscle called gastrocnemius externus, -which, uniting with 2. the gastrocnemius internus, forms 3. the tendo -achillis, which is inserted into 4. the heel.] - -[Illustration: Fig. CIII. - -View of the muscles which extend the toes and bend the foot. 1. The -common extensor; 2. the tendons of the same muscle inserted into the -toes; 3. the anterior annular ligament of the foot.] - -[Illustration: Fig. CIV. - -View of the muscles in the sole of the foot. 1 The muscle which draws -the great toe from the other toes; 2. the muscle which draws the little -toe from the other toes; 3. the muscle called the short flexor of the -toes, which assists in bending the four smaller toes.] - -208. The muscles which extend the toes and bend the foot are seated -on the fore part of the leg (fig. CIII.); split into tendons like the -analogous muscles of the fingers (fig. CIII. 2); and are bound down -by a ligament (fig. CIII. 3), exactly the same in name, disposition, -and office, as that which belongs to the hand (fig. CIII. 3). Numerous -minute muscles are placed in the sole of the foot (fig. CIV.), which -act on the toes as the small muscles in the palm of the hand act on the -fingers (fig. LXXXVI.). - -209. Such are the moving powers which put in action the complicated -mechanism provided for the function of locomotion. And these powers are -adequate to their office; but they are what may be termed expensive -powers; agents requiring a high degree, of organization and the utmost -resources of the economy to support and maintain them. Hence in the -construction of the framework of the machine which they have to move, -whatever mechanical contrivance may economize their labour, is adopted. -The construction, form, and disposition of the several parts of that -framework have all reference to two objects: first, the combination -of strength with lightness; and secondly, security to tender organs, -with the power of executing rapid, energetic, and, sometimes, violent -motions. The combination is effected and the object attained in a mode -complicated in the detail, simple in the design, and perfect in the -result. The weight of the body transmitted from the arch of the pelvis -to a second arch, formed by the neck of the thigh-bone, and from this, -in a perpendicular direction, to a third arch formed by the foot, is -ultimately received by the heel behind, and by the metatarsal bones -and the first phalanges of the toes before, and more especially by the -metatarsal joints belonging to the great and little toe, which have a -special apparatus of muscles, for the purpose of preserving steadily -their relative situation to the heel. The weight of the body is thus -sustained on a series of arches, from which it is, in succession, -transmitted to the ground, where it ultimately rests upon a tripod: -forms known and selected as the best adapted to afford support, and to -give security of position. Columns of compact bone superimposed one -upon another, and united at different points by bands of prodigious -strength, form the pillars of support. But these bony columns never -touch each other; are never in actual contact; are all separated by -layers of elastic matter which, while they assist in binding the -columns together, enable them to move one upon another, as upon so many -pliant springs. The layers of cartilage interposed between the several -vertebræ; the layer of cartilage interposed between the vertebral -column and the pelvis; the layer of cartilage that lines the acetabulum -and that covers the head of the femur; the layer of cartilage that -covers the lower extremity of the femur and the upper extremity of the -tibia and fibula and the tarsus; the successive layers of cartilage -interposed between the several bones of the tarsus; and finally, -the layer of cartilage that covers both the tarsal and the digital -extremities of the metatarsal bones; are so many special provisions to -prevent the weight of the body from being transmitted to the ground -with a shock; and, at the same time, so many barriers established -between the ground and the spinal cord, the brain and the soft and -tender organs contained in the thoracic and abdominal cavities, to -prevent these organs from being injured by the reaction of the ground -upon the body. The excellence of this mechanism is seen in its results; -in contemplating "from what heights we can leap—to what heights we can -spring—to what distances we can bound—how swiftly we can run—how -firmly we can stand—how nimbly we can dance—and yet how perfectly we -can balance ourselves upon the smallest surfaces of support!" - -210. It is necessary, in order to complete this general view of the -structure of the human body, and of the combination and arrangement -of its various parts, to denote the several regions into which, for -the purpose of describing with accuracy the situation and relation of -its more important organs, the body is divided. It is not needful to -the present purpose to describe the regions of the head, because its -internal cavity contains only one organ, the brain, and its external -divisions do not differ materially from those which are common -and familiar; but the chest, the abdomen, and the upper and lower -extremities are mapped out into regions, of which it is very important -to have an exact knowledge, which may be acquired by the study of the -annexed diagrams. - -[Illustration: Fig. CV. - -Anterior view of the regions of the body. 1. Region of the neck; 2. -region of the chest or thorax. Abdominal regions: 3. epigastric; 4. -umbilical; 5. hypogastric region. Regions of the upper extremities. 6. -shoulder; 7. arm; 8. elbow; 9. fore-arm; 10. wrist; 11. ball of thumb; -12. the axilla or armpit. Regions of the lower extremities: 13. thigh; -14. knee; 15. leg; 16. ankle; 17. instep and foot.] - -[Illustration: Fig. CVI. - -Posterior view of the regions of the body: 18. region to the scapula; -19. of the back; 20. of the loins; 21. of the hips; 22. of the ham; 23. -of the calf of the leg; 24. of the heel and foot.] - -[Illustration: Fig. CVII. - -Lateral view of the regions of the body: 25. arch of the foot.] - -[Illustration: Fig. CVIII. - -Anterior view of the situation of the more important internal organs: -1. lungs, right and left; 2. heart; 3. line representing the edge of -the diaphragm; 4. liver; 5. stomach; 6. small intestines; 7. colon; 8. -urinary bladder.] - -[Illustration: Fig. CIX. - -Posterior view of the situation of the more important internal organs: -9. kidnies, right and left; 10. the course of the spinal cord.] - -[Illustration: Fig. CX. - -Lateral view of the situation of the more important internal organs.] - - - - -CHAPTER VI. - -OF THE BLOOD. - - Physical characters of the blood: colour, fluidity, - specific gravity, temperature: quantity—Process - of coagulation—Constituents of the blood: - proportions—Constituents of the body contained in the - blood—Vital properties of the blood—Practical applications. - - -211. Supposing the human body to have been built up in the manner now -described, and to be in the full exercise of all its functions, the -integrity of its various structures is maintained, and their due action -excited by the blood. Out of this substance is formed the blandest -fluid, as the milk, and the firmest solid, as the compact bone. The -heart, capable of untiring action, as long as the blood is in contact -with its internal surface, becomes immovable soon after the supply of -this fluid is withdrawn; and in less than one minute from the time -it ceases to flow in due quantity and of proper quality through the -vessels of the brain, the eye is no longer capable of seeing, nor the -ear of hearing, nor the brain of carrying on any intellectual operation. - -212. At the moment, and for some time after it has issued from its -vessel, the appearance of the blood is that of a thick, viscid, and -tenacious fluid; yet it is essentially a solid, composed of several -substances, each possessing its own distinct and peculiar properties, -the relation and combination of which cannot be considered without -exciting the feeling that our admiration of the structure of the animal -frame ought not to be confined to the mechanism of its solid parts, but -that the whole is admirable, from the common material of which it is -composed, to its most delicate and elaborate instrument. - -213. The colour of redness is universally associated with the idea of -blood; but redness of colour is not essential to blood. There are many -animals with true, yet without red, blood; and there is no animal in -which the blood is red in all the parts of its body. The blood of the -insect is transparent; that of the reptile is of a yellowish colour; -that of the fish, in the greater part of its body, is colourless. Even -the red blood of the human body is not equally red in every part of it, -there being two distinct systems of blood-vessels, distinguished from -each other by carrying blood of different colours. - -214. In the state of health, the specific gravity of human blood, water -being 1000, is 1080; from which standard it is capable of varying from -1120, the maximum, to 1026, the minimum. - -215. The natural temperature of the human blood is 98°. From this it -is capable of varying from 104°, the maximum, to 86°, the minimum; -these changes being always the effect of disease. - -216. It is estimated that the fluids circulating in the adult -man amount to about fifty pounds; of these it is calculated that -twenty-eight consist of red blood. - -217. Fluid and homogeneous as the blood appears while flowing in its -vessel, when a mass of it is collected and allowed to stand at rest, it -soon undergoes a very remarkable change. First, a thin film is formed -upon its surface; this is followed by the conversion of the whole mass -into a soft jelly: this jelly separates into two portions, a fluid and -a solid portion. The solid portion again separates into two parts, into -a substance of a yellowish-white colour, occupying the upper surface, -and into a red mass always found at the under surface. - -218. The process by which the constituents of the blood are thus -spontaneously disunited, and afforded in a separate form, is -denominated COAGULATION; the fluid portion separated by the process is -termed the SERUM; the solid portion the COAGULUM or CLOT; the white -substance forming the upper part of the clot, the FIBRIN; and the red -mass forming the under part of it, the RED PARTICLES. - -219. Probably the process of coagulation commences the moment the -blood leaves its living vessel. In three minutes and a half it is -visible to the eye; in seven minutes the mass is formed into a jelly; -in from ten to twelve minutes the serum separates from the clot; in -about twenty the clot is divided into fibrin and red particles, when -the coagulation is complete; but occasionally the clot continues to -grow firmer and firmer for the space of twenty-four hours. - -220. As soon as the coagulation commences, and during all the time the -blood preserves its heat, an aqueous vapour arises from it, termed -the HALITUS. The halitus consists of water holding in solution a -small quantity of animal and saline matter, which communicate to it a -fœtid odour of a strong and peculiar nature, manifest on approaching -a slaughter-house, and still more manifest in the slaughter-house of -human beings, a field of battle. - -221. During the process of coagulation, as in every other in which a -fluid is converted into a solid, caloric is evolved. - -222. During the process of coagulation carbonic acid is also extricated. - -223. The process of coagulation affords three distinct substances, -the chief constituents of the blood, namely, serum, fibrin, and red -particles. - -224. The serum, the fluid portion of the blood, when obtained -perfectly pure, is of a light straw colour, tinged with green. -Its taste is saline, and its consistence adhesive. It is composed -principally of water holding in solution animal and saline matter. -The animal matter gives it its adhesive consistence, and the saline -its peculiar salt taste. The chief animal matter contained in it is -the proximate principle termed albumen, which may be separated from -the water that holds it in solution by the application of heat and -by certain chemical agents. Heat being applied, when the temperature -reaches 160°, fluid serum is converted into a white opaque solid -substance of firm consistence. This is found to be albumen, which may -be also separated from the watery portion by the application of spirits -of wine, acids, oxymuriate of mercury, and several other chemical -substances. The quantity of albumen contained in 1000 parts of serum -varies from about 78, the maximum, to 58, the minimum. - -225. If the albumen yielded by the serum be subjected to pressure, or -be cut into small pieces, there flows from it a watery fluid which is -termed the serosity. In meat dressed for the table, the serum of the -blood contained in the blood-vessels is converted by the heat into -solid albumen, from which, when cut, the serosity flows in the form of -gravy. - -226. Besides albumen, serum holds in solution both a fatty and an oily -matter, in the proportion of about one part of each to 1000 parts of -serum. The proportion of its saline substances is about ten in 1000 -parts. According to M. le Canu, who has made the most recent chemical -analysis of serum, 1000 parts contain, of - - Water 906·00 - Albumen 78·00 - Animal matter, soluble in water - and alcohol 1·69 - Albumen combined with soda 2·10 - Crystallizable fatty