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diff --git a/39751-8.txt b/39751-8.txt new file mode 100644 index 0000000..355d054 --- /dev/null +++ b/39751-8.txt @@ -0,0 +1,11321 @@ +The Project Gutenberg EBook of Being Well-Born, by Michael F. Guyer + +This eBook is for the use of anyone anywhere at no cost and with +almost no restrictions whatsoever. You may copy it, give it away or +re-use it under the terms of the Project Gutenberg License included +with this eBook or online at www.gutenberg.org + + +Title: Being Well-Born + An Introduction to Eugenics + +Author: Michael F. Guyer + +Editor: M. V. O'Shea + +Release Date: May 21, 2012 [EBook #39751] + +Language: English + +Character set encoding: ISO-8859-1 + +*** START OF THIS PROJECT GUTENBERG EBOOK BEING WELL-BORN *** + + + + +Produced by Bryan Ness and the Online Distributed +Proofreading Team at http://www.pgdp.net (This file was +produced from images generously made available by The +Internet Archive.) + + + + + + + + + +BEING WELL-BORN + + + + + BEING WELL-BORN + + AN INTRODUCTION TO EUGENICS + + + _By_ + MICHAEL F. GUYER, PH. D. + Professor of Zoology, The University of Wisconsin + + + Childhood and Youth Series + + _Edited by_ M. V. O'SHEA + Professor of Education, The University of Wisconsin + + + INDIANAPOLIS + THE BOBBS-MERRILL COMPANY + PUBLISHERS + + + + + COPYRIGHT 1916 + THE BOBBS-MERRILL COMPANY + + PRESS OF + BRAUNWORTH & CO. + BOOKBINDERS AND PRINTERS + BROOKLYN, N. Y. + + + + +TO MY WIFE + +HELEN M. GUYER + + + + +EDITOR'S INTRODUCTION + + +The writer recalls that when he was a young boy, he heard the grown-up +people in the community earnestly and incessantly debating the question: +Does heredity play a greater part in shaping one's mind and body than does +his environment? From that day to this he has listened to men and women in +every walk of life discussing the relation of heredity to environment in +determining human traits. Teachers and parents are constantly asking: "Are +such and such characteristics in my children due to their inheritance or +to the way they have been trained?" Students of juvenile delinquency and +of mental defect and deficiency are searching everywhere for light on this +matter. It is not to be wondered at that practically all people are +peculiarly interested in this problem, since it concerns intimately one's +personal traits, and it constantly confronts any one who is responsible +for the care and culture of the young. + +It is suggestive to note how people differ in their views regarding the +extent to which a child's physical and mental qualities and capacities are +fixed definitely by his inheritance. The writer has often heard students +in university classes discuss the subject; and their handling of the +problem has shown how superficially and even superstitiously most persons +regard the mechanism and functions of heredity. It is significant also to +observe what extreme views many people hold regarding the possibility of +affecting a child's traits and abilities by subjecting him to specific +influences during his prenatal life. In any group of one hundred persons +chosen at random, probably seventy-five will believe in specific prenatal +influence. Many of them will believe in birthmarks due to peculiar +experiences of the mother. A popular book recently published asserts among +other things that if a mother will look upon beautiful pictures and listen +to good music during the prenatal period of her child, the latter will +possess esthetic traits and interests in high degree. On the other hand, +people generally do not seem to think that degenerate parents beget only +degenerate children. Alcoholics, feeble-minded persons and the like are +permitted to bring children into the world. + +Very few people have any precise knowledge of the mechanism of heredity. +The whole thing is inscrutable to them, and is shrouded in mystery. +Superstition flourishes among even intelligent persons in respect to +heredity, and errors due to education, and tragedies resulting from +vicious social organization are all alike ascribed to its uncontrollable +forces. Most people are none the wiser because they do not know to what +extent the physical and mental defects and deviations of individuals are +due to inheritance or to the malign influences of the individual's +environment and training. + +Professor Guyer, who has studied the whole problem in a thoroughgoing, +scientific way, has prepared this book with a view to illuminating some of +the mysteries that surround the subject of heredity, and to dispelling +the illusions that persist regarding it. He shows the method which nature +follows in the development of the individual. He presents the laws which +have become established respecting the extent to which and the manner in +which immediate and remote ancestors contribute to the child's physical +and mental organism. He answers many questions which those who are engaged +in social work or in education in the home or the school are asking +to-day. He discusses subjects upon which every serious-minded person +wishes to be informed. He has thus made a book which is both of +theoretical and of practical interest. + +He has written in a style which should make his book attractive to the +parent and the teacher as well as to the student of the complicated +mechanism of inheritance. Only a few special terms are used, and these +should not give any reader trouble, because the treatment throughout is so +concrete that the meaning of the terms will be easily grasped. Further, +the book is illustrated, with many attractive and instructive +illustrations which will show at a glance the working of the principles of +inheritance which are developed in the text. + +This book may be heartily commended to all who are interested in questions +of human nature, education and social reform. It should enable the parent, +the teacher and the legislator to understand more clearly than most of +them now do in how far children's traits and possibilities are or can be +fixed by inheritance as contrasted with environmental conditions and +nurture in home, school, church and institutional life. + +M. V. O'SHEA. + +Madison, Wisconsin. + + + + +PREFACE + + +One of the most significant processes at work in society to-day is the +awakening of the civilized world to the rights of the child; and it is +coming to be realized that its right of rights is that of being well-born. +Any series of publications, therefore, dealing primarily with the problems +of child nature may very fittingly be initiated by a discussion of the +factor of well-nigh supreme importance in determining this nature, +heredity. + +No principles have more direct bearing on the welfare of man than those of +heredity, and yet on scarcely any subject does as wide-spread ignorance +prevail. This is due in part to the complexity of the subject, but more to +the fact that in the past no clear-cut methods of attacking the manifold +problems involved had been devised. Happily this difficulty has at least +in part been overcome. + +It is no exaggeration to say that during the last fifteen years we have +made more progress in measuring the extent of inheritance and in +determining its elemental factors than in all previous time. Instead of +dealing wholly now with vague general impressions and speculations, +certain definite principles of genetic transmission have been disclosed. +And since it is becoming more and more apparent that these hold for man as +well as for plants and animals in general, we can no longer ignore the +social responsibilities which the new facts thrust upon us. + +Since what a child becomes is determined so largely by its inborn +capacities it is of the greatest importance that teachers and parents +realize something of the nature of such aptitudes before they begin to +awaken them. For education consists in large measure in applying the +stimuli necessary to set going these potentialities and of affording +opportunity for their expression. Of the good propensities, some will +require merely the start, others will need to be fostered and coaxed into +permanence through the stereotyping effects of proper habits; of the +dangerous or bad, some must be kept dormant by preventing improper +stimulation, others repressed by the cultivation of inhibitive tendencies, +and yet others smothered or excluded by filling their place with desirable +traits before they themselves come into expression. + +We must see clearly, furthermore, that even the best of pedagogy and +parental training has obvious limits. Once grasp the truth that a child's +fate in life is frequently decided long before birth, and that no amount +of food or hospital service or culture or tears will ever wholly make good +the deficiencies of bad "blood," or in the language of the biologist, a +faulty germ-plasm, and the conviction must surely be borne home to the +intelligent members of society that one thing of superlative importance in +life is the making of a wise choice of a marriage mate on the one hand, +and the prevention of parenthood to the obviously unfit on the other. + +In the present volume it is intended to examine into the natural +endowment of the child. And since full comprehension of it requires some +understanding of the nature of the physical mechanism by which hereditary +traits are handed on from generation to generation, a small amount of +space is given to this phase. Then, that the reader may appreciate to +their fullest extent the facts gathered concerning man, a review of the +more significant principles of genetics as revealed through experiments in +breeding plants and animals has been undertaken. The main applications of +these principles to man is pointed out in a general discussion of human +heredity. Finally, inasmuch as all available data indicate that the fate +of our very civilization hangs on the issue, the work concludes with an +account of the new science of eugenics which is striving for the +betterment of the race by determining and promulgating the laws of human +inheritance so that mankind may intelligently go about conserving good and +repressing bad human stocks. + +In order to eliminate as many errors as possible and to avoid oversights I +have submitted various chapters to certain of my colleagues and friends +who are authorities in the special field treated therein. While these +gentlemen are in no way responsible for the material of any chapter they +have added greatly to the value of the whole by their suggestions and +comments. Thus I am indebted to Professor Leon J. Cole for reading the +entire manuscript; to Professors A. S. Pearse and F. C. Sharp for reading +Chapter VII; to Professor C. R. Bardeen for reading special parts; to +Doctor J. S. Evans for reading Chapter VI and part of V; to Doctor W. F. +Lorenz, of the Mendota Hospital, for reading Chapter VIII; to Judge E. Ray +Stevens for reading Chapter IX, and to Helen M. Guyer for several readings +of the entire manuscript. + +Grateful acknowledgment is made to all of these readers, to various +publishers and periodicals for the use of certain of the illustrations, to +the authors of the numerous books and papers from which much of the +material in such a work as this must necessarily be selected, and to my +artist, Miss H. J. Wakeman, for her painstaking endeavors to make her work +conform to my ideas of what each diagram should show. + +M. F. G. + + + + +CONTENTS + + + CHAPTER PAGE + + I HEREDITY 1 + + Blood heritage--Kind determined by origin--Ancestry a network-- + Ancestry in royalty--Offspring derived from one parent only--Dual + ancestry an aid in studying heredity--Reversion--Telegony-- + Prenatal influences apart from heredity--Parent body and germ not + identical--A hereditary character defined--Hereditary mingling a + mosaic rather than a blend--Determiners of characters, not + characters themselves, transmitted--Our knowledge of heredity + derived along three lines--The method of experimental breeding-- + The statistical method--Galton's law of regression--Correlations + between parents and offspring--The biometrical method, + statistical, not physiological--Mental as well as physical + qualities inheritable. + + + II THE BEARERS OF THE HERITAGE 20 + + The cell the unit of structure--Unicellular organisms--Importance + of cell-theory--Heredity in unicellular forms--Reproduction and + heredity in colonial protozoa--Conjugation--Specialization of + sex-cells--The fertilized ovum--Advancement seen in the Volvox + colony--Natural death--Specialization in higher organisms--Sexual + phenomena in higher forms--Cell-division--Chromosomes constant in + number and appearance--Significance of the chromosomes--Cleavage + of the egg--Chief processes operative in building the body--The + origin of the new germ-cells--Significance of the early setting + apart of the germ-cells--Individuality of chromosomes--Pairs of + chromosomes--Reduction of the number of chromosomes by one-half-- + Maturation of the sperm-cell--Maturation of the egg-cell--Parallel + between the two processes--Fertilization--Significance of the + behavior of the chromosomes--A single set of chromosomes + sufficient for the production of an organism--The duality of the + body and the singleness of the germ--The cytoplasm in + inheritance--Chromosomes possibly responsible for the + distinctiveness of given characters--Sex and heredity--Many + theories of sex determination--The sex-chromosome--Sex-linked + characters in man--In lower forms. + + III MENDELISM 67 + + New discoveries in the field of heredity--Mendel--Rediscovery of + Mendelian principles--Independence of inheritable characters-- + Illustration in the Andalusian fowl--The cause of the ratio-- + Verification of the hypothesis--Dominant and recessive-- + Segregation in the next generation--Illustrated in guinea-pigs-- + Terminology--The theory of presence and absence--Additional + terminology--Dominance not always complete--Modifications of + dominance--Mendel's own work--Dihybrids--Getting new combinations + of characters--Segregations of the determiners--Four kinds of + gametes in each sex--The 9:3:3:1 ratio--Phenotype and genotype-- + The question of blended inheritance--Nilsson-Ehle's discoveries-- + Such cases easily mistaken for true blends--Skin-color in man-- + Questionable if real blends exist--The place of the Mendelian + factors in the germ-cell--Parallel between the behavior of + Mendelian factors and chromosomes--A single chromosome not + restricted to carrying a single determiner. + + IV MENDELISM IN MAN 97 + + Probably applicable to many characters in man--Difficult to get + correct data--A generalized presence-absence formula--Indications + of incomplete dominance--Why after the first generation only half + the children may show the dominant character--Eye-color in man-- + Hair-color--Hair-shape--Irregularities--Digital malformations--Eye + defects--Other defects inherited as dominants--Recessive + conditions more difficult to deal with--Albinism--Other recessive + conditions in man--Breeding out defects--Other inheritable + conditions in man. + + V ARE MODIFICATIONS ACQUIRED DIRECTLY BY THE BODY INHERITED? 121 + + Which new characters are inherited?--Examples of somatic + modifications--Use and disuse--The problem stated--Special + conditions in mammals--Three fundamental questions--External + influences may directly affect the germ-cells--Such effects + improbable in warm-blooded animals--Poisons may affect the + germ-plasm--How can somatic modifications be registered in + germ-cells?--Persistence of Mendelian factors argues against such + a mode of inheritance--Experiments on insects--On plants--On + vertebrates--Epilepsy in guinea-pigs--Effects of mutilations not + inherited--Transplantation of gonads--Effects of body on germ, + general not specific--Certain characters inexplicable as inherited + somatic acquirements--Neuter insects--Origin of new characters in + germinal variation--Sexual reproduction in relation to new + characters--Many features of an organism characterized by + utility--Germinal variation a simpler and more inclusive + explanation--Analysis of cases--Effects of training--Instincts-- + Disease--Reappearance not necessarily inheritance--Prenatal + infection not inheritance--Inheritance of a predisposition not + inheritance of a disease--Tuberculosis--Two individuals of + tubercular stock should not marry--Special susceptibility less of + a factor in many diseases--Deaf-mutism--Gout--Nervous and mental + diseases--Other disorders which have hereditary aspects--Induced + immunity not inherited--Social, ethical and educational + significance of non-inheritance of somatic modifications--No cause + for discouragement--Improved environment will help conserve + superior strains when they do appear. + + VI PRENATAL INFLUENCES 151 + + All that a child possesses at birth not necessarily hereditary-- + The myth of maternal impressions--Injurious prenatal influences-- + Lead poisoning--The expectant mother should have rest--Too short + intervals between children--Expectant mothers neglected-- + Alcoholism--Unreliability of most data--Alcohol a germinal and + fetal poison--Various views of specialists on the effects of + alcoholism on progeny--The affinity of alcohol for germinal + tissue--Innate degeneracy versus the effects of alcohol-- + Experimental alcoholism in lower animals--Further remarks on the + situation in man--Much inebriety in man due to defective nervous + constitution--Factors to be reckoned with in the study of + alcoholism--Venereal diseases--The seriousness of the situation-- + Infantile blindness--Syphilis--Some of the effects--A blood test-- + Many syphilitics married--Why permit existing conditions to + continue?--Ante-nuptial medical inspection--The perils of venereal + disease must be prevented at any cost--Bad environment can wreck + good germ-plasm. + + VII RESPONSIBILITY FOR CONDUCT 195 + + All mental process accompanied by neural process--Gradations in + nervous response from lower organisms to man--Behavior of many + animals often an automatic adjustment to simple external agents-- + Tropisms--Certain apparently complex volitions probably only + tropisms--Complicating factors--Many tropic responses apparently + purposeful--Tropisms grade into reflex actions and instincts-- + Adjustability of instincts opens the way for intelligent + behavior--Modification of habits possible in lower animals--Some + lower vertebrates profit by experience--Rational behavior-- + Conceptual thought probably an outgrowth of simpler psychic + states--The capacity for alternative action in higher animals--The + elemental units of the nervous system are the same in lower and + higher animals--Neuron theory--Establishment of pathways through + the nervous system--Characteristic arrangements of nerve cells + subject to inheritance--Different parts of the cortex yield + different reactions--Skill acquired in one branch of learning + probably not transferred to another branch--Preponderance of + cortex in highest animals--Special fiber tracts in the spinal cord + of man and higher apes--Great complexity in associations and more + neurons in the brain of man--The nervous system in the main + already staged at the time of birth--Many pathways of conduction + not yet established--The extent of the modifiable zone unknown-- + Various possibilities of reaction in the child--Probable origin of + altruistic human conduct--Training in motive necessary--Actual + practise in carrying out projects important--Interest and + difficulty both essential--The realization of certain + possibilities of the germ rather than others is subject to + control--We must afford the opportunity and provide the proper + stimuli for the development of good traits--Moral responsibility. + + VIII MENTAL AND NERVOUS DEFECTS 228 + + Prevalence of insanity--Imperfect adjustments of the brain + mechanism inheritable--Many mental defectives married-- + Disproportionate increase in number of mental defectives--Protests + voiced by alienists--Examples of hereditary feeble-mindedness-- + Difficult to secure accurate data--Feeble-mindedness and insanity + not the same--Many types of insanity--Not all insanities of the + same eugenical significance--Difficulties of getting genealogies + of specific forms of insanity--Certain forms of insanity seem to + behave as Mendelian recessives--Grades of feeble-mindedness--About + two-thirds of feeble-mindedness inherited--Some results of + non-restraint of the feeble-minded--Not all cases of mental + deficiency inherited--Epileptics--Feeble-mindedness probably a + recessive--Many apparently normal people are carriers of + neuropathic defects--Tests for mental deficiency--The backward + child in school--The exceptionally able child--Cost of caring for + our mentally disordered--Importance of rigid segregation of the + feeble-minded--Importance of early diagnosis of insanity--Opinion + of competent psychiatrists essential--Some insanities not + hereditary--Importance of heredity in insanity not appreciated. + + IX CRIME AND DELINQUENCY 263 + + Heredity and environment in this field--Feeble-mindedness often a + factor--Many delinquent girls mentally deficient--Institutional + figures misleading--Many prisoners mentally subnormal--Inhibitions + necessary to social welfare--The high-grade moron a difficult + problem--Degenerate strains--Intensification of defects by + inbreeding--Vicious surroundings not a sufficient explanation in + degenerate stocks--Not all delinquents defectives--No special + inheritable crime-factor--What is a born criminal?--Epileptic + criminal especially dangerous--The mental disorders most + frequently associated with crime--Bearing of immigration on crime + and delinquency--Sexual vice--School instruction in sex-hygiene-- + Mere knowledge not the crux of the sex problem--Early training in + self-restraint an important preventive of crime and delinquency-- + Multiplication of delinquent defectives must be prevented. + + X RACE BETTERMENT THROUGH HEREDITY 289 + + Questionable charity--Past protests--An increasing flood of + defectives--Natural elimination of defectives done away with--Why + not prevent our social maladies?--Eugenics defined--Improved + environment alone will not cure racial degeneracy--Heredity and + environment--Inter-racial marriage--Human conservation--Kindness + in the long run--The problem has two phases--Constructive eugenics + must be based on education--Inferior increasing more rapidly than + superior stocks--An unselected population may contain much + valuable material--The lack of criteria for judging fitness--The + college graduate--Native ability, independence and energy + eugenically desirable--Four children to each marriage required to + maintain a stock--Factors contributing to low birth-rate in + desirable strains--The educated public must be made to realize the + situation--Utilization of family pride as a basis for constructive + eugenics--The tendency for like to marry like--Public opinion as + an incentive to action--Choosing a marriage mate means choosing a + parent--The best eugenic marriage also a love match--The + elimination of the grossly unfit urgent--Suggested remedies-- + Inefficacy of laws which forbid marriage of mental defectives-- + Systems of mating impracticable in the main--Corrective mating + presupposes knowledge of eugenics--Segregation has many + advocates--Sterilization as a eugenic measure--To what conditions + applicable--In insanity--In feeble-mindedness--In cases of + epilepsy--Sterilization laws--Social dangers in vasectomy--Our + present knowledge insufficient--Sterilization laws on trial--An + educated public sentiment the most valuable eugenic agent--The + question of personal liberty--Education of women in eugenics + needed--Much yet to be done--A working program--Which shall it be? + + GLOSSARY 343 + + REFERENCES FOR FURTHER READING AND STUDY 355 + + INDEX 361 + + + + +BEING WELL-BORN + + + + +CHAPTER I + +HEREDITY + + +It is a commonplace fact that offspring tend to resemble their parents. So +commonplace, indeed, that few stop to wonder at it. No one misunderstands +us when we say that such and such a young man is "a chip off the old +block," for that is simply an emphatic way of stating that he resembles +one or the other of his parents. The same is true of such familiar +expressions as "what's bred in the bone," "blood will tell," and kindred +catch phrases. All are but recognitions of the same common fact that +offspring exhibit various characteristics similar to those of their +progenitors. + +=Blood Heritage.--=To this phenomenon of resemblance in successive +generations based on ancestry the term heredity is applied. In man, for +instance, there is a marked tendency toward the reappearance in offspring +of structures, habits, features, and even personal mannerisms, minute +physical defects, and intimate mental peculiarities like those possessed +by their parents or more remote forebears. These personal characteristics +based on descent from a common source are what we may call the blood +heritage of the child to discriminate it from a wholly different kind of +inheritance, namely, the passing on from one generation to the next of +such material things as personal property or real estate. + +=Kind Determined by Origin.--=It is inheritance in the sense of community +of origin that determines whether a given living creature shall be man, +beast, bird, fish, or what not. A given individual is human because his +ancestors were human. In addition to this stock supply of human qualities +he has certain well-marked features which we recognize as characteristics +of race. That is, if he is of Anglo-Saxon or Italian or Mongolian +parentage, naturally his various qualities will be Anglo-Saxon, Italian, +or Mongolian. Still further, he has many distinctive features of mind and +body that we recognize as family traits and lastly, his personal +characteristics such as designate him to us as Tom, Harry, or James must +be added. The latter would include such minutiæ as size and shape of ears, +nose or hands; complexion; perhaps even certain defects; voice; color of +eyes; and a thousand other particulars. Although we designate these +manifold items as individual, they are in reality largely more or less +duplicates of similar features that occur in one or the other of his +progenitors, features which he would not have in their existing form but +for the hereditary relation between him and them. + + "O Damsel Dorothy! Dorothy Q.! + Strange is the gift that I owe to you; + + * * * * * + + What if a hundred years ago + Those close-shut lips had answered 'No,' + + * * * * * + + Should I be I, or would it be + One-tenth another, to nine-tenths me?" + + "Soft is the breath of a maiden's yes; + Not the light gossamer stirs with less; + But never a cable that holds so fast + Through all the battles of wave and blast, + And never an echo of speech or song + That lives in the babbling air so long! + There were tones in the voice that whispered then + You may hear to-day in a hundred men." + +When life steps into the world of matter there comes with it a sort of +physical immortality, so to speak; not of the individual, it is true, but +of the race. But the important thing to note is that the race is made up, +not of a succession of wholly unrelated forms, but a continuation of the +same kind of living organisms, and this sameness is due to the actual +physical descent of each new individual from a predecessor. In other +words, any living organism is the kind of organism it is in virtue of its +hereditary relation to its ancestors. + +It is part of the biologist's task to seek a material basis, a continuity +of actual substance, for this continuity of life and form between an +organism and its offspring. Moreover, inasmuch as the offspring is never +precisely similar to its progenitors he must determine also what qualities +are susceptible of transmission and in what measure. + +=Ancestry a Network.--=From the fact that each child has all of the +ancestors of its mother as well as of its father, arises the great +complications which are met with in determining the lineage of an +individual. A person has two parents, four grandparents, eight great +grandparents, and thus following out pedigree it is plain to be seen that +through this process of doubling in each generation, in the course of a +few centuries one's ancestry is apparently enormous. By actual +computation, according to Professor D. S. Jordan, if we count thirty +generations back to the Norman invasion of England in 1066, at this ratio +of duplication, the child of to-day would have had at that time an +ancestry of 8,598,094,592 persons. But we know that the total number of +inhabitants in England during the time of William the Conqueror was but a +small fraction of this enormous aggregate. This means that we shall have +to modify our inference that a child has twice as many ancestors as its +parents; a condition which at first sight seems evident, but which is not +literally true. The fact is that the parents of the child, in all +probability, have many ancestors in common--a state of affairs which is +brought about through the intermarriage of relatives, and this is +especially frequent among remoter descendants of common progenitors. Time +after time in genealogy strains of blood have crossed and recrossed until +it is not improbable that a man of to-day who is of English origin has the +blood in his veins from every inhabitant of England who lived during the +time of William the Conqueror and left fruitful descendants. Instead of +conceiving of ancestry as an ever branching and widening tree-like system +as it recedes into the past, it is more accurate, therefore, to regard it +in the light of an elaborate meshwork. The "family tree" in reality +becomes the family net. + +=Ancestry in Royalty.--=The pedigrees of royal families have proved to be +of much importance in the study of human inheritance, not that royal +traits are any more heritable than any other, but simply because the +records have been carefully kept so that they are the most comprehensive +and easily followed pedigrees available. The netlike weave of ancestry is +particularly well exemplified in some of these families because of much +close intermarriage. Their heritage typifies on an intensified scale the +heritage of the mass of mankind. For example, if we go six generations +back in the ancestry of Frederick the Great instead of the expected +sixty-four individual ancestors we find only forty; or in a still more +closely woven stock, in the Spanish royal line of Don Carlos we find in +six generations instead of sixty-four individual ancestors, only +twenty-eight. While the present German emperor might have had four +thousand ninety-six ancestors in the twelfth generation back, it is +estimated that owing to intermarriage he probably had only five hundred +thirty-three. + +=Offspring Derived from One Parent Only.--=So far in our reckoning of +heredity we have counted elements from both father and mother, and the +complications which arise from such a double ancestry are manifestly very +perplexing ones. If we could do away with the elements of sex and find +offspring that are derived from one parent only, it would seemingly +simplify our problem very much for we should thus have a direct line of +descent, free from intermingling. This, in fact, occurs to a greater or +less extent among lower animals in a number of instances. There may be +only female forms for a number of generations and the eggs which they +produce develop directly into new individuals. Moreover, many of the +simpler organisms have the power of dividing their bodies into two and +thus giving rise to two new forms, each of which resembles the parent. +This shows plainly that we may have inheritance without the appearance of +any male ancestor at all, hence sex is not always a necessary factor in +reproduction or heredity. The development of eggs asexually, that is, +without uniting first with a male cognate, is termed _parthenogenesis_. +The ordinary plant louse or aphid which is frequently found upon geraniums +is a familiar example of an animal which reproduces largely in this way. +During the summer only the females exist and they are so astonishingly +fertile that one such aphid and her progeny, supposing none dies, will +produce one hundred million in the course of five generations. In the last +broods of the fall, males and females appear and fertile eggs are produced +which lie dormant through the winter to start the cycle of the next year. +Again, the eggs of some kinds of animals which normally have to unite with +a male germ before they develop, can be made to develop by merely treating +them with chemical solutions. The difference between an offspring derived +in such a manner, and one which has developed from an egg fertilized by +the male is that it is made up of characteristics from only one source, +the maternal. + +=Dual Ancestry an Aid in Studying Heredity.--=Although we have the factors +of heredity in a more simplified form in the case of asexual +transmission, as a matter of fact most of our insight into the problems +of heredity has been attained from a study of sexually reproducing forms, +because the very existence of two sets of more or less parallel features +offers a kind of checking up system by which we can follow a given +characteristic. + +=Reversion.--=Occasionally, however, plants and animals do not develop the +complete individuality we might expect, but stop short at or re-attain +some ancestral stage along the line of descent, and thus come to resemble +some progenitor perhaps many generations back of their own time. Thus it +is well known that as regards one or more characteristics a child may +resemble a grandparent or often some remote ancestor much more closely +than it does its immediate parent. The reappearance of such ancestral +traits the student of heredity designates as _Reversion_ or _Atavism_. + +Reversion may occur apparently in any class of plants or animals. It is +especially pronounced among domesticated forms, which through man's +selection have been produced under more or less artificial conditions. For +example, among fancy breeds of pigeons, there may be an occasional return +to the old slaty blue color of the ancestral rock-pigeon, with two dark +cross-bars on the wings, from which all modern breeds have been derived. +This is almost sure to happen if the fancy varieties are inter-crossed for +two or three generations. Another example of reversion frequently cited is +the occasional reappearance in domestic poultry of the reddish or brownish +color pattern of the ancestral jungle-fowl to which, among modern forms, +the Indian game seems most nearly related in color. Still another example +is the cross-bars or stripes occasionally to be seen on the forelegs of +colts, particularly mules, reminiscent of the extinct wild progenitors +which were supposedly striped. + +Fig. 1, p. 9, is a picture of a hybrid between the common fowl and the +guinea-fowl. The chevron-like markings on certain feathers show a +reversion to a type of color pattern that is prevalent among both the +primitive pheasants (the domestic chicken is a pheasant) and the primitive +guinea-fowls. Although the common spotted guinea-fowl may be crossed with +a black chicken which shows no trace of barring, nevertheless the hybrid +offspring are likely to bear a chevron-like pattern such as that shown in +the picture. + +There has been much quibbling over the relative meanings of reversion and +atavism. The general idea, whichever term we use, is that there is a +"throwing back" in a noticeable degree through inheritance to some +ancestral condition beyond the immediate parents. A few recent authors +have taken the term atavism in a restricted sense and use it to signify +specifically those not uncommon cases in which a particular character of +an offspring resembles the corresponding character of a grandparent +instead of a parent. Such, for example, as the blue eye-color of a child +with brown-eyed parents, each of whom in turn has had a blue-eyed parent. +The tendency of other authors is to abandon the term entirely because of +the diversity of meaning that has been attached to it in the past. + + +[Illustration: FIG. 1 + +Hybrid between the guinea-fowl and the common fowl, showing in many +feathers reversion to a primitive chevron-like barring.] + + +Certain classes of so-called reversions, such as the case of the eye-color +just cited, are readily explicable on Mendelian principles as we shall see +in a later chapter, but probably not all kinds of phenomena described as +reversion can be so explained. For example, some seem to be cases of +suppressed development. The word reversion, indeed, must be looked on as +a convenient descriptive term rather than as the name of a single specific +condition. + +=Telegony.