matter 1·20 - Oily matter 1·00 - Hydrochlorate of soda and - potash 6·00 - Subcarbonate and phosphate of - soda, and sulphate of potash 2·10 - Phosphate of lime, magnesia, - and iron, with subcarbonate - of lime and magnesia ·91 - Loss 1·00 - -227. All the animal and saline matter held in solution in the serum -being removed, the fluid that remains is water, the proportion of which -in 1000 parts varies from 853, the maximum, to 779, the minimum. - -228. The second constituent of the blood, the fibrin, is the most -essential portion of it, being invariably present, whatever other -constituent be absent. While circulating in the living vessel, -fibrin is fluid and transparent; by the process of coagulation, it -is converted into a solid and opaque substance of a yellowish white -colour, consisting of stringy fibres, disposed in striæ, which -occasionally form a complete net-work (fig. CXI.). These fibres are -exceedingly elastic. In their general aspect and their chemical -relations they bear a close resemblance to pure muscular fibre, that -is, to muscular fibre deprived of its enveloping membrane and of its -colouring matter, and they form the basis of muscle. According to M. -le Canu, the proportion of the fibrin varies from seven parts in 1000, -the maximum, to one part in 1000, the minimum, the medium of twenty -experiments being four parts in 1000. - -[Illustration: Fig. CXI. - -A portion of the fibrin of the blood, showing its fibrous structure and -the striated or net-like arrangement of its fibres.] - -229. The third constituent of the blood, the matter upon which its red -colour depends, though, as has been stated, entirely absent in certain -classes of animals, and in all animals in some parts of their body, -seems to be essential, at least to the organic organs, whenever they -perform their functions with a high degree of perfection. Thus in the -lowest class of vertebrated animals, the fish, while the principal part -of its body receives only a colourless fluid, its organic organs, as -the heart, the gills, the liver, are provided with red blood. - -230. The red matter, wherever present, is invariably heavier than -the fibrin, and consequently, during the process of coagulation, it -gradually subsides to the lower surface, and is always found forming -the bottom of the clot. Its proportion to the other constituents varies -very remarkably, the maximum being 148, the minimum 68, and the medium -108, in 1000 parts of blood. - -231. All observers are agreed that the red matter of the blood consists -of minute particles, having a peculiar and definite structure; but in -regard to the nature of that structure, there is considerable diversity -of opinion, which is not wonderful, since the particles in question -are so minute that they can be distinguished only by the microscope, -and since, of all microscopical objects, they are perhaps the most -difficult to examine, because, being soft and yielding, their figure -is apt to change, and because there is reason to suppose that their -substance is not uniform in its refractive power. - -232. The earlier observers describe the red particles as being of -a globular figure, and accordingly name them globules. They conceive -that each globule consists of a central solid particle, enveloped in a -transparent vesicle. Recently, Sir Everard Home and Mr. Bauer in this -country, and MM. Prevost and Dumas on the continent, have revived this -opinion, and describe the red particle as consisting of a central solid -white corpuscle contained in an external envelop of a red colour. When -the blood is observed with the microscope in a living animal, flowing -in its vessels, only two substances can be distinguished, namely, -a transparent fluid and the red corpuscles. MM. Prevost and Dumas -contend that these two substances are the only component parts of the -blood. When the blood coagulates, they conceive that the red envelop -separates from the central white corpuscle; that these white corpuscles -unite together; that the aggregates resulting from this combination -are disposed in the form of filaments, which filaments constitute the -fibrin, while the red matter at the bottom of the clot is nothing but -the disintegrated envelops of the central particle. But this view is -not the common one. In general, physiologists conceive the fibrin to -be one constituent and the red particles to be another constituent of -the blood. Mr. Lister, who has successfully laboured to improve the -microscope, and who, together with his friend Dr. Hodgkin, have very -carefully examined with their improved instrument the red particles, -contend that the figure of these bodies is not globular, although -they state that the instant the particles are removed from the living -blood-vessels many things are capable of making them assume a globular -appearance; such, for example, as the application of water. With a -rapidity which, in spite of every precaution, the eye in vain attempts -to follow, the particles change their real figure for a globular form -on the application of the smallest quantity of pure water; while, -if the water contain a solution of saline matter, little alteration -is occasioned in the figure of the particles. According to these -observers, the red particles are flattened cakes, having rounded and -very slightly thickened margins (fig. CXII. 1). The thickness of the -margin gives to both surfaces the appearance of a slight depression -in the middle (fig. CXII. 1), so that the particles bear a close -resemblance to a penny piece. There is no appearance of an external -envelop. The circular and flattened cake is transparent; when seen -singly it is nearly if not quite colourless (fig. CXII. 1); it assumes -a reddish tinge only when aggregated in considerable masses. - -[Illustration: Fig. CXII. - -1. A particle of the human blood as it appears when transparent and -floating; 2. the same dry, seen as opaque, illuminated by a leiberkuhn; -3. the same as it appears when half the leiberkuhn is darkened; 4. a -particle of the frog's blood floating; 5. the same seen on its edge. -All the above objects are magnified 500 diameters[5].] - -233. The red particle of the human blood is circular (fig. CXII. 1, 2, -3). It is circular also in all animals belonging to the class mammalia; -but in the three lower classes of vertebrated animals, the bird, the -reptile, and the fish, it is elliptical (fig. CXII. 4, 5). - -234. The magnitude of the red particle of the human blood is variously -estimated from the two-thousandth to the six-thousandth part of an inch -in diameter. Bauer estimates it at the two-thousandth, Hodgkin and -Lister at the three-thousandth, Kater at the four-thousandth, Wollaston -at the five-thousandth, and Young at the six-thousandth part of an -inch. Its magnitude is uniformly the same in all individuals of the -same species, but differs exceedingly in the different classes. The -elliptical particles are larger than the circular, but proportionally -thinner; larger in fishes than in any other class of animals, and -largest of all in the skate. - -235. When perfect and entire, the red particles indicate a disposition -to arrange themselves in a definite mode. They combine spontaneously -into columns of variable length (fig. CXIII.). In order to observe this -tendency, a small quantity of blood, the moment it is taken from its -living vessel, should be placed between two strips of glass or covered -with a bit of talc and placed under the microscope. When thus arranged, -a considerable agitation at first takes place among the particles. -As soon as this motion subsides, the particles apply themselves to -each other by their broad surfaces, and thus form piles or columns of -Considerable length (fig. CXIII.). The columns often again combine one -among another, the end of one being attached to the side of another, -sometimes producing very curious ramifications (fig. CXIII.). In -like manner, the elliptical particles apply themselves to each other -by their broad surfaces, but they are not so exactly matched as the -circular, one particle partially overlapping another, so that they form -less regular columns than the circular. - -[Illustration: Fig. CXIII. - -Columnar arrangement which the particles of the human blood assume -immediately after it is drawn from its vessel.] - -236. The red particles, as far as is known, constitute a distinct and -peculiar form of animal matter: the red colour, according to some, -depending on an impregnation of iron; according to others, on an animal -substance of a gelatinous nature. - -237. The exact proportion of the different substances contained in the -blood, according to the most recent analysis of it, that by M. le Canu, -is as follows, namely, - - Water 786·500 - Albumen 69·415 - Fibrin 3·565 - Colouring matter 119·626 - Crystallizable fatty matter 4·300 - Oily matter 2·270 - Extractive matter, soluble in - alcohol and water 1·920 - Albumen combined with soda 2·010 - Chloruret of sodium and potassium, - alkaline phosphate, - sulphate, and subcarbonates 7·304 - Subcarbonate of lime and magnesia, - phosphates of lime, - magnesia and iron, peroxide - of iron 1·414 - Loss 2·586 - -------- - 1000· - -238. From the results of this analysis it is manifest that all the -proximate principles of which the different tissues are composed exist -in the blood, namely, albumen, the proximate principle forming the -basis of membrane; fibrin, the proximate principle forming the basis -of muscle; fatty matter, forming the basis of nerve and brain; and -various saline and mineral substances, forming a large part of bone, -and entering more or less into the composition of every fluid and solid. - -239. The blood, which contains all the proximate constituents of the -body, and which, by distributing them to the various tissues and -organs, maintains their integrity and life, is itself alive. The -vitality of the blood is proved,— - -240. i. By its undergoing the process of death, which it does just as -much as the heart or the brain, every time it is removed from the body. -While flowing in its living vessel, the blood is permanently fluid. -Its fluidity depends on a force of mutual repulsion exerted by its -particles on each other. That repulsive force is a vital endowment, -probably derived from the organic nerves so abundantly distributed -to the inner coat of the blood-vessels. When this vital influence -is withdrawn, which happens on the removal of the blood from its -vessel, the mass is no longer capable of remaining fluid; the fibrin -is converted into a solid; the red particles, instead of repelling, -attract each other, forming the crude aggregate at the bottom of -the clot; coagulation is thus a process of death; its commencement -indicates a diminution of the vital energy of the blood; during its -progress that energy is constantly growing less and less; the blood is -dying; and when complete, the blood is dead. - -241. Hence in every state of the system in which the vital energy of -the blood is preternaturally increased, coagulation is proportionably -slow; in every state in which its energy is diminished, coagulation -is rapid. By copious and repeated blood-letting, the vital energy -is rapidly exhausted. The effect of blood-letting on coagulation -is determined by experiments instituted for the express purpose of -ascertaining it. Blood was received from a horse at four periods, about -a minute and a half intervening between the filling of each cup. - - Minutes. Seconds. - - In cup No. 1. coagulation began in 11 10 - " 2. " " " 10 5 - " 3. " " " 9 55 - " 4. " " " 3 10 - -242. In like manner three cups were filled with the blood of a sheep, -at the interval of half a minute. - - Minutes. Seconds. - - In cup No. 1. coagulation began in 2 10 - " 2. " " " 1 45 - " 3. " " " 0 55 - -The same result was obtained in blood taken from a human subject. A -pound and a half of blood was removed from the arm of a woman labouring -under fever, a portion of which, received into a tea-cup on the first -effusion, remained fluid for the space of seven minutes; a similar -quantity, taken immediately before tying up the arm, was coagulated -in three minutes thirty seconds. These experiments demonstrate that -coagulation is rapid or slow as the vital energy of the blood is -exhausted or unexhausted, or that in proportion to the degree of life -possessed by the blood is the space of time it takes in dying. - -243. This result is referable to the principle already shown to be -characteristic of living substance,—namely, the power of resisting, -within a certain range, the ordinary influence of physical agents. -The operation of this power is illustrated in a beautiful manner in -a series of experiments performed by Mr. Hunter on the egg and on -blood. This physiologist exposed a live, that is, a fresh egg to the -temperature of the 17th and the 15th degrees of Fahrenheit; it took -half an hour to freeze it. The egg was then thawed and exposed to 10° -less cold, namely, to the 25th degree of Fahrenheit; it was now frozen -in a quarter of an hour. A living egg and one that had been killed by -having been first frozen and then thawed, were put together into a -freezing mixture at 15°: the dead was frozen twenty-five minutes sooner -than the living egg. The undiminished vitality of the fresh egg enabled -it to resist the low temperature for the space of twenty-five minutes; -the vitality of the frozen egg having been destroyed, it yielded at -once to the influence of the physical agent. On subjecting blood to -analogous experiments, the result was found to be the same. Blood -immediately taken from the living vessel, and blood previously frozen -and then thawed, being exposed to a freezing mixture, a much shorter -period and a much less degree of cold were required to freeze the -latter than the former. - -244. ii. The vitality of the blood is proved by the change it -undergoes in becoming a constituent part of an organized tissue. -The blood conveys to the several tissues the constituents of which -they are composed; each tissue selects from the mass of blood its -own constituents and converts them into its own substance, in which -conversion, since the blood always goes to the tissue in a fluid -form, the blood must necessarily pass from a fluid into a solid. In -the vessels the vital endowment of the blood maintains it permanently -fluid; in the structures the same power makes it and keeps it -solid. One and the same substance in one and the same body, in one -part is always fluid, in another always solid; the fluid is every -moment passing into the solid and the solid into the fluid, without -intermixture and without interference. Nothing analogous to this is -ever witnessed in inorganic matter, in physical mechanism; it is -peculiar to the organized body and distinctive of the mechanism of -life. Sometimes in physical mechanism we can perceive the mechanical -arrangements and distinctly trace them from beginning to end: in vital -mechanism, even when we can discern the mechanical arrangements, we can -seldom trace them beyond a step or two, and never from beginning to -end; but arrangement and adaptation we know there must be in that which -goes beyond, no less than in that which keeps within, our perception, -and we ought scarcely to question the existence of adjustments, because -they elude our sense, when probably the very reason why they do so is -that their delicacy and perfection immeasurably exceed any with which -sense has made us acquainted. - -245. iii. The vitality of the blood is proved by the process of -organization. We can trace only a few steps of this process, but these -are sufficient to establish the point in question. Blood effused from -living vessels into the substance, or upon the surface of living -organs, solidifies without losing vitality. If a clot of blood be -examined some time after it has thus become solid, it is found to -abound with blood-vessels. Some of these vessels are obviously derived -from the surrounding living parts. The minute vessels of these parts, -as can be distinctly traced, elongate and shoot into the clot. The -clot thus acquires blood-vessels of its own. By degrees a complete -circulation is established within it. The blood-vessels of the clot act -upon the blood they receive just as the vessels of any other part act -upon their blood, that is transform it into the animal matter it is -their office to elaborate. In this manner a clot of blood is converted -into a component part of the body, and acquires the power of exercising -its own peculiar and appropriate functions in the economy. - -246. But while, in this process, some of the vessels of the clot can -be distinctly traced from the surrounding living parts, others appear -to have no communication with those parts, at all events no such -communication can be traced. These vessels, the origin of which cannot -be found external to the clot, are supposed by some physiologists to -be formed within it. Within the living egg, during incubation, certain -motions or actions are observed spontaneously to arise, which terminate -in the development of the chick. Analogous motions arising within the -clot terminate, it is conceived, in the development of blood-vessels. -According to this view, a simultaneous action takes place in the clot, -and in the living part with which it is in contact; each shooting out -vessels which elongate, approximate, unite, and thus establish a direct -vital communication. Whether this view of the process of organization -be the correct one or not does not affect the present argument. It -is certain that a clot of blood surrounded by living parts becomes -organized; it is certain that no dead substance surrounded by living -parts becomes organized; it follows that the blood possesses life. - -247. Health and life depend on the quantity, quality, and distribution -of the blood. The chief source from which the blood itself is derived -is the chyle: hence too much or too little food, or too great or too -little activity of the organs that digest it, may render the quantity -of the blood preternaturally abundant or deficient; or though there be -neither excess nor deficiency in the quantity of nourishment formed, -parts of the blood which ought to be removed may be retained, or -parts which ought to be retained may be removed, and hence the actual -quantity in the system may be superabundant or insufficient. - -248. The relative proportion of every constituent of the blood -is capable of varying; and of course in the degree in which the -healthy proportion is deranged, the quality of the mass must undergo -a corresponding deterioration. The watery portion is sometimes so -deficient, that the mass is obviously thickened; while at other times -the fluid preponderates so much over the solid constituents, that the -blood is thin and watery. The albumen, the quantity of which varies -considerably even in health, in disease is sometimes twice as great, -and at other times is less than half its natural proportion. In some -cases the fibrin preponderates so much, that the coagulum formed by -the blood is exceedingly coherent, firm and dense; in other cases the -quantity of fibrin is so small, that the coagulation is imperfect, -forming only a soft, loose and tender coagulum, and in extreme cases -the blood remains wholly fluid. When the vital energy of the system -is great, the red particles abound; when it is depressed, they are -deficient. In the former state, they are of a bright red colour; in -the latter, dusky, purple, or even black. When the depression of -the vital energy is extreme, the power of mutual repulsion exerted -by the particles would seem to be so far destroyed as to admit of -their adhering to each other partially in certain organs; while in -other cases they seem to be actually disorganised, and to have their -structures so broken up, that they escape from the current of the -circulation as if dissolved in the serum, through the minute vessels -intended only for the exhalation of the watery part of the blood. -This fearful change is conceived to have an intimate connexion with -a diminution of the proportion of the saline constituents. Out of -the body, as has been shown, the red particles change their figure -instantaneously, and are rapidly dissolved when in contact with -pure water; while they undergo little change of form if the water -hold saline matter in solution. It would seem that one use of the -saline constituents of the blood is to preserve entire the figure and -constitution of the red particles. It is certain that any change in the -proportion of the saline constituents produces a most powerful effect -on the condition of the red particles. It is no less certain that -changes do take place in the proportion of the saline constituents. -In the state of health, the taste of the blood is distinctly salt, -depending chiefly on the quantity of muriate of soda contained in -it. In certain violent and malignant diseases, such, for example, as -the malignant forms of fever, and more especially that form of it -termed pestilential cholera, this salt taste is scarcely, if at all, -perceptible; and it is ascertained that, in such cases, the proportion -of saline matter is sensibly diminished. - -249. The quality of the blood may be also essentially changed -by the disturbance of the balance of certain organic functions: -digestion, absorption, circulation, respiration, are indispensable -to the formation of the blood and to the nourishment of the tissues. -Absorption, nutrition, secretion, circulation, render the blood impure, -either by directly communicating to it hurtful ingredients, or by -allowing noxious matters to accumulate in it, or by destroying the -relative proportion of its constituents. Organs are specially provided, -the main function of which is to separate and remove from the blood -these injurious substances. Organs of this class are called depurating, -and the process they carry on is denominated that of depuration. The -lungs, the liver, the kidneys, are depurating organs, and one result at -least of the functions they perform is the purification or depuration -of the blood. If the lung fail to eliminate carbon, the liver bile, -the kidney urine, carbon, bile, urine, or at least the constituents -of which these substances are composed, must accumulate in the blood, -contaminate it, and render it incapable of duly nourishing and -stimulating the organs. - -250. But though the blood be good in quality and just in quantity, -health and life must still depend upon its proper distribution. It -may be sent out to the system too rapidly or too slowly. It may be -distributed to different portions of the system unequally; too much may -be sent to one organ, and too little to another: consequently, while -the latter languishes, the former may be oppressed, overwhelmed or -stimulated to violent and destructive action. In either case health is -disturbed and life endangered. - -251. Of the mode and degree in which food, air, moisture, temperature, -repletion, abstinence, exercise, indolence, influence the quantity, -quality, and distribution of the blood; of the mode in which the -condition of the blood modifies the actions both of the organic and -the animal organs; of the reason why health and disease are wholly -dependent on those states and actions, a clear and just conception -may be formed when the several functions have been described, and the -precise office of each is understood. - - - - -CHAPTER VII. - -OF THE CIRCULATION. - - Vessels connected with the heart: chambers of the - heart—Position of the heart—Pulmonic circle: - systemic circle—Structure of the heart, artery, and - vein—Consequences of the discovery of the circulation to the - discoverer—Action of the heart: sounds occasioned by its - different movements—Contraction: dilatation—Disposition - and action of the valves—Powers that move the blood—Force - of the heart—Action of the arterial tubes: the pulse: - action of the capillaries: action of the veins—Self-moving - power of the blood—Vital endowment of the capillaries: - functions—Practical applications. - - -252. The blood, being necessary to nourish the tissues and to -stimulate the organs, must be in motion in order to be borne to them. -An apparatus is provided partly for the purpose of originating an -impelling force to put the blood in motion, and partly for the purpose -of conveying the blood when in motion to the different parts of the -body. - -253. The heart is the impelling organ; the great vessels in immediate -connexion with it are the transmitting organs (fig. CXIV. 1, 2). The -heart is divided into two sets of chambers (fig. CXIV. 3, 4, 10, 11), -one for the reception of the blood from the different parts of the body -(fig. CXIV. 3, 10); the other for the communication of the impulse -which keeps the blood in motion (fig. CXIV. 4, 11). The chamber which -receives the blood is termed an auricle (fig. CXIV. 3, 10), and is -connected with a vessel termed a vein (fig. CXIV. 1, 2, 9); that which -communicates impulse to the blood is termed a ventricle (fig. CXIV. 4, -11), and is connected with a vessel termed an artery (fig. CXIV. 7, -12). The vein carries blood to the auricle; the auricle transmits it to -the ventricle; the ventricle propels it into the artery; the artery, -carrying it out from the ventricle, ultimately sends it again into the -vein, the vein returns it to the auricle, the auricle to the ventricle, -the ventricle to the artery, and thus the blood is constantly moving in -a circle; hence the name of the process, the circulation of the blood. - -[Illustration: Fig. CXIV. - -View of the heart with its several chambers exposed, and the great -vessels in connection with them. 1. The superior vena cava; 2. the -inferior vena cava; 3. the chamber called the right auricle; 4. the -chamber called the right ventricle; 5. the line marking the passage -between the two chambers, and the points of attachment of one margin of -the valve; 6. the septum between the two ventricles; 7. the pulmonary -artery arising from the right ventricle, and dividing at 8, into right -and left for the corresponding lungs; 9. the four pulmonary veins -bringing the blood from the lungs into 10, the left auricle; 11. the -left ventricle; 12. the aorta arising from the left ventricle, and -passing down behind the heart to distribute blood, by its divisions and -subdivisions, to every part of the body.] - -254. In nourishing the tissues and stimulating the organs, the blood -parts with its nutritive and stimulating constituents, and receives in -return some ingredients which can no longer be usefully employed in the -economy, and others which are positively injurious. An apparatus is -established for its renovation and depuration; this organ is termed the -lung (fig. LIX. 5), and to this organ the blood must in like manner be -conveyed. Thus the blood moves in a double circle, one from the heart -to the body and from the body back to the heart, termed the systemic -circle; the other from the heart to the lung and from the lung back -to the heart, termed the pulmonic circle. Hence in