--=There is yet a wide-spread belief in the supposed influence +of an earlier sire on offspring born by the same mother to a later and +different sire. This alleged phenomenon is termed _telegony_. For example, +many dog-breeders assert that if a thoroughbred bitch has ever had pups by +a mongrel father, her later offspring, although sired by a thoroughbred, +will show taints of the former mongrel mating. In such cases the female is +believed to be ruined for breeding purposes. Other supposed instances of +such influences have been cited among horses, cattle, sheep, pigs, cats, +birds, pets of various kinds and even men. The historic case most +frequently quoted is that of Lord Morton's mare which bore a hybrid colt +when bred to a quagga, a striped zebra-like animal now extinct. In later +years the same mare bore two colts, sired by a black Arabian horse. Both +colts showed stripes on the neck and other parts of the body, particularly +on the legs. It was inferred that this striping was a sort of after effect +of the earlier breeding with the quagga. In recent times, however, +Professor Ewart has repeated the experiment a number of times with +different mares using a Burchell zebra as the test sire. Although his +experiments have been devised so as to conduce in every way possible to +telegony his results have been negative. Moreover, it has been pointed out +that the stripes on the legs of the two foals alleged to show telegony +could not have been derived from the quagga sire for, unlike zebras, +quaggas did not have their legs striped. Furthermore it is known that the +occurrence of dark brown stripes on the neck, withers and legs of ordinary +colts is not uncommon, some cases of which have exhibited more zebra-like +markings than those of the colts from Lord Morton's mare. It seems much +more probable, therefore, that the alleged instances are merely cases of +ordinary reversion to the striped ancestral color pattern which probably +characterized the wild progenitors of the domesticated horse. + +Various experiments on guinea-pigs, horses, mice and other forms, +especially devised to test out this alleged after-influence of an earlier +sire, have all proved negative and the general belief of the biologist +to-day is that telegony is a myth. + +=Prenatal Influences Apart from Heredity.--=In discussing the problems of +heredity it is necessary to consider also the possibilities of external +influences apart from lineage which may affect offspring through either +parent. Although modifications derived directly by the parent, and +prenatal influences in general, are of extremely doubtful value as of +permanent inheritable significance, nevertheless they must be reckoned +with in any inventory of a child's endowment at birth. Impaired vitality +on the part of the mother, bad nutrition and physical vicissitudes of +various kinds all enter as factors in the birthright of the child, who, +moreover, may bear in its veins slumbering poisons from some progenitor +who has handed on blood taints not properly attributable to heredity. Of +such importance is this kind of influence to the welfare of the immediate +child that it will be necessary to discuss it in considerable detail in a +later chapter. + +=Parent Body and Germ Not Identical.--=Inasmuch as each new individual +appears to arise from material derived from its parent, taking the +evidence at its face value one might suppose that any peculiarity of +organization called forth in the living substance of the parent would +naturally be repeated in the offspring, but a closer study of the +developing organism from its first inception to maturity shows this to be +probably a wrong conclusion. The parent-body and the reproductive +substance contained in that body are by no means identical. It becomes an +important question to decide, in fact, how much effect, if any, either +permanent or temporary, the parent-body really has on the germ. + +A given fertile germ (Fig. 2, p. 13) gives rise by a succession of +divisions to a body which we call the individual, but such a germ also +gives rise to a series of new germ-cells which reside in that individual, +and it is these germ-cells, not something derived from the body, that pass +on the determiners of distinguishing features or qualities from generation +to generation. It is only by grasping the significance of this fact that +we can understand how in certain cases a totally different set of +characters may appear in an offspring than those manifested in either +parent. + +=An Hereditary Character Defined.--=By a _character_, in discussions in +heredity, is meant simply a trait, feature or other characteristic of an +organism. Where we can pick out a single definable characteristic which +acts as a unit in heredity, for greater accuracy we term it a +_unit-character_. Many traits are known to be inherited on a unit basis or +are capable of being analyzed into factors which are so inherited. These +unit-characters are in large measure inherited independently of one +another apparently, although cases of characters inherited as a unit along +with other characters are known. + +=Hereditary Mingling a Mosaic Rather Than a Blend.--=The independence of +unit-characters in inheritance leads us to the important conclusion that +the mingling of two lines of ancestry into a new individual is in no sense +bringing them into the "melting pot," as it has been picturesquely +expressed, but it is rather to be regarded as the mingling of two mosaics, +each particle of which retains its own individuality, and which, even if +overshadowed in a given generation, may nevertheless manifest its +qualities undimmed in later generations when conditions favorable to its +expression transpire. + + +[Illustration: FIG. 2 + +Diagram illustrating germinal continuity. Through a series of divisions a +germ-cell gives rise to a body or a soma and to new germ-cells. The +latter, not the body, give rise in turn to the next generation.] + + +=Determiners of Characters, Not Characters Themselves, Transmitted.--=The +fact should be thoroughly understood that the actual thing which is +transmitted by means of the germ in inheritance is not the character +itself, but something which will _determine_ the character in the +offspring. It is important to remember this, for often these +_determiners_, as they are called, may lie unexpressed for one or more +generations and may become manifest only in later descendants. The truth +of the matter is, the child does not inherit its characters from +corresponding characters in the parent-body, but parent and child are +alike because they are both products of the same line of germ-plasm, both +are chips from the same old block. + + +METHODS OF STUDYING HEREDITY + +Before entering into details it will be well to get some idea of the +methods which are commonly employed in arriving at conclusions in the +field of heredity. Some of these are extremely complex and all that we can +do in an elementary presentation is to get a glimpse of the procedures. + +=Our Knowledge of Heredity Derived Along Three Lines.--=Our modern +conceptions of heredity have been derived mainly from three distinct lines +of investigation: First, from the study of embryology, in which the +biologist concerns himself with the genesis of the various parts of the +individual, and the mechanism of the germs which convey the actual +materials from which these parts spring; second, through experimental +breeding of plants and animals to compare particular traits or features in +successive generations; and third, through the statistical treatment of +observations or measurements of a large number of parents and their +offspring with reference to a given characteristic in order to determine +the average extent of resemblance between parents and children in that +particular respect. + +=The Method of Experimental Breeding.--=A tremendous impetus was given to +the method of experimental breeding when it was realized that we can +itemize many of the parts or traits of an organism into entities which are +inherited independently one of another. Such traits, or as we have already +termed them, unit-characters, may be not only independently heritable but +independently variable as well. The experimental method seeks to isolate +and trace through successive generations the separate factors which +determine the individual unit-characters of the organism. In this attempt +cross-breeding is resorted to. Forms which differ in one or more respects +are mated and the progeny studied. Next these offspring are mated with +others of their own kind or mated back with the respective parent types. +In this way the behavior of a particular character may often be followed +and the germinal constitutions of the individuals concerned can be +formulated with reference to it. Inasmuch as we shall give much +consideration to this method in the chapter on Mendelism we need not +consider it further here. + +=The Statistical Method.--=The statistical method seeks to obtain large +bodies of facts and to deal with evidence as it appears through +mathematical analysis of these facts. The attempt of its followers is to +treat quantitatively all biological processes with which it is concerned. +Historically Sir Francis Galton was the first to make any considerable +application of statistical methods to the problems of heredity and +variation. In his attempts to determine the extent of resemblance between +relatives of different degree as regards bodily, mental and temperamental +traits, he devised new methods of statistical analysis which constitute +the basis of modern statistical biology, or _biometry_ as it is termed by +its votaries. Professor Karl Pearson in particular has extended and +perfected the mathematical methods of this field and stands to-day as +perhaps its most representative exponent. The system is in the main based +on the calculus of probability. The methods often are highly specialized, +requiring the use of higher mathematics, and are therefore only at the +command of specially trained workers. + +Just as insurance companies can tell us the probable length of human life +in a given social group, since although uncertain in any particular case, +it is reducible in mass to a predictable constant, so the biometrician +with even greater precision because of his improved methods can often, +when a large number of cases are concerned, give us the intensity of +ancestral influence with reference to particular characters. + +For example, it is clear that by measuring a large number of adult human +beings one can compute the average height or determine the height which +will fit the greatest number. There will be some individuals below and +some above it, but the greater the divergence from this standard height +the fewer will be the individuals concerned. + +Galton compared the heights of 204 normal English parents and their 928 +adult offspring. In order to equalize the measurements of men and women he +found he had to multiply each female height by 1.08. Then, to take both +parents into account when comparing height of parents to that of children +he added the height of the father to the proportionately augmented height +of the mother and divided by two, thus securing the height of what he +termed the "mid-parent." He found that the mid-parental heights of his +subjects ranged from 64.5 to 72.5 inches, and that the general _mode_ was +about 68.5 inches. It should be mentioned that the _mode_, in a given +population, represents the group containing the largest number of +individuals of one kind; it may or may not coincide with the average. The +children of all mid-parents having a given height were measured next and +tabulated with reference to these mid-parents. The results of Galton's +measurements may be expressed simply as follows: + + ----------------------------------------------------------------- + |MODE| + ----------------------------------------|----|------------------- + Height of mid-parent| | | | | | | | | + in inches |64.5|65.5|66.5|67.5|68.5|69.5|70.5|71.5|72.5 + | | | | | | | | | + Average height of | | | | | | | | | + offspring |65.8|66.7|67.2|67.6|68.3|68.9|69.5|69.9|72.2 + ----------------------------------------------------------------- + +=The Law of Regression.--=It is plain from this table that the offspring +of short mid-parents tend to be under average or modal height though not +so far below as their parents. Likewise children of tall parents tend to +be tall but less tall than their parents. This fact illustrates what is +known as Galton's _law of regression_; namely, that if parents in a given +population diverge a certain amount from the mode of the population as a +whole, their children, while tending to resemble them, will diverge less +from this mode. It is clear that the extent of regression is an inverse +measure of the intensity of inheritance from the immediate parents; if the +deviation of the offspring from the general mode were nearly as great as +that of their parents then the intensity of the inheritance must be high; +if but slight--that is, if the offspring regressed nearly to the +mode--then the intensity of the inheritance must be ranked as low. In the +example in question it must be ranked as relatively high. Computations +show that as regards stature the fraction two-thirds represents +approximately the amount of resemblance between the two generations where +both parents are considered. + +=Correlations Between Parents and Offspring.--=In modern researches the +conception of mid-parent and mid-grandparent as utilized by Galton has +been largely abandoned. It has been found more convenient as well as more +accurate to keep the measurements of the two parents separate and to deal +with correlations between fathers and sons, fathers and daughters, mothers +and sons, mothers and daughters, brother and brother, etc. Professor +Pearson and his pupils have found for a number of characters that the +correlation between either parent and children, whether sons or daughters, +is relatively close. The correlation between brother and brother, sister +and sister, and brother and sister, usually ranges a little higher than +the corresponding relation between parents and children. + +=The Biometrical Method, Statistical, Not Physiological.--=While biometry +may in certain cases go far toward showing us the average intensity of +the inheritance of certain characters it can not replace the method of +the experimental breeder which deals with particular characters in +individual pedigrees. It must be borne in mind that the biometrical method +is a statistical and not a physiological one and that it is applicable +only when large numbers of individuals are considered in mass. It is most +valuable in cases where we are unable sharply to define single characters, +due probably to the concurrent action of a number of independent causes, +or where experiment is impossible so that we have to depend solely on +numerical data gained by observation. + +=Mental Qualities Inheritable.--=Galton showed by this method long ago, +and Pearson and his school have extended and more clearly established the +work, that exceptional mental qualities tend to be inherited. While on the +average the children of exceptional parents tend to be less exceptional +than their parents, still they are far more likely to be exceptional than +are the children of average parents. By this method Professor Pearson has +shown that such mental and temperamental attributes as ability, vivacity, +conscientiousness, temper, popularity, handwriting, etc., are as +essentially determined as are physical features through the hereditary +endowment. + + + + +CHAPTER II + +THE BEARERS OF THE HERITAGE + + +Before we can make any detailed analysis of the inheritance of characters +we should have some general idea of the physical structure of animals and +particularly some familiarity with the development of an individual from +the egg, as well as some knowledge of the nature of the germ-cells. + +=The Cell the Unit of Structure.--=If we examine one of the higher +animals, as, for example, the horse, the dog, or man, we find that it is +made up of a large number of constituents, such as bones, muscles, nervous +elements, blood and other tissues. Each kind of tissue is composed of a +number of living units, ordinarily microscopic in size, which are known as +cells. A careful examination of various cells reveals that although they +may differ greatly in size, shape and minor details, they all alike +possess certain well-marked characteristics. Each when reduced to its +fundamental form is seen to consist of a small mass of living matter +termed protoplasm in which may usually be distinguished two regions--the +cell-body or _cytoplasm_, and the _nucleus_ (Fig. 3, p. 21). Any cell, +whether it be of the brain, of the liver, or from any organ of an animal +or plant, has this same fundamental structure. In addition, a limiting +membrane or wall of some kind is generally present, although it is not a +necessary constituent of all cells. + + +[Illustration: FIG. 3 + +Diagram of a cell showing various parts.] + + +=Unicellular Organisms.--=While such a structure as a tree or a horse is +composed of countless millions of cells, on the other hand numerous +organisms, both plant and animal, exist which consist of only one cell. +Yet this cell is just as characteristically a cell as are the components +of a complex animal or plant. It has the necessary parts, the cell body +and the nucleus. Moreover it exhibits all of the fundamental activities of +life, though in a simplified form, that a complex higher organism does. + +=Importance of Cell-Theory.--=This discovery that every living thing is a +single cell or an aggregation of cooperating cells and cell-products is +one of our most important biological generalizations because it has +brought such a wide range of phenomena under a common point of view. In +the first place, the structure of both plants and animals is reducible to +a common fundamental unit of organization. Moreover, both physiological +and pathological phenomena are more readily understood since we recognize +that the functions of the body in health or disease are in large measure +the result of the activities of the individual cells of the functioning +part. Then again, the problems of embryological development have become +much more sharply defined since it could be shown that the egg is a single +cell and that it is through a series of divisions of this cell and +subsequent changes in the new cells thus formed that the new organism is +built up. And lastly, the problem of hereditary transmission has been +rendered more definite and approachable by the discovery that the male +germ is likewise a single cell, that fertilization of the egg is therefore +the union of two cells, and that in consequence the mechanism of +inheritance must be stowed away somehow in these two cells. + +=Heredity in Unicellular Forms.--=In unicellular animals one can readily +see how it is possible for an individual always to give rise to its own +kind. One of the simplest of the single-celled animals is the _Ameba_ +(Fig. 4, p. 24). + +The ameba eats and grows as do other animals. Sooner or later it reaches a +size beyond which it can not increase advantageously, yet it is +continuously taking in new food material which stimulates it to further +growth. Here then is a problem. The ameba solves this difficulty by +dividing to form two amebæ. Such a division is illustrated in Fig. 4, p. +24. First the nucleus divides, then the cell-body. When the two new amebæ +separate completely each renews the occupation of eating and growing. But +what has become of the parent? Here, where once existed a large adult +ameba are two young amebæ. The parent individual as such has disappeared, +yet there has been no death, for we have simply two bits of living jelly +in place of one. They will in turn repeat the same process, so will their +offspring, and thus, barring accident, this growth and reproduction, or +overgrowth as we may regard it, may go on forever, as far as we know. Here +the problem of heredity, or the resemblance of offspring to parent, is not +a very complicated one. The substance of the cell-body and cell-nucleus +divides into two similar halves, so that each descendant has the substance +of the parent in its own body, only it has but half as much. It differs +from the parent, not in quality or kind, but in size. + + +[Illustration: FIG. 4 + +Six successive stages in the division of _Ameba polypodia_ (after +Schulze). The nucleus is seen as a dark spot in the interior.] + + +=Reproduction and Heredity in Colonial Protozoa.--=There are enormous +numbers of these single-celled animals existing in all parts of the world. +Some are simple like the ameba, others are very complex in structure. +Many, after division, move apart and pursue wholly independent courses of +existence. On the other hand we find a modification appearing in some +which is of the greatest importance. After division instead of moving +apart the two cells may remain side by side and divide further to form +two more, these in turn may divide and thus the process goes on until +there is formed what is known as a colony. Each cell of such a colony +resembles the original ancestral cell because each is a part of the actual +substance of that cell. As in the ameba, the first two cells are the +ancestral cell done up in two separate packets, and thus finally the full +quota of cells must be so many separate packets of the same kind of +material. Inasmuch as each is but a repetition of its original ancestor, +it can, and at times does, produce a colony of the same kind as that +ancestor produced. + +=Conjugation.--=At longer or shorter intervals, however, we find that two +individuals, on the disruption of the old colony, instead of continuing +the routine of establishing new colonies through a series of cell +divisions, very radically alter their behavior. They unite and fuse into a +single larger individual. This process is called _conjugation_. We find it +occurring even in some species of ameba. The conjugating cells in some +colonies are alike in size and appearance, in others different. + +=Specialization of Sex-Cells.--=A beautiful sphere-shaped colony known as +_Volvox_ is to be found occasionally in roadside pools. Depending on the +species of _Volvox_ to which it belongs, the colony may be made up of from +a few hundred to several thousand individuals arranged in a single layer +about the fluid-filled center of the sphere and bound together by a clear +jelly-like inter-cellular substance. Each individual cell also connects +with its neighbors by means of thin threads of living matter. One of the +largest species is _Volvox globator_, one edge of which is represented in +Fig. 5, p. 27. Mutual pressure of the cells gives them a polygonal shape +when viewed from the surface. Each cell, with a few exceptions to be noted +immediately, bears two long flagella, whip-like structures which project +out into the water. The lashing of these flagella gives the ball a rotary +motion and thus it moves about. When the colony has reached its adult +condition and is ready to reproduce itself, certain cells without flagella +and somewhat larger than the ordinary cells become more rounded in outline +and increase considerably in size through the acquisition of food +materials. They are then known as egg cells or ova. Each ovum finally +enters on a series of cell-divisions forming a mass of smaller and smaller +cells which gradually assumes the form of a hollow sphere like the parent +colony. The young colonies thus formed drop into the interior of the +parent colony to escape later to the outside as independent swimming +organisms when the old colony dies and disintegrates. + +=The Fertilized Ovum Termed a Zygote.--=After a number of generations of +such asexual reproduction, sexual reproduction occurs. The ova arise as +usual. Certain members of the colony, on the other hand, go to the other +extreme and divide up into bundles of from sixty-four to one hundred +twenty-eight minute slender cells, each provided with flagella for +locomotion. When mature these small flagellate cells, now known as +_spermatozoa_, escape into the interior of the parent colony and swim +about actively. Ultimately each ovum is penetrated by a spermatozoon, the +two cells fuse completely and thus form the single _fertilized ovum_ or +_zygote_. The body-cells of the mother colony finally disintegrate. After +a period of rest each zygote, through a series of cell-divisions, develops +into an adult Volvox. In some species of Volvox a still further advance is +seen, in that instead of both kinds of gametes being produced in the same +colony, the ova may be produced by one colony and the spermatozoa by +another. Here, then, we have the foreshadowings of two sexes as separate +individuals, a phenomenon of universal occurrence among the highest forms +of animal life. + + +[Illustration: FIG. 5 + +_Volvox globator_ (from Hegner after Oltmanns). Half of a sexually +reproducing colony: _o_, eggs; _s_, spermatozoa.] + + +=Advancement Seen in the Volvox Colony.--=In the Volvox colony there is a +distinct advance over the conditions met with in various lower protozoan +colonies in that only certain individuals of the colony take part in the +process of reproduction and these individuals are of two distinct types; +one is a larger, food-laden cell or egg and the other a small, active, +fertilizing cell. The motile forms are produced in much greater numbers +than the eggs, plainly because they have to seek the egg and many will +doubtless perish before this can be accomplished. This disparity in number +is only a means of insuring fertilization of the egg. The remaining cells +of the body carry on the ordinary activities of the colony such as +locomotion and nutrition and have ceased to take any part in the +production of new colonies. + +=Natural Death Appears With the Establishment of a Body Distinct from the +Germ.--=Volvox is an organism of unusual interest because in it we see a +prophecy of what is to come. Although still regarded as a colony of +single-celled individuals, it represents in reality a transition between +the whole group of unicellular animals termed protozoa and the many celled +animals characterized by the possession of distinct tissues, known as +_Metazoa_. Moreover, it shows an interesting stage in the establishment of +a body or _soma_ distinct from special reproductive cells which have taken +on the function of reproducing the colony. In such colonial forms natural +death is found appearing for the first time, the reproductive cells alone +continuing to perpetuate the species. Then again Volvox represents an +important step in the establishment of sex in the animal kingdom for in +its sexual reproduction the conjugating cells known as _gametes_ are no +longer alike in appearance but have become differentiated into definite +ova and spermatozoa. + +In Volvox as in the other organisms which we have studied we find that all +of the cells including the germ-cells are produced by the repeated +division of a parent cell, and consequently each must contain the +characteristic living substance of that parent. Many other forms might be +cited to illustrate reproduction in single-celled animals, whether free or +in colonies, but all such cases would be practically but repetitions or +modifications of those we have already examined. + +=Specialization in Higher Organisms.--=If we pass on to the higher animals +and plants which are not single cells or colonies of similar cells but +organisms made up of many different kinds of cells, we find a pronounced +extension of the phenomenon met with in Volvox. Instead of each cell +executing independently all of the life relations, certain ones are set +apart for the performance of certain functions to the exclusion of other +functions which are carried on by other members of the aggregation. Thus +the organism as a whole has all the life relations carried on, but, as it +were, by specialists. + +=Sexual Phenomena in Higher Forms.--=In the reproduction of multicellular +organisms, one sees likewise but a continuation of the phenomena exhibited +in Volvox. Ordinarily, each new form is produced by the successive +divisions of a single germ-cell which in the vast majority of cases has +conjugated with another germ-cell. In the development of the egg, as the +divisions proceed, groups of cells become modified for their particular +work until the entire organism is completed. During development certain +cells are set apart for reproduction of the form just as they were in +Volvox. These two kinds of reproductive cells in multicellular organisms +are derived ordinarily from two separate individuals known as male and +female, though there are some exceptions. The main difference between +these cells which will have to unite to form a single fertile germ-cell, +is that they have specialized in different directions; one is small and +active, the other large, food-laden and passive. But with two such +germ-cells coming as they do from two individuals, one the male, the other +the female, it is obvious that the actual living substance of which each +germ is composed will be distinctive of its own parental line and that +when the germs unite these distinctive factors commingle, hence the +complications of double ancestry arise. + +=Structure of the Cell.--=Before we can understand certain necessary +details of the physical mechanism of inheritance we must inquire a little +further into the finer structure of the cell and into the nature of cell +division. A typical cell, as it would appear after treatment with various +stains which bring out the different parts more distinctly, is shown in +Fig. 3, p. 21. Typical, not that any particular kind of living cell +resembles it very closely in appearance, but because it shows in a +diagrammatic way the essential parts of a cell. In the diagram, there are +two well-marked regions; a central _nucleus_ and a peripheral cell-body or +_cytoplasm_. Other structures are pictured but only a few of them need +command our attention at present. At one side of the nucleus one observes +a small dot or granule surrounded by a denser area of cytoplasm. This body +is called the _centrosome_. The nucleus in this instance is bounded by a +well-marked nuclear membrane and within it are several substances. What +appear to be threads of a faintly staining material, the _linin_, traverse +it in every direction and form an apparent network. The parts on which we +wish particularly to rivet our attention are the densely stained +substances scattered along or embedded in the strands of this network in +irregular granules and patches. This substance is called _chromatin_. It +takes its name from the fact that it shows great affinity for certain +stains and becomes intensely colored by them. This deeply colored portion +of the cell, the chromatin, is by most biologists regarded as of great +importance from the standpoint of heredity. One or more larger masses of +chromatin or chromatin-like material, known as _chromatin nucleoli_, are +often present, and not infrequently a small spheroidal body, differing in +its staining reactions from the chromatin-nucleolus and sometimes called +the _true nucleolus_, exists. + +=Cell-Division.--=In the simplest type of cell-division the nucleus first +constricts in the middle, and finally the two halves separate. This +separation is followed by a similar constriction and final division of the +entire cell-body, which results in the production of two new cells. This +form of cell-division is known as _simple_ or _direct division_. Such a +simple division, while found in higher animals, is less frequent and +apparently much less significant than another type of division which +involves profound changes and rearrangements of the nuclear contents. The +latter is termed _mitotic_ or _indirect_ cell-division. Fig. 6, p. 33, +illustrates some of the stages which are passed through in indirect +cell-division. The centrosome which lies passively at the side of the +nucleus in the typical cell (Fig. 6_a_, p. 33) awakens to activity, +divides and the two components come to lie at the ends of a fibrous +spindle. In the meantime, the interior of the nucleus is undergoing a +transformation. The granules and patches of chromatin begin to flow +together along the nuclear network and become more and more crowded until +they take on the appearance of one or more long deeply-stained threads +wound back and forth in a loose skein in the nucleus (Fig. 6_b_, p. 33). +If we examine this thread closely, in some forms it may be seen to consist +of a series of deeply-stained chromatin granules packed closely together +intermingled with the substance of the original nuclear network. + +As the preparations for division go on the coil in the nucleus breaks up +into a number of segments which are designated as _chromosomes_ (Fig. +6_c_, p. 33). The nuclear membrane disappears. The chromosomes and the +spindle-fibers ultimately become related in such a way that the +chromosomes come to lie at the equator of the spindle as shown in Fig +6_d_, p. 33. Each chromosome splits lengthwise to form two daughter +chromosomes which then diverge to pass to the poles of the spindle (Figs. +6_e_ and _f_, p. 33). Thus each end of the spindle comes ultimately to be +occupied by a set of chromosomes. Moreover each set is a duplicate of the +other, because the substance of any individual chromosome in one group has +its counterpart in the other. In fact this whole complicated system of +indirect division is regarded by most biologists as a mechanism for +bringing about the precise halving of the chromosomes. + + +[Illustration: FIG. 6 + +Diagram showing representative stages in mitotic or indirect +cell-division: _a_, resting cell with reticular nucleus and single +centrosome; _b_, the two new centrosomes formed by division of the old one +are separating and the nucleus is in the spireme stage; _c_, the nuclear +wall has disappeared, the spireme has broken up into six separate +chromosomes, and the spindle is forming between the two centrosomes; _d_, +equatorial plate stage in which the chromosomes occupy the equator of the +spindle; _e_, _f_, each chromosome splits lengthwise and the daughter +chromosomes thus formed approach their respective poles; _g_, +reconstruction of the new nuclei and division of the cell body; _h_, +cell-division completed.] + + +The chromosomes of each group at the poles finally fuse and two new +nuclei, each similar to the original one, are constructed (Figs. 6_g_ and +_h_, p. 33). In the meantime a division of the cell-body is in progress +which, when completed, results in the formation of two complete new cells. + +As all living matter if given suitable food, can convert it into living +matter of its own kind, there is no difficulty in conceiving how the new +cell or the chromatin material finally attains to the same bulk that was +characteristic of the parent cell. In the case of the chromatin, indeed, +it seems that there is at times a precocious doubling of the ordinary +amount of material before the actual division occurs. + +=Chromosomes Constant in Number and Appearance.--=With some minor +exceptions, to be noted later, which increase rather than detract from the +significance of the facts, the chromosomes are always the same in number +and appearance in all individuals of a given species of plants or animals. +That is, every species has a fixed number which regularly recurs in all of +its cell-divisions. Thus the ordinary cells of the rat, when preparing to +divide, each display sixteen chromosomes, the frog or the mouse, +twenty-four, the lily twenty-four, and the maw-worm of the horse only +four. The chromosomes of different kinds of animals or plants may differ +very much in appearance. In some they are spherical, in others rod-like, +filamentous or perhaps of other forms. In some organisms the chromosomes +of the same nucleus may differ from one another in size, shape and +proportions, but if such differences appear at one division they appear at +others, thus showing that in such cases the differences are constant from +one generation to the next. + +=Significance of the Chromosomes.