the human body the -heart is double, consisting of two corresponding parts precisely the -same in name, in nature, and in office; the one appropriated to the -greater, or the systemic, and the other to the lesser, or the pulmonic -circulation (fig. CXIV.). - -255. There is a complete separation between these two portions of the -heart (fig. CXIV. 6), formed by a strong muscular partition which -prevents any communication between them except through the medium of -vessels. - -256. The heart is situated between the two lungs (fig. LIX. 2, 5), -in the lower and fore part of the chest, nearly in the centre, but -inclining a little to the left side. Its position is oblique (fig. -LIX. 2, 5). Its basis is directed upwards, backwards, and towards the -right (fig. LIX. 2); its apex is directed downwards, forwards, and -towards the left, opposite to the interval between the cartilages -of the fifth and sixth ribs (fig. LIX. 2). It is inclosed in a bag -termed the pericardium (fig. CXV.), which consists of serous membrane. -The pericardium is considerably larger than the heart, allowing -abundant space for the action of the organ (fig. CXV.). One part of -the pericardium forms a bag around the heart (fig. CXV.); the other -part is reflected upon the heart so as to form its external covering -(fig. CXV.), and is continued for a considerable distance upon the -great vessels that go to and from the heart in such a manner that this -bag, like all the serous membranes, constitutes a shut sac. Both that -portion of the pericardium which is reflected upon the heart, and that -which forms the internal surface of the bag around it, is moistened -during life by a serous fluid, which, after death, is condensed into a -small quantity of transparent water. That portion of the pericardium -which rests on the diaphragm (fig. LXX. 1) is so firmly attached to it -that it cannot be separated without laceration, and by this attachment, -together with the great vessels at its base, the heart is firmly held -in its situation, although in the varied movements of the body it is -capable of deviating to a slight extent from the exact position here -described. - -[Illustration: Fig. CXV. - -View of the heart enveloped in its pericardium, the fore part of the -latter being cut open and reflected back.] - -257. When the interior of the heart is laid open there are brought -into view four chambers (fig. CXIV. 3, 4, 10, 11), two for each circle. -Those belonging to the pulmonic circle are on the right (fig. CXIV. 3, -4), those to the systemic on the left side of the body (fig. CXIV. 10, -11); hence the terms right and left are applied to these respective -parts of the heart. - -258. The veins which carry the blood to the right or the pulmonic -chambers are two, one of which brings it from the upper, and the other -from the lower parts of the body: the first is called the superior and -the second the inferior vena cava (fig. CXIV. 1, 2). Both pour their -blood into the first chamber, termed the right auricle (fig. CXIV. -3); from the right auricle the blood passes into the second chamber, -denominated the right ventricle (fig. CXIV. 4): from which springs -the artery which carries the blood from the heart to the lung, the -pulmonary artery (fig. CXIV. 7). This is the pulmonic circle. From -the lung the blood is returned to the heart by four veins, termed the -pulmonary veins (fig. CXIV. 9), which pour the blood into the third -chamber of the heart, the left auricle (fig. CXIV. 10). From the left -auricle it passes into the fourth chamber, the left ventricle (fig. -CXIV. 11), from which springs the artery which carries out the blood -to the system, termed the aorta (figs. CXIV. 12, and CXVII. 11). This -is the systemic circle. In the system the minute branches of the aorta -unite with the minute branches that form the venæ cavæ, which return -the blood to the right auricle of the heart, and thus the double circle -is completed. - -259. The two chambers called the auricles occupy the basis of the -heart (fig. CXIV. 3, 10). The right auricle is situated at the basis -of the right ventricle (figs. CXIV. 3, and CXVI. 4). It is partly -membranous and partly muscular. At its upper and back part is the -opening of the vena cava superior (fig. CXVI. 1), which returns the -blood to the heart from the head, neck, and all the upper parts of the -body. At its lower part is the opening of the vena cava inferior (fig. -CXVI. 2), which returns the blood from all the lower parts of the body. - -[Illustration: Fig. CXVI. - -View of the heart with the great vessels in connection with it, on the -right side, its different chambers being laid open and its structure -shown. 1. The vena cava superior; 2. the vena cava inferior; 3. cut -edge of the right auricle turned aside to show, 4. the cavity of the -right auricle into which the two venæ cavæ pour the blood returned -from all parts of the body; 5. hook suspending the reflected portion -of the wall of the auricle; 6. the right ventricle; 7. cut edge of the -wall of the ventricle, a portion of which has been removed to show 8. -the cavity of the ventricle; 9. situation of the opening between the -auricle and ventricle, called the auricular orifice of the ventricle; -10. valve placed between the auricle and ventricle, one margin being -firmly attached to the auriculo-ventricular opening in its entire -extent, the other lying loose in the cavity of the ventricle; 11. -probe passed from the auricle into the ventricle underneath the valve, -showing the course of the blood from the former chamber to the latter; -12. the columnæ carneæ attached by one extremity to the walls of the -ventricle, the other extremity ending in tendinous threads attached to -the loose margin of the valve; 13. passage to the pulmonary artery; -14. the three semilunar valves placed at the commencement of 15. the -pulmonary artery; 16. the two great branches into which the trunk of -the pulmonary artery divides, one branch going to each lung.] - -260. The auricle communicates with its corresponding ventricle by a -large opening, termed the auricular orifice of the ventricle (figs. -CXIV. 5, and CXVI. 9). All around the opening is placed a thin but -strong membrane (fig. CXVI. 10), one margin of which is firmly attached -to the wall of the ventricle (figs. CXIV. 5, and CXVI. 9), while the -other is free (fig. CXVI. 10). This membrane receives the name, and, as -will be seen immediately, performs the office of a valve. - -261. The ventricle is much thicker and proportionally stronger than the -auricle (fig. CXVI. 3, 6). It is composed almost entirely of muscular -fibre. Over nearly the whole extent of its internal surface are placed -irregular masses of muscular fibres, many of which stand out from the -wall of the ventricle like columns or pillars (fig. CXVI. 12); hence -they are called fleshy columns (columnæ carneæ). Some of these fleshy -columns are adherent by one extremity to the wall of the ventricle, -while the other extremity terminates in tendinous threads which are -attached to the membrane that forms the valve (fig. CXVI. 12). - -262. From the upper and right side of this chamber springs the -pulmonary artery (fig. CXVI. 15); at the entrance of which are placed -three membranes of a crescent or semilunar shape, termed the semilunar -valves (fig. CXVI. 14). - -263. The structure of the left side of the heart is perfectly analogous -to that of the right. Its auricle, like that on the left side, is -placed at the base of the ventricle (figs. CXIV. 10, and CXVII. 2), and -like it also is thin, being composed chiefly of membrane. At its upper -and back part (figs. CXIV. 9, and CXVII. 1) are the openings of the -four pulmonary veins, two from the right, and two from the left lung. - -264. At the passage of communication between the left auricle and -ventricle is placed a valve analogous to that on the right side (fig. -CXVII. 7). - -[Illustration: Fig. CXVII. - -View of the heart with the great vessels in connection with it, on the -left side, its chambers being laid open as in the preceding figure. -1. The four pulmonary veins opening into, 2. the cavity of the left -auricle; 3. the cut edge of the wall of the auricle; 4. the appendix -of the auricle; 5. the cavity of the left ventricle; 6. the cut edge -of the wall of the ventricle, the greater portion of the wall having -been removed to show the interior of the chamber; 7. valve placed -between the auricle and ventricle; 8. columnæ carneæ terminating in -tendinous threads attached to the loose margin of the valve; 9. probe -passed underneath the valve and its tendinous threads, raising them -from the wall of the ventricle similar to a refluent current of blood; -10. passage to 11. the aorta; 12. two of the semilunar valves placed -at the mouth of the aorta, the third having been cut away; 13. arch of -the aorta; 14. the three semilunar valves at the commencement of the -pulmonary artery seen in action, completely closing the mouth of the -vessel.] - -265. The walls of the left ventricle are nearly as thick again as those -of the right, and its fleshy columns are much larger and stronger. From -the upper and back part of this fourth chamber (fig. CXVII. 11) springs -the great systemic artery, the aorta, around the mouth of which are -placed three semilunar valves (fig. CXVII. 12), similar to those at the -mouth of the pulmonary artery. - -266. The partition which divides the two sets of chambers from each -other (fig. CXIV. 6) is wholly composed of muscular fibres, and is -called the septum of the heart. - -267. The external surface of the heart is covered by a thin but -strong membrane continued over it from the pericardium. Between this -membranous covering and its fleshy substance is lodged, even when the -body is reduced to the greatest degree of thinness, a quantity of -fat. Immediately beneath this fat are the fleshy fibres that compose -the main bulk of the organ. These fibres are arranged in a peculiar -manner. The arrangement is not perceptible when the heart is examined -in its natural state, but after it has been subjected to long-continued -boiling, which, besides separating extraneous matters from the fibres, -hardens and loosens without displacing them, the manner in which they -are disposed is manifest. Just at the point where the muscular fibres -that constitute the septum of the auricles are set upon those which -form the septum of the ventricles, and parallel with the origin of the -aorta, the heart is not muscular but tendinous. The substance called -tendon, it has been shown, is often employed in the body to afford -origin or insertion to muscular fibres, performing, in fact, the -ordinary office of bone, and substituted for it in situations where -bone would be inconvenient. From the tendinous matter just indicated -most of the fibres that constitute the muscular walls of the heart -take their origin. From this point the fibres proceed in different -directions: those which go to form the wall of the auricles ascend; -those which form the wall of the ventricles pursue an oblique course -downwards, and the arrangement of the whole is such, that a general -contraction of the fibres must necessarily bring all the parts of the -heart towards this central tendinous point. The object and the result -of this arrangement will be manifest immediately. - -268. The internal surface of the chambers of the heart, in its whole -extent, is lined by a fine transparent serous membrane, which renders -it smooth and moist; and, like all other organs which have important -functions to perform, it is plentifully supplied with blood-vessels and -nerves. - -269. Such is the structure of the organ that moves the blood. The -artery, the tube that carries it out from the heart, is a vessel -composed of three distinct layers of membrane superimposed one upon -another, and intimately united by delicate cellular tissue. These -layers are termed tunics or coats. The external coat (fig. CXVIII. 3), -which is also called the cellular, consists of minute whitish fibres, -which are dense and tough, and closely interlaced together in every -direction. They form a membrane of great strength, the elasticity of -which, especially in the longitudinal direction, is such that, in -addition to its other names, it has received that of the elastic coat. - -[Illustration: Fig. CXVIII. - -Portion of an artery, showing the several coats of which it is composed -separated from each other. 1. The internal or serous coat; 2. the -middle or fibrous coat; 3. the external or cellular coat.] - -270. The middle or the fibrous tunic is composed of yellowish -flattened fibres which pass in an oblique direction around the calibre -of the vessel, forming segments of circles, which, uniting, produce -complete rings (fig. CXVIII. 2). This tunic is thick, consisting of -several layers of fibres which it is easy to peel off in succession. -They form a firm, solid, elastic, but, at the same time, brittle -membrane. - -271. The inner tunic, thin, colourless, nearly transparent, and -perfectly smooth, is moistened by a serous fluid, and is thence called -the serous coat (fig. CXVIII. 1). To the naked eye it presents no -appearance of fibres, yet notwithstanding its extreme delicacy, it is -so strong that, after the other coats of the artery have been entirely -removed in a living animal, it is capable of resisting the impetus of -the circulation, and of preventing the dilatation of the artery. The -arteries themselves are supplied with arteries, vessels that nourish -their tissues, and which are sent to them from neighbouring branches, -seldom or never from the vessel itself to which they are distributed. -Each individual part of an artery is supplied by its own appropriate -vessels, which form but few communications above and below, so that -if care be not taken in surgical operations to disturb these nutrient -arteries very little, the vessel will perish for want of sustenance. - -272. The vein, the tube that carries back the blood to the heart, -is composed of the same number of tunics as the artery, which, with -the exception of the middle, are essentially the same in structure, -but they are all much thinner. The external tunic consists of a less -dense and strong cellular membrane; the middle tunic, instead of being -formed of elastic rings, is composed of soft and yielding fibres, -disposed in a longitudinal direction; while the inner coat, which is -still more delicate than that of the artery, is arranged in a peculiar -manner. The inner coat of most veins, at slight intervals, is formed -into folds (fig. CXX. 5), one margin of which is firmly adherent to -the circumference of the vessel, while the other margin is free and -turned in the direction of the heart. These membranous folds are termed -valves. In all veins the diameter of which is less than a line the -valves are single; in most veins of greater magnitude they are placed -in pairs, while in some of the larger trunks they are triple, and in -a few instances quadruple, and even quintuple. The veins, like the -arteries, are supplied with nutrient vessels and nerves. - -273. All the arteries of the body proceed from the two trunks already -described; that connected with the pulmonic circle, the pulmonary -artery, and that connected with the systemic circle, the aorta. These -vessels, as they go out from the heart and proceed to their ultimate -termination, are arborescent, that is, they successively increase in -number and diminish in size, like the branches of a tree going off from -the trunk (fig. CXIX. 1, 2, 3). Each trunk usually ends by dividing -into two or more branches (fig. CXIX. 1, 2), the combined area of which -is always greater than that of the trunk from which they spring, in -the proportion of about one and a half to one. As the branch proceeds -to its ultimate termination it divides and subdivides, until at length -the vessel becomes so minute, that it can no longer be distinguished -by the eye. These ultimate branches are called capillary vessels, -from their hair-like smallness (fig. CXIX. 4); but this term does not -adequately express their minuteness. It has been stated (234) that the -red particle of the blood, at the medium calculation, is not more than -the three-thousandth part of an inch in diameter; yet vast numbers of -the capillary vessels are so small that they are incapable of admitting -one of these particles, and receive only the colourless portion of the -blood. - -[Illustration: Fig. CXIX. - -View of the manner in which an artery divides and subdivides into its -ultimate branches. 1. Trunk of the artery; 2. large branches into which -it subdivides; 3. small branches, successively becoming smaller and -smaller until they terminate in 4. the capillary branches.] - -274. Every portion of an artery, by reason of the elasticity of its -coats, preserves nearly a cylindrical form, and as the area of the -branches is greater than that of the trunks, the blood, in proceeding -from the heart to the capillaries, though passing through a series of -descending cylinders, is really flowing through an enlarging space. - -275. The disposition of the veins, like that of the arteries, is -arborescent, but in an inverse order; for the course of the veins is -from capillary vessels to visible branches, and from visible branches -to large trunks (fig. CXX. 1, 2, 3). In every part of the body where -the capillary arteries terminate the capillary veins begin, and -the branches uniting to form trunks, and the small to form large -trunks, and the trunks always advancing towards the heart, and always -increasing in magnitude as they approach it, form at length the two -veins which it has been stated (258) return all the blood of the body -to the right auricle of the heart. - -[Illustration: Fig. CXX. - -View of the manner in which the minute branches of the vein unite to -form the larger branches and the trunks. 1. Capillary venous branches; -2. small branches formed by the union of the capillary; 3. larger -branches formed by the union of the smaller and gradually increasing in -size, to form the great trunk, 4. a portion of which is laid open to -show its inner surface and the arrangement of 5. the valves formed by -its inner coat.] - -276. The veins are very much more numerous than the arteries, for -they often consist of double sets, and they are at the same time -more capacious and more extensible. Reckoning the whole of the blood -at one-fifth of the weight of the body, it is estimated that, of -this quantity, about one-fourth is in the arterial and the remaining -three-fourths in the venous system. The combined area of the branches -of the veins is much greater than that of the two trunks in which they -terminate (fig. CXX. 1, 2, 3, 4): the blood, therefore, in returning to -the heart, is always flowing from a large into a smaller space. - -277. The divisions and subdivisions of the artery freely communicate -in all parts of the body by means of what are called anastomosing -branches, and this communication of branch with branch and trunk with -trunk is termed anastomosis. The same intercommunication, but with -still greater freedom and frequency, takes place among the branches -of veins. In both orders of vessels the communication is frequent in -proportion to the minuteness of the branch and its distance from the -heart. It is also more frequent in proportion as a part is exposed -to pressure; hence the minute arteries and veins about a joint are -distinguished for the multitude of their anastomosing branches; and -above all, it is frequent in proportion to the importance of the organ; -hence the most remarkable anastomosis in the body is in the brain. By -this provision care is taken that no part be deprived of its supply of -blood; for if one channel be blocked up, a hundred more are open to the -current, and the transmission of it to any particular region or organ -by two or more channels, instead of through one trunk, is a part of the -same provision. Thus the fore-arm possesses four principal arteries -with corresponding veins, and the brain receives its blood through four -totally independent canals[6]. - -278. That the blood is really a flowing stream, and that it pursues the -course described (258), is indubitable. For, - -(1.) With the microscope, in the transparent parts of animals, the -blood can be seen in motion (fig. CXXI.); and if its course be -attentively observed, its route may be clearly traced. - -[Illustration: Fig. CXXI. - -View of the circulation of the blood as seen under the microscope in -the web of the frog's foot.] - -(2.) The membranes termed valves are so placed as to allow of the -freest passage to the blood in the circle described, while they either -altogether prevent or exceedingly impede its movement in any other -direction. - -(3.) The effect of a ligature placed around a vein and an artery, and -of a puncture made above the ligature in the one vessel and below it in -the other, demonstrate both the motion of the blood and the course of -it. When a ligature is placed around a vein, that part of the vessel -which is most distant from the heart becomes full and turgid on account -of the accumulation of blood in it; while the part of the vessel which -is between the ligature and the heart becomes empty and flaccid, -because it has carried on its contents to the heart, and it can receive -no fresh supply from the body. When, on the contrary, a ligature is -placed around an artery, that portion of the vessel which lies between -the ligature and the heart becomes full and turgid, and the other -portion empty and flaccid. This can only be because the contents of -the two vessels move in opposite directions,—from the heart to the -artery, from the artery to the vein, and from the vein to the heart. -At the same time, if the vein be punctured above the ligature, there -will be little or no loss of blood; while if it be punctured below -the ligature, the blood will continue to flow until the loss of it -occasions death, which could not be unless the blood were in motion, -nor unless the direction of its course were from the artery to the vein -and from the vein to the heart. - -(4.) If fluids be injected into the veins or arteries, whether of the -dead or of the living body, they readily make their way and fill the -vessels, if thrown in the direction stated to be the natural course -of the circulation; but they are strongly resisted if forced in the -opposite direction. - -279. Such is the description, and with the exception of the first -proof, such the evidence of the circulation of the blood in the -human body, pretty much as it was given by the discoverer of it, the -illustrious Harvey. Before the time of Harvey, a vague and indistinct -conception that the blood was not without motion in the body had been -formed by several anatomists. It is analogous to the ordinary mode -in which the human mind arrives at discovery (chap. iii., p. 103), -that many minds should have an imperfect perception of an unknown -truth, before some one mind sees it in its completeness and fully -discloses it. Having, about the year 1620, succeeded in completely -tracing the circle in which the blood moves, and having at that -time collected all the evidence of the fact, with a rare degree of -philosophical forbearance, Harvey still spent no less than eight years -in re-examining the subject, and in maturing the proof of every point, -before he ventured to speak of it in public. The brief tract which at -length he published was written with extreme simplicity, clearness, -and perspicuity, and has been justly characterised as one of the most -admirable examples of a series of arguments deduced from observation -and experiment that ever appeared on any subject. - -280. Cotemporaries are seldom grateful to discoverers. More than one -instance is on record in which a man has injured his fortune and lost -his happiness through the elucidation and establishment of a truth -which has given him immortality. It may be that there are physical -truths yet to be brought to light, to say nothing of new applications -of old truths, which, if they could be announced and demonstrated -to-day, would be the ruin of the discoverer. It is certain that there -are moral truths to be discovered, expounded, and enforced, which, if -any man had now penetration enough to see them, and courage enough to -express them, would cause him to be regarded by the present generation -with horror and detestation. Perhaps, during those eight years of -re-examination, the discoverer of the circulation sometimes endeavoured -in imagination to trace the effect which the stupendous fact at the -knowledge of which he had arrived would have on the progress of his -favourite science; and, it may be, the hope and the expectation -occasionally arose that the inestimable benefit he was about to confer -on his fellow men would secure to him some portion of their esteem -and confidence. What must have been his disappointment when he found, -after the publication of his tract, that the little practice he had -had as a physician, by degrees fell off. He was too speculative, -too theoretical, not practical. Such was the view taken even by his -friends. His enemies saw in his tract nothing but indications of a -presumptuous mind that dared to call in question the revered authority -of the ancients; and some of them saw, moreover, indications of a -malignant mind, that conceived and defended doctrines which, if not -checked, would undermine the very foundations of morality and religion. -When the evidence of the truth became irresistible, then these persons -suddenly turned round and said, that it was all known before, and -that the sole merit of this vaunted discoverer consisted in having -circulated the circulation. The pun was not fatal to the future fame of -this truly great man, nor even to the gradual though slow return of the -public confidence even during his own time; for he lived to attain the -summit of reputation. - -281. It is then indubitably established that the whole blood of the -body in successive streams is collected and concentrated at the heart. -The object of the accumulation of a certain mass of it at this organ -is to subject it to the action of a strong muscle, and thereby to -determine its transmission with adequate force and precision through -the different sets of capillary vessels. - -282. In the accomplishment of this object the heart performs a twofold -action; that of contraction and that of dilatation. The auricles -contract and thereby diminish their cavities, then dilate and thereby -expand them, and the one action alternates with the other. There is the -like alternate contraction and dilatation of the ventricles. The first -action is termed systole, the second diastole, and both are performed -with force. - -283. When the heart is laid open to view in a living animal, and its -movements are carefully observed, it is apparent that the two auricles -contract together; that the two ventricles contract together; that -these motions alternate with each other, and that they proceed in -regular succession. The interval between these alternate movements