--=The question naturally arises as to +what is the significance of the chromosomes. Why is the accurate +adjustment which we have noted for their division necessary? The very +existence of an elaborate mechanism so admirably adapted to their precise +halving, predisposes one toward the belief that the chromosomes have an +important function which necessitates the retention of their individuality +and their equal division. Many biologists accept this along with other +evidence as indicating that in chromatin we have a substance which is not +the same throughout, that different regions of the same chromosome have +different physiological values. + +When the cell prepares for divisions, the granules, as we have seen, +arrange themselves serially into a definite number of strands which we +have termed chromosomes. Judging from all available evidence, the granules +are self-propagating units; that is, they can grow and reproduce +themselves. So that what really happens in mitosis in the splitting of the +chromosomes is a precise halving of the series of individual granules of +which each chromosome is constituted, or in other words each granule has +reproduced itself. Thus each of the two daughter cells presumably gets a +sample of every kind of chromosomal particle, hence, the two cells are +qualitatively alike. To use a homely illustration we may picture the +individual chromosomes to ourselves as so many separate trains of freight +cars, each car of which is loaded with different merchandise. Now, if +every one of the trains could split along its entire length and the +resulting halves each grow into a train similar to the original, so that +instead of one there would exist two identical trains, we should have a +phenomenon analogous to that of a dividing chromosome. + +=Cleavage of the Egg.--=It is through a series of such divisions as these +that the zygote or fertilized egg-cell builds up the tissues and organs of +the new organism. The process is technically spoken of as _cleavage_. +Cleavage generally begins very shortly after fertilization. The fertile +egg-cell divides into two, the resulting cells divide again and thus the +process continues, with an ever-increasing number of cells. + +=Chief Processes Operative in Building the Body.--=Although of much +interest, space will not permit of a discussion in detail of the building +up of the special organs and tissues of the body. It must suffice merely +to mention the four chief processes which are operative. These are, (1) +infoldings and outfoldings of the various cell complexes; (2) +multiplication of the component cells; (3) special changes (_histological +differentiation_) in groups of cells; and (4) occasionally resorption of +certain areas of parts. + +=The Origin of the New Germ-Cells.--=On account of the unusual importance +from the standpoint of inheritance, which attaches to the germ-cells, a +final word must be said about their origin in the embryo. While the +evidence is conflicting in some cases, in others it has been well +established that the germ-cells are set apart very early from the cells +which are to differentiate into the ordinary body tissues. Fig. 7_A_, p. +38, shows a section through the eight-celled stage of _Miastor_, a fly, in +which a single large, primordial germ-cell (_p. g. c._) has already been +set apart at one end of the developing embryo. The nuclei of the rest of +the embryo still lie in a continuous protoplasmic mass which has not yet +divided up into separate cells. The densely stained nuclei at the opposite +end of the section are the remnants of nurse-cells which originally +nourished the egg. Fig. 7_B_, p. 38, is a longitudinal section through a +later stage in the development of _Miastor_; the primitive germ-cells +(oög) are plainly visible. Still other striking examples might be cited. +Even in vertebrates the germ-cells may often be detected at a very early +period. + +=Significance of the Early Setting Apart of the Germ-Cells.--=It is of +great importance for the reader to grasp the significance of this early +setting apart of the germ-cells because so much in our future discussion +hinges on this fact. The truth of the statement made in a previous chapter +that the body of an individual and the reproductive substance in that body +are not identical now becomes obvious. For in such cases as those just +cited one sees the germinal substance which is to carry on the race set +aside at an early period in a given individual; it takes no part in the +formation of that individual's body, but remains a slumbering mass of +potentialities which must bide its time to awaken into expression in a +subsequent generation. Thus an egg does not develop into a body which in +turn makes new germ-cells, but body and germ-cells are established at the +same time, the body harboring and nourishing the germ-cells, but not +generating them (Fig. 2, p. 13). The same must be true also in many cases +where the earliest history of the germ-cells can not be visibly followed, +because in any event, in all higher animals, they appear long before the +embryo is mature and must therefore be descendants of the original +egg-cell and not of the functioning tissues of the mature individual. This +need not necessarily mean that the germ-cells have remained wholly +unmodified or that they continue uninfluenced by the conditions which +prevail in the body, especially in the nutritive blood and lymph stream, +although as a matter of fact most biologists are extremely skeptical as to +the probability that influences from the body beyond such general +indefinite effects as might result from under-nutrition or from poisons +carried in the blood, modify the intrinsic nature of the germinal +substances to any measurable extent. + + +[Illustration: FIG. 7 + +A--Germ-cell (_p. g. c._) set apart in the eight-celled stage of cleavage +in _Miastor americana_ (after Hegner). The walls of the remaining seven +somatic cells have not yet formed though the resting or the dividing (_M +p_) nuclei may be seen; _c R_, chromatin fragments cast off from the +somatic cells. + +B--Section lengthwise of a later embryo of _Miastor_; the primordial +egg-cells (_oög__{3}) are conspicuous (after Hegner).] + + +=Germinal Continuity.--=The germ-cells are collectively termed the +_germinal protoplasm_ and it is obvious that as long as any race continues +to exist, although successive individuals die, some germinal protoplasm is +handed on from generation to generation without interruption. This is +known as the theory of _germinal continuity_. When the organism is ready +to reproduce its kind the germ-cells awaken to activity, usually +undergoing a period of multiplication to form more germ-cells before +finally passing through a process of what is known at _maturation_, which +makes them ready for fertilization. The maturation process proper, which +consists typically of two rapidly succeeding divisions, is preceded by a +marked growth in size of the individual cells. + +=Individuality of Chromosomes.--=Before we can understand fully the +significance of the changes which go on during maturation we shall have to +know more about the conditions which prevail among the chromosomes of +cells. As already noted each kind of animal or plant has its own +characteristic number and types of chromosomes when these appear for +division by mitosis. In many organisms the chromosomes are so nearly of +one size as to make it difficult or impossible to be sure of the identity +of each individual chromosome, but on the other hand, there are some +organisms known in which the chromosomes of a single nucleus are not of +the same size and form (Fig. 8, p. 41). These latter cases enable us to +determine some very significant facts. Where such differences of shape and +proportion occur they are constant in each succeeding division so that +similar chromosomes may be identified each time. Moreover, in all ordinary +mitotic divisions where the conditions are accurately known, these +chromosomes of different types are found to be present as pairs of similar +elements; that is, there are two of each form or size. + +=Pairs of Similar Chromosomes in the Nucleus Because One Chromosome Comes +from Each Parent.--=When we recall that the original fertilized egg from +which the individual develops is really formed by the union of two +gametes, ovum and spermatozoon, and that each gamete, being a true cell, +must carry its own set of chromosomes, the significance of the pairs of +similar chromosomes becomes evident; one of each kind has probably been +contributed by each gamete. This means that the zygote or fertile ovum +contains double the number of chromosomes possessed by either gamete, and +that, moreover, each tissue-cell of the new individual will contain this +dual number. For, as we have seen, the number of chromosomes is, with +possibly a few exceptions, constant in the tissue-cells and early +germ-cells in successive generations of individuals. For this to be true +it is obvious that in some way the nuclei of the conjugating gametes have +come to contain only half the usual number. Technically the tissue-cells +are said to contain the _diploid_ number of chromosomes, the gametes the +reduced or _haploid_ number. + + +[Illustration: FIG. 8 + +A--Chromosomes of the mosquito (_Culex_) after Stevens. + +B--Chromosomes of the fruit-fly (_Drosophila_) after Metz. + +Both of these forms have an unusually small number of chromosomes.] + + +=In Maturation the Number of Chromosomes Is Reduced by One-Half.--=This +halving, or as it is known, _reduction_ in the number of chromosomes is +the essential feature of the process of maturation. It is accomplished by +a modification in the mitotic division in which instead of each chromosome +splitting lengthwise, as in ordinary mitosis, the chromosomes unite in +pairs (Fig. 9_b_, p. 42), a process known technically as _synapsis_, and +then apparently one member of each pair passes entire into one new +daughter cell, the other member going to the other daughter cell (Fig. +9_c_, p. 42). In the pairing preliminary to this _reduction division_, +leaving out of account certain special cases to be considered later, +according to the best evidence at our command the union always takes place +between two chromosomes which match each other in size and appearance. +Since one of these is believed to be of maternal and the other of +paternal origin, the ensuing division separates corresponding mates and +insures that each gamete gets one of each kind of chromosome although it +appears to be a matter of mere chance whether or not a given cell gets the +paternal or the maternal representative of that kind. + + +[Illustration: FIG. 9 + +Diagram to illustrate spermatogenesis: _a_, showing the diploid number of +chromosomes (six is arbitrarily chosen) as they occur in divisions of +ordinary cells and spermatogonia; _b_, the pairing (synapsis) of +corresponding mates in the primary spermatocyte preparatory to reduction; +_c_, each secondary spermatocyte receives three, the haploid number of +chromosomes; _d_, division of the secondary spermatocytes to form _e_, +spermatids, which transform into _f_, spermatozoa.] + + +=Maturation of the Sperm-Cell.--=In the maturation of the male gamete the +germ-cell, now known as a _spermatogonium_, increases greatly in size to +become a _primary spermatocyte_. In each primary spermatocyte the pairing +of the chromosomes already alluded to occurs as indicated in Fig. 9_b_, p. +42, where six is taken arbitrarily to indicate the ordinary or _diploid_ +number of chromosomes, and three the reduced or _haploid_ number. The +division of the primary spermatocyte gives rise to two _secondary +spermatocytes_ (_c_), the paired chromosomes separating in such a way that +a member of each pair goes to each secondary spermatocyte. Each secondary +spermatocyte (_d_) soon divides again into two _spermatids_ (_e_), but in +this second division the chromosomes each split lengthwise as in an +ordinary division so that there is no further reduction. In some forms the +reduction division occurs in the secondary spermatocytes instead of the +primary. Each spermatid transforms into a mature spermatozoon (_f_). The +spermatozoa of most animals are of linear form, each with a head, a +middle-piece and a long vibratile tail which is used for locomotion. The +head consists for the most part of the transformed nucleus and is +consequently the part which bears the chromosomes. + +=Maturation of the Egg-Cell.--=As regards the behavior of the chromosomes +the maturation of the ovum parallels that of the sperm-cell. There are not +so many primordial germ-cells formed and only one out of four of the +ultimate cells becomes a functional egg. As in maturation of the +sperm-cell there is a growth period in which _oögonia_ enlarge to become +_primary oöcytes_ (Fig. 10_b_, p. 45). In each primary oöcyte as in the +primary spermatocyte the chromosomes pair and two rapidly succeeding +divisions follow in one of which the typical numerical reduction in the +chromosomes occurs. A peculiarity in the maturation of the ovum is that +there is a very unequal division of the cytoplasm in cell division so that +three of the resulting cells usually termed _polar bodies_ are very small +and appear like minute buds on the side of the fourth or egg-cell proper. + +The scheme of this formation of the polar bodies is indicated in Fig. 10, +p. 45. In Fig. 10_b_ the chromosomes are seen paired and ready for the +first division; that is, for the formation of the first polar body. Figs. +10_c_, _d_, p. 45, show the giving off of this body. Note that while only +a small proportion of the cytoplasm passes into this tiny cell, its +chromatin content is as great as that of the ovum. A second polar body +(Figs. 10_e_, _f_, p. 45) is formed by the egg, but in this case each +chromosome splits lengthwise, as in ordinary mitosis, and there is no +further numerical reduction. In the meantime, typically, a third polar +body is formed by division of the first. (Stages _e_, _f_, _g_.) + +=Parallel Between the Maturation of Sperm- and Egg-Cell.--=This rather +complex procedure of the germ-cells will be rendered more intelligible +through a careful study of Figs. 9 and 10, pp. 42 and 45, and Fig. 11, p. +46, which indicates the parallel conditions in spermotogenesis and +oögenesis. + + +[Illustration: FIG. 10 + +Diagram to illustrate oögenesis: _a_, showing the diploid number of +chromosomes (six is arbitrarily chosen) as they occur in ordinary cells +and oögonia; _b_, the pairing of corresponding mates preparatory to +reduction; _c_, _d_, reduction division, giving off of first polar body; +_e_, egg preparing to give off second polar body, first polar body ready +for division; _f_, _g_, second polar body given off, division of first +polar body completed. The egg nucleus, now known as the female pronucleus, +and each body contain the reduced or haploid number of chromosomes.] + + +The view now generally held regarding the polar bodies is that they are +really abortive eggs. They later disappear, taking no part in +embryo-formation. It can readily be seen how such an unequal division is +advantageous to the large cell, for it receives all of the rich store of +food material that would be distributed among the four cells if all were +of equal size. This increased amount of food is a favorable provision for +the forthcoming offspring whose nourishment is thus more thoroughly +insured. + + +[Illustration: FIG. 11 + +Diagram showing the parallel between maturation of the sperm-cell and +maturation of the ovum.] + + +On the other hand, all of the sperm-cells develop into complete active +forms, which, as aforesaid, usually become very much elongated and develop +a motile organ of some kind. In such cells an accumulation of food to any +large extent would hinder rather than help them, because it would +seriously interfere with their activity. + +=Fertilization.--=In fertilization (Fig. 12, p. 48) the spermatozoon +penetrates the wall of the ovum and after undergoing considerable +alteration its nucleus fuses with the nucleus of the egg. In some forms +only the head (nucleus) and middle-piece enter, the tail being cut off by +a so-called fertilization membrane which forms at the surface of the egg +and effectually blocks the entrance of other spermatozoa. Thus normally +only one spermatozoon unites with an egg. In some forms while several may +enter the egg only one becomes functional. As soon as the nucleus of the +spermatozoon, now known as the male _pronucleus_, reaches the interior of +the egg, it enlarges and becomes similar in appearance to the female +_pronucleus_. It swings around in such a way (Fig. 12_b_, p. 48) that the +middle piece, now transformed into a centrosome, lies between it and the +female pronucleus. The two pronuclei (_c_, _d_, _e_), each containing the +reduced number of chromosomes, approach, the centrosome divides, the +nuclear walls disappear, the typical division spindle forms, and the +chromosomes of paternal and maternal origin respectively come to lie side +by side at the equator of the spindle ready for the first division or +cleavage (_f_, _g_). It will be noted that the individual chromosomes do +not intermingle their substance at this time, but that each apparently +retains its own individuality. There is considerable evidence which +indicates that throughout life the chromosomes contributed by the male +parent remain distinct from those of the female parent. Inasmuch as each +germ-cell, after maturation, contains only half the characteristic number +of chromosomes, the original number is restored in fertilization. + + +[Illustration: FIG. 12 + +Diagram to illustrate fertilization; [male], male pronucleus; [female], +female pronucleus; observe that the chromosomes of maternal and paternal +origin respectively do not fuse.] + + +=Significance of the Behavior of the Chromosomes.--=The question confronts +us as to what is the significance of this elaborate system which keeps the +chromosomes of constant size, shape and number; which partitions them so +accurately in ordinary cell-divisions; and which provides for a reduction +of their numbers by half in the germ-cell while yet securing that each +mature gamete gets one of each kind of chromosome. Most biologists look on +these facts as indicating that the chromosomes are specifically concerned +in inheritance. + +In the first place it is recognized that as regards the definable +characters which separate individuals of the same species, offspring may +inherit equally from either parent. And it is a very significant fact that +while the ovum and spermatozoon are very unequal in size themselves, the +chromosomes of the two germ-cells are of the same size and number. This +parity in chromosomal contribution points clearly to the means by which an +equal number of character-determiners might be conveyed from each parent. +Moreover it is mainly the nucleus of the sperm-cell in some organisms +which enters the egg, hence the determiners from the male line must exist +wholly or largely somewhere in the nucleus. And the bulk of the nucleus in +the spermatozoon consists of the chromosomes or their products. + +=A Single Set of Chromosomes Derived from One Parent Only Is Sufficient +for the Production of a Complete Organism.--=That a single or haploid set +of chromosomes as seen in the gametes is sufficient contribution of +chromatin for the production of a complete organism is proved by the fact +that the unfertilized eggs of various animals (many echinoderms, worms, +mollusks, and even the frog) may be artificially stimulated to development +without uniting at all with a spermatozoon. The resulting individual is +normal in every respect except that instead of the usual diploid number it +has only the single or haploid number of chromosomes. Its inheritance of +course is wholly of maternal origin. The converse experiment in +echinoderms in which a nucleus of male origin (that is, a spermatozoon) +has been introduced into an egg from which the original nucleus has been +removed shows that the single set of chromosomes carried by the male +gamete is also sufficient to cooperate with the egg-cytoplasm in +developing a complete individual. + +=The Duality of the Body and the Singleness of the Germ.--=Since every +maternal chromosome in the ordinary cell has an equivalent mate derived +from the male parent, it follows therefore, supposing the chromosomes do +have the significance in inheritance attributed to them, that as regards +the measurable inheritable differences between two individuals, the +ordinary organism produced through the union of the two germ-cells is, +potentially at least, dual in nature. On the other hand through the +process of reduction the gametes are provided with only a single set of +such representatives. This duality of the body and singleness of the +mature germ is one of the most striking facts that come to light in +embryology. How well the facts fit in with the behavior of certain +hereditary characters will be seen later in our discussions of Mendelism. + +=The Cytoplasm Not Negligible in Inheritance.--=Just what part is played +by the cytoplasm in inheritance is not clear, but it is probably by no +means a negligible one. The cytoplasm of a given organism is just as +distinctive of the species or of the individual of which it forms a part +as are the chromosomes. It is well established that neither nucleus nor +cytoplasm can fully function or even exist long without the other, and +neither can alone produce the other. They undoubtedly must cooperate in +building up the new individual, and the cytoplasm of the new individual is +predominantly of maternal origin. It is obvious that all of the more +fundamental characters which make up an organism, such, for instance, as +make it an animal of a certain order or family, as a human being or a dog +or a horse, are common to both parents, and there is no way of measuring +how much of this fundamental constitution comes from either parent, since +only closely related forms will interbreed. In some forms, moreover, the +broader fundamental features of embryogeny are already established before +the entrance of the spermatozoon. It is probable therefore that instead of +asserting that the entire quota of characters which go to make up a +complete individual are inherited from each parent equally, we are +justified only in maintaining that this equality is restricted to those +measurable differences which veneer or top off, as it were, the +individual. We may infer that in the development of the new being the +chromosomes of the egg together with those derived from the male work +jointly on or with the other germinal contents which are mostly +cytoplasmic materials of maternal origin. + +=The Chromosomes Possibly Responsible for the Distinctiveness of Given +Characters.--=It seems probable that in the establishment of certain basic +features of the organism the cooperation of the cytoplasm with chromatin +of either maternal or paternal origin might accomplish the same end, but +that certain distinctive touches are added or come cumulatively into +expression through influences carried, predominantly at least, in the +chromatin from one as against the other parent. These last distinctive +characters of the plant or animal constitute the individual differences of +such organisms. In this connection it is a significant fact that in young +hybrids between two distinct species the early stages of development, +especially as regards symmetry and regional specifications, are +exclusively or predominantly maternal in character, but the male influence +becomes more and more apparent as development progresses until the final +degree of intermediacy is attained. + +From the evidence at hand this much seems sure, that the paternal and +maternal chromosomes respectively carry substances, be they ferments, +nutritive materials or what not, that are instrumental in giving the final +parity of personal characters which we observe to be equally heritable +from either line of ancestry. It is clear that most of the characters of +an adult organism can not be merely the outcome of any unitary substance +of the germ. Each is the product of many cooperating factors and for the +final outcome any one cooperant is probably just as important in its way +as any other. The individual characters which we juggle to and fro in our +breeding experiments seem apexed, as it were, on more fundamental features +of organic chemical constitution, polarity, regional differentiation, and +physiological balance, but since such individual characters parallel so +closely the visible segregations and associations which go on among the +chromosomes of the germ-cells it would seem that they, at least, are +represented in the chromosomes by distinctive cooperants which give the +final touch of specificity to those hereditary characters which can be +shifted about as units of inheritance. + +=Sex and Heredity.--=Whatever the origin of fertilization may have been in +the world of life, or whatever its earliest significance, the important +fact remains that to-day it is unquestionably of very great significance +in relation to the phenomena of heredity. For in all higher animals, at +least, offspring may possess some of the characteristics originally +present in either of two lines of ancestry, and this commingling of such +possessions is possible only through sexual reproduction. As has already +been seen, in the pairing of chromosomes previous to reduction, the +corresponding members of a pair always come together so that in the final +segregation each gamete is sure to have one of each kind although whether +a given chromosome of the haploid set is of maternal or paternal origin +seems to be merely a matter of chance. Thus, for instance, if we +arbitrarily represent the chromosomes of a given individual by _ABC_ +_abc_, and regard _A_, _B_ and _C_ as of paternal and _a_, _b_ and _c_ as +of maternal origin, then in synapsis only _A_ and _a_ can pair together, +_B_ and _b_ and _C_ and _c_, but each pair operates independently of the +other so that in the ensuing reduction division either member of a pair +may get into a cell with either member of the other pairs. That is, the +line up for division at a given reduction might be any one of the +following, ABC/abc ABc/abC Abc/aBC AbC/aBc. This would yield the following +eight kinds of gametes, _ABC_, _abc_, _ABc_, _abC_, _Abc_, _aBC_, _AbC_, +_aBc_, each bearing one of each kind of chromosome required to cover the +entire field of characters necessary to a complete organism. And since +each sex would be equally likely to have these eight types of gametes and +any one of the eight in one individual might meet any one of the eight of +the other, the possible number of combinations in the production of a new +individual from such germ-cells would be 8x8, or 64. With the larger +numbers of chromosomes which exist in most animals it is readily seen that +the number of possible combinations becomes very great. Thus any +individual of a species with twenty chromosomes--and many animals, +including man, have more--would have ten pairs at the reduction period and +could therefore form (2)^{10}, or 1,024 different gametes in each sex. And +since any one of these in one sex would have an equal chance of meeting +with any one in the opposite sex, the total number of possible different +zygotes that might be produced would be (1,024)^{2}, or 1,048,576. Sex +therefore, through recombinations of ancestral materials, undoubtedly +means, among other things, the production of great diversity in +offspring. + + +DETERMINATION OF SEX + +=Many Theories.--=From earliest times the problem of sex determination has +been one of keen interest, and needless to say hundreds of theories have +been propounded to explain it. Geddes and Thomson say that Drelincourt +recorded two hundred sixty-two so-called theories of sex production and +remark that since his time the number has at least been doubled. The +desirability of controlling sex has naturally appealed strongly to +breeders of domesticated animals. + +A study of animals born in litters, or of twins, is enough in itself to +make us skeptical of theories of sex-determination based on nutritional or +external factors. In a litter of puppies, for example, there are usually +both males and females, although in their prenatal existence they have all +been subject to the same nutritional and environmental conditions. +Likewise in ordinary human twins one may be a boy, the other a girl, +whereas if the nutritional condition of the mother were the fact +determining sex, both should be boys or both girls. However, there are +twins known as _identical twins_ who are remarkably alike and who are +always of the same sex. But there is reason to suppose that identical +twins in reality come from the same zygote. Presumably in early +embryogeny, probably at the two-celled stage of cleavage, the two +blastomeres become separated and each gives rise to a complete individual +instead of only the half of one it would have produced had the two +blastomeres remained together. Such twins are monochorial; that is, they +grow inside the same fetal membrane, whereas each ordinary twin has its +own fetal membrane and has obviously originated from a separate ovum. It +has been established experimentally in several kinds of animals that early +cleavage blastomeres when isolated can each develop into a complete +individual. In man, ordinary twins are no more alike than ordinary +brothers and sisters, but identical twins are strikingly similar in +structure, appearance, habits, tastes, and even susceptibility to various +maladies. The fact that they are invariably of the same sex is a strong +reason for believing that sex was already developed in the fertile ovum +and consequently in the resulting blastomeres from that ovum. + +The young of the nine-banded armadillo in a given litter are invariably of +the same sex and are closely similar in all features. Newman and Patterson +have shown that all the members of a litter come from the same egg. +Patterson has established the fact that cleavage of the egg takes place in +the usual manner, but later separate centers of development appear in the +early embryonic mass and give rise to the separate young individuals. + +Again in certain insects where one egg indirectly gives rise to a chain of +embryos, or to a number of separate larvæ, possibly as many as a thousand, +all of the latter are of the same sex. Even in some plants researches have +shown that sex is already determined at the beginning of development. +Then, too, much evidence has come to light recently showing that +sex-characters in certain cases behave as heritable characters and are +independent of external conditions. Lastly there is visible and convincing +evidence obtainable through microscopical observations that sex is +determined by a mechanism in the germ-cells themselves. It is chiefly to +these latter facts that I wish to direct attention for the present. + +=The Sex Chromosome.--=The evidence centers about a special chromosome or +chromosome-group commonly designated as the _sex-chromosome_ or +_X-element_, which has been found in various species of animals, including +man. In the males of such animals this chromosome is present in addition +to the regular number of pairs, thus giving rise to an _uneven_ instead of +the conventional even number of chromosomes. This element remains +undivided in one of the maturation divisions of the spermatocytes, in some +forms in the first in others in the second, and passes entire to one pole +of the spindle (Fig. 13, p. 58). This results in the production of two +classes of cells, one containing the _X_-element and one not. The outcome +is that two corresponding classes of spermatozoa are produced. The +phenomena involved are diagrammatically represented in Fig. 13. It has +been clearly demonstrated in several cases that eggs fertilized by +spermatozoa which possess this _X_-element, always become females, those +fertilized by spermatozoa which do not possess it always develop into +males. + + +[Illustration: FIG. 13 + +Diagram illustrating the behavior of the _x_-element or sex-chromosome in +the maturation of the sperm-cell. In one of the two maturation divisions +(represented here as in the first) it passes undivided to one pole (_a_, +_b_, _c_), in the other it divides. Since the cell without the _x_-element +also divides the result is that ultimately from the original primary +spermatocyte (_a_) four cells are formed (_f_), two with the _x_-element +and two without it. Half of the spermatozoa therefore will bear an +_x_-element, half will be without it. In _a_ the ordinary chromosomes, +arbitrarily indicated as 10, are supposed to have already paired for +reduction so that the original diploid number in spermatogonia and +body-cells of the male would be 20 plus the _x_-chromosome.] + + +It has been found, furthermore, that in species in which the males possess +this extra element the females have two of them. That is, if the original +number in the somatic cells of the male were twenty-three, twenty-two +ordinary and one _X_-element, the number in the somatic cells of the +female would be twenty-four, or twenty-two ordinary and two _X_-elements. +It has been found that when the chromosomes of the female pair for the +reduction division, each chromosome uniting with its corresponding fellow, +the two _X_-elements in the female pair in the usual way so that every +egg-cell possesses an _X_-element. Thus every mature egg has an +_X_-element, while only half of the spermatozoa have one. That is, if we +assume twenty-three as the diploid number present originally in the +somatic cells of the male and twenty-four as the number in the female, +then one-half the spermatozoa of the male would contain the haploid number +eleven, and the other half, the number twelve, whereas every mature ovum +would contain twelve. Since there are equal numbers of the spermatozoa +with the _X_-element and without it, and inasmuch as presumably under +ordinary conditions one kind is as likely to fertilize the egg as the +other, then there are equal chances at fertilization of producing a zygote +with two _X_-elements or with but one. + + Thus, Spermatozoon + _X_ by Ovum + _X_ = Zygote + _XX_. + Spermatozoon (no _X_) by Ovum + _X_ = Zygote + _X_. + +We have already seen that the former is always female, the latter male. It +thus becomes possible to distinguish the sex of an embryo by counting the +chromosomes of its cells. This has been accomplished in several cases. + +In some instances[1] the conditions may be much more complex than the +ones indicated--too complex in fact to warrant detailed discussion in an +elementary exposition--but the principle remains the same throughout, the +very complexity when thoroughly understood, strengthening rather than +weakening the evidence. In a few forms an interesting reversal of +conditions has been found in that the eggs instead of the spermatozoa show +the characteristic dimorphism. + +Just what the exact relationship between sex-differentiation and the +_X_-element is has never been clearly established. It is possible that +this element is an actual sex-determinant, in the ordinary cases one +_X_-element determining the male condition and two _X_-elements producing +the female condition. On the other hand it might be argued that it is not +the determining factor but the expression of other cell activities which +do determine sex; that is, a sex accompaniment. Or again, it may be one of +several essential factors which must cooperate to determine sex. + + +SEX-LINKED CHARACTERS + +The discovery of the remarkable behavior of certain characters in heredity +which can only be plausibly explained by supposing that they are linked +with a sex-determining factor still further strengthens our belief in the +existence of such a definite factor. Such characters are commonly termed +sex-linked characters. + +=Sex-Linked Characters in Man.--=Since there are a number of them in man +we may choose one of these, such as color-blindness, for illustration. The +common form of color-blindness known as Daltonism in which the subject +can not distinguish reds from greens, a condition which seems to be due to +the absence of something which is present in individuals of normal color +vision, is far commoner in men than in women. Its type of inheritance, +sometimes termed "crisscross" heredity, has been likened to the knight +moves in a game of chess. The condition is transmitted from a color-blind +man through his daughter to half of her sons. Or, to go more into detail, +a color-blind father and normal mother have only normal children whether +sons or daughters. The sons continue to have normal children but the +daughters, although of normal vision themselves, transmit color-blindness +to one-half of their own sons. If such a woman marries a color-blind man, +as might easily happen in a marriage between cousins, then as a rule +one-half her daughters as well as one-half her sons will be color-blind. + + +[Illustration: FIG. 14 + +Diagram illustrating the inheritance of a sex-limited character such as +color-blindness in man on the assumption that the factor in question is +located in the sex-chromosome (from Loeb after Wilson). The normal +sex-chromosome is indicated by a black =X=, the one lacking the factor for +color perception, by a light X. It is assumed that a normal female is +mated with a color-blind male.] + + +In such cases what appears to be a mysterious procedure becomes very +simple if we assume that the defective character is associated with the +sex-determining factor, or to make it concrete let us say with the +_X_-element. The chart shown in Fig. 14, p. 62, indicates what the +germinal condition would be under the circumstances. The column to the +right represents the maternal, the one to the left the paternal line. +Since two _X_ means female and one _X_ male, and inasmuch as we have +assumed that the physical basis of the defect to which color-blindness is +due is conveyed by the _X_-element, we may represent the defective single +_X_ of the male in outline only (see first row). It is obvious that after +the reduction divisions (second row) the mature sex-cells of the female +will each contain a single normal _X_, the corresponding sex cells of the +male will contain either no _X_ or a defective _X_. Since if any member of +the class of spermatozoa containing no _X_, fertilizes an egg the +resulting zygote (row three) will have but one _X_ and that a normal one, +the individual which develops from the zygote will be normal as regards +color vision and moreover will be male because the condition one _X_ +always means maleness. On the other hand, if any member of the class of +spermatozoa containing the defective _X_ fertilizes an egg two +_X_-elements are brought together and this of itself means femaleness. In +this case one of the _X_-elements is defective but the single normal _X_ +is sufficient in itself to produce normal color vision. But when it comes +to the maturation of the sex-cells of this female, the pair of +_X_-elements are separated in the usual way with the result that half of +the mature ova contain a normal _X_ and half a defective _X_ (row four). +Since in a normal male, however, the mature reproductive cells will +contain either a normal _X_ or no _X_ (fourth row), any one of four +different kinds of matings may result. A sex-cell carrying normal _X_ of +the male may combine with an ovum containing normal X producing a normal +female (row five). Or such a cell may combine with an ovum carrying the +defective _X_, also producing a female but one who although of normal +color vision herself, like her mother, is a carrier of the defect. On the +other hand, any one of the spermatozoa without an _X_ may combine with an +ovum containing the normal _X_, in which case a normal male is produced +and, moreover, one who, like his mother's brothers, is incapable of +transmitting the defect. However, the sperm-cell devoid of an _X_ is just +as likely to fertilize an ovum carrying the defective _X_, in which event +the resulting individual, a male, must be color-blind because he contains +the defective _X_ alone. In other words, the chances are that one-half the +sons of a woman whose father was color-blind will be color-blind, the +other half perfectly normal; and that all of the daughters will be of +normal color vision although one-half of them will probably transmit the +defect to one-half of their sons. From a glance at the diagram it is +readily seen also that a color-blind female could result from the union of +a color-blind man (see first row) and the daughter of a color-blind man +(see third row). For half of the gametes of such a female would bear the +defect as would also that half of the gametes of the male which carry _X_, +hence the expectation would be that half of the daughters of such a union +would be color-blind and half would be carriers of color-blindness; and +that half of the sons would be color-blind and half normal. All the sons +of a color-blind woman would be color-blind because she has only defective +_X_-elements to pass on. + +The inheritance of various other conditions in man follows more or less +accurately the same course as color-blindness. Among these may be +mentioned: _hemophilia_, a serious condition in which the blood will not +clot properly, thus rendering the affected individual constantly liable to +severe or fatal hemorrhage; near-sightedness (_myopia_) in some cases; a +degenerative disease of the spinal cord known as _multiple sclerosis_; +progressive atrophy of the optic nerve (_neuritis optica_); Gower's +_muscular atrophy_; some forms of _night-blindness_; in some cases +_ichthyosis_, a peculiar scaly condition of the skin. In one of my own +tabulations of a case of inheritance of "webbed" digits or _syndactyly_, a +condition in which two or more fingers or toes are more or less united, a +sex-linked inheritance is clearly indicated (Fig. 15), although from the +pedigrees recorded by other investigators this condition usually appears +in some of both the sons and daughters of an affected individual. + + +[Illustration: FIG. 15 + +Chart showing the inheritance of a case of syndactyly after the manner of +a sex-linked character. The affected individuals are represented in black; +squares indicate males, circles females. The condition is seen to be +inherited by males through unaffected females.] + + +=The Occurrence of Sex-Linkage in Lower Forms Renders Experiments +Possible.--=The course followed by such characters in man can be inferred +only from the pedigrees we can obtain from family histories. Fortunately, +however, such sex-linkage also occurs in lower animals and we are able +therefore to verify and extend our observations by direct experiments in +breeding. Several sex-linked characters have been found to exist in a +small fruit-fly known as _Drosophila_. Extensive breeding experiments with +this fly by Professor T. H. Morgan and his pupils have borne out +remarkably the interpretation that the characters in question are really +linked with a sex-determining factor. + + + + +CHAPTER III + +MENDELISM + + +=New Discoveries in the Field of Heredity.--=Writing in 1899, one of +America's well-known zoologists asserts that, "It is easier to weigh an +invisible planet than to measure the force of heredity in a single grain +of corn." And yet only two or three years later we find another prominent +naturalist saying regarding heredity that, "The experiments which led to +this advance in knowledge are worthy to rank with those that laid the +foundation of the atomic laws of chemistry." Again, "The breeding pen is +to us what the test-tube is to the chemist--an instrument whereby we +examine the nature of our organisms and determine empirically their +genetic properties." Here is a decided contrast of statement and yet both +were justifiable at the time of utterance. For even at the writing of the +first statement the investigations were in progress which, together with +the rediscovery of certain older work, were to transfer our knowledge of +heredity from the realm of speculation to that of experiment and disclose +certain definite principles of genetic transmission. + +Through a knowledge of these principles in fact, the shifting of certain +characters is reducible to a series of definitely predictable proportions +and the skilled breeder may proceed to the building up of new and +permanent combinations of desirable characters according to mathematical +ratios and, what is of equal importance, he can secure the elimination of +undesirable qualities. While there are many limitations in the application +of these principles and while new facts and modifications are constantly +being discovered concerning them, nevertheless they represent the first +approximations to definite laws of hereditary transmission that we have +ever been able to make, and the practical fact confronts us that whatever +our theoretical interpretations may be, the principles are so definite +that through their application important improvements of crops and +domesticated animals have already actually been secured and one may +confidently expect still others to follow. + +=Mendel.--=The principles involved are called the Mendelian principles +after their discoverer, Gregor Johann Mendel, abbot of a monastery at +Brünn, Austria. After eight years of patient experimenting in his cloister +garden with plants, chiefly edible peas, he published his results and +conclusions in 1866, in the _Proceedings of the Natural History Society of +Brünn_. While known to a few botanists of that day, the full importance of +the contribution was not recognized, and in the excitement of the +post-Darwinian controversy, the facts were lost sight of and ultimately +forgotten. + +=Rediscovery of Mendelian Principles.--=In 1900 three men, Correns, De +Vries and Tschermak, working independently--in different countries, in +fact--rediscovered the principles and called attention anew to the +long-forgotten work of Mendel which they had come upon in looking over the +older literature on plant breeding. These investigators added other +examples from their own experiments. Since their rediscovery the +principles have been confirmed in essential features and extended by +numerous experimentalists with regard to a wide range of hereditary +characters in both animals and plants. + +=Independence of Inheritable Characters.--=It has been found that many +truly heritable characteristics or traits of an individual, whether plant +or animal, are comparatively independent of one another and may be +inherited independently. Where there are contrasted characters in father +and mother, such as white plumage and black plumage in fowls, smooth coat +and wrinkled coat in seed, horns and hornlessness in cattle, long fur and +short fur in rabbits, beard and beardlessness in wheat, albino condition +and normal condition, etc., there is obviously a bringing together of the +determiners of the two traits in the resulting offspring. In the third +generation, however, in the progeny of these offspring, the two distinct +characters may be set apart again, thus showing that in the second +generation while perhaps one only was visible, the factors which determine +both were nevertheless present, and moreover, they were present in a +separable condition. + +=Illustration of Mendelism in the Andalusian Fowl.--=Let us take as a +simple example the case of the Andalusian fowl. Although it is not a case +established by Mendel it illustrates certain of the essential conditions +underlying Mendelism in a more obvious way than the cases worked out by +Mendel himself. The so-called blue Andalusian fowl results from a cross of +a color variety of the fowl which is black with one which is white with +black-splashed feathers. The result is the same irrespective of which +parent is black. When bred with their like, whether from the same parents +or different parents, these blue fowls produce three kinds of progeny, +approximately one-fourth of which are black like the one grandparent, +one-fourth white like the other grandparent, and the remaining half, blue +like the parents (Fig. 16). Moreover, the black fowls obtained in this way +will, when interbred, produce only black offspring and the same is true of +the white fowls. To all appearances as far as color is concerned they are +of as pure type as the original grandparents. With the blue fowls, +however, the case is different, for when bred together they will produce +the same three kinds of progeny that their parents produced and in the +same proportions. Again the white and the black are true to type but the +blue will always yield the three classes of offspring and this through +generation after generation. + + +[Illustration: FIG. 16 + +Diagram showing the scheme of inheritance in the blue Andalusian fowl.] + + +These facts may be illustrated graphically as follows where the word +"black" indicates the original black parent, "white" the original white +(black splashed) parent and "blue" the hybrid offspring. + + Parental + Generation (P) Black × White Black × White + | | + First Filial | | + Generation (F_{1}) Blue × Blue + | + +------------------------------------------+ + | | | + Second Filial Black Blue White + Generation (F_{2}) (25%) (50%) (25%) + | | | + | +-------------------------+ | + | | | | | + Third Filial Black Black Blue White White + Generation (F_{3}) | (25%) (50%) (25%) | + | | | | | + | | +-------------+ | | + | | | | | | | + Fourth Filial Black Black Black Blue White White White + Generation (F_{4}) (25%) (50%) (25%) + +=The Cause of the Mendelian Ratio.--=Concerning the cause of this peculiar +ratio of inheritance in crossed forms Mendel suggested a simple +explanation. Animals or plants that can be cross-bred, obviously must be +forms that produce a new individual from the union of two germ-cells, one +of which is provided by each parent. Mendel's idea was that there must be +some process of segregation going on in the developing germ-cells of each +hybrid whereby the factors for the two qualities are set apart in +different cells with the result that half of the germ-cells of a given +individual will contain the determiner of one character and half, the +determiner of the other. That is, a given germ-cell carries a factor for +one or the other of the two alternate characters but not the factors for +both. In a plant, for example, in the male line, half of the pollen grains +would bear germ-cells carrying the determiner of one character and half, +that of the other. Similarly, in the female line, half of the ovules would +contain the determiner of the one character and half, that of the other. +Likewise in animals as regards such pairs of characters there would be two +classes of germ-cells in the male and two in the female. In the case of +the blue Andalusian fowls under discussion this would mean that half of +the mature germ-cells of the male carry the black-producing factor, and +half carry the white-producing factor, and the same is true of the +germ-cells of the female. Thus when two such crossed forms are mated, +there are, by the laws of chance, four possible combinations, namely: (1) +white-determining sperm-cells and white-determining ovum; (2) +white-determining sperm-cells and black-determining ovum; (3) +black-determining sperm-cells and white-determining ovum; and (4) +black-determining sperm-cells and black-determining ovum. Manifestly, the +first combination can only give white offspring; the second, white and +black, gives blue (by such a cross the original blues were established); +likewise, the third, black and white, gives blue; and the fourth +combination can only give black offspring. This matter may be graphically +represented by the following formulæ in which B indicates the determiner +of Black in the germ-cell and W the determiner of White: [male] signifies +male; [female] female. + + +IN THE ORIGINAL PARENTS + + W × B = WB = Blue + +IN THE HYBRIDS + + [male] [female] + germ- germ- + cells cells [male] [female] + W----W W × W = WW = White + \/ W × B = WB = Blue + /\ or B × W = BW = Blue + B----B B × B = BB = Black + +Thus of the four possible combinations one only can produce white fowls, +two (WB or BW) can produce blue fowls, and one black fowls. That is, the +ratio is 1:2:1 or the 25, 50 and 25 per cent., respectively, of our +diagram. The black fowls or the white fowls will breed true in subsequent +generations when mated with those of their own color because the +determiner of the alternative character has been permanently eliminated +from their germ-plasm; but the blue fowls will always yield three types of +offspring because they still possess the two classes of germ-cells. + +=Verification of the Hypothesis.--=The hypothesis that germ-cells of +crossed forms are of two classes with respect to a given pair of Mendelian +characters is further substantiated by the following facts. If in the case +of the fowls under discussion one of the blue fowls is mated with an +individual of the white variety, half of the progeny will be blue and +half white. For the hybrid has two kinds of germ-cells, black producing, +which we have designated by the letter B, and white producing (or W) in +equal number while the white parent has only one kind, white producing. It +is obvious that if half the germ-cells of the hybrid form are of the type +B then half the progeny will be of the BW type, which is blue, and the +other half will be of the WW type, which is white. In the same way if we +mate a hybrid and a black fowl, half of the progeny will be black and half +will be blue, that is, there could only be WB and BB types. + +The fact must not be lost sight of that since the pairings are wholly +determined by the laws of chance the proportions are likely to be only +approximate. It is obvious that the greater the number of individuals, the +nearer the results will approach the expected ratio. + + +DOMINANT AND RECESSIVE + +=One Character May Mask the Other.--=In a large number of cases, however, +the actual condition of affairs is not so evident as in the Andalusian +fowl, for instead of being intermediate or different in appearance, the +generation produced by crossing resembles one parent to the exclusion of +the other. Such an overshadowing is spoken of as _dominance_, and the two +characters are termed _dominant_ and _recessive_. Thus when brown +ring-doves and white ring-doves are mated the progeny are all brown, or if +wild gray mice are mated to white mice the progeny are all gray. So black +is dominant to white in rose-comb bantams; brown eyes to blue eyes in man; +beardlessness to beard in wheat, and likewise rough chaff to smooth, and +thick stem to thin; tallness to dwarfness in various plants; normal +condition to the peculiar waltzing condition in the Japanese waltzing +mouse. Numerous other cases might be cited but these are sufficient to +illustrate the condition. + +=Segregation in the Next Generation.--=But now the question arises, what +do such crosses as show dominance transmit to the next generation? +Experiments show regarding any given pair of these alternate characters +that they are set apart again in the succeeding generation, returning in a +definite percentage to the respective grandparental types. + + +[Illustration: FIG. 17 + +Diagram showing the scheme of inheritance in guinea-pigs when black and +albino forms are crossed.] + + +=Dominance Illustrated in Guinea-Pigs.--=In guinea-pigs for example (Fig. +17), when an individual (either male or female) of a black variety, is +crossed with one of a white variety, the F_{1} generation are all black +like the black parent. When these are interbred or bred with other blacks +which have had one black and one white parent, only two visible types of +progeny appear, viz., black and white, and these approximately in the +ratio of three to one. + +Analysis by further breeding shows, however, that there are in reality +three types, but since dominance is complete the pure extracted dominant +and the mixed dominant-and-recessive type are indistinguishable to our +eye. That is, while the blacks are three times as numerous as the whites, +two out of every three of these blacks are really hybrid and correspond to +the blue fowls of our former example. + +The condition is readily comprehended when expressed diagrammatically +thus: + + Generation P Black × White Black × White + | | + Generation F_{1} Black (White) × Black (White) + | + +-------------------------------------+ + | | | + Generation F_{2} 1 Black 2 Black (White) 1 White + +In other words, the germ-cells of the one original parent (Gen. P) would +contain only determiners for black and that of the other parent would +contain only determiners for white. The condition of the individuals +produced by the cross would be represented by the formula B(W). But these +determiners segregate in the germ-cells of the crossed form, whether it be +male or female, into B and W. Hence half the spermatozoa of the male +hybrid (generation F_{1}) would carry the B determiners and half the W +determiners. The same is true of the mature ova of the female hybrid. +Consequently, in mating there are always four equally possible +combinations, viz., BB, B(W), (W)B, and WW. Since B is always dominant +three out of the four matings would yield black individuals, or in other +words the ratio would be 3:1. + +The pure blacks when mated together will breed true in subsequent +generations, likewise the whites, but the blacks carrying white as a +recessive will yield when interbred the same ratio of whites and black as +did their hybrid parents (Fig. 17, p. 75). + +=Terminology.--=As work in the study of Mendelian inheritance has +progressed and expanded the need of a more precise terminology has become +evident and such is gradually being established. Thus Professor Bateson +has coined the term "allelomorph" (Gk. _one another_, and _form_) to +express more exactly what we have thus far been calling a pair of +alternate or opposite characters. In the blue Andalusian fowls discussed, +the white condition in the one parent is the allelomorph of the black +condition in the other. The term generally means one of the pair of +Mendelian characters themselves as expressed in the individual plants or +animals but when the germinal basis of such phenomena is under discussion, +it is sometimes used to refer to the determiners of such characters. And +by determiner is meant simply the condition which is necessary in the germ +to bring about the occurrence of a definite character. For example, when +we are studying a cross between a red flower and a white flower with +reference to the color factors, the difference between the two plants may +lie in the fact that one produces a red coloring matter and the other +does not. That is, the determiner for red is absent from the white +variety. What the exact relation of color production is to the parts of +the germ-cell we do not know. It could be the function of a single +definite body or the resultant of several cooperating bodies. The latter +is far more likely to be the case. We may suppose that a group of +cooperating substances function to produce red in the red flower but that +in the white flowers one of these bodies is absent or fails to perform its +red-producing function. + +It is customary where practicable to refer to the determiner of a +character by the initial letter of the name of the character. The letter +when written as a capital indicates the determiner but when written as a +small letter the absence of the determiner. Thus R may be taken to +represent the determiner for red coloring matter and r its absence. It is +convenient also to have a brief symbol to denote a given generation and +for this purpose Bateson has introduced the symbol F_{1} for the hybrid +progeny of the first cross, the initial letter of the word "filial." F_{2} +would indicate the next generation, F_{3} the third and so on. Likewise P +denotes the original parent generation. + +=The Theory of Presence and Absence.--=Many, if not all, allelomorphs +consist of the presence and absence respectively of a given determiner. In +such cases the character represented by the presence of the determiner is +dominant over the character represented by the absence of a determiner. +Thus in the crosses from the wild gray mice and albino mice the progeny +are all gray mice since one parent had the determiner or group of +determiners for grayness and the hybrid offspring must also possess it. +Likewise the presence of black in black guinea-pigs is dominant to its +absence in albino guinea-pigs and the resulting progeny are all black. + +However, it has already been mentioned that beardlessness in wheat is +dominant to beard and that the absence of horns in cattle is dominant to +their presence, that is, the progeny of hornless by horned cattle are +without horns except for occasional traces of imperfect horns. Facts like +these would seem at first sight to contradict the assertion just made that +presence is dominant to absence, but it is fairly well established that in +such cases one is not dealing with true absences but with suppressions. +The polled breeds of cattle, for example, are hornless not because of the +absence of determiners for horns but because of the presence of an +additional inhibiting factor which prevents these determiners from +functioning. The horned breeds are without this inhibitor. When horned and +hornless individuals are crossed the presence of the inhibitor from one +line of ancestry is sufficient to suppress the development of horns in the +progeny. A similar explanation would, of course, apply to beardlessness in +wheat. + +In writing double-lettered formulæ to denote the determiners of characters +in hybrids the condition is represented merely by the capital and small +letter. Thus Rr indicates that red is dominant to its absence. + +=Additional Terminology.--=In pure breeds where the determiners are alike +as BB in black or bb in albino guinea-pigs, the individual is said to be a +_homozygote_ (like things united) with reference to that character, while +in those in which the determiners are unlike, as Bb, the individual is +termed a _heterozygote_ (unlike things united) with reference to the +character. Or to use the adjective forms, a pure black guinea-pig is +homozygous for black pigment, an albino guinea-pig is homozygous for +absence of pigment, while a cross between the two is heterozygous for +pigment. Also, where the determiner of a given character is present in +double quantity, that is, from both lines of ancestry, the individual is +said to be _duplex_, where represented in only the single form as in +heterozygous individuals, _simplex_, and where the determiner is absent +entirely, _nulliplex_, with reference to the character in question. Thus +black guinea-pigs of formula BB are duplex with regard to the determiner +for black color, individuals of formula Bb are simplex with reference to +this determiner, and those of formula bb are nulliplex. + +A heterozygote in which dominance prevails can be identified with +certainty by breeding to a known recessive and noting the kind of +offspring produced. If the individual was really a heterozygote, +approximately fifty per cent. of the offspring should be of the recessive +type. + +=Dominance Not Always Complete.--=As a matter of fact close inspection +shows that in numerous instances dominance is not absolute since traces of +the recessive character may be detectable. For example, in the cross +between smooth and bearded wheat while smoothness is regarded as the +dominant character and beardlessness as the recessive, nevertheless in the +hybrid offspring a slight tendency toward bearding is not infrequently +seen. Or again when horned breeds of cattle are crossed with hornless +ones, a small proportion of such progeny will show traces of imperfect +horns. + +In some cases instead of either character dominating the other a form +intermediate between the two parents may result, as we have seen already +in the case of the Andalusian fowl. Thus, certain white-flowered plants +and certain red-flowered plants when crossed produce pink hybrids, and +longheaded and shortheaded wheats when crossed give offspring with heads +of intermediate length. Or again, crosses between white and red cattle may +yield red roans, and between black and white cattle, blue roans. + +Thus, while for such pairs of alternative characters as have been studied, +dominance to some considerable degrees at least, seems to be the rule, +still we have gradations down to the intermediate condition, and in some +instances the hybrid with respect to a given character may be unlike +either parent. The things of chief importance in the Mendelian discovery +are the independent, unitary nature of the characters and their +segregation in the offspring of cross-bred forms. + +=Modifications of Dominance.--=It should be noted also that there is such +a condition as _delayed dominance_. Davenport found, for example, that +chicks produced by crossing pure white with pure black Leghorn fowls are +speckled black and white, but later in the adult form white becomes +dominant. Likewise conditions of delayed dominance are known in man in +eye-color and notably in color of hair. Some few cases have been recorded +where a character is dominant at one time, recessive at another. +According to Davenport extra toe in fowls may behave in this way. + +=Mendel's Own Work.--=Mendel[2] himself worked out his principles on seven +pairs of characters which he found in common culinary peas. Placing the +dominant characters first, these may be enumerated as follows: (1) Tall by +dwarf; (2) green pod (unripe) by yellow; (3) pod inflated by pod +constricted between the individual peas; (4) flowers arranged along the +axis of the plant by flowers bunched together at the top; (5) seed skin +colored by seed skin white; (6) cotyledons yellow by cotyledons green; (7) +seed rounded by seed wrinkled. + +He found that each pair of characters followed the same law as any other +pair when more than one pair of the characters occurred in the same +plants, but that each pair behaved independently of the other. The meaning +of this is that we may get various combinations of characters not +associated in the original pure stocks, the number of such combinations +depending on the number of pairs of allelomorphs there are. + + +DIHYBRIDS + +=Getting New Combinations of Characters.--=Since this principle is well +illustrated in peas, let us take two pairs of their characters, viz., +greenness and yellowness (of the cotyledons) and roundness and angularity +to see exactly what happens when two pairs of allelomorphs are involved. +When a specific kind of yellow pea is crossed with a particular kind of +green pea the offspring are always yellow (Fig. 18, opposite p. 84). When +these hybrids (generation F_{1}) are self-fertilized there is the usual +Mendelian segregation; one-fourth the resulting offspring will be green, +one-fourth pure yellow, and one-half, although yellow in appearance, will +be of the mixed type. The exact numbers found by Mendel were 6,022 yellow +seeds to 2,001 green seeds. Now of the original peas (generation P) the +yellow ones are round and the green ones angular (really wrinkled). +Choosing this roundness and angularity respectively as a pair of +characters they are found to follow the same law that the colors follow +(Mendel obtained in the F_{2} generation 5,474 round and 1,850 wrinkled +seed), but independently of the latter. For while in the progeny of the +hybrids (Gen. F_{1}), twenty-five per cent. will be round and of pure type +as regards roundness, twenty-five per cent. angular, and fifty per cent. +round but containing hidden factors of angularity (i. e., roundness is +dominant), the roundness and the yellowness, or the angularity and the +greenness will not always go together as they did in the original +grandparental strains, but there will be in addition some new types of +round green peas and some of angular yellow ones. That is, the factors of +color and of shape have been inherited independently of one another, so +that instead of the two original kinds of peas, four have been produced, +viz., (1) round-yellow (one of the original types); (2) round-green (new +type); (3) angular-yellow (new type); and (4) angular-green (one of the +original types). Furthermore, these will be found to stand in the ratio of +9:3:3:1 respectively. + +=Segregations of the Determiners.--=How these combinations come about in +this definite proportion is easily understood if the matter is expressed +in terms of determiners and the possible matings tabulated (Fig. 18). If +we represent the yellow determiner by Y and the green determiner by y, and +likewise the determiners of roundness and angularity by R and r +respectively, then the formulæ for the determiners of these two pairs of +characters in the body cells (that is, in the unreduced condition) of the +pure forms and of the F_{1} generation hybrids respectively are as +follows: + + In pure round yellow peas RR YY + In pure angular green peas rr yy + In the hybrid Rr Yy + +But now in the segregation of these determiners in the germ-cells of the +hybrids (generation F_{1}) the pair of determiners Rr and the pair Yy +operate entirely independently of one another. Their only compulsion is +that each pair be separated into the single determiners, R and r in the +one case and Y and y in the other. So in the separating division which +brings about this divorcement R separates from r irrespective of whether +it is accompanying Y or y into the resulting daughter cell. Thus in some +cases R and Y would pass into one germ-cell, in others R and y, in others +r and Y, and in still others r and y, depending entirely upon the +chance relations of the respective pairs to the plane of division. That +is, the segregation is equally likely to be RY/ry giving gametes RY and +ry, or Ry/rY giving gametes Ry and rY. + + +[Illustration: + + \[Female] + [Male]\ RY Ry rY ry + +-------+--------+--------+--------+ + RY | RRYY | RRYy | RRYY | RrYy | + +-------+--------+--------+--------+ + Ry | RRYy | RRyy | RrYy | Rryy | + +-------+--------+--------+--------+ + rY | RrYY | RrYy | rrYY | rrYy | + +-------+--------+--------+--------+ + ry | RrYy | Rryy | rrYy | rryy | + +-------+--------+--------+--------+ + + (1) 1 RRYY (4) 2 RrYY (7) 1 rrYY + (2) 2 RRYy (5) 4 RrYy (8) 2 rrYy + (3) 1 RRyy (6) 2 Rryy (9) 1 rrYy + 9:3:3:1 + +FIG. 18 + +Diagram showing the possible combinations arising in the second filial +generation (F_{2}) following a cross between yellow, round (YYRR) and +green, angular or wrinkled (yyrr) peas. Y, presence of factor for yellow; +y, absence of such a factor; R, presence of factor for smoothness or +roundness; r, absence of such a factor; [male] male; [female] female.] + + +=Four Kinds of Gametes in Each Sex Means Sixteen Possible +Combinations.--=There are, therefore, with reference to the two pairs of +characters under consideration, four kinds of gametes (or mature +germ-cells) produced in equal numbers in each hybrid, viz., RY, Ry, rY, +and ry. That is, in the first type roundness and yellowness are +associated, in the second roundness and greenness, in the third angularity +(lack of roundness) and yellowness, and in the fourth angularity and +greenness. + +But since both males and females have these four kinds of gametes, when +they are mated there will be sixteen possible combinations. These may be +tabulated as in Fig. 18, opposite p. 84. + +=The 9:3:3:1 Ratio.--=While there are sixteen possible and equally +probable combinations, these will give only nine distinct kinds because +some of the matings are alike. The numbers of the various kinds of matings +are as follows: + + (1) 1 RRYY (4) 2 RrYY (7) 1 rrYY + (2) 2 RRYy (5) 4 RrYy (8) 2 rrYy + (3) 1 RRyy (6) 2 Rryy (9) 1 rrYy + +Since roundness (R) and yellowness (Y) are dominant to angularity (r) and +greenness (y) in all combinations containing R or Y, the alternative +determiners r or y would be obscured, with the result that individuals +having certain of the combinations would look alike to our eye. For +example, the individuals represented by numbers 1, 2, 4 and 5, since they +contain dominant R and Y, would all appear round and yellow, although in +reality No. 1 would be the only one of pure type (both elements +homozygous) and hence the only one that would breed true in subsequent +generations. The two individuals represented in No. 2 would breed true as +regards shape (RR) but not color (Yy). Just the reverse is true of No. 4 +since shape is heterozygous (Rr) and color homozygous (YY). The four +individuals represented in No. 5 are heterozygous with regard to both +elements. Thus nine individuals (1 plus 2 plus 2 plus 4 = 9) represented +in Nos. 1, 2, 4 and 5 would be round and yellow, three individuals (Nos. 3 +and 6) would be round and green, three (Nos. 7 and 8) would be angular and +yellow, and only one (No. 9) would be angular and green. That is to say, +the four classes discernible to the eye in generation F_{2} would be +present in the ratio of 9:3:3:1. + +=Phenotype and Genotype.--=Forms such as those represented in Nos. 1, 2, 4 +and 5 which to the eye appear to be alike, regardless of their germinal +constitution, are said to be of the same _phenotype_. Those of the same +hereditary constitution, as the two individuals represented in No. 8, or +the four individuals in No. 5, are said to be of the same _genotype_, that +is, they are of identical gametic constitution. + +As we have seen, it is from the genotypical not the phenotypical +constitution that an offspring is derived and what a given form will bring +forth depends then on its genotype. + +=Crosses With More Than Two Pairs of Characters.