is, -however, exceedingly short, and can scarcely be perceived when the -heart is acting with full vigour; but it is evident when its action is -somewhat languid. - -284. When the ventricles contract, the apex of the heart is drawn -upwards, and at the same time raised or tilted forwards. It is during -this systole of the ventricles, and in consequence of this result of -their action, that the apex of the heart gives that impulse against the -walls of the chest which is felt in the natural state between the fifth -and sixth ribs, and which just perceptibly precedes the pulse at the -wrist. - -285. When the ear is applied to the human chest, over the situation of -the heart, a dull and somewhat prolonged sound is heard, which precedes -and accompanies the impulse of the heart against the chest. This dull -sound is immediately succeeded by a shorter and sharper sound: after -this there is a short pause; and then the dull sound and impulse are -again renewed. The duller sound and stronger impulse are ascribed to -the contraction of the ventricles, and the sharper sound and feebler -impulse to that of the auricles. - -286. The movement of the heart is effected by the contraction of its -muscular fibres. Those fibres rest, as upon a firm support, on the -tendinous matter to which they are attached, from which they diverge, -and towards which their contraction must necessarily bring all the -parts of the heart (267). The result of their contraction is the -powerful compression of all the chambers of the heart, and thereby the -forcible ejection of their contents through the natural openings. - -287. But the chambers, alternately with forcible contraction, perform -the action of forcible dilatation. This movement of dilatation is -effected by the reaction of the elasticity of the tendinous matter on -which the muscular fibres are supported (267). This highly elastic -substance, by the contraction of the fibres, is brought into a state of -extreme tension. The contraction of the fibres ceasing, that moment the -tense tendon recoils with a force exactly proportionate to the degree -of tension into which it had been brought. Thus the very agent that is -employed forcibly to close the chamber is made the main instrument of -securing its instantaneous re-opening. A vital energy is appointed to -accomplish what is indispensable, and what nothing else can effect, -the origination of a motive power; a physical agent is conjoined to -perform the easier task to which it is competent; and the two powers, -the vital and the physical, work in harmony, each acting alternately, -and each, with undeviating regularity and unfailing energy, fulfilling -its appropriate office. - -288. When the chambers of the heart which open into each other, and -which as freely communicate with the great vessels that enter and -proceed from them, are forcibly closed, and the blood they contain is -projected from them, how is one uniform forward direction given to the -current? Why, when the right ventricle contracts, is the blood not sent -back into the right auricle, as well as forward into the pulmonary -artery? There is but one mode of preventing such an event, which is to -place a flood-gate between the two chambers; and there a flood-gate -is placed, and that flood-gate is the valve. As long as the blood -proceeds onwards in the direct course of the circulation, it presses -this membrane close to the side of the heart, and thereby prevents it -from occasioning any impediment to the current. When, on the contrary, -the blood is forced backwards, and attempts to re-enter the auricle, -being of course driven in all directions, some of it passes between the -wall of the ventricle and the valve. The moment it is in this situation -it raises up the valve, carries it over the mouth of the passage, and -shuts up the channel. There cannot be a more perfect flood-gate. - -289. This is beautiful mechanism; but there is another arrangement -which surpasses mere mechanism, however beautiful. It has been shown -(260) that one edge of the membrane that forms the valve is firmly -adherent to the wall of the ventricle, while the other edge, when not -in action, appears to lie loosely in the ventricle (fig. CXVI. 10). -Were this edge really loose the refluent current would carry it back -completely into the auricle, and so counteract its action as a valve; -but it is attached to the tendinous threads proceeding from the fleshy -columns that stand along the wall of the ventricle (fig. CXVI. 12). By -these tendinous threads, as by so many strings, the membrane is firmly -held in its proper position (fig. CXVI. 10, 12); and the refluent -current cannot carry it into the auricle. Thus far the arrangement is -mechanical. But each of these fleshy columns is a muscle, exerting -a proper muscular action. Among the stimulants which excite the -contractility of the muscular fibre, one of the most powerful is -distension. The refluent current distends the membrane; the distension -of the membrane stretches the tendinous threads attached to it; the -stretching of its tendinous threads stretches the fleshy column; by -this distension of the column it is excited to contraction; by the -contraction of the column its thread is shortened; by the shortening -of the thread the valve is tightened, and that in the exact degree -in which the thread is shortened. So, the greater the impetus of the -refluent blood, the greater the distension of the membrane; and the -greater the distension of the membrane, the greater the excitement of -the fleshy column; the greater the energy with which it is stimulated -to act, the greater, therefore, the security that the valve will be -held just in the position that is required, with exactly the force that -is needed. Here, then, is a flood-gate not only well constructed as far -as regards the mechanical arrangement, but so endowed as to be able to -act with additional force whenever additional force is requisite; to -put forth on every occasion, as the occasion arises, just the degree of -strength required, and no more. - -290. The contraction of the heart is the power that moves the blood; -and this contraction generates a force which is adequate to impel it -through the circle. From experiments performed by Dr. Hales it appears -that if the artery of a large animal, such as the horse, be made to -communicate with an upright tube, the blood will ascend in the tube to -the height of about ten feet above the level of the heart, and will -afterwards continue there rising and falling a few inches with each -pulsation of the heart. In this animal, then, the heart acts with a -force capable of maintaining a column of ten feet. Now a column of ten -feet indicates a pressure of about four pounds and a half in a square -inch of surface. Suppose the human heart to be capable of supporting -a column of blood eight feet high, this will indicate a pressure of -four pounds to the square inch; but the left ventricle of the heart, -while it injects its column of blood into the aorta, has to overcome -the inertia of the quantity of blood projected; of the mass already -in the artery, and of the elasticity of the vessel yielding to a -momentary increase of pressure: it is probable, therefore, that the -heart acts with a force of six pounds on the inch. The left ventricle, -when distended, has about ten square inches of internal surface; -consequently the whole force exerted by it may be about sixty pounds. -According to the calculation of Hales, it is fifty-one and a half. -Now, it is proved by numerous experiments, that, after death, a slight -impulse with the syringe, certainly much less than that which is acting -upon the blood in the same artery during life, is sufficient to propel -a solution of indigo, or fresh drawn blood, from a large artery into -the extreme capillary. If, therefore, after death, a slight force will -fill the capillaries, a force during life equal to sixty pounds must be -adequate to do so. - -291. The heart, with a force equal to the pressure of sixty pounds, -propels into the artery two ounces of blood at every contraction. It -contracts four thousand times in an hour. There passes through the -heart, therefore, every hour, eight thousand ounces or seven hundred -pounds of blood. It has been stated (216) that the whole mass of blood -in an adult is about twenty-eight pounds: on an average the entire -circulation is completed in two minutes and a half; consequently a -quantity of blood equal to the whole mass passes through the heart -from twenty to twenty-four times in an hour. But though the average -space of time requisite to accomplish a complete circulation may be -two minutes and a half, yet when a stream of blood leaves the heart, -different portions of it must finish their circle at very different -periods, depending in part upon the length of the course which they -have to go, and in part upon the degree of resistance that obstructs -their passage. A part of the stream, it is obvious, finishes its course -in circulating through the heart itself; another portion takes a longer -circuit through the chest; another extends the circle round the head; -and another visits the part placed at the remotest distance from the -central moving power. Such is the velocity with which the current -sometimes goes, that, in the horse, a fluid injected into the great -vein of the neck, on one side, has been detected in the vein on the -opposite side, and even in the vein of the foot, within half a minute. - -292. It has been shown (282) that the different chambers of the -heart have a tendency to perform their movements in a uniform manner, -and in a successive order; that they contract and dilate in regular -alternation, and at equal intervals; but, moreover, they continue -these movements equally without rest and without fatigue. On go the -motions, night and day, for eighty years together, at the rate of -a hundred thousand strokes every twenty-four hours, alike without -disorder, cessation, or weariness. The muscles of the arm tire after -an hour's exertion, are exhausted after a day's labour, and can by no -effort be made to work beyond a certain period. There is no appreciable -difference between the muscular substance of the heart and that of the -arm. It is true that the heart is placed under one condition which -is peculiar. Muscles contract on the application of stimuli; and -different muscles are obedient to different stimuli,—the voluntary -muscles to the stimulus of volition, and the heart to that of the -blood. The exertion of volition is not constant, but occasional; the -muscle acts only when it is excited by the application of its stimulus: -hence the voluntary muscle has considerable intervals of rest. The -blood, on the contrary, is conveyed to the heart without ceasing, in a -determinate manner, in a successive order; and this is the reason why -through life its action is uniform: it uniformly receives a due supply -of its appropriate stimulus. But why it is unwearied, why it never -requires rest, we do not know. We know the necessities of the system -which render it indispensable that it should be capable of untiring -action, for we know that the first hour of its repose would be the -last of life; but of the mode in which this wonderful endowment is -communicated, or of the relations upon which it is dependent, we are -wholly ignorant. - -293. The force exerted by the heart is vital. It is distinguished from -mechanical force in being produced by the very engine that exerts it. -In the best-constructed machinery there is no real generation of power. -There is merely concentration and direction of it. In the recoil of the -spring, in the reaction of condensed steam, the energy of the expansive -impulse is never greater than the force employed to compress or -condense, and the moment this power is expended all capacity of motion -is at an end. But the heart produces a force equal to the pressure of -sixty pounds by the gentlest application of a bland fluid. Here no -force is communicated to be again given out, as in every mechanical -moving power; but it is new power, power really and properly generated; -and this power is the result of vital action, and is never in any case -the result of action that is not vital. - -294. The heart projects the blood with a given force into the arterial -tubes. The arteries in the living body are always filled to distension, -and somewhat beyond it, by the quantity of blood that is in them. It -has been shown that the elasticity of their coats is such as to give -to them, even after death, the form of open hollow cylinders (274). -During life they are kept in a state of distension by the quantity of -blood they contain. By virtue of their elasticity they react upon -their contents with a force exactly proportioned to the degree of their -distension, that is, with a force at least adequate to keep them always -open and rigid. - -295. These open and rigid tubes, already filled to distension, and -somewhat beyond it, receive at every contraction of the heart a -forcible injection of a new wave of blood. The first effect of the -injection of this new wave into a tube previously full to distension, -is to cause the current to proceed by jerks or jets, each jerk or -jet corresponding to the contraction of the heart. And, accordingly, -by this jet-like motion, the flow of the blood in the artery is -distinguished from that in the vein, in which latter vessel the current -is an equal and tranquil stream. - -296. The second effect of this new wave is to occasion some further -distension