--=In crosses in which +more than two pairs of contrasted characters are involved the underlying +principles are in no way different, only with each pair of additional +characters there is, of course, a greater number of possible combinations. +Thus with three pairs of characters there will be eight different classes +of gametes in each sex and consequently sixty-four possible combinations +in mating, giving eight different phenotypes in the proportion of +27:9:9:9:3:3:3:1. The largest class manifests the three dominant +characters; the smallest class, the three recessives; the three classes in +the proportion of 9 each exhibit two dominant and one recessive +characters; and those in the proportion of 3 each display two recessive +and one dominant characters. + + +THE QUESTION OF BLENDED INHERITANCE + +We come now to certain types of inheritance in which there seems to be a +true fusion or blend of the contributions from the two parents, the +intermediate condition apparently persisting in subsequent generations +without segregation. Numerous cases of blended inheritance have been cited +in earlier literature of heredity, but as our knowledge of genetics has +progressed many experimental breeders have come to believe that the +blends in such cases are apparent rather than real and that the phenomena +can be best explained on a non-blending unit-character basis, just as we +would explain ordinary Mendelian phenomena. + +=Nilsson-Ehle's Discoveries.--=To get their point of view we may review +certain experiments on wheat made by Nilsson-Ehle, together with their +Mendelian interpretation. Nilsson-Ehle found that a certain brown-chaffed +wheat when crossed with a white-chaffed strain yielded a brown-chaffed +hybrid, apparently in accordance with the simple principle of Mendelian +dominance. But these heterozygous brown-chaffed individuals did not in +turn give the expected ratio of 3:1 in the F_{2} generation but a ratio of +15 brown to 1 white, and furthermore the browns were not all of the same +degree of brownness. To be exact, from fifteen different crosses of the +strains he obtained 1,410 brown-chaffed and 94 white-chaffed plants. + +This apparent anomaly in segregation was easily explained, however, when +it was finally figured out that there were really two independent +determiners for brown color, either of which alone could produce a brown +individual, but when combined produced individuals of correspondingly +deeper shades of brown. In such a case then Nilsson-Ehle discovered that +he was dealing merely with a Mendelian dihybrid where two different +determiners B and B´ and their respective absences b and b´ are involved. +The original brown wheat had both B and B´ and the original white b and +b´. The formula for the F_{1} heterozygote was therefore BbB´b´. The four +possible types of gametes for male and female are BB´, Bb´, bB´, bb´, and +the tabulation would be as follows: + + +----------------------------------- + | BB´ | Bb´ | bB´ | bb´ + -----+--------+--------+--------+-------- + BB´ | BBB´B´ | BBB´b´ | BbB´B´ | BbB´b´ + -----+--------+--------+--------+-------- + Bb´ | BBB´b´ | Bb´Bb´ | BbB´b´ | Bbb´b´ + -----+--------+--------+--------+-------- + bB´ | BbB´B´ | BbB´b´ | bbB´B´ | bbB´b´ + -----+--------+--------+--------+-------- + bb´ | BbB´b´ | Bbb´b´ | bbB´b´ | bbb´b´ + ----------------------------------------- + +It will be observed that there are more brown determiners in some +combinations than others. For instance one of the sixteen contains four +such determiners, viz., B, B´, B, B´, four contain three determiners, six +contain two, four contain only one, and one contains none. Thus all but +one of the sixteen contain at least one determiner and will therefore be +brown in color but the depth of color will depend on the number of brown +determiners in a given individual. This is more graphically represented in +Fig. 19, p. 90. The largest number of similar individuals, six in all, +contain two determiners each and represent an intermediate "blend" between +the original brown-chaffed and white-chaffed strains. The deeper and the +lighter browns due to more or fewer determinants in an individual would if +one did not know the units in this case look like the fluctuations around +this average which we might expect in a blend. + + +[Illustration: FIG. 19 + +Diagram illustrating the proportionate distribution of determiners where +either of two different determiners produces the same character, the +degree of expression of the character depending on the number of the +determiners present. The numerals indicate the number of brown determiners +present in an individual.] + + +Nilsson-Ehle found another significant case in wheat where one particular +red-grained strain of Swedish wheat when crossed with white-grained +strains produced red-grained offspring, but when these were interbred the +F_{2} generation gave approximately sixty-three red to one white-grained +individual. Here it was found that in the original red wheat there are +three separate determiners which act independently of one another in +heredity, any one of which would make red color; and that they together +with their absences simply follow the Mendelian laws for a trihybrid. + +=Such Cases Easily Mistaken for True Blends.--=If we should tabulate the +possible combinations as we did the dihybrid we should see that we would +get individuals having varying numbers of red determiners. Only one of the +sixty-four possible combinations would be without a factor for red. Of the +sixty-four, one would have six determiners for red, six would have five, +fifteen would have four, twenty would have three, fifteen would have two, +six would have one, and one would have none. Since here every additional +red factor means deeper redness in the individual there would be varying +degrees of redness in the F_{2} generation with those having three +determiners, the largest group, standing apparently intermediate. Not +knowing the factors involved we might easily mistake such a case for a +true blend with fluctuations about an average intermediate form. +Nilsson-Ehle finally proved his interpretation by rearing an F_{3} +generation from isolated and self-fertilized plants of this F_{2} +generation. + +This same principle of cumulative determiners has also been established in +America by East with field corn. + +As the number of duplicate determiners increases it can be readily seen +that the number of apparent blends of different degrees of intermediacy +between the two extremes would rapidly increase. + +=Skin-Color in Man.--=In man, the skin-color of the hybrids between +negroes and whites is often cited as a case of blended inheritance in +contradistinction to Mendelian inheritance. The skin-color of the mulatto +of the F_{1} generation is intermediate between that of the white and +black parent. This same degree of intermediacy is commonly supposed to +persist in subsequent generations, but as a matter of fact, careful +investigation has shown that while mulattoes rarely produce pure white or +pure black children, there is considerably greater range in the shades of +color in the F_{2} generation and subsequent generations than in the F_{1} +generation. This is exactly what one would expect of a Mendelian character +in which several cooperating factors were involved. Indeed, Davenport who +has made extensive studies[3] on the inheritance of skin-color in man has +come to the conclusion that the case is really one of Mendelian +inheritance in which several factors for skin-color are concerned. Even +the skin of a white man is pigmented in some degree under normal +conditions. Davenport has shown in the skin of both whites and blacks that +there is a mixture of black, yellow and red pigments. He concludes that +"there are two double factors (AABB) for black pigmentation in the +full-blooded negro of the west coast of Africa and these are separably +inheritable." Since these factors are lacking in white persons the +intermediate color of an F_{1} mulatto would therefore be heterozygous for +pigmentation, and subsequent generations, following the laws for +segregation where a number of factors are concerned, would show different +degrees of color because of the varying combinations of factors. + +=Some Investigators Would Question the Existence of Real Blends.--=Still +other reputed blends such as ear length in rabbits and the like have been +shown to be analyzable into Mendelian behavior if one will but postulate +numerous or multiple factors. Just how far we are justified in so +accounting for blends has not yet been established. Some of our most +careful experimentalists in heredity still believe that real blends exist, +particularly where the character is quantitatively expressed--that is, as +more or less of a given size or amount--while others would maintain that +all alleged blends will probably be found to be resolvable into factors +which follow Mendelian rule. It must be left for future investigations to +demonstrate which school is correct. + + +THE PLACE OF THE MENDELIAN FACTORS IN THE GERM-CELLS + +=Parallel Between the Behavior of Mendelian Factors and Chromosomes.--=The +question arises as to whether there is any evidence from the study of +germ-cells themselves to bear out the Mendelian conception of separation +of contrasted characters in the gametes of the F_{1} generation. In the +discussion of the maturation of germ-cells (Chap. II) it has already been +seen that the chromosomes of the germ-cells are in all probability +arranged in homologous pairs, one member being of maternal and the other +of paternal origin, and that furthermore they are closely associated with +the phenomena of heredity. And since in maturation there is an actual +segregation of the chromosomes into two sets, half going to one cell and +half to its mate, a physical basis adequate to the necessities of the case +is really at hand. It will be recalled that the individuals of a pair +separate in such a way at the reduction division that the paternal member +goes to one cell and the maternal member to the other, although each pair +seemingly acts independently of the others with the result that any mature +germ-cell may contain chromosomes from each of the original parents but +never the two chromosomes which earlier made up a pair. The close parallel +between the behavior of chromosomes and the behavior of Mendelian factors, +although the two sets of phenomena were discovered wholly independently of +each other, is obvious. If we suppose that each chromosome bears the +determiner of a Mendelian character and that chromosomes bearing +allelomorphic characters make up the various pairs which are seen in the +early germ-cells of an individual before reduction occurs, then the +segregation of the individuals of an allelomorphic pair into different +gametes must result in consequence of the passing of the corresponding +chromosomes into separate gametes. Fig. 20, p. 95, from Professor Wilson +represents equally well the segregations of pairs of chromosomes or pairs +of Mendelian characters. + + +[Illustration: FIG. 20 + +Diagram showing union of factors from the two separate parents in +fertilization and their segregation in the formation of germ-cells (after +Wilson). With four pairs of factors (_Aa_, _Bb_, _Cc_, _Dd_), sixteen +types of gametes are possible, as shown in the series of small circles at +the right. The same diagram equally well represents the pairings and +segregations of chromosomes.] + + +=A Single Chromosome not Restricted to Carrying a Single Determiner.--=It +has been objected that there may be more pairs of independently heritable +allelomorphic characters than there are pairs of chromosomes. It is true +that there are more pairs of characters than pairs of chromosomes but +there is no reason for supposing that a given chromosome is restricted to +carrying a single unit-determiner. On the contrary it probably carries +several or many. Some workers have pointed out that certain units might be +interchanged during the pairing of chromosomes before the reduction +division, others that inasmuch as the chromosomes become diffuse and +granulated during the intervals between divisions it is not improbable +that the individual units may become separated from their original system +during such times and that it is a matter of chance into which of the +homologous chromosomes, A or a, they enter with the re-establishment of +the chromosomes. On the other hand, cases are known where two or more +separate characters are permanently associated in inheritance, that is, if +they enter a crossed form together they come out together in the +grandchildren as if they were carried in the same unit-body in the +germ-cell. The only observable unit-bodies that fulfil the necessities of +such cases are the chromosomes. This tendency of characters to exist in +groups which are inherited independently of one another is coming more and +more into evidence as we penetrate farther into the intricacies of +inheritance, and it is exactly what we would expect on the supposition +that each chromosome carries the determiners of a number of characters +instead of a single one. + + + + +CHAPTER IV + +MENDELISM IN MAN + + +=The Mendelian Principles Probably Applicable to Many Characters of +Man.--=We are really just beginning to make the proper observations and +collect the necessary data with reference to the application of Mendelian +principles to the traits of man. Yet brief as has been our study we have +disclosed much significant evidence which makes it seem highly probable +that many of his characters, good and bad, of mind and body are as +subservient to these laws as are the traits and features of lower forms. +Davenport and Plate record over sixty human characters or defects which +are seemingly inherited in Mendelian fashion. Although about fifty of +these are pathological or abnormal conditions, this does not mean that +such conditions are more prone to follow Mendelian inheritance but merely +that being relatively conspicuous or isolated they are easier to follow +and tabulate. + +=Difficult to get Correct Data.--=While it must be said that in many cases +no simple form of Mendelian tabulation has been unequivocally established, +yet the general behavior of the various inheritable traits in question is +so obviously related to the conventional Mendelian course that there seems +little reason for doubting that they are at bottom the same. Failure to +obtain exact proportions may be attributable in part to the probability +that what we loosely regard as a character should in reality be analyzed +into more elemental components, and above all to the fact that from the +very nature of the conditions under which human records must be obtained, +there is considerable chance of inaccuracy or error in such accounts. How +many human traits follow Mendelian rules remains largely for future +investigators to establish. + +We are handicapped at the outset in man by the many difficulties of +getting correct data from the genealogies on which we must depend, or in +fact of getting any genealogy at all, for in this country at least, most +families keep imperfect records of births and deaths and many of the +institutions for the various kinds of defectives have little in their +records that will help us in following out hereditary conditions. Then in +matters of disease we meet with the fact that many former diagnoses were +erroneous. In yet other cases, and this is particularly true among mental +and moral defectives, we are often not sure of the paternity of a given +child. Furthermore, one is likely to be misled by the proportions which +may occur in the very limited number of children of any given couple. + +Still other difficulties exist. Among these is the fact, for example, that +in many cases of defect or susceptibility to disease, a given individual +in the stock may have the trait in an expressible and transmissible form, +yet it never comes to expression because that individual has been +fortunate enough to escape the environmental stimulus which would call it +forth. Thus one highly susceptible to tuberculosis might escape infection, +or persons hovering on the verge of insanity might never receive the +precipitating stimulus which would topple them into actual insanity; yet +each would be wrongfully recorded in a genealogy looking to such traits as +perfectly normal. Or again if it be a question of intellectual brilliancy +as shown by accomplishment in the realm of scholarship, or of worldly +affairs, the ones who although possessing them have had no chance to +display unusual talents would be tabulated as average whereas in fact they +should be recorded as of high rank. That this is particularly likely to +happen in the case of women is evident. + +=A Generalized Presence-Absence Formula for Man.--=In man as in lower +forms some characters or traits are due presumably to the presence of +determiners or to their absence. Likewise, dominance and recessiveness are +as much in evidence, for in tracing back pedigrees of various traits we +find the same forms of tabulation that obtain for these conditions in +plants and lower animals hold good. For typical cases in man let us use a +generalized presence-absence formula and the arbitrary symbol A for the +presence of the determiner of the character (double in the individual, +single in the germ) and a for its absence. Thus AA represents a condition +in which similar determiners have been derived from both parents and the +individual is _duplex_ as regards the character in question; each mature +germ-cell will have the determiner. Aa represents a condition in which the +individual has received the determiner from only one parent and is +therefore _simplex_ with regard to the character; half of the gametes of +such an individual will have the determiner and half will lack it. Lastly, +aa represents total absence of the determiner. Such an individual is +_nulliplex_. He or she will not have the determiner represented in any of +the gametes, and can not, of course, transmit a trait represented by the +determiner. + +It is evident that six kinds of gametic matings are possible among +individuals representing these various formulæ. These matings are as +follows: + + Possible + couplings + Matings of gametes Product + + 1. Nulliplex x Nulliplex (aa x aa) == a------a == all nulliplex + \/ + /\ + a------a + + 2. Nulliplex x Simplex (aa x Aa) == a------A == 50 per cent. + \/ with character + /\ nulliplex and + a------a 50 per cent. + with it + simplex. + + 3. Nulliplex x Duplex (aa x AA) == a------A == all with characters + \/ simplex + /\ + a------A + + 4. Simplex x Simplex (Aa x Aa) == A------A == 25 per cent. + \/ with characters + /\ duplex, 50 per + a------a cent. with it + simplex and 25 + per cent. with + it nulliplex. + + 5. Simplex x Duplex (Aa x AA) == A-------A == 50 per cent. + \/ with character + /\ duplex and 50 + a-------A per cent. with + it simplex. + + 6. Duplex x Duplex (AA x AA) == A-------A == all duplex. + \/ + /\ + A-------A + +=Indications of Incomplete Dominance.--=While in cases of strict Mendelian +dominance it is not possible to distinguish directly the simplex from the +duplex condition, as a matter of fact the individual of simplex +constitution sometimes has the character represented in the single +determiner less perfectly developed than in the corresponding character of +duplex origin. In studying defects in man due to the absence of a +determiner, where theoretically presence of the determiner (normality) is +dominant over its absence in individuals of simplex constitution, one +finds it recorded with increasing frequency that such individuals are more +or less "intermediate" or are "tainted" with the defect; thus showing that +the defect though obscured is not wholly in abeyance. Thus individuals +carrying epilepsy or feeble-mindedness which are regarded as recessive +traits, while not showing specific feeble-mindedness or epilepsy, may +nevertheless apparently show a neuropathic taint in the form of migraine, +alcoholism or other lapse from normality. The condition is seemingly more +akin in some cases to that found in the offspring of certain red flowers +crossbred with white flowers, which though red do not show the same +intensity of color as the original red parent. Just as here the single +determiner or single "dose" of redness is insufficient to produce the +intensity of color that appears when the offspring receive two determiners +for red, one from each parent, so in man a single determiner for normality +of a specific character is inadequate in some cases to make the individual +wholly normal. Or possibly some cases are more of the type of those in +which the character in question, for instance the red color of some wheats +and corn, may be produced by any one of two or three determiners, the +intensity of the characters (red color, e. g.) depending on whether one, +two or three determiners are present. + +=Why After the First Generation Only Half the Children May Show the +Dominant Character.--=If the trait is a simple dominant one it is clear +that it will appear in each generation and always spring from an affected +individual. By referring back to our tabulation of possible matings on +page 100 where the dominant character is represented by the letter A, this +can be seen at a glance. If the trait is present in the duplex condition +in one parent and absent from the other, then formula 3 applies; all +children will show the trait, but in the simplex form (Aa). If the trait +is present in the simplex form in one parent and absent in the other, +formula 2 applies. Fifty per cent. of the children will have the character +in the simplex form (Aa) which means also an even chance of transmitting +it to their offspring; fifty per cent. will not inherit it and will be +incapable, furthermore, of transmitting it, since they have become +nulliplex (aa). In human genealogies if an individual having an unusual +trait which is inherited as a dominant marries a normal person and half of +the offspring show the trait (and this is common), this means that the +parent manifesting the trait had it represented only in the simplex +condition, otherwise all of the children would have shown it. Even though +the original ancestor who first developed the condition or structure may +have had it in a duplex form, it would after the first mating, if this +were with an individual lacking the trait, be represented only in the +simplex form (see formula 5) and could never become duplex again unless +two individuals both having the character married, and then only in +twenty-five per cent. of the offspring (see formula 3). If the trait is a +defect all the children showing it, even though marrying normal +(nulliplex) individuals, will pass it on again to half their children, but +those who do not show it may ordinarily marry with impunity since its +non-expression in their make-up means, as far as we know at present, that +their germ-plasm has been purged of the defect and that they are therefore +nulliplex with reference to it. + +=Eye-Color in Man.--=Of normal characters in man which follow the +Mendelian formula perhaps eye-color is the best established. Brown or +black eye-color is due to a _melanin_ pigment absent from the blue or gray +eye. That is, a brown eye is practically a blue eye plus an additional +layer of pigment on the outer surface of the iris. The different shades of +brown and the black are due to the relative abundance of this pigment. +Gray color and the shades of blue seem to be a modification of an original +dark blue, due to structural differences in the fibrous tissues of the +iris. + +In inheritance brown or black is dominant to blue or gray, or in other +words the _presence_ and _absence_ of a pigment P constitutes a pair of +allelomorphs. Hence two brown-eyed parents, if P is duplex in both (or +duplex in one and simplex in the other) can have only brown-eyed children. +Thus, + + 1. PP × PP = PP, or all duplex brown. + + 2. PP × Pp = PP and Pp, half duplex brown and half simplex brown. + +If each parent has brown eyes but in simplex condition, then one-fourth +of children will have blue or gray eyes; for example, + + Mating Gametic Product + couplings + + Pp × Pp = P--P = PP, Pp, pP, and pp, or one-fourth + \/ duplex brown, one-half simplex + /\ brown, and one-fourth blue or + p--p gray. + +If both parents have blue or gray eyes they can not have children with +black or brown eyes, since the recessive condition in each parent means +total absence of brown pigment in both. + +If one pair is duplex brown and the other blue, then all children will +have brown eyes but of simplex type. + +If one parent has simplex brown eyes (type Pp) and one blue (pp) then +one-half of the children will have brown eyes of simplex type and one-half +will have blue eyes. + +Occasional objections have been raised against the Mendelian +interpretation of inheritance in eye-color, but the cases cited in +evidence against the theory usually narrow down to those in which the +color is so diluted as to render classification uncertain. For example, +hazel eyes are sometimes called gray; they belong however to the melanic +pigmented type although the brown pigment may be much diluted and occur +mainly around the pupil. So-called green eyes are due to yellow pigment on +a blue background. In the rare cases where in the same individual one eye +is brown and the other blue, the individual should probably be rated as +brown-eyed on the supposition that in the one eye the development of brown +pigment has in some way been suppressed. + +=Hair-Color.--=The inheritance of hair-color has also been the subject of +considerable study and while the conditions are not so simple as in the +case of eye-color, there is little doubt that it belongs in the Mendelian +category. In human hair, color has as its foundation apparently two +pigments, black and red. Absence of one or both or various combinations or +dilutions of these seemingly account for the prevailing colors in human +hair. In general dark hair is dominant to light, although because of the +delay sometimes in the darkening of the hair in children this fact is +often obscured. Black is dominant to red. People with glossy black hair, +according to Davenport, are probably simplex for black, the glossiness +being due usually to recessive red. The expectation would be for some of +the children of such a pair to have red hair. + +In man occasionally a congenital white lock contrasting strikingly with +the remaining normally pigmented hair occurs. It behaves as a simple +dominant in heredity. + +=Hair-Shape.--=Again, straight and curly hair seem to be distinct +inheritable characters. Curly is incompletely dominant to straight, the +simplex condition yielding wavy hair. + +Not to enter into details of the matings, statistics gathered by Mr. and +Mrs. Davenport show that, two flaxen-haired parents have flaxen-haired +children; two golden-haired parents have only golden-haired children; two +parents with light brown hair have children with hair of that color or +lighter, but never darker; two parents each with dark brown or black hair +may have children with all the varieties of hair-color. Summing together +a series of recessives Davenport points out that two blue-eyed, flaxen or +golden and straight-haired parents will have only children like +themselves. + + +[Illustration: FIG. 21 + +Diagram showing descent of brachydactyly through five generations; black +symbols indicate affected individuals; [male], male; [female], female +(after Farabee).] + + +=Irregularities.--=If a dominant trait or defect depends on more than a +single factor, as is sometimes the case, or if it is modified by sex or +other conditions, as is true of certain characters, some of which, such as +color-blindness, have already been examined, then we shall find some +apparently non-affected individuals having affected offspring. Certain +diseases, for example, are generally transmitted by affected members of +the family to their children in the expected Mendelian ratio for a +dominant, yet an occasional skip of a generation may appear in which an +apparently perfectly normal individual transmits to his children what, +except for the omission in his own case, appears to be an ordinary +dominant character. This occasional lapse in the appearance of a +character when theoretically it should appear is doubtless due in some +instances to the fact that what is really inherited is a _tendency_, and +although this is present in the apparently normal individual, for some +reason the condition itself has not appeared. This might especially be +true in the case of a disease which does not manifest itself until late in +life. In other cases there are undoubtedly complicating accessory +conditions which modify the behavior of the trait somewhat. + + +OTHER CASES OF DOMINANCE IN MAN + +Among other normal characters in man, as far as available evidence goes, +dark skin is dominant to light skin; normally pigmented condition to +albino; and nervous temperament to phlegmatic. + +=Digital Malformations.--=An interesting and easily followed defect is a +condition known as _brachydactylism_, in which the digits are shortened +because of the absence or rudimentary condition of one segment. The +fingers, therefore, appear to be only two-jointed like the thumb. Several +families showing this defect have been charted and it appears to behave as +a typical dominant. In looking over such a chart (Fig. 21, p. 106) one is +struck by the fact that only half of the children from most of the matings +show the defect, but when we recall that the affected parent, after the +first generation, probably carried the condition in only the simplex form +and married a normal individual, such a result is just what would be +expected (see formula 2). + +_Polydactylism_ (Figs. 22, 23, pp. 109, 110) is a condition in which there +are extra digits on hands or feet. The character, with apparently slight +exceptions in a few records, behaves as a typical dominant. Among other +digital defects which are inherited as a dominant is a condition known as +_syndactylism_ (Fig. 24, p. 111), in which two or more digits are fused +side by side. For an example of syndactyly which seems to be in the class +of sex-linked characters, see Fig. 15, p. 65. + +=Eye Defects.--=_Congenital cataract_ is another not uncommon defect in +man which is transmitted as a dominant (Fig. 25, p. 112) with occasional +irregularities. It is a condition of opacity of the lens of the eye which +produces partial or total blindness. In a paper on _Hereditary Blindness +and Its Prevention_, Clarence Loeb (1909) mentions 304 families of which +pedigrees have been published. Of the 1,012 children in these families +589, or 58 per cent., were affected. It is obvious that this is near the +expected percentage in the case of a dominant trait where matings of +affected with normal individuals prevailed. An unfortunate circumstance +about this malady from the eugenic standpoint is the fact that it is +frequently of the presenile form which comes on late in life so that it is +usually impossible to predict whether an individual of marriageable age is +immune or will later become affected. + + +[Illustration: FIG. 22 + +Radiograph (Courtesy of Dr. W. B. Helm) showing polydactyly in a child's +hand. For genealogy of this see Fig. 23, p. 110.] + + +[Illustration: FIG. 23 + +Chart showing a history of polydactylism through five generations in the +B---- family. The individual whose hand is pictured in Fig. 22, p. 109, is +of the fifth generation. Squares represent males, circles females.] + + +Another defect of the eye following the course of a dominant in heredity +is a pigmentary degeneration of the retina known as _retinitis +pigmentosa_. Atrophy of the optic nerve is also involved and the final +result is blindness. Still another example frequently cited is that of +hereditary night blindness (_hemeralopia_), a disease in which the +affected person can not see by any but the brightest light. In most +affected families the final outcome is usually total blindness. One of the +most remarkable pedigrees of defects in man ever collected is one of this +disease published by Nettleship. He succeeded in tracing the defect +through nine generations, back to the seventeenth century. The genealogy +includes 2,116 persons. The character behaves as a single dominant in +males, but frequently, though not always, females may be carriers of the +defect in transmissible form though not exhibiting it themselves. That is, +males in which the condition is simplex (Aa) develop the defect but +females of similar simplex constitution (Aa) frequently do not. It +follows, therefore, that normal males of such strains will have normal +offspring but normal females may have affected children. + + +[Illustration: FIG. 24 + +Radiograph (Courtesy of Dr. W. B. Helm) showing a partial syndactyly in +each hand of an individual. Some degree of webbing between the more distal +portions of the affected parts is usual.] + + +[Illustration: FIG. 25 + +Pedigree of a family with presenile cataract (black symbols); numbers in +circles indicate unaffected individuals (after Davenport).] + + +=Other Defects Inherited as Dominants.--=Not to go into details other +defects which behave as dominants or modified dominants in human +inheritance may be mentioned. The following list is not complete and it +must be understood that in some cases the statistics are insufficient to +justify us in making anything but a tentative decision. We may thus +enumerate as dominant over normality: _Achondroplasy_ (abnormally short +limbs with normal head and body); _Keratosis_ (thickening of epidermis); +_Epidermolysis_ (excessive formation of blisters); _Hypotrichosis_ +(hairless, toothless condition); _Diabetes insipidus_; _Diabetes +mellitus_; ordinary (not Gower's) _muscular atrophy_; _Glaucoma_ (internal +swelling and pressure of eye-ball); displaced lens; _Coloboma_ (open +suture in iris); spottedness of hair-coat; and corneal opacity. + +As a final illustration of a serious malady in man which acts as a +dominant in inheritance, let us take _Huntington's chorea_. Ordinary +_chorea_, or St. Vitus' dance, a disorder characterized by involuntary +muscular movements, is commonly though not always confined to children and +usually ends in recovery, but _Huntington's chorea_ appears typically in +middle life and is a much more dangerous malady. Fig. 26, p. 114, +represents the family history of one of five cases which have been studied +by Doctor Lorenz in the Mendota Hospital for the Insane. All charts which +have been platted of this malady show it to be inherited as a dominant. +This means that half of the children of an individual who carried the +malady in the simplex condition, and all the children of one who carries +it in the duplex condition, are probably marked for this terrible end. And +the true horror of it can only be appreciated by one who has seen the last +stages of the malady. The victim once in its grasp gradually becomes +wrecked in mind and body; the muscular twitchings and disorders of +movement continually increase and dementia progresses until at last death +ensues. Fig. 27, p. 115, is another chart showing inheritance of +_Huntington's chorea_. In still a third case at the Mendota Hospital, the +gravity of the situation can be appreciated when one realizes that the +patient is the father of ten children, ranging in age from one to +seventeen and one-half years. The calamitous fact that this disease does +not manifest itself usually until middle life makes it likely that these +children will all reach maturity, marry and in turn probably produce +offspring before the doomed members of the family realize their fate. + + +[Illustration: FIG. 26 + +Chart showing descent of _Huntington's chorea_ in the P---- family +(courtesy of Dr. W. F. Lorenz). Squares represent male, circles female; +shaded figures are choreic members of the family; partially shaded +figures, slightly affected or very "nervous" members. The members of the +last generation are for the most part still too young to show their +condition. The cross indicates the individual in the asylum from whom the +record was traced back.] + + +CASES OF RECESSIVENESS IN MAN + +=Recessive Conditions More Difficult to Deal With Because They Are +Frequently Masked.--=Coming now to the question of recessive conditions in +man, we find that defects are more likely to be of recessive than of +dominant type. Apparently normality usually means the presence of normal +determiners and abnormality, the absence of some essential determiner. In +the latter case, a unit-factor has seemingly been lost out in some way in +the germ-plasm, and the product of such germ-plasm is therefore +incomplete. As long as the loss is counterbalanced by the presence of a +single determiner from the other line of ancestry, that is, as long as the +simplex (Aa) condition prevails, the loss may not be in evidence, except +in cases of incomplete dominance (taints, etc.), but any mating which +permits of the production of the nulliplex condition will bring the defect +to expression again. + + +[Illustration: FIG. 27 + +Chart showing inheritance of _Huntington's chorea_ in the R---- family +(courtesy of Dr. W. F. Lorenz); 1, 2 have been patients at Mendota +Hospital for the Insane; 3, died of "paralysis"; the fourth or last +generation indicated by the cross, ranging in age from 6 to 14, are too +young yet to show their condition as regards this malady.] + + +The obscure nature of recessives makes such conditions more difficult to +deal with than dominant defects. For as regards the latter we have seen +that marriage of unaffected members of the family as far as that +particular trait is concerned, is perfectly safe, even to a cousin, for +once the germ-plasm is purged of such a positive factor, it, in so far as +we know, remains pure. But in the case of a recessive character due to the +absence of some necessary determiner a normal offspring of simplex +constitution (Aa) will probably transmit to half of his children the +capacity for handing on the defect, or if mated to another normal +individual of simplex constitution (Aa) is likely to have the actual +defect revealed again in one-fourth of his children and latent in +two-thirds of the remainder. + +=Albinism a Recessive.--=As an easily understood illustration of this type +of case we may take human albinism, a condition which is due to the +absence of a pigment-developing determiner. According to Davenport the +albinic condition is recessive to normal condition. If albino (aa) is +mated with albino (aa) nothing but albino children may be expected. An +albino (aa) mated with a normal individual will have normal offspring +(Aa), but they will have the capacity for transmitting albinism to their +descendants. Thus the normal offspring (Aa) of an albino (aa) and a normal +parent (AA) if mated to another normal individual (Aa) who has also had an +albino parent will probably transmit actual albinism to one-fourth of his +children and the same capacity that he himself has of producing albinos, +to one-half of his children, although the latter will appear to the eye to +be normal. + +=Other Recessive Conditions in Man.--=If for albinism we substitute +certain forms of insanity, hereditary feeble-mindedness (Fig. 28, p. 118), +or hereditary epilepsy, all of which apparently follow the same law, we +can readily understand how unfit such matings are where both strains are +affected. Marriage with similarly defective stock will result in the +affection appearing in one-fourth of the progeny, and one-half of them, +though apparently normal themselves, will have the capacity for +transmitting the imperfection. It is in the existence of such hidden +factors that the chief danger in the marriage of cousins, or in fact any +consanguineous marriage lies. + +A few of the various defects which seem to be inherited as recessives when +mated with normality are: susceptibility to cancer; _chorea_ (St. Vitus' +dance); true dwarfism (all parts proportionately reduced); _Alkaptonuria_ +(urine darkens after passage); alcoholism and criminality, where based on +mental deficiency; hereditary _hysteria_; _multiple sclerosis_ (diffuse +degeneration of nervous tissue); _Friedreich's disease_ (degeneration of +upper part of the spinal cord); _Merriere's disease_ (dizziness and +roaring in ears); _Thomsen's disease_ (lack of muscular tone); hereditary +_ataxia_; possibly the tendency to become hard of hearing with increased +age; and possibly, non-resistance to tuberculosis. + +Of non-pathological conditions in man which are inherited as recessives, +apparently either very great or very small intellectual ability are +examples. + + +[Illustration: FIG. 28 + +Chart showing descent of feeble-mindedness as a typical recessive (after +Goddard). Squares represent males, circles females; DD, homozygous +dominant; DR, heterozygous dominant (i. e. normal although a carrier); RR, +pure recessive; N, normal; F, feeble-minded; A, alcoholic.] + + +=Breeding Out Defects.--=Even though recessive defects occur in a stock, +there is the possibility of diluting out the imperfection in successive +generations if care is taken always to marry into a stock wholly free from +it. For example, a normal individual carrying a recessive defect will bear +the abnormality in half of his or her germ-cells. This means that when +such an individual marries a normal, non-carrier, half of their children +will be wholly normal (AA) and half will be carriers; normal but of +simplex constitution (Aa). If now this generation, carriers and +non-carriers, marry only into normal strains of duplex constitution, then +their combined issue will be likewise normal with only one-fourth of them +carriers of the imperfections. This means that even if all of this last +generation were married to persons having the defect only one out of four +would have children showing it although the remaining children would be +carriers. On the other hand if mated to normals only one-eight of the next +generation would be carriers. Thus by continually marrying into strong +strains liability to manifest any recessive defect can be diminished in a +few generations until the descendants are no more likely to have defective +children than are members of our ordinary population. + +The proportion in which the recessive defect would appear in successive +generations if all persons in a given generation married only normal +individuals who were non-carriers is indicated in the following table +where AA indicates a normal individual, Aa one who is normal but a +carrier, and aa an individual with the imperfection expressed; to indicate +proportions simply after the first generation, four is arbitrarily chosen +as the number of children which results from each marriage: + + Matings Children + Generation 1 aa × AA = Aa + + Generation 2 Aa × AA = 2AA + 2Aa + + Generation 3 AA × AA = 4AA + AA × AA = 4AA + Aa × AA = 2AA + 2Aa + Aa × AA = 2AA + 2Aa + ---------- + 12AA + 4Aa + +=Other Inheritable Conditions in Man.--=While many pedigrees show beyond +dispute that such qualities as musical ability, literary ability, memory, +calculating ability, mechanical skill, longevity, peculiarities of +handwriting, obesity and muscular strength, for example, are inherited, +their modes of inheritance have not yet been sufficiently analyzed to +express them exactly. + + + + +CHAPTER V + +ARE MODIFICATIONS ACQUIRED DIRECTLY BY THE BODY INHERITED? + + +=Which New Characters Are Inherited?--=Any new feature which appears in a +given organism may have had its origin in some change which has come about +in the germ from which it sprang, or it may be merely the product of some +unusual stimulus operating on the body. While the outcome, as far as the +present individual is concerned, is in each case a definite modification, +the matter of inheritance is a very different question. On the first +alternative where the new character is the outcome of germinal change, it +is obvious that the altered germ-plasm will find expression in a similar +way in succeeding generations as long as the new germinal combinations +persist. On the other hand, if the new character has resulted merely from +some influence operating on the body of the individual, then to be +inherited it would also have in some way to be transferred to and +incorporated in the germ-plasm. Inasmuch as the body or soma of any +individual is highly plastic and since various of its ultimate features +may be mere somatic modifications, it is important to decide if possible +whether or not somatic variations which are not of germinal origin can be +inherited. + +=Examples of Somatic Modifications.--=For example, the small foot of the +Chinese woman of certain caste is the result of inherent germinal factor +for the production of a foot plus the effects of binding which are in no +wise germinal. The hand of the skilled pianist is a normal hand of +germinal origin and normal environment plus the effects of special +training. Again, the head of the Flathead Indian is a normal head of +germinal origin and environment plus the effects of flattening. Similarly, +almost any malformation of extrinsic origin may be cited, ranging from +mutilations and amputations, scars and the like to monstrosities such as +one-eyed fish which may be produced by subjecting a developing embryo to +adverse conditions of development. + +=Use and Disuse.--=Even reactions set up through the organism's own +activities must produce changes. For example, a muscle has a certain +average of normal development in the average man; it comes to this through +the innate nature of its component cells plus a certain average amount of +exercise. It may, however, be developed far beyond this average by +excessive exercise. On the other hand, it is a well-known fact that an +unused organ weakens or may remain but partially developed. Thus either +use or disuse may play an important part in the molding of a given +individual. But whether or not in doing this it similarly affects the germ +is a very different matter. + +=The Problem Stated.--=The question is can such enhanced or suppressed +development, or can new or modified characters, produced in an individual +by external agencies be so reflected on the germ-cell of the individual +that they tend to reappear _as such_ in its offspring without requiring +the same external factors for their production? + +=Special Conditions Prevail in Mammals.--=Before proceeding further we +must recognize clearly the very special conditions which exist in most +mammals. With them environment is in part an intra-maternal environment +and in part independent of parental influences. Thus the formula for most +non-mammalia would be-- + + Individual == egg + non-parental environment; but + +for most mammals, including man-- + + Individual == egg + intra-maternal environment + non-parental + environment. + +This condition in mammals introduces a complicating factor which is likely +to obscure the whole issue unless we bear it constantly in mind. In other +words, we must discriminate sharply, in the discussion of inheritance in +man, for instance, between two classes of influences which may exist in +the infant at birth, that is, which are _congenital_; namely, those which +were truly inherent--were in the germ-cells--at the very inception of the +young individual, and (2) those which might later have been derived from +either parent by the yet unborn offspring. The latter are not regarded as +truly hereditary. Since certain diseases or their effects belong here we +occasionally find a physician using the term inheritance for such prenatal +influences, but the more careful ones now employ the term _transmission_ +to discriminate between such conditions and true inheritance. In its +biological usage inheritance always refers to germinal constitution and +never to any condition that may be thrust on a developing organism before +birth. It is clear, then, that congenital conditions are not all +necessarily cases of inheritance. + +=Three Fundamental Questions.--=To get at the question of the inheritance +of body modifications with the least confusion, let us examine it in the +form of three fundamental questions, as follows: + +1. Can external influences directly affect the germ-cells? + +2. Can external influences, operating through the intermediation of the +parental body, affect the germ-cells? If so, is the effect a specific and +a permanent one which persists in succeeding generations independently of +external influences similar to those which originally produced it? Only +such a condition as this would rank as the inheritance of a somatic +modification. + +3. Can the appearance of new characters be explained on any other ground, +or on any more inclusive basis, than through the transmission of somatic +acquirements, or do organisms possess heritable characters which are +inexplicable as inheritance of such modifications? + +Obviously the only way the question can be settled is through careful +experimentation in which all possible sources of error have been foreseen +and guarded against. Much experimental work has been undertaken for the +solution of this problem as the goal and we may therefore select typical +ones of these experiments and apply the results toward answering our three +questions. + +=External Influences May Directly Affect the Germ-Cells.--=There is +evidence that under special conditions external influences may in certain +organisms affect the germ-cells, but that this occurs commonly is +extremely doubtful. For example, Professor MacDougal, by treating the +germ-cells of the evening primrose with various solutions, such as sugar, +zinc sulphate and calcium nitrate, has apparently succeeded in producing +definite germinal mutations. He injected the solution into the ovary of +the flower the forenoon of the day at the close of which pollination would +occur. He reports that in this way changes were produced in the germ which +found expression in new and permanent characters. + +Professor Tower has experimented for a number of years with various +species of _Leptinotarsa_, the potato beetle. By varying the conditions of +temperature, humidity and atmospheric pressure when females were laying +their eggs, he reports having produced variations in the young which came +from these eggs although the mothers themselves were not changed. +According to Professor Tower slight increase or decrease in these +environmental factors stimulated the activity of the color producing +ferments, giving rise to melanic or darker individuals. Greater increase +or decrease, inhibited them and produced albinos. He found also that at +times the same stimulus might show different results in different eggs. +The effect, therefore, is a general and not a specific one. Ordinarily the +eggs of these beetles are laid in batches. When one of these batches was +laid and left under normal conditions, the usual form of young hatched +from it, but other batches from the same female under abnormal conditions +resulted in the production of atypical forms. For example, a normal +two-brooded form became five-brooded. The commonest modification was the +production of various color types. These once established, according to +Professor Tower, behave as independent, inheritable units. + +The experiments of Doctor Bardeen with X-rays and of others with X-rays, +radium and other agents on the sperm and ova of amphibia show that these +are very susceptible to injurious influence at or near the time of +fertilization. + +=Such Effects Improbable in Warm-Blooded Animals.--=However possible it +may be to bring about germinal changes in invertebrata or lower vertebrata +by such external agents as temperature and the like it is obvious that the +probability of such extrinsic influences affecting the germ-cells of +warm-blooded animals is very remote indeed. In the latter the germ-cells +are more or less distant from the exterior and are at practically a +constant temperature. Such experiments, therefore, beyond showing the +possibility of producing changes in germ-cells, do not have very direct +bearing on the problem of how inheritable variations are produced in man. +In his case about the only avenue of approach through which germ-cells +might be influenced is the blood or lymph. + +=Poisons in the Blood May Affect the Germ-Cells.--=Any poisonous material +in the latter might injuriously affect the gametes. We know, in fact, that +such poisons as alcohol, lead and various drugs, and also the toxins of +various diseases, do so affect germ-cells. It seems plausible to suppose +that changing conditions of nutrition may affect the constitution of the +germ-cells and thus induce changes in the organism which arise from these +cells, but such nutritional effect is not yet a matter of established +fact. + +=Difficulty of Explaining How Somatic Modifications Could be Registered in +Germ-Cells.--=As to our second query concerning the possibility of +affecting the germ-cells through the intermediation of parental tissues, +it is evident at a glance that since the germ-cells are built up along +with the body and are not a product of it (Fig. 2, p. 13), if such effects +are possible they must take place through the agency of some transporting +medium. The germ-cells, being lineal descendants of the original fertile +germ or zygote, already have the same possibilities of developing into an +adult that the zygote had, and so the problem becomes one of modifying a +complete germ already organized rather than of establishing a new germ by +getting together samples of every part of the body. This is all the more +evident when one realizes that usually the germ-cells are set apart long +before the body becomes adult, that is, before the body has developed most +of its characteristics. Moreover, among lower animals many instances are +known where the immature young or even larvæ will produce offspring which +nevertheless ultimately manifest all the structures of the adult +condition. + +But supposing specific modifications of the germinal mechanism were +possible, it is difficult to comprehend how an influence at a distant +point of the body could reach the germ-cell, to say nothing of the even +greater difficulty of understanding how it could become registered in the +germ in a specific way as affecting a particular part. For it must be +remembered that the organs of the adult do not exist as such in the germ +but are present there only as potentialities. How, for example, can a +change in the biceps muscle of one's arm be registered in a germ-cell in +which there is no biceps muscle, but merely the possibilities of +developing one? Or how can increased mental ability which is contingent on +the elaboration of certain brain-cells be impressed on a germ which has no +brain-cells but only the capacity under certain conditions of producing +such cells? For the brain of a child is not descended from the brain of +his parent, but from a germ-cell carried by that parent. + +=Persistence of Mendelian Factors Argues Against Such a Mode of +Inheritance.--=On the face of things, the apparent inviolability of +Mendelian factors which may remain unexpressed in the germ for one or many +generations--indeed the whole matter of genotypical differences in the +gametes of the same individual--shows the improbability of somatic +interference with the germ-plasm. But notwithstanding this, because of the +great importance of the issue, it is well to review in some considerable +detail the various phases and possibilities of the question. + +=Experiments on Insects.--=Some of the attempts to secure evidence of the +transmission of personally acquired parental modifications in insects are +very interesting. Many insects in the larval stages, particularly just +after pupation seem to be especially susceptible to external influences. +They have been much used, therefore, for purposes of experiment. It has +long been known that differences in size, in color and even in the shape +of wings can be produced by various agents if applied at this period of +development. From the standpoint of heredity, however, the important +consideration is to determine if these experimentally induced changes have +been reflected on to the germ-cells so that they reappear in the offspring +of the modified individuals. + +It has been found that in some cases where male and female are of +different color, the color of the female can be changed to that of the +male by altering the conditions of temperature. In certain cases types can +be changed by cold so that they resemble varieties of the same species +found farther north, and by heat, varieties found farther south. But not +all individuals of a given lot are affected, and often different +individuals of the same kind show different effects. Moreover, in some +cases the same aberrations were produced by heat as by cold. This +indicates that it is not so much a question of specific effects as a +general physiological change, apparently mainly a matter of direct +influence of temperature on the chemical composition of the pigments. The +Countess von Linden in fact has shown that the extracted pigments can be +made to undergo the same changes of color in a test-tube by heat and cold +as in the pupæ. But there is no evidence that the germ-cells of the living +insect were affected in a specific way. In a small fraction of the +offspring of such modified individuals abnormalities appeared, but these +were not always of the same kind as those which had been produced in the +parent. That is, there was no evidence of a trait or character having been +acquired by the body and handed on to the germ-cell. Where an effect was +produced on the germ-cell it was probably produced directly as in the +first cases discussed. + +Size, colors and markings of butterflies have also been altered by +subjecting the caterpillars or the pupæ to such influences as strong +light, electricity, various chemical substances, centrifuging, diminished +oxygen supply, etc., but the results were in the main confined to the +immediate generations. In the few cases where permanent inheritable +changes were seemingly produced they were more reasonably interpreted as +the effects of direct action on the germ-cells than as examples of +inherited somatic modifications. + +Starvation experiments which resulted in the dwarfing of adult individuals +have been performed on various insects, and while the dwarf condition may +persist through one or two generations due to a diminished food supply in +the eggs of the dwarf, the stock in question when returned to normal food +conditions soon resumes its original characteristic size. + +=Experiments on Plants.--=Many experiments have been performed with +plants, inasmuch as they are particularly prone to become modified by +changes of food supply, or climate. For example, plants which grow +luxuriantly in a warm moist climate or a rich soil may become stunted and +markedly changed if transplanted to a cold climate or a poor soil. +Naturally, their progeny will exhibit the same behavior as long as they +are kept under the new conditions. Experiments carried on through numerous +generations, however, practically all show that the germinal constitution +of the plants remains unchanged, for when their seeds are planted under +the original favorable conditions of soil or climate, the plants resume +their former habits of growth. Naegeli, for instance, who made a study of +many varieties of Alpine plants, and who carried on experiments with many +of them for years in the Garden of Munich, concluded that no permanent +effects had been produced by the Alpine climate and conditions in plants +from other regions which had come under its influence. A few botanists +have claimed to have found that the changes produced by the Alpine climate +have persisted for a generation or two and have then worn off. More recent +experiments on various of our field grains which have been stunted and cut +down in productivity by growing for a number of generations under adverse +conditions show that they have not been permanently modified by such +treatment, for they resume normal productivity and size when grown again +under favorable conditions. + +On the other hand, Lederbaur found that a common weed, _Capsella_, when +transplanted from an Alpine habitat to the lowlands did not return to the +lowland type of the weed, but retained certain of its Alpine +characteristics. It is not clear, however, that this particular species +during its long sojourn of many generations in Alpine conditions may not +have undergone a series of germinal variations and have developed into a +new variety or species quite independently of changes wrought in the germ +by reflected somatic effects. Indeed, in face of the preponderance of +other cases to the contrary, this interpretation would seem to be the more +plausible one. + +=Experiments on Vertebrates.--=In the vertebrates we may also find +examples of various somatic modifications experimentally produced, but +evidence of their inheritance is as difficult to establish as in the +invertebrates. Let us examine a few of the more significant of these which +are alleged by some to bear evidence of such inheritance. + +By decreasing the amount of water in an aquarium Marie von Chauvin was +able to transform the aquatic, gill-breathing salamander _Axolotl_ into +the gill-less land form _Ambystoma_, heretofore regarded by systematists +as a different species. Either of these forms when sexually mature +produces its like. The salamanders in question have both lungs and gills, +but after a time the ones which are to be land forms lose their gills and +become exclusively lung-breathers. What seems to have been accomplished +then is the accelerating or forcing of normal natural tendencies already +inherent in the organism instead of introducing something new into the +inheritance by way of the soma. _Axolotl_ is in all probability merely a +larval form of _Ambystoma_ which with high temperature and an abundance of +water reproduces without advancing to the final possible stage of its life +cycle. + +=Epilepsy in Guinea-Pigs.--=Perhaps the most frequently cited case and the +one in which the defenders of the idea of somatic inheritance usually take +final refuge is that of Doctor Brown-Sequard's guinea-pigs, +notwithstanding the fact that no one has had convincing success in +repeating the experiments and that the original results are apparently +open to more than one interpretation. This experimenter rendered +guinea-pigs epileptic by certain injuries to the nervous system. Epilepsy +appeared in some of the offspring of these operated animals. He regarded +this as an example of the inheritance of an artificially induced epilepsy. +An indirect loss of toes occurred in some of the parents as a result of +the operations on the nervous system. Some of their young also had missing +toes. However, as has been pointed out by various critics, guinea-pigs are +strongly predisposed toward epileptic-like seizures, and the epilepsy in +the young may have been merely a coincidence. Voison and Peron believe +they have shown that in epilepsy a toxin is produced that may affect the +unborn fetus. That is, the result might have been due to a poison derived +directly from the mother. The experiments in fact show that it was mainly +in the offspring of affected mothers that the condition appeared. Others +maintain that we do not know the exact nature of epilepsy, that in some +cases it may be the result of infection by disease-germs, and that +Brown-Sequard's cases may, therefore, have been merely the communication +of a disease from parent to child. As to the disappearance of toes it is a +well-known fact that rodents in particular are likely to gnaw off the toes +of their young very soon after birth, and little credence can be put in a +lack of toes in such young as cases of inheritance except under conditions +of much more careful observation than existed in Brown-Sequard's +experiments. A fuller account of these experiments will be found in +Romanes' _Darwin and After Darwin_, Vol. II, Chap. 6. + +=Effects of Mutilations Not Inherited.--=Many experiments have been +performed by investigators to determine whether or not the results of +mutilation are transferred to succeeding generations, but so far only with +negative results. Many such experiments have been unwittingly carried on +for many generations, in fact, by breeders and fanciers, in the docking of +horses, dogs and sheep, the dehorning of cattle and the like, yet no +satisfactory evidence of the transmission of such conditions in any degree +has ever been forthcoming. The mutilations or distortions of the human +body through various rites or social customs also fails to yield any +convincing examples. Foot-binding, head-binding, or waist-binding must be +repeated in each successive generation to produce the particular type of +"beauty" that results from such deformities. And lucky it is for man that +injuries do not persist in subsequent generations, otherwise the modern +human being would be but a maimed relic of past misfortunes. + +=Transplantation of Gonads.--=An interesting experimental test regarding +the effect of the body on the germ was made recently by Castle and +Phillips with guinea-pigs. It will be recalled from the discussion on +Mendelism that when a black guinea-pig is mated with a white one the +offspring are always black. These experimenters transplanted the ovaries +from a young black guinea-pig to a young white female whose own ovaries +had been previously removed. This white female was later mated to a white +male. Although she produced three different litters of young, six +individuals in all, the latter were all black. That is, not a trace of +coat-color of the white father or of the white foster-mother was impressed +on the transplanted germ-cells or the developing young. Later experiments +of the same kind by Castle and Phillips, with other varieties of +guinea-pigs, have yielded the same results. The body of the mother, +indeed, seems to serve merely as a protective envelope and a source of +nutrition. + +=Effects of Body on Germ-Cells General, Not Specific.--=As far as the +evidence regarding the modification of the germ-plasm by the body is +concerned, we must conclude then that while under special circumstances +the germ-cells may be affected, the effect is general rather than specific +and the result as seen in the offspring has no discoverable correlation +with any particular part or structure of the parental soma. The effect is +presumably of much the same nature as where the germ is directly affected +by external agents. Where a new character or a modification of one already +existing is produced by a given condition of environment, in our +experience so far to have the same repeated in the offspring, a similar +evocative condition must prevail in the environment of the latter. Or in +other words the new character is not a permanent one which persists in +succeeding generations independently of external influences similar to +those which originally produced it. + +=Certain Characters Inexplicable as Inherited Somatic Acquirements.--=It +would require remarkable credulity, in fact, to believe that some of the +most striking features about certain plants or animals could have been +developed by means of the inheritance of somatic modifications. For +example, many animals such as the quail, the rabbit, or the leaf-butterfly +are protectively colored. That is, they harmonize in color-pattern with +their surroundings so closely that they are overlooked by their enemies. +But how can this oversight on the part of an enemy so affect the bodies +and through them the germ-cells of such individuals as to develop so high +a degree of protective coloration? Or how, indeed, could any of numerous +adaptive structures which one can think of, such as the color or scent of +flowers to lure insects for cross-pollenation, the various grappling +devices on many seeds to secure wide distribution by animals, or the like, +have been directly produced by use or disuse or by any variation produced +in them by the agents to which they are adapted? + +=The Case of Neuter Insects.--=A very instructive example of the +improbability that great skill, highly specialized structures, or certain +instincts are first developed in the parental body as the result of use +and then passed on to the offspring, is seen in the case of neuter +insects. In bees, for example, there are three classes of individuals: the +drones or males; the queens or functional females; and the workers, which +are neuter, that is, take no part in reproduction. The latter are really +sexually undeveloped females. The queen can lay either fertilized or +unfertilized eggs. The latter always give rise to males. The workers +gather the food, attend the queen, wait on the young, construct the comb, +and in short perform all the ordinary functions of the colony except the +reproductive. They have many highly specialized structures on various +parts of their bodies for carrying on their many activities, as well as +the very highly specialized instincts necessary to the maintenance of the +colony. But now, complex and highly developed as these workers are, since +they do not give rise to offspring, no matter how much experience or +structural modifications they may acquire during their lifetime, it can +not be handed on to another generation. Nor can they have come to their +present highly organized state through such a form of transmission since +they are not the descendants of workers but of a queen. Any new +modifications that appear in the workers of a colony must therefore have +their origin in changes which have taken place in the germ-cells of the +queen, and not in the soma of some other worker. It has been argued that +the worker has not always been infertile; that at a more primitive stage +of the evolution of the bee colony every female was both worker and +mother, and that individual somatic acquirements might therefore have been +transmitted, but this argument can not hold for many of the instincts or +features of the modern bee because these have to do only with the +conditions of life which exist in the colony in its present form. It is +obviously absurd to maintain, for instance, that all the highly +specialized instincts incident to queen production, queen attendance and +the like were functionally produced through usage before there was any +queen to produce or attend, while on the other hand, the very necessity of +queen production and maintenance is the outcome of the infertility of the +workers. Some workers have been known to lay eggs, but as these are few in +number and are never fertilized, which means if they develop they can only +produce males, they can play no considerable part in inheritance. + + +ORIGIN OF NEW CHARACTERS + +=Origin of New Characters in Germinal Variation.--=This brings us to our +last query as to whether the appearance of new characters can be explained +on any other or any more inclusive ground than that which infers that +changes undergone by the parent-body are in some way registered in the +germ-cells so as to be repeated in a certain measure in the body of the +offspring. The answer to the question of how inheritable variations do +come to appear in offspring if not through changes produced in the body of +the parent, is uncertain; nevertheless most biologists believe that they +do not have such a somatic origin but arise directly as germinal +variations. Some would attribute them to the fluctuating nature of living +substance in general. The instability of protoplasm is one of its striking +characteristics. It is constantly being broken down and built up, or, in +other words, undergoing waste and repair. Like all other protoplasm, that +of the germ-cells must also undergo these metabolic changes and it is +possible though not proved that in this give and take of substances small +changes occur in their constitution which find expression in the offspring +as variations. As already seen, substances in the blood other than food +may also affect the constitution of the germ-cells. + +=Sexual Reproduction in Relation to New Characters.--=Some biologists +attribute great importance to sexual reproduction as a basis of variation +and the origin of new characters. They argue that the mingling of +determiners from two different lines must produce many new combinations +and expressions of germinal potentialities. Plausible as the argument +seems at first sight no one has succeeded as yet in securing proof that +absolutely new characters can be originated in this way. What seems to +occur under such circumstances is merely a reshuffling or sorting of old +unit-characters. Although innumerable permutations and combinations of +these may be made which find new expression outwardly, this is obviously +not creating determiners of new unit-characters in the germ-plasm. While +many biologists would not deny the possibility or even the probability +that the determiners of unit-characters may sometimes combine or influence +one another so as to form actual permanent new characters, the proof of +such performance is wholly lacking. On the other hand, there are not a few +biologists who argue that sexual reproduction accomplishes just the +reverse of increasing the extent of variation or creating new characters; +according to them it tends to annul exceptional peculiarities of either +parent by throwing the offspring back to the average racial type. It is +thus looked on by these advocates as a stabilizer which reduces the +amplitude of variations instead of increasing them. As a matter of fact +the two ideas are not mutually exclusive; sexual reproduction may +accomplish both of these ends. A limited number of observations and +experiments have been made to test out the correlation between sexual +reproduction and variation, but they have so far been too few or too +inconclusive to enable us to come to a satisfactory conclusion. + +While we are uncertain about the method of origin of new characters the +fact remains that they do arise in abundance as abrupt mutations or +otherwise and become a part of the permanent heritage of a stock. It is +clear that sexual reproduction may be one important means by which a given +new character which has arisen in one or a few individuals may become +incorporated in the species at large. Through Mendelian combinations and +segregations it would by cross-breeding be spread and gradually introduced +into more and more strains of the general population. + +=Why So Many Features of an Organism Are Characterized by +Utility.