of the already distended artery, and accordingly, when -the vessel is exposed in a living animal, and its action carefully -observed, a slight augmentation of its diameter is distinguishable at -every contraction of the heart. This new wave while it distends must at -the same time slightly elongate the vessel; cause its straight portions -to bend a little, and its curved portions to bend still more; and, -consequently, in some situations, to lift it a little from its place, -giving it a slight degree of locomotion;—and these two causes combined -produce the pulse. When the finger is pressed gently on an artery, at -the instant of the contraction of the heart, the vessel is felt to -bound against the finger with a certain degree of force: this, as just -stated, is owing to a slight distension of the vessel by the new wave -of blood, together with a slight elongation of it, and a gentle rising -from its situation. - -297. The blood, in flowing through the arterial trunks and branches -to the capillaries, through the arterial to the venous capillaries, and -through the venous branches and trunks back to the heart, is exposed -to numerous and powerful causes of retardation: such, for example, -as the friction between the blood and the sides of the vessels, the -numerous curves and angles formed by the branches in springing from the -trunks, the tortuous course of the vessels in many parts of the body, -and the increasing area of the arterial branches as they multiply and -subdivide. Yet the extraordinary fact has been recently discovered, -that the blood moves with the same momentum or force in every part of -the arterial system, in the aorta, in the artery in the neck which -carries the blood to the head (the carotid artery), in the artery of -the arm (the humeral artery), in the artery of the lower extremity -(the femoral artery); in a word, in the minute and remote capillary, -and in the large trunk near the heart. Having contrived an instrument -by which the force of the blood as it flows in its vessel could be -accurately indicated by the rise of mercury in a tube, M. Poiseuille -found that the elevation of the mercury is uniformly the same in the -different arteries of the same animal, whatever the size of the artery -and its distance from the heart. This tube was inserted, for example, -into the common carotid artery of a horse: the diameter of the vessel -was 34/100ths of an inch; its distance from the heart was thirty-nine -inches; the height to which the mercury rose in the graduated tube was -accurately marked. The tube was then inserted into a muscular branch of -the artery in the thigh: the diameter of this vessel was 7/100ths of an -inch, and its distance from the heart 67½ inches. According to the mean -of nine observations, the mercury rose in both tubes to precisely the -same elevation. Here is another instance of the beautiful adjustments -everywhere established in the living economy. The blood is sent by a -living engine, moving under laws peculiar to the state of life, into -living vessels, which in their turn acting under laws peculiar to the -state of life, so accommodate themselves to the current as absolutely -to offer no resistance to its progress; so accommodate themselves to -the moving power, as completely and everywhere to obviate the physical -impediments to motion inseparable from inorganic matter. - -298. That the arterial tubes do possess and exert a truly vital power, -modifying the current of the blood they contain, is indubitably -established. - -1. If in a living animal the trunk of an artery be laid bare, the mere -exposure of it to the atmospheric air causes it to contract to such a -degree, that its size becomes obviously and strikingly diminished. This -can result only from the exertion of a vital property, for no dead tube -is capable in such a manner of diminishing its diameter. - -2. If during life an artery be opened and the animal be largely bled, -the arteries become progressively smaller and smaller as the quantity -of blood in the body diminishes. If the bleeding be continued until the -animal dies, and the arteries of the system be immediately examined, -they are found to be reduced to a very small size; if again examined -some time after death, they are found to have become larger, and they -go on growing successively larger and larger until they regain nearly -their original magnitude, which they retain until they are decomposed -by putrefaction. - -3. M. Poiseuille distended with water the artery of an animal just -killed. This water was urged by the pressure of a given column of -mercury. The force of the reaction of the artery was now measured by -the height of a column of mercury which the water expelled from the -artery could support. It was found that the artery reacted with a -force greater than that employed to distend it, and greater than the -same artery could exert some time after death; but since mechanical -reaction can never be greater than the force previously exerted upon -it (293), it follows that the excess of the reaction indicated in this -case was vital. - -4. If an artery be exposed and a mechanical or chemical stimulus be -applied to it, its diameter is altered, sometimes becoming larger and -sometimes smaller, according to the kind of agent employed. - -299. Any one of these facts, taken by itself, affords a demonstration -that the arterial trunks and branches are capable of enlarging and -diminishing their diameter by virtue of a vital endowment. There is -complete evidence that the exertion of this vital power on the part -of the arterial trunk is not to communicate to the blood the smallest -impulsive force; the engine constructed for the express purpose of -working the current generates all the force that is required; but the -labour of the engine is economized by imparting to the tubes that -receive the stream a vital property, by which they wholly remove the -physical obstructions to its motion. - -300. Driven by the heart through the arterial branches into the -capillaries, the blood courses along these minute vessels urged by the -same power. The most careful observers, from Haller and Spalanzani -down to the present time, concur in stating that the pulsatory -movement communicated by the heart to the blood in the great arteries -is distinctly visible under the microscope in the capillaries. "I -have often observed in frogs and tadpoles, and once in the bat," says -Wedemeyer, "that when the circulation was becoming feeble, the blood -in the finest capillaries advanced by jerks, corresponding with the -contractions of the heart. I remarked the same appearance in the fine -veins several times in the toad and tadpole, and once in the frog." If -an experimenter so dispose the circulation of the limb of an animal -that the flow of blood be confined to the branches of a single artery, -and a corresponding vein, it is found that the blood stagnates in the -vein whenever the current in the artery is stopped by a ligature, but -no sooner is the ligature removed from the artery, than the blood -begins again to flow freely along the vein, the capillaries of the -artery which have to send on the current to those of the vein being -now again within the influence of the heart. And if the impulse of -the heart be removed from the capillary system, by placing a ligature -around the aorta, the capillary circulation is uniformly and completely -stopped. - -301. It was found by Dr. Hales, that, under ordinary circumstances, -the blood rises in a tube connected with a vein to the height only of -six inches, while it has been shown (290) that in the artery it ascends -as high as ten feet. This prodigious difference between the venous and -the arterial tension led to the conclusion that the impulsive force of -the heart was all but exhausted before the blood reached the veins, and -set physiologists on the search for other powers to carry on the venous -circulation. It was overlooked that the blood has an open and ready -escape from the great trunks of the veins through the right chambers of -the heart, and that in consequence of this free escape of their fluid, -these vessels indicate no greater tension than is just sufficient to -lift the blood to the heart, and to overcome friction[7]. M. Magendie -having laid bare the chief artery and vein of a living limb, and having -raised the vessels in such a manner that he could place a ligature -around the former, without including the latter, found that the flow -of blood from a puncture made below a ligature on the vein, was rapid -or slow, according as the heart was allowed to produce a greater or -less degree of tension in the artery, which tension was regulated by -compressing the artery between the fingers. After a similar preparation -of a limb, a ligature was placed around the vein; a tube was then -inserted into it; it was found that the blood ascended in the tube from -the obstructed vein just as high as from the artery. - -302. Thus we are able to trace the action of the heart from the -beginning to the end of the circle. Of this circle it is the sole -moving power; but it is a living engine acting in combination with -living vessels. The force it exerts is a vital force, economized by the -agency of a vital property communicated to the vessels, by virtue of -which they spontaneously and completely remove all physical obstruction -to the progress of the stream through its channels. - -303. Some German physiologists of great eminence, after a careful and -patient observation of the blood, have satisfied themselves that in -addition to the contraction of the heart, it is necessary to admit a -second original and independent motive force, namely, a self-moving -power inherent in the particles of the blood itself. The blood we -know is a living substance. No reason can be assigned why the power -of originating motion should not be communicated to such a substance -as well as to the muscular fibre, of which, indeed, one constituent -of the blood affords the basis. Such a power, if found to be inherent -in the particles of the blood, would explain some phenomena connected -with the circulation not yet clearly elucidated; but the proof of the -self-moving power of the blood does not yet seem to be complete. It -is, however, impossible to explain the phenomena of the circulation, -or to obtain a satisfactory view of some of the other functions of the -economy, without supposing the particles of the blood to be endowed -with a vital power of repulsion, in consequence of which they are -prevented from uniting when in contact, and the fluidity of the mass is -maintained. - -In this account of the powers that move the blood, no notice has been -taken of the physical agents supposed to act as auxiliaries to the -heart, in carrying on the circulation, such as the suction power of the -thorax, and of the auricles of the heart, and the capillary attraction -of the vessels; because, without questioning the existence of such -agents, or denying that advantage may be taken of them, it seems pretty -clear that their influence is but trivial, and they assumed importance -only when the vital endowments of the tissues were not well understood. - -304. The ultimate end for which the apparatus of the circulation is -constructed, and for which all its action is exerted, is to convey -arterial blood to the capillary arteries. These vessels are totally -distinct in structure and in office from the larger arterial tubes. All -the tunics of these minute vessels diminish in thickness and strength -as the tubes lessen in size, but more especially the middle or the -fibrous coat; which, according to Wedemeyer, may still be distinguished -by its colour in the transverse section of any vessel whose internal -diameter is not less than the tenth of a line; but that it entirely -disappears in vessels too small and too remote to receive the wave of -blood in a manifest jet. But while the membranous tunics diminish, -the nervous filaments distributed to them increase: the smaller and -thinner the capillary, the greater the proportionate quantity of its -nervous matter; and this is most manifest in organs of the greatest -irritability. The coats of the capillaries successively becoming -thinner and thinner, at length disappear altogether, and the vessels -ultimately terminate in membraneless canals formed in the substance of -the tissues. "The blood in the finest capillaries," says Wedemeyer, -"no longer flows within actual vessels; it is not contained in tubes -whose parietes are formed by a membranous substance distinguishable by -its texture and compactness from the adjoining cellular tissue: it is -contained in the different tissues in channels which it forms in them -for itself; and, under the microscope, the stream is seen easily and -rapidly to work out for itself a new passage in the tissues which it -penetrates." - -305. Some of these fine capillaries, before they entirely lose their -membranous tunics, communicate directly with veins. Of the capillaries -which terminate by direct communication with veins, some are large -enough to admit of three or four of the red particles of the blood -abreast; the diameter of others is sufficient to admit only of one; -while others are so small that they can transmit nothing but the serum -of the blood. As long as the capillary is of sufficient magnitude -to receive three or four of the particles abreast, it is evident -that it possesses regular parietes; but by far the greater number, -before they communicate with veins, lose altogether their membranous -coats. There are no visible openings or pores in the sides or ends -of the capillaries by means of which the blood can be extravasated, -preparatory to its being imbibed by the veins. There is nowhere -apparent a sudden passage of the arterial into the venous stream; no -abrupt boundary between the division of the two systems. The arterial -streamlet winds through long routes, and describes numerous turns -before it assumes the nature and takes the direction of a venous -streamlet. The ultimate capillary rarely passes from a large arterial -into a large venous branch. - -306. The vital power which it has been shown (298) is possessed by -the arterial trunks and branches, is still more intense in the minute -capillaries. If alcohol, strong acetic acid, naphtha, and other -stimulating fluids, be injected into the arteries of a living animal, -it is found that they are not transmitted through the capillaries -at all, or, at all events, that they make their way through them -with extreme difficulty; whereas mild, unirritating fluids pass with -rapidity and ease. Wedemeyer exposed and divided the main artery in -the fore-leg of a horse, together with the corresponding vein in the -shoulder. Several syringes-full of tepid water were now injected into -the lower end of the artery. The gentlest pressure was sufficient to -force the fluid through the capillaries. At each injection the water -issued in a full stream from the aperture of the vein, the flow of the -fluid ceasing as soon as the injection was stopped. Next, instead of -water, four syringes-full of pure cold brandy were injected. To propel -this fluid through the capillaries, so as to render its smell and taste -perceptible at the aperture of the vein, required a great degree of -pressure; and when at last the fluid issued from the vein, it merely -trickled in a feeble stream. - -The experiment being repeated on another horse with vinegar, six -syringes-full of which being injected in rapid succession, at first -this fluid passed as easily as water, afterwards it flowed with greater -difficulty and in a small stream; before long the force required to -propel it was extreme, and at last the obstruction to its passage -became complete, so that no fluid whatever issued from the vein. - -These experiments, whenever repeated, afforded the same result, and -they demonstrate that the capillaries are capable of being stimulated -to contract upon their contents, and that they can contract with such -force as to stop the current. It is manifest that the power by which -they do this is vital, because after death all fluids, the mildest and -the most acrid, pass through them with equal facility. - -307. Drs. Thompson, Philip, Hastings, and others in this country, -have applied stimulants of various kinds to the capillary arteries, -in order to observe with the microscope the changes which the vessels -undergo. The results of these experiments, performed independently, -agree with each other; and all the observers concur in stating that -those results are so obvious and decisive as to admit of no question. -Wedemeyer, fully aware of all that had been done on this subject by -the English physiologists, repeated their experiments with his usual -patience and care, vigilantly watching the effects with his microscope. -His observations completely coincide with those of our countrymen. The -circulation being observed in the mesentery of the frog and in the web -of its foot, it was apparent that no change whatever took place in -the diameter of the small arteries, nor in that of the capillaries, -as long as the circulation was allowed to go on in its natural state; -but as soon as stimulants were applied to them, an alteration of their -diameter was visible. Alcohol, without much apparent contraction of the -vessels, stopped the flow of the blood. Muriate of soda, in the course -of three or four minutes, caused the vessels to contract one-fifth of -their calibre, which contraction was followed by dilatation and gradual -retardation and stoppage of the blood. Ammonia caused immediate and -direct dilatation, and the effect of galvanism was still more striking. -In a space of time varying from ten to thirty seconds, nay, sometimes -immediately after the completion of the galvanic circle, the vessels -contracted, some a fourth, others half, and others three-fourths, of -their calibre. The flow of the blood through the contracted vessels -was accelerated. The contraction sometimes lasted a considerable time, -occasionally several hours; in other instances the contraction ceased -in ten minutes, and the vessels resumed their natural diameter. A -second application of galvanism to the same capillaries seldom caused -any material contraction. - -308. The evidence, then, is abundant that stimulants are capable of -modifying to a great extent the action of the capillary arteries, -sometimes causing them to contract, at other times to dilate; sometimes -quickening the flow of blood through them, at other times retarding it, -and frequently altogether arresting its motion. This contractile power -of the capillaries must be a vital endowment, for no such property is -possessed by any substance destitute of life, and there is satisfactory -evidence that it is communicated, regulated, and controlled by the -organic nerves, which, as has been shown, increase as the size of the -vessels and the thickness of their membranous tunics diminish. The -powerful influence of these nerves upon the capillary vessels is placed -beyond doubt or controversy by the obvious local changes produced in -the capillary circulation by sudden, and even by mental, impressions, -by the flush of the cheek and the sparkle of the eye, at a thought -conceived or a sound heard; changes which can be effected, as far as we -have any knowledge, by no medium excepting that of the nerves. The part -performed by electricity, the physical agent by which it is conceived -the nerves operate, will be considered hereafter. - -309. Exerting upon each other a vital force of repulsion, under a -vital influence derived from the organic nerves, urged by the vital -contraction of the heart, the particles of the blood reach the extreme -capillaries. Most of these capillaries terminate (304) in canals, which -they work out for themselves in the substance of the tissues. The -tissues are endowed with a vital attractive force, which they exert -upon the blood—an elective as well as an attractive force: for in -every part of the body, in the brain, the heart, the lung, the muscle, -the membrane, the bone, each tissue attracts only those constituents -of which it is itself composed. Thus the common current, rich in all -the proximate constituents of the tissues, flows out to each. As the -current approaches the tissue, the particles appropriate to the tissue -feel its attractive force, obey it, quit the stream, mingle with the -substance of the tissue, become identified with it, and are changed -into its own true and proper nature. Meantime, the particles which are -not appropriate to that particular tissue, not being attracted by it, -do not quit the current, but passing on, are borne by other capillaries -to other tissues, to which they are appropriate, and by which they -are apprehended and assimilated, When it has given to the tissues the -constituents with which it abounded, and received from them particles -no longer useful, and which would become noxious, the blood flows into -the veins to be returned by the pulmonic heart to the lung, where, -parting with the useless and noxious matter it has accumulated, and, -replenished with new proximate principles, it returns to the systemic -heart, by which it is again sent back to the tissues. - -310. Particles of blood are seen to quit the current and mingle with -the tissues; particles are seen to quit the tissues and mingle with -the current. But all that we can see, with the best aid we can get, -does but bring us to the confines of the grand operations that go on, -of which we are altogether ignorant. Arterial blood is conveyed by -the arteries to the capillaries; but before it has passed from under -the influence of the capillaries it has ceased to be arterial blood. -Arterial blood is conveyed by the carotid artery to the brain; but -the cerebral capillaries do not deposit blood, but brain. Arterial -blood is conveyed by its nutrient arteries to bone, but the osseous -capillaries do not deposit blood, but bone. Arterial blood is conveyed -by the muscular arteries to muscle, but the muscular capillaries do not -deposit blood, but muscle. The blood conveyed by the capillaries of -brain, bone, and muscle is the same, all comes alike from the systemic -heart, and is alike conveyed to all tissues; yet in the one it becomes -brain, in the other bone, and in the third muscle. Out of one and the -same fluid these living chemists manufacture cuticle, and membrane, and -muscle, and brain, and bone; the tears, the wax, the fat, the saliva, -the gastric juice, the milk, the bile, all the fluids, and all the -solids of the body. - -311. And they do still more; for they are architects as well as -chemists; after they have manufactured the tissue, they construct the -organ. The capillaries of the eye not only form its different membranes -and humours, but arrange them in such a manner as to constitute the -optical instrument; and the capillaries of the brain not only form -cerebral matter, but build it up into the instrument of sensation, -thought, and motion. - -312. The practical applications of these phenomena are numerous and -most important; but they can be clearly and impressively stated -only when the operation of the physical agents which influence the -circulation, and which proportionally affect life and health, has been -explained. - - - - -FOOTNOTES. - - -[1] Computationi in alimentis faciendæ hanc formam esse Ulpianus -scribit, ut _à primâ ætate_ usque ad annum vicesimum quantitas -alimentorum triginta annorum computetur, ejusque quantitatis Falcidia -præstetur: _ab annis verò viginti_ usque ad annum vicesimumquintum -annorum viginti octo: _ab annis vigintiquinque_ usque ad annos -triginta, annorum vigintiquinque: _ab annis triginta_ usque ad annos -trigintaquinque annorum viginti duo; _ab annis trigintaquinque_ -usque ad annos quadraginta annorum viginti: _ab annis quadraginta_ -usque ad annos quinquaginta tot annorum computatio fit quot ætate -ejus ad annum sexagesimum deerit, remisso uno anno: _ab anno verò -quinquagesimo_ usque ad annum quinquagesimumquintum annorum novem: -_ab annis quinquagintaquinque_ usque ad annum sexagesimum annorum -septem: _ab annis sexaginta_, cujuscunque ætatis sit, annorum quinque; -eoque nos jure uti Ulpianus ait, et circa compu tationem ususfructus -faciendam. Solitum est tamen _à primâ ætate_ usque ad annum trigesimum -computationem annorum triginta fieri: _ab annis verò triginta_ tot -annorum computationem inire, quot ad annum sexagesimum deesse videntur; -nunquam ergo amplius quam triginta aunorum computatio initur. Sic -denique, et si Reipublicæ ususfructus egetur, sive simpliciter, sive -ad ludos, triginta annorum computatio fit. Si quis ex heredibus rem -propriam esse contendat, deinde hereditariam esse convincatur: quidem -putant ejus quoque Falcidiam non posse retineri; quià nihil intersit, -subtraxerit an hereditariam esse negaverit. Quod Ulpianus rectè -improbat. (Vide Justin. Pandect. lib. 35, tit. 2, ad Legem Falcidiam.) - -[2] Which maximum is a little above the highest point hitherto any -where attained. - -[3] Hence in the preparation of jelly as an article of diet, the parts -of young animals, as the feet of the calf, are principally employed; -whereas soups made from beef contain a large proportion of albumen, -while in those made from veal the proportion of jelly preponderates. - -[4] Treatise on Ligaments, by Bransby B. Cooper, Esq. - -[5] For these illustrations I am indebted to Mr. Lister, who has been -so kind as to make drawings of the objects for me. - -[6] Whenever there is any interruption to the ordinary flow of the -circulating fluids, the powers of the anastomosing circulation are -capable of being increased to a surprising extent. The aorta itself -has frequently been tied in animals of considerable size without -destroying life; in the human body it has also been found obliterated -by disease in different parts of its course, in one case as high -as the termination of its curvature. In the cure for aneurism the -external iliac artery has been tied by Mr. Abernethy with success; the -subclavian artery below the clavicle by Mr. Keate; the common carotid -by Sir Astley Cooper; the subclavian artery above the clavicle by -Mr. Ramsden; the internal iliac artery by Dr. Stevens; the arteria -innominata by Dr. Mott, of New York; and lastly, the abdominal aorta -itself, by Sir A. Cooper. Mr. Grainger tied the abdominal aorta of a -dog; when the animal had recovered from that operation, the carotids -and the great trunks of the anterior extremities were tied: in this -manner the whole course of the circulation was altered. The dog, which -was of very large size, survived all these operations, and appeared to -enjoy its ordinary health. Grainger's General Anatomy, p. 251-253. - -[7] See this matter very ably discussed in Dr. Arnott's excellent work -on the Elements of Physics, vol. i. - - -END OF VOL. I. - - -London: Printed by W. CLOWES and SONS, Stamford Street. - - - - -TRANSCRIBER'S NOTES. -1. (Figure LXXIV.) was incorrectly labeled as (Figure LXXVI.). - This has been corrected. -2. 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