--=Germinal variations are seemingly at first more or less hit or +miss affairs as far as utility to the organism is concerned. Useless +variations, so long as they are not actually harmful, may persist and +apparently be indefinitely inherited. However, a special premium is put on +variations which happen to be useful for they help the organism to succeed +in its struggle for life and since success in the world of life means not +only mere individual survival but also the production of progeny, through +this very means insured transmission to subsequent generations. It is +probable that the very many useful features of any organism, that is, its +_adaptations_, have thus been established. It is possible also that many +variations which at their inception are indifferent may wax in strength in +successive generations until they reach a point where they must become +either useful or harmful. In the former case they would mean increased +insurance of survival for their possessors, in the latter, elimination. +With such an automatic process as this operative in nature it is not +astonishing that the main features of any organism are characterized by +their utility to it. + +=Germinal Variation a Simpler and More Inclusive Explanation.--=The gist +of the whole matter regarding the source of new characters in offspring +seems to be that the explanation based on the idea of germinal variation +is in last analysis the simpler and more inclusive, and there is no +alleged case of inheritance of parental modification, which can not be +equally well explained as the result of a germinal variation. There are +numerous cases which can not be explained as transmissions of somatic +acquirements even if this transmission could be established in certain +cases. So, many biologists argue, why have two explanations when one is +sufficient, especially when the other has never been conclusively +established as true in any case and is obviously untrue in certain test +cases? The attitude of most investigators is that of the open mind. While +feeling that the weight of probability is very decidedly against the +theory of the inheritance of somatic modifications, they still stand ready +and willing to accept any evidence in its favor which when weighed in the +balance is not found wanting. + + +ANALYSIS OF CASES + +While space will not permit extended discussion, in order further to fix +the nature of the problem in mind as well as to exemplify the conditions +that must be satisfied to form convincing evidence of inherited somatic +acquirements, it will be well perhaps to analyze a few typical cases as +they are frequently cited. + +=Are the Effects of Training Inherited?--=Breeders and trainers very +commonly believe that the offspring of trained animals inherit in some +measure the effects of the training. Thus the increased speed of the +American trotting horse is often pointed to as strong evidence of such +transmission. According to W. H. Brewer, the earliest authentic record of +a mile in three minutes was made in 1818. The improvement, approximately +by decades, from that time was as follows: + + During 1st decade after 1818, improved to 2:34 + 2nd " " " " " 2:31-1/2 + 3rd " " " " " 2:29-1/2 + 4th " " " " " 2:24-1/2 + 5th " " " " " 2:17-1/2 + 6th " " " " " 2:13-1/2 + 7th " " " " " 2:08-1/2 + +By 1892, the date of Professor Brewer's publications (See _Agricultural +Science_, Vol. 4, 1892) the record had reached 2:08-1/2. Since then it has +been lowered still further. + +On the face of it this looks like a good case of inheritance of training, +and Brewer himself believed it such. If so this would mean that colts of a +highly trained trotter would be faster than they would have been if their +parent had remained untrained. It is impossible to get positive proof in +the case of any trained horse since there is no way of establishing just +how speedy the progeny would have been had the parent remained untrained. +If it could be shown that colts sired by a trotter late in life were on +the whole faster than those sired by the same father when younger and as +yet not highly exercised in trotting, then the facts might give some +evidence of value, but unfortunately no such records are available. + +On the other hand, even ignoring the fact that improvement in track and +sulky are probably the biggest items in the shortening of records in +recent times, _selection_ instead of inheritance of the effects of +training will equally well account for any innate progress in trotting. +And since, as pointed out by Professor Ritter, there are even more +striking cases of similar improvements in other fields, such as college +athletics, where the factor of use-inheritance is entirely precluded, it +is wholly unnecessary to postulate it in the case of the trotter. + +For example an inspection of the records of college athletics for the last +thirty-five years in running, hurdling, pole-vaulting, jumping, putting +the shot, etc., shows on the whole a steady advance year by year. +Moreover, the greatest improvement has occurred in those events in which +skill and practise count for most together with selection of the +inherently ablest candidate for the events. But in the case of athletics +the improvements shown in thirty-five years have all come within a single +generation and hence the inheritance of the effects of training is ruled +out as a factor. Selection and improved training are the only factors +operative. + +In the case of the trotter inheritance undoubtedly has also been a factor, +but inheritance based on selection of what the race-track has shown to be +the speediest individual, not inheritance of the effects of training. In +other words, horses which have shown the capacity for being trained to the +highest degree of speed have naturally been selected as sires and dams +and so through selection generation after generation a speedier strain has +gradually been established. + +=Instincts.--=When we turn to the realm of mental traits, particularly of +instincts, we meet with a whole host of activities which are frequently +pointed to by transmissionists as examples of inherited acquirements. Thus +according to them, habits at first acquired through special effort +ultimately become instinctive, or according to some, instinct is "lapsed +intelligence." Instances often cited are the pointing of the bird-dog, the +extraordinary crop-inflation of the pouter-pigeon, or the tumbling of the +tumbler pigeon. We can not stop to discuss these cases beyond pointing out +as many others have done that practically all dogs have more or less of an +impulse to halt suddenly, crouch slightly and lift up one fore-foot when +they scent danger or prey, that all pigeons pout more or less, and that +practically all show more or less instincts of tumbling when pursued by a +hawk. Thus in all of these cases the fundamental germinal tendency is +already at hand for the fancier to base his choice on and thus through +selection build up the type desired. Just as in the fan-tailed pigeon, by +repeatedly selecting for breeding purposes individuals which showed an +unusual number of tail-feathers he has built up a type with an upright, +fan-like tail having many more feathers than the twelve found in the tail +of the ordinary pigeon, so by similar procedure in the case of other forms +he has markedly enhanced certain features. The idea of instincts being +"lapsed intelligence" is so clearly and concisely criticized in an +article by the late Professor Whitman[4] that I can not do better than +quote an excerpt. His views to the contrary are as follows: + + "The view here taken places the primary roots of instinct in the + constitutional activities of protoplasm and regards instinct in every + stage of its evolution as action depending essentially upon + organization. It places instinct before intelligence in order of + development, and is thus in accord with the broad facts of the present + distribution and relations of instinct and intelligence, instinct + becoming more general as we descend the scale, while intelligence + emerges to view more and more as we ascend to the higher orders of + animal life. It relieves us of the great inconsistencies involved in + the theory of instinct as "lapsed intelligence." Instincts are + universal among animals, and that can not be said of intelligence. It + ill accords with any theory of evolution, or with known facts, to make + instinct depend upon intelligence for its origin; for if that were so, + we should expect to find the lowest animals free from instinct and + possessed of pure intelligence. In the higher forms we should expect + to see intelligence lapsing more and more into pure instinct. As a + matter of fact, we see nothing of the kind. The lowest forms act by + instinct so exclusively that we fail to get decided evidence of + intelligence. In higher forms not a single case of intelligence + lapsing into instinct is known. In forms that give indubitable + evidence of intelligence we do not see conscious reflection + crystallizing into instinct, but we do find instinct coming more and + more under the sway of intelligence. In the human race instinctive + actions characterize the life of the savage, while they fall more and + more into the background in the more intellectual races." + +For further discussion of this field the reader is referred to an +excellent chapter on "Are Acquired Habits Inherited?" in C. Lloyd Morgan's +book, _Habit and Instinct_. + +=Disease.--=Perhaps in the realm of disease more than in any other has an +interest in the inheritance of somatic acquirements been manifested. The +problem arising here is not essentially different from other questions of +inheritance but since it is a matter of such practical importance to man, +we may well give it special attention. We have to deal simply with the old +questions of what is constitutionally in the germ, what is acquired by the +body, and lastly, whether the somatically acquired is inherited. While we +all know in a general way what is meant by disease, especially if some +specific disorder such as scarlet fever, malaria or tuberculosis is +mentioned, an attempt to give an accurate definition is much like trying +to define a weed, inasmuch as what is functionally all right at one time +or place may be all wrong at another, or what is normal in one animal may +be abnormal in another. In general we may say that disease is derangement +or failure of physiological function. + +=Reappearance of a Disorder in Successive Generations Not Necessarily +Inheritance.--=In attempting to study the inheritance of diseases we must +recognize clearly at the outset that reappearance of a disease in +successive generations by no means necessarily signifies inheritance. +Before it can be pronounced such we must make sure that it is not a case +of reimpressing similar modifications on the individuals of successive +generations. For example, in England there is a well-recognized condition +known as collier's lung which results from constant working in coal mines. +And while both father and son may exhibit it, because of their similar +occupations, there is nothing hereditary about the malady. Likewise there +is what is known as emery grinder's lung, and practically every large +manufacturing city with soot-laden atmosphere leaves its impress on the +lungs of the inhabitants. This will occur, of course, generation after +generation, as long as such pollutions of the atmosphere continue to +exist. It is clear that any unhealthy occupation is likely to cause the +reappearance of an associated typical disease generation after generation +as long as the children follow the calling of their parents. The common +misconception that deformities or postures associated with a trade, such +as a shoemaker's or tailor's, is genetically stamped on offspring by the +end of the third or fourth generation results from failure to discriminate +between real inheritance and mere reappearances under similar conditions +of environment. + +=Prenatal Infection Not Inheritance.--=Again, we must recognize that +prenatal infection is not inheritance. We have already seen that the young +mammal undergoes a certain period of intra-maternal development, but +influences operating on it during this period of gestation must be +reckoned with as environmental, not germinal. For example, it is said that +an unborn child may take smallpox from its mother but this and all similar +occurrences are cases of contagion. We find the great pathologist, +Virchow, who with many others of his time was a believer in the +inheritance of acquired characters, saying nevertheless regarding such +instances that, "What operates on the germ after the fusion of the +sex-nuclei, modifying the embryo, or even inducing an actual deviation in +the development, can not be spoken of as inherited. It belongs to the +category of early acquired deviations which are therefore frequently +congenital." + +=Inheritance of a Predisposition Not Inheritance of a Disease.--=We must +discriminate sharply also between the inheritance of a predisposition and +the inheritance of a disease itself. + +We often hear the statement made that tuberculosis is inherited and have +cited in evidence certain consumptive families or strains. But +tuberculosis is a bacterial disease and children of tuberculous parents +are never born with the disease except in the rarest of instances. + +=Tuberculosis.--=What is really inherited is a constitutional +susceptibility to this particular germ. While almost any individual may +contract tuberculosis when in a state of depressed vitality, or under +stress of adverse surroundings, there is no doubt that certain families +are more easily infected than others and much less resistant to the +ravages of the disease when once it gains a foothold. However, a +predisposition is a vastly different thing from the inheritance of the +actual disease. For just as we are born with a nose well adapted to +eye-glasses but not with eye-glasses on our nose, so many of us are born +tuberculizable though not tuberculous, and every sanitary advance we make +toward lessening the chances of infection is just so much more insurance +for the susceptible. + +The whole problem of tuberculosis is an extremely complex one. We do not +know just the measure of the inheritance of the predisposition. Some +writers in the past have maintained that tuberculosis is mainly a question +of infection and not of inherent susceptibility, but steadily increasing +evidence all points the other way. + +Where the predisposition exists the chances of infection are still, even +under the conditions of present-day sanitation, very great. The close +association between a consumptive and other members of the family through +a prolonged period of time, of course, renders the latter likely to +infection unless unusual care is exercised. Very often where a parent is +consumptive a child contracts the malady shortly after birth and is +particularly likely to do so if the mother, who nurses it and cares for it +most intimately, is the tubercular member of the family. Where the mother +is tubercular, indeed, the probabilities are that the child has already +before birth had its vitality lowered through the toxins circulating in +her blood or through defective nutrition, and in consequence does not +resist well any diseases. + +Undoubtedly a large proportion of our infant mortality is of tubercular +origin. It is now a well-established fact that much tuberculosis in +children is attributable to drinking milk from tuberculous cows, yet we +find individuals so uninformed and dairymen so mercenary that they fight +all attempts of the commonwealth to test out cattle for tuberculosis so as +to condemn the infected individuals and thus save our babies. Recent +investigations made in some of our large pork-packing establishments also +indicate that hogs, especially such as have been around tubercular +cattle, are often shot through and through with tuberculosis and that such +flesh when used as food, if not thoroughly cooked, may become a serious +menace to our health. + +With the wide prevalence of bovine and human tuberculosis it is little +wonder that nearly every human being becomes more or less infected at some +period of life. Autopsies on large numbers of individuals in some of our +great hospitals have shown that as many as ninety-nine per cent. of the +subjects show tubercular lesions of some kind. While it is true that the +class of people who would come to autopsy in such public hospitals would +perhaps be more likely to be tubercular than the average of the community, +still it can not be denied that a very large degree of infection exists. +Pearson, from statistics gathered in Europe, has shown that about eighty +to ninety per cent. of the population have tubercular lesions before the +age of eighteen. Hamburger found that in Vienna ninety-five per cent. of +the children of the poor, between twelve and thirteen years of age, were +infected with tubercular bacilli and he estimates that all would be before +maturity. According to Doctor Mott, pathologist to the London County +Asylums, the insane between the ages of fifteen and thirty-five are about +fifteen times as likely to acquire tuberculosis as the sane are. + +Yet the mortality from tuberculosis, great though it be, is obviously not +in proportion to the enormous degree of infection. The crux of the +situation is mainly the matter of resistance. From the standpoint of +heredity, therefore, the question largely resolves itself into one of the +inheritance or non-inheritance of constitutional resistance. Some are +predisposed to be non-resistant and hence succumb. + +The work of Karl Pearson[5] and other recent researches forcibly indicate +that hereditary constitutional predisposition is one of the chief factors +concerned in subjects who develop well defined attacks of the disease. Yet +we must not forget that there are degrees of susceptibility and that +therefore a constitutional predisposition which might be of little +significance under good average conditions of nutrition and sanitation +might be insufficient under unfavorable conditions. + +Before we can make any relatively accurate estimate of the exact degree to +which the malady is based on inheritance we must have more data. Many +difficulties beset the path of the investigator. In the first place, when +one gets back a generation or two he finds that diagnosis was crude and +uncertain; a given malady may or may not have been tuberculosis. The main +error however was probably on the side of not recognizing it in mild or +obscure cases. Then again the questions of virulence of the infection, of +size and frequency of the dose, etc., are also complicating factors. +Moreover, in very many cases the infection is a mixed one and hence we are +dealing with other factors than straight tuberculosis. + +=Two Individuals of Tubercular Stocks Should Not Marry.--=However, +sufficient is now known of the inheritance of susceptibility to the +disease that we can have little conscience toward the welfare of the race +if we in any way countenance the marriage of two individuals who come each +of tubercular strains, and marriage of even a normal person into a badly +tainted strain, where the one married is tubercular, is extremely +hazardous looked at from the standpoint of the children likely to be born +of such a union. The Supreme Court of New York recently held that the +fraudulent concealment of tuberculosis by a person entering into a +marriage relation is ground for the annulment of the marriage. + +=Special Susceptibility Less of a Factor in Many Diseases.--=With some +diseases such as leprosy, typhoid fever, smallpox and cholera there seems +to be less a question of special susceptibility since nearly all persons +are vulnerable. Yet in cases of typhoid, at least, there are some +indications that certain families are more likely to take the disease than +others under similar exposure. We know of no inherited effects of such +diseases, however. For instance, children of lepers do not inherit leprosy +and if kept out of leper districts remain normal. + +=Deaf-Mutism.--=In certain abnormal states there is danger of confusing +similar conditions which may have two entirely different sources of +origin. Deafness, for example, may be strictly inborn as the outcome of a +germinal variation or it may result from extraneous influences such as +accidents, infective diseases, neglected tonsils and the like. The former +is inheritable, the latter not. Bell in 1906 in a special census report to +the United States government showed that deaf-mutism is markedly +hereditary, particularly where deaf-mutes intermarry as they are prone to +do. Fay's extensive studies on _Marriage of the Deaf in America_ also +demonstrate the hereditary nature of the congenital forms of deafness. Cut +off as such individuals are from communication with normal people, the +association of the two sexes in special schools and institutions is of +course highly conducive to such marriages. The defect seems to behave in +the manner of a Mendelian recessive. Two deaf-mutes should not have +children and yet such marriages are occurring every day. Even if two +persons marry from families which tend to become hard of hearing the +evidence indicates that their children are likely also to develop this +partial deafness as they grow older, although it seems safe for a person +of such tendency to marry into a family without it. + +=Gout.--=In such disorders as gout there is little question but that a +tendency to it runs in families. On the other hand it may also be acquired +without special susceptibility. There is no evidence, however, that +because a father has gout the effect of the gout is reflected on his +germ-cells and the son has gout as a result. Indeed, often a son who +becomes gouty was born long before the father became gouty. Son and father +both have gout then, because each has innate germinal tendencies which +when subjected to certain evocative stimuli become expressed as gout. + +=Nervous and Mental Diseases.--=Inasmuch as the question of nervous and +mental diseases has become one of such overshadowing importance at the +present day, a discussion of the subject at some length will be presented +in a separate chapter. I shall merely point out here that the general +verdict of experts in nervous and mental disorders is to the effect that +externally induced mental disorders are of rare occurrence except as the +result of general poisoning or enfeeblement of the system in some way, or +by traumatic conditions such as a blow on the head, and that there is no +evidence of the transmission of the effects of such conditions. In most +cases of insanity, supposedly caused by fright or worry, a close study of +the family stock will reveal nervous instability of some kind. The +supposed cause has been merely the precipitating stimulus which has +brought to expression a dormant weakness of germinal origin. The stress +and strain of modern life is particularly likely to test out and reveal +such neurally unstable individuals. + +=Other Disorders Which Have Hereditary Aspects.--=Space will not permit +discussion of various other specific disorders which are known to have +important hereditary aspects, although none shows any convincing evidence +of having become hereditary in nature through first affecting the soma. +Some of these, such as epilepsy and other nervous affections, +tuberculosis, color-blindness, cataract and various malformations, have +already been mentioned. Others that may be listed are cancer, +arterio-sclerosis, obesity and certain forms of rheumatism, and of heart +and kidney diseases. In practically all of these cases in which heredity +enters as a factor the condition is one of inheriting a special +susceptibility and not the disease itself. Which means simply that the +disorder in question is much more easily called forth in such persons by +appropriate bacterial or other stimulus, than in the case of the normal +individual. + +=Induced Immunity Not Inherited.--=Lastly, it is well known that various +animals, including man, after recovery from an attack of any one of +certain diseases, become more or less immune from further attacks of the +same disease. Moreover in some instances as in inoculation against typhoid +or diphtheria, immunity may be artificially induced by means of +anti-toxins. The question arises as to whether such immunity is +transmitted to offspring. Experiments have been made (see _Bulletin No. +30, U. S. Hygienic Laboratory_) to test this and it has been found that +the condition is not inherited. Young guinea-pigs, for instance, born of +mothers immunized during pregnancy are immune at birth but they lose their +immunity in the course of a few weeks. The effect is clearly one of direct +transference from the blood of the mother. The same temporary immunity can +be produced in the young, in fact, by merely having them nurse from an +immunized mother. + +=Non-Inheritance of Parental Modifications Has Social, Ethical and +Educational Significance.--=Like many other biological conclusions these +relative to the non-inheritance of parental modifications are of extreme +importance to humanity. It is clear that they have not only physical but +social, ethical and educational significance. For if the education which +we give our children of to-day, or the desirable moral conduct which we +inculcate does not affect the offspring of succeeding generations through +inheritance, then the actual progress of the race is much slower than is +commonly supposed, and the advance of modern over ancient times lies more +in an improvement in extraneous conditions through invention and the +accumulation and rendering accessible of knowledge, than in an actual +innate individual superiority. And when we face the issue squarely we have +to admit that there is no more indication of the inheritance of parentally +acquired characters as regards customs, knowledge, habits and moral +traditions than there is of physical features. In fact, if such +acquirements were inherited then we should soon have a race which would +naturally, spontaneously as it were, do what its ancestors did with +effort. Yet we do not find the children in our schools reading, doing sums +and developing proper social relations without ceaseless prompting and +urging on the part of the teacher. Indeed I can testify that this +necessity carries over even into a university. In short, the habits and +standards of each generation have to be instilled into the succeeding +generation. + +=No Cause for Discouragement.--=At first glance when we realize that +notwithstanding our individual advancement, that in spite of all our +painstaking efforts toward self-improvement, we can not add one jot or +tittle to the native ability of our children, that, aside from possible +advantageous germinal variations, they will have to start in at +approximately the same level as we did, and like us will have to struggle, +or be coaxed, pulled or spurred up to the higher reaches of attainments, +we are apt to feel discouraged and to look on heredity as the hand of fate +which irrevocably bars progress. But there is another side to the picture. +This very fact of heredity which can not be altered at will is the +conservative factor which maintains the excellence of our standard strains +of plants and animals, and sustains man himself at his present level of +accomplishment. While we are denied advancement through the efforts of the +flesh, we are also largely protected from our misfortunes and follies, as +witness the non-inheritance of mutilations, of various maladies of +extrinsic origin, or of personally acquired bad habits. + +=Improved Environment Will Help Conserve the Superior Strains When They Do +Appear.--=If we can not hand on to our descendants a personally enhanced +blood heritage, we at least can do our share toward building up a social +heritage of established truth, of efficient institutions and of +stimulating ideals, through which their dormant capacities may be led to +expand more surely and more effectively to their uttermost limits. Each +advance in such social heritage will tend more and more to create an +atmosphere which will make it sure that the occasional real progressive +and permanent variations which occur from time to time will find adequate +expression and preservation in future lines of descendants. It will reduce +the numbers of our "mute, inglorious Miltons" by more certainly disclosing +the individual of exceptional talents and insuring for him an opportunity +of revealing them to the best advantage. Above all, since surrounding +influences are especially powerful on young and developing organisms, we +should realize that great care must be exercised in behalf of the young +child to secure an environment which is saturated with wholesome +influences. For it is a rule of development that if the environment is +faulty the organism is impaired. + + + + +CHAPTER VI + +PRENATAL INFLUENCES + + +=All That a Child Possesses at Birth Not Necessarily Hereditary.--=We come +now to the more specific discussion of what may happen to offspring of +mammals, and particularly man, in the interval between fertilization and +birth; that is, during the intra-maternal period. We have already seen +that anything affecting the offspring during this period has to be +reckoned as environmental, our formula reading, Mammal = germ + +intra-maternal environment + external environment. It is evident, then, +that all that a child possesses at birth is not necessarily hereditary, +since the unborn child may be influenced by conditions prevailing in +either parent. + +=The Myth of Maternal Impressions.--=In order to clear the way for more +urgent matters let us first inquire into the question of the production of +changes in the unborn child as a result of "maternal impressions." As the +tale generally goes, structural changes are produced in the unborn child +corresponding to some mental experience of the mother, usually a vivid +impression of strong emotion, but when a given individual is pinned down +to sources, it is usually a case of hearsay. + +Stock examples are: The mother sees a mouse with the result that a +mouse-shaped birthmark occurs on the child; or she sees a crushed hand +and in consequence bears a child later with some of the bones of the hand +missing; the mother touches her body when frightened and thus marks the +unborn child on the corresponding part of the body; or she produces beauty +in the child by long contemplation of a picture of a beautiful child; and +so on almost endlessly. The favorite is usually the production of a red +birthmark or marks on the child's body by strong desire on the part of the +mother for strawberries, tomatoes, etc.--the fruit must be red since the +mark is red--or by fright from seeing a fire. As a matter of fact it is +not uncommon for the capillary blood vessels of the skin of a new-born +infant to remain dilated in spots instead of contracting as they normally +should do. The result is more or less of a red or "flame" spot. It is easy +to see, therefore, why such birthmarks are so frequently referred back by +the credulous mother to her desire for or fear of some red object. + +An analysis of the case of a child shuddering at the sight of peaches is +of interest in this connection. The child showed the greatest aversion to +peaches, particularly to the fuzzy covering. The mother's explanation was +that peaches were unusually plentiful the year the child was born and that +she had worked hour after hour at peeling and canning peaches shortly +before his birth until she had become thoroughly sick of them. This +acquired aversion on her part she believed had been transferred to the +child. A few questions revealed the fact, however, that the mother, +herself, had never liked peaches and when asked if they were distasteful +to any other member of her own family she exclaimed, "Oh, yes, my mother +would shudder and shake if a peach were brought near her." And there we +have it. The idiosyncrasy was an inherited one as many similar +peculiarities are. The mental impression produced in the mother by her own +experience with peaches had nothing to do with its occurrence in the +child. + +Very frequently also one encounters the mother who is sure she has +engendered musical ability in her child by constant practise and study of +music during pregnancy. The child is musical; what better evidence does +one want! It seems never to occur to such a mother that the child is +musically inclined because she herself is, as is evinced by her own desire +in the matter even if she is not a skillful performer. + +When we take into account the extreme credulity of many people, the +unconscious tendency of mankind to give a dramatic interpretation to +events where causes are not certainly known, the hosts of coincidences +that occur in life, and the multitude of cases where something should +happen but nothing does, we are compelled to believe that the whole matter +of direct specific influence of the mother's mind on the developing fetus +is a myth. After seeing the conditions which prevail in Mendelism, for +example, it will take strong faith to believe that a mother with duplex +brown eyes can "think" or "will" blue eyes on her baby, yet this would be +a mild procedure compared to some we are asked to accept by believers in +the transmission of maternal impressions. Most of all, however, when we +recall the actual relation between the embryo and the mother--a narrow +umbilical cord is the sole means of communication between the two--the +physical impossibility of a connection between some particular mental +happening of the mother and a corresponding specific modification in the +fetus becomes evident. For there are no nerves in the umbilical cord, the +only path of communication between mother and fetus being the indirect one +by way of the blood stream. Even this method of communication is limited +inasmuch as the mother's blood does not circulate through the blood +vessels of the fetus. Gaseous and dissolved substances are merely +interchanged through the thin walls of the capillary blood vessels in the +placenta. + +=Injurious Prenatal Influences.--=However, the denial that a particular +mental impression of the mother is associated with a particular structural +defect in a child does not carry with it the implication that prenatal +influences of all kinds are negligible factors. On the contrary any +deleterious effect which can reach the fetus through absorption from the +blood of the mother may be of grave consequence. There is not the least +doubt that malnutrition or serious ill-health on the part of the mother +often has a prejudicial effect on the unborn offspring. Severe shock or +grief, worry, nervous exhaustion, the influence of certain diseases, +poisons in the blood or tissues of the parent, such as lead, mercury, +phosphorus, alcohol and the like, may all act detrimentally, but they +operate either by rendering nutrition defective, by direct poisoning, or +by generating toxins in the blood of the parent which then poison the +fetus. Among the latter may be mentioned the toxic products of +tuberculosis and certain other bacterial diseases. Such factors operating +on the unborn young or even on the germ-cells may cause malformations, +arrests of development, instabilities of the nervous system, and general +physical or mental weakness. The effects are general, however, and not +specific. + +To distinguish certain of these prenatal effects, particularly those of +certain diseases or poisons, from true hereditary influences they are +frequently spoken of as cases of _transmission_ rather than inheritance +from parents. Some writers use the technical term _blastophthoria_, or +false-heredity, extending the meaning so as to include also any damage +that might be inflicted on the germ-cells. + +=Lead Poisoning.--=By way of illustration of how certain cumulative +poisons may act we may examine a tabulation of eighty-one cases of lead +poisoning as reported by Constantin Paul (Fig. 29, p. 164). + +The table requires little comment. The disastrous effects of such +poisoning are apparent in every class of cases. The sixth class where the +husband alone was exposed to lead shows that the poison can operate +directly through the germ-cell. Other observers note that in the children +of workers in lead, there is a distressing frequency of feeble-mindedness +and epilepsy. + +That lead poisoning operating through the germ-cells of the father can +affect the development of the young harmfully is well shown in Fig. 30, p. +165, which is a photograph of two young rabbits from the same litter The +white young one is from a normal albino mother mated to an albino father +which had received lead treatment. The pigmented young one is from the +same albino mother by a normal pigmented father. Although the white +father was considerably larger than the pigmented father, nevertheless the +young of the former, because of the harmful effects of the lead, is +distinctly smaller and less lively. A number of litters, each from the +same mother but in part from a lead-poisoned father and in part from a +normal father, have been secured. All show more or less the same results. +The experiments are still in progress in the department of experimental +breeding at the University of Wisconsin. + + -------------------------------------------------------------------- + |Number of cases. + | +---------------------------------------- + | |Number of pregnancies. + | | +--------------------------------- + | | |Abortions, premature labor, and + | | | stillbirths. + | | | +--------------------------- + | | | |Infants born living. + | | | | +-------------------- + | | | | |Remarks. + ---------------------|-----|------|-----|------|-------------------- + 1. Mother showing | | | | |One infant died + symptoms of plubism | 4 | 15 | 13 | 2 | within 24 hours. + | | | | | + 2. Mother working in | | | | | + type foundry, all | | | | | + of whose previous | | | | | + pregnancies had | | | | |Four of these died + been normal | 5 | 36 | 29 | 7 | in first year. + | | | | | + 3. Mother who during | | | | | + period of work in | | | | |After ceasing to + type foundry had | | | | | work had + five pregnancies | 1 | 5 | 5 | 0 | healthy child. + | | | | | + 4. Mother working | | | | |When away from + intermittently in | | | | | work for some + type foundry; | | | | | period of time + while working | | | | | gave birth to + there | 3 | 3 | 3 | 0 | healthy children. + | | | | | + 5. Mother in whom | | | | | + blue line on gum | | | | | + the only sign of | | | | | + lead poisoning | 6 | 29 | 21 | 8 | + | | | | |Of these, eight died + 6. Husband alone | | | | | in first year, + exposed to lead | ? | 32 | 12 | 20 | four in second, + | | | | | five in third. + -------------------------------------------------------------------- + +FIG. 29 + +Tabulation of eighty-one cases of lead poisoning recorded by Constantin +Paul (from Adami). + + +[Illustration: Fig. 30 + +Photograph of young rabbits from the same litter, the smaller one stunted +by lead-poisoning of its father (Courtesy of Professor L. J. Cole).] + + +=The Expectant Mother Should Have Rest.--=The mere matter of rest on the +part of the pregnant mother is, judging from the work of Pinard, a +Frenchman, and his pupils, an important one. In a number of detailed +investigations they have shown that rest on the part of the working mother +during the last three months before the child is born results in the +production of markedly larger and more robust children than those born of +mothers equally healthy but who have not had such rest. Moreover the +danger of premature birth is considerably lessened. + +=Too Short Intervals Between Children.--=Too short an interval between +childbirths would also seem to be an infringement on the rights of the +child as well as of the mother. Thus Doctor R. J. Ewart ("The Influence of +Parental Age on Offspring," _Eugenic Review_, October, 1911) finds that +children born at intervals of less than two years after the birth of the +previous child still show at the age of six a notable deficiency in +height, weight and intelligence, when compared with the children born +after a longer interval, or even with first-born children. + +=Our Duty to Safeguard Motherhood.--=Doubtless the unventilated factory +and tenement also do their share, even though we can give no exact +quantitative measure of it. Obviously, it becomes a civic duty to protect +as much as possible all members of our social system from such injurious +factors as have just been discussed. It is particularly necessary to +safeguard mothers before confinement, especially working mothers. + +=Expectant Mothers Neglected.--=According to the claims of life insurance +men, expectant mothers are the most neglected members of our population. +Doctor Van Ingen, of New York City, estimates that ninety per cent. of +women in this country are wholly without prenatal care. Yet every +prospective mother should be taught the probable meaning of such symptoms +as headache, hemorrhages, swelling of the feet and disturbed vision. She +should realize the importance of submitting a sample of urine for analysis +at least once a month before childbirth and twice a month for a while +thereafter. She should be specially informed regarding work, exercise, +diet and dress. A recent government bulletin written by Mrs. Max West +which may be had free by writing to the Children's Bureau, Department of +Labor, Washington, D. C., gives much useful information on this subject. + + +ALCOHOLISM + +=Unreliability of Much of the Data.--=One of the most important poisons +that plays a prominent part among ante-natal influences is alcohol. But +when it comes to a study of the problem of alcoholism from the standpoint +of heredity and parental influences we meet with many difficulties, +prominent among which are the inaccuracy and unreliability of many of the +statistics brought forward in this connection. Many of the results are +vitiated by the prejudices of propagandists who propose to make a case +either for or against alcohol as a beverage whether or not the facts +justify their conclusions. When one tries to view the matter with an open +mind he finds that there is a deplorable lack of statistics which are not +susceptible to more than one interpretation. However, using as much as +possible what seems to be unbiased data, the evidence is almost wholly +against alcohol as a beverage, at least to any immoderate extent. + +=Alcohol a Germinal or Fetal Poison.--=The bad effects as far as offspring +are concerned reveal themselves in the main under the category of "false +heredity," i. e., germinal or fetal poisonings rather than of heritable +changes induced in the germ-cells. Most investigators feel that there are +too many criminal, imbecile, insane and unhealthy persons among the +offspring of drunkards to dismiss the matter as a coincidence. In an +investigation of Imbault, for example, we find recorded of one hundred +tuberculous children that while forty-one were of tuberculous parentage, +thirty-six per cent, were the offspring of inebriates. Furthermore Imbault +cites the observations of Arrivé on 1,506 cases of juvenile meningitis to +the effect that this malady is twice as frequent in the children of +alcoholic as in those of tuberculous parentage. It has been proved by +Nicloux (_L'Obstetrique_, Vol. 99, 1900) that in dogs and guinea-pigs +alcohol passes through the placenta and may be detected in fetal tissues; +hence it is in position to influence the fetus. He found that in a very +short time the amount of alcohol in the blood of the fetus about +paralleled that in the blood of the mother. + +=Progressive Increase in Death-Rate of Offspring of Inebriate Women.--=In +an investigation on the effects of parental alcoholism on the offspring, +Sullivan (_Journal of Mental Science_, Vol. 45, 1899) gives some +important figures. To avoid other complications he chose female drunkards +in whom no other degenerative features were evident. He found that among +these the percentage of abortions, still-births and deaths of infants +before their third year was 55.8 per cent. as against 23.9 per cent. in +sober mothers. In answer to the objection that this high percentage may be +due merely to neglect, and not to impairment of the fetus by alcoholism, +he points out the fact based on the history of the successive births, that +there was a progressive increase in the death-rate of offspring in +proportion to the length of time the mother had been an inebriate, thus: + + ------------------------------------------------------------- + |No. of|Per cent.|Per cent. dying| Total + |cases |born dead| before 3 |percentage + -----------------|------|---------|---------------|---------- + First births | 80 | 6.2 | 27.5 | 33.7 + Second births | 80 | 11.2 | 40.8 | 50.0 + Third births | 80 | 7.6 | 45.0 | 52.6 + Fourth and fifth | 111 | 10.8 | 54.9 | 65.7 + Sixth to tenth | 93 | 17.2 | 54.8 | 72.0 + ------------------------------------------------------------- + +=Views of a Psychiatrist on Alcohol.--=Forel, who for years was the +psychiatrist at the head of a large insane asylum at Zurich, Switzerland, +has this to say about the effects of narcotic poisons and alcohol in +particular: + + "The offspring tainted with alcoholic blastophthoria suffer various + bodily and physical anomalies, among which are dwarfism, rickets, a + predisposition to tuberculosis and epilepsy, moral idiocy, and idiocy + in general, a predisposition to crime and mental diseases, sexual + perversions, loss of suckling in women, and many other misfortunes." + +In another passage he[6] remarks as follows: + + "But what is of much greater importance is the fact that acute and + chronic alcoholic intoxication deteriorates the germinal protoplasm of + the procreators.... The recent researches of Bezzola seem to prove + that the old belief in the bad quality of children conceived during + drunkenness is not without foundation. Relying on the Swiss census of + 1900, in which there figure nine thousand idiots, and after careful + examination of the bulletins concerning them, this author has proved + that there are two acute annual maximum periods for the conception of + idiots (calculated from nine months before birth); the periods of + carnival and vintage, when the people drink most. In the wine-growing + districts the maximum conception of idiots is enormous, while it is + almost nil at other periods. Moreover, these two maximum periods come + at the time of year when conception is at a minimum among the rest of + the population, the maximum of normal conceptions occurring at the + beginning of summer." + +Another interpretation of Bezzola's results has been suggested to the +effect that the license of these periods enables the defective members of +the community, such as the feeble-minded, an opportunity of mating more +readily and that consequently the result is direct inheritance of idiocy +and allied defects instead of idiocy produced through alcoholic poisoning +of the parental germ-cell. + +=Other Views.--=There are indeed many competent investigators who believe +that alcoholism in parents has little or no part in the direct production +of mental defects in children. For instance, Tredgold quotes Doctor +Ireland's observations that although at New Year, when the fishermen +return, the whole population of certain villages in Scotland gets drunk, +there is no noticeable excess of defectives born nine months later, and +remarks further that, "I have histories of idiots conceived under such +circumstances, but so I have of normal children, and my opinion is, that +while this may be a cause in some cases, the number of instances in this +country at any rate is exceedingly small." Again, Goddard, one of our best +known American students of feeble-mindedness, who has made careful study +of this point under especially favorable conditions, feels that his data +do not prove that alcoholism of either the father or the mother causes +feeble-mindedness in the child. He concludes, "Everything seems to +indicate that alcoholism itself is only a symptom; that it for the most +part occurs in families where there is some form of neurotic taint, +especially feeble-mindedness." Goddard, however, in common with many other +observers, notes that miscarriages and deaths in infancy are far higher +among inebriates than among abstainers. + +Doctor Mjöen cites an interesting parallel between the increase of +feeble-mindedness in Norway and a period from 1816 to 1835, when every one +was permitted to distil brandy. In some districts many of the farmers +distilled brandy from corn and potatoes, and in such regions during this +period feeble-mindedness increased nearly one hundred per cent. Later the +home distillation of brandy was stopped. According to Doctor Mjöen, "The +enormous increase in idiots came and went with the brandy." He is +inclined to believe, however, that the alcohol operated injuriously mainly +on stocks already defective. + +=The Affinity of Alcohol for Germinal Tissue.--=Nicloux and Renault have +shown that alcohol has a decided affinity for the reproductive glands. In +individuals who have recently taken alcohol the proportion of alcohol in +the gonads is soon almost equal to the amount found in the blood. Thus in +experiments on mammals it was found that the proportion of alcohol in the +ovary to that in the blood was as three to five, and in the testis as two +to three. This would afford abundant opportunity for alcohol to act +directly on the spermatozoon or the ovum. + +A number of different investigators concur in finding that the germ-glands +of the male human inebriate in many cases show more or less atrophy and +other degenerative changes. In guinea-pigs which have been repeatedly +intoxicated with alcohol, Stockard found that while he could detect no +visible abnormality in the gonad, nevertheless their defective and +weakened progeny showed that the germ-cells had been affected. + +=Innate Degeneracy Versus the Effects of Alcohol.--=Many observations on +human beings have been brought forward which at first sight seem to +indicate that noticeable defects, particularly mental and nervous, occur +with appalling frequency in children resulting from conception during +intoxication, although, unfortunately, the evidence is rarely clear as to +whether the defects are really due to the effects of the alcohol or to the +fact that the parent or parents were degenerate to begin with. + +A very interesting human case cited by Forel on the authority of +Schweighofer is that of a normal woman who had three sound children when +married to a normal man. After the death of this husband she married an +inebriate by whom she had three other children. One of these suffered from +infantilism, one turned out to be a drunkard, and the third became a +social degenerate and drunkard. Moreover the first two contracted +tuberculosis, although hitherto the family stock had been free from this +malady. Ultimately the woman married again and by this third husband, who +was normal, she again had sound children. Similar cases might be cited, +as, for example, a record of eighty-three epileptics, of whom sixty had +drunken parents, but it can be urged against all of them, of course, that +the defective offspring were due to an innate degeneracy of the drunken +parent which made him a drunkard rather than to the effects of the alcohol +he took. While one is skeptical as to the validity of this objection in +all of the many cases which occur with such monotonous frequency in man, +there is no way of escaping such an interpretation with the evidence at +hand. It must be admitted, moreover, that there are many families with one +or both parents alcoholic in which the children are not mentally +defective. + +=Experimental Alcoholism in Lower Animals.--=Many of the objections that +exist in the case of man, however, do not apply in that of lower animals. +If normal animals are experimentally alcoholized and are shown to produce +defective offspring under such conditions, then in their cases at least, +the disorders in the offspring must be due to the effects of alcohol and +not to an innately degenerate condition of the parent. Disorders similar +to some of those seen in the children of alcoholics do actually result in +alcoholized animals of one kind or another. + +Against the earlier experiments on animals it has been urged that too few +individuals were used to give conclusive results, but this objection can +not be brought against the recent experiments of Stockard. While he has +published accounts of his work in various scientific periodicals lately, +the reader will find a full statement of his own experiments, together +with a review of the whole subject of experimental alcoholism in animals +and the effects on progeny in _The American Naturalist_, Vol. XLVII, +November, 1913, together with a useful bibliography. + +Before taking up Stockard's results we may select a few of the more +significant experiments made earlier by other investigators. + +Laitinen alcoholized rabbits and guinea-pigs. He found that the treated +individuals had more still-born young than the control, and also that +growth of the living young was retarded. His alcoholized rabbits and +guinea-pigs produced more young than did the normal individuals used as a +control. Laitinen's studies on man, together with three other studies of +the Eugenics Laboratory in London, show that in man also more children are +born to alcoholics than to normal parents. Goddard's investigations in +America corroborate this fact. + +Ceni found that only 43 per cent. of the eggs from alcoholized fowls +developed normally, as against 77 per cent. of normal development in the +controls. Moreover the eggs of alcoholic fowls were shown to be less +resistant to adverse conditions than normal eggs from the fact that +fluctuations of temperature at the beginning of incubation kept all the +alcoholic eggs from developing perfectly, while 27 per cent. of the +control eggs developed normally under the same adverse circumstances. + +Hodge made a pair of dogs alcoholic. Of 23 pups obtained from the pair, 8 +were deformed and 9 were dead; 4 alone were viable. From a control pair of +dogs 45 pups were obtained, of which 4 were deformed, none were born dead, +and 41 were viable. + +=Stockard's Experiments on Guinea-Pigs.--=Stockard's experiments +demonstrate that the offspring of mammals may be injured or modified in +their development by treating either parent repeatedly with alcohol. The +guinea-pigs used in the experiment were all first tested by normal matings +and found to yield normal offspring. The alcohol was given to them by +inhalation. It was found to be readily taken into the animals' blood and +to produce intoxication. While guinea-pigs alcoholized in this way as +often as six times a week for two and one-half years would maintain their +own bodily vigor and health apparently, the deleterious effects on their +progeny were marked. The defects were general rather than specific, +although the central nervous system and special sense organs were +apparently affected most. + +Out of 119 total young produced by the alcoholic animals, only 52, or less +than 44 per cent., survived, whereas out of 64 young produced from normal +parents used as a control for the experiment, 56, or over 87 per cent., +survived. In some cases alcoholic males were mated with normal females, in +other, alcoholic females with normal males. In still other instances both +parents were alcoholic. + +The results are summarized in the accompanying table (Fig. 31), taken from +Stockard's paper: + + CONDITION OF THE OFFSPRING FROM GUINEA-PIGS TREATED WITH ALCOHOL + + ----------------------------------------------------------------- + |Number of Matings + | +-------------------------------------- + | |Negative Result or Early Abortion + | | +--------------------------------- + | | |Stillborn Litters + | | | +---------------------------- + | | | |Number Stillborn Young + | | | | +--------------------- + | | | | |Living Litters + | | | | | +---------------- + | | | | | |Young Dying Soon + | | | | | | After Birth + | | | | | | +--------- + Condition of | | | | | | |Surviving + the Animals | | | | | | | Young + --------------------|-----|----|----|------|----|------|--------- + Alcoholic [male] by | | | | | | | + normal [female] | 59 | 25 | 8 | 15 | 26 | 21 | 33 + Normal [male] by | | | | | | | + alcoholic [female]| 15 | 3 | 3 | 9 | 9 | 9 | 10 + Alcoholic [male] by | | | | | | | + alcoholic [female]| 29 | 15 | 3 | 6 | 11 | 7 | 9 + SUMMARY | 103 | 43 | 14 | 30 | 46 | 37 | 52 + Normal [male] by | | | | | | | + normal [female] | 35 | 2 | 1 | 4 | 32 | 4 | 56 + 2d generation | | | | | | | + by normal | 3 | 0 | 0 | 0 | 3 | 0 | 4 + 2d generation | | | | | | | + by alcoholic | 3 | 0 | 2 | 5 | 1 | 0 | 2 + | | | |1 def.| | | + 2d generation | | | | | | | + by 2d generation | 19 | 7 | 0 | 0 | 12 | 6 | 13 + | | | | | |1 def.| + Female treated | | | | | | | + during pregnancy | 4 | 0 | 0 | 0 | 4 | 1 | 7 + ----------------------------------------------------------------- + +FIG. 31 + +Table showing condition of the offspring from guinea-pigs treated with +alcohol (after Stockard). + +Lines four and five give a comparison between the 103 total matings of all +treated individuals and 35 normal matings. In the first case almost 42 per +cent. of the matings gave negative results or early abortions, whereas in +the normal control matings, failure to yield a full-term litter occurred +in only two cases. The 103 matings of alcoholic animals gave only 46 +living litters, or about 45 per cent. On the other hand the 35 control +matings produced 32 living litters, or 91-1/2 per cent. It will be +observed also that from such of the 103 matings of alcoholics as produced +young there were 30 still-born, 37 which died soon after birth, and only +52 surviving young, whereas from the 35 matings of normal individuals +there were only 4 still-born young, 4 which died soon after birth, and 56 +surviving young. + +The bottom line of the table, although, as Stockard points out, containing +too few cases to prove wholly convincing, indicates that alcoholizing +erstwhile normal females during pregnancy was not particularly harmful to +the embryos _in utero_. + +Some of the most interesting results were obtained when offspring termed +second generation animals, derived from alcoholic parents though not +themselves treated with alcohol, were mated in various ways. When such +individuals were mated with normal individuals, although the litters were +small, the results were normal, the normal mate having seemingly +counteracted any defects which might have lurked in the second generation +animal. On the other hand, out of three matings of second generation +animals with alcoholic individuals, two produced still-born young, of +which one was markedly deformed, while the third yielded two living young. + +However, the most striking results were obtained when two second +generation individuals, the offspring of alcoholic parents, were bred +together. Although themselves untreated, these individuals, of which 19 +matings were made, produced as many or more defective young than did their +alcoholic parents. Seven of the matings were unfruitful. The remaining 12 +matings gave living litters consisting of 19 individuals in all. Six of +these showed various nerve disorders (spasms, epileptic-like seizures, +etc.) soon after birth; one was eyeless and otherwise deformed. + +=Stockard's Interpretation.--=Stockard's interpretation of his experiments +is as follows: "Mammals treated with injurious substances, such as +alcohol, ether, lead, etc., suffer from the treatments by having the +tissues of their bodies injured. When the reproductive glands and +germ-cells become injured in this way they give rise to offspring showing +weak and degenerative conditions of a general nature, and every cell of +these offspring having been derived from the injured egg or sperm-cell are +necessarily similarly injured and can only give rise to other injured +cells and thus the next generation of offspring are equally weak and +injured and so on. The only hope for such a line of individuals is that it +can be crossed by normal stock, in which case the vigor of the normal +germ-cell in the combination may counteract, or at any rate reduce, the +extent of injury in the body cells of the resulting animal." + +He also believes that various deformities and developmental arrests such +as harelip and cleft-palate may similarly be cases of transmission rather +than true inheritance, due to the weakening of the germ-cells in some way, +or to some lack of full vigor in the uterine environment. + +=Further Remarks on the Situation in Man.--=Returning now to the question +of alcoholism in man, it seems in view of the strong circumstantial +evidence in the case of man himself, together with the result of +experiments on animals, that little doubt remains that excessive +alcoholism might result in the production of defective offspring. On the +other hand an antecedent degeneracy or neural instability undoubtedly +plays an important part in many cases, in the original production of +drunkards, and when such occurs, it, as well as the direct effects of +alcoholic poisoning, must be reckoned with in the effects on progeny. +Studies carried on by Pearson, Elderton and Barrington of the Eugenic +Laboratory in London lead these investigators to the conclusion that +extreme alcoholism is a _result_ not a _cause_ of degeneracy. That is, the +degeneracy is due to the defective stock, not to alcohol. They cite in +evidence their records of four thousand school children of alcoholic and +of sober parents, which fail to show any unfavorable effect of alcohol on +offspring. Some of their critics, however, maintain that they did not +choose subjects who were sufficiently alcoholic to give the injurious +results that might legitimately be expected among the offspring of +excessive drinkers or habitual drunkards. + +Where children show a hereditary inclination toward drink, unquestionably +one of the strongest factors is the inheritance of the same disposition, +the same unstable nervous constitution and its accompanying lack of +self-control which led the parent to drink, rather than the inheritance of +the effects of the drink on the parent. For in many cases a parent may not +become a drunkard until after the children who also become drunkards are +born. That the tendency to drink immoderately is frequently due to a +strain of feeble-mindedness or epilepsy becomes more evident every day. +In many of the so-called "periodical" drunkards, the accompanying features +of their periodic attacks of drink-craving, such as clouding of memory, +restlessness and depression, are those commonly associated with ordinary +epileptic attacks. + +=Probably Over Fifty Per Cent. of Inebriety in Man Due to Defective +Nervous Constitution.--=Branthwaite, an English authority on drunkenness, +finds that about sixty-three per cent. of the inebriates who come to his +notice are mentally defective. In alcoholic insanities heredity is a +potent factor. It is coming to be realized more and more that pronounced +alcoholism is due in a large percentage of cases, perhaps over half, to a +defective nervous make-up. While it is true that many drunkards would not +develop without free access to alcohol, on the other hand many would never +develop without a bad heredity back of them, which gives them a peculiar +nervous constitution that renders alcohol an undue stimulus. In a recent +report of the New York State Hospital Commission it is stated that in +fifty-four per cent. of the cases of alcoholic insanity, a family history +of insanity, epilepsy or nervous disease exists. Thus in the presence of +alcohol most of these unfortunates are helpless pawns of a hereditary +weakness. + +So when the question of alcoholism is viewed from all angles, the children +of the human drunkard would seem to run a double menace of misfortune, +since they may be subject both to the direct poisoning effects of alcohol +and the results of an inheritable degeneracy. + +=Factors to Be Reckoned With in the Study of Alcoholism.--=In any +thoroughgoing study of alcoholism in man many factors will have to be +reckoned with. First of all there is the question of inherent lack of +control. This is probably the principal thing inherited where heredity +truly enters as a factor. That example and social environment are +important factors in addition to or in place of heredity is clear, too, +when we observe that often it is the boys only who take after a drunken +father, for there is no evidence that the inherited tendency when it +really exists is at all sex-linked. Again, in certain occupations carried +on under unwholesome influences relief is frequently sought in alcoholic +stimulants, and such custom may easily crystallize into habit. +Furthermore, the accustoming young children to doses of alcohol, or the +unborn young to alcohol through the body of a drunken mother, may be +strongly contributory toward establishing inebriety in certain cases. As +we have seen from an abundance of experimental data on animals, moreover, +the nurture effects on germ-cells may result in the production of weakened +offspring. Such offspring in the case of man are probably less able to +withstand temptations of all kinds and hence readily succumb to the +habit-forming effects of alcohol if once its use is begun. Lastly, it must +not be forgotten that alcoholism in the father usually means poverty and +the subsequent accompaniment of malnutrition and neglect of the children, +and this in itself may not only account for poor development of the +latter, but may also be strongly contributory toward establishing the +habit of alcoholism in them. + +An inherent bias plus most of the other conditions just enumerated is the +not unusual lot of the offspring of drunkards. + +=Venereal Diseases.--=There is yet another very considerable class of +maritally unfit who in any conscientious discussion of unfitness for +marriage or of racial improvement must be considered. I refer to those who +are afflicted with the diseases which are inseparably associated with the +so-called "social evil." To _gonorrhea_, one of the most prevalent of +these diseases, more than one-fourth of our total one hundred and ten +thousand blind in the United States are said to owe their affliction. +Milder types of eye disease may also result from such infections. As much +as eighty per cent., or some say practically all blindness in children +born blind is caused by it, the infection occurring at the time of birth +or within a few days thereafter. The terrible consequences of this disease +to the innocent wife would alone make its discussion imperative. + +=The Seriousness of the Situation.--=Unfortunately the insidious nature of +gonorrheal infections is unknown to most persons. A cure is apparently +effected, yet as a matter of fact the germs may live for years and, if in +the male, later be transmitted to the wife, subjecting her to a future of +invalidism and misery. Reliable statistics from various medical +authorities reveal the appalling fact that seventy-five per cent. or more +of the surgical operations for inflammatory pelvic disorders peculiar to +women, such as pus tubes and peritonitis, are attributable to this +disease, as is also the involuntary sterility of forty-five per cent. of +childless women. Unwelcome as the fact is there is an abundance of +evidence to show that a large percentage of men in particular have at +some period of their life been infected with venereal disease. Of our +fourteen million males in the United States under the age of thirty we +find estimates by some specialists in venereal diseases to the effect that +five million of them, that is, one out of three, suffer from some one of +the social diseases or their consequences. Doctor Hugh Cabot, one of the +chief surgeons of the Massachusetts General Hospital at Boston, a member +of the faculty of the Harvard Medical School and president of the American +Association of Genito-Urinary Surgeons, has this to say about the +situation: "We have of late years heard much about the frequency and +serious consequences of tuberculosis; it has been dubbed the 'white +plague,' and so active has been the campaign that a wide-spread +understanding of this serious disease has resulted. It may safely be +averred that in the urban population at least there are two, and perhaps +three, individuals with syphilis to every one with tuberculosis. The +frequency of gonococcus infection is much higher." He believes that over +half the male population acquire a gonococcus infection at some period of +their career. While as a layman, one can not but feel that a specialist's +estimate may run unduly high because of the fact that he is encountering +an inordinate proportion of such maladies every day, still such +specialists are in position to get at the truth as no other person can and +their calculations are probably not grossly in error. In any event any one +who has progressed in worldly knowledge beyond the naïveté of a child must +recognize the appalling prevalence of these maladies. + +=Infantile Blindness.--=So serious has the matter of infantile blindness +become that some state boards of health and some city health departments +supply all physicians and midwives with specially prepared packages +containing cotton and nitrate of silver solution for preventive or +curative treatment of the eyes of all new-born children. At the time of +the first bath each eye is carefully washed with a separate pledget of +cotton saturated with boric acid solution. Each then receives a drop of +the silver solution, which is made just strong enough to kill any +gonococci that might be present without itself inflaming the eye. Water +used in bathing the baby's body of course is not allowed to come in +contact with its eyes. Such treatment should be given every child no +matter how unsuspicious the circumstances may be. German authorities who +have been following this method now for some years assure us that +nineteen-twentieths of the blindness of infancy can thus be prevented. + +=Syphilis.--=As to _syphilis_, another and even more terrible of these +diseases, we have before us the absurd fact that while thousands upon +thousands of dollars are being spent to establish a rigid inspection and +preventive measures against the spread of a very similar disease in the +horse, this malady in man is allowed to pass unchallenged and we are +confronted by the gruesome certainty that there are hundreds of these +diseased persons about us to-day who, on their mere affirmation that they +are unmarried and of age, will be given the right to marry and thus +produce families of infected children irrevocably doomed to early death or +to lifelong misery. + +While syphilis is most commonly spread through relations between the +sexes, it may be acquired in various other ways, as for example, through a +cut in shaving with the same razor an infected individual has used. It is +commonly transmitted from parent to child. Practically every prostitute is +a center of dissemination. Katherine Bement Davis has shown in her studies +made at the New York State Reformatory for Women that while ordinary +clinical tests show that apparently only twenty-one per cent. of these +women are infected with venereal disease, more careful laboratory tests +showed at least ninety per cent. to be infected. + +Syphilis is caused by _Treponema pallidum_, a small unicellular animal +parasite. Given access to the blood by any means whatever, possibly even +through an abrasion in the lip by means of a kiss, it multiplies rapidly +and any part or organ of the body may be attacked. Usually a small sore +occurs at the point of entrance to the body, but often it heals up readily +with little indication of the seriousness of the infection. + +The development of the malady is insidious and long continued. As a matter +of clinical convenience physicians divide its progress into successive +stages although in reality the transitions are frequently variable and ill +marked. The symptoms that arise within the first few months or even years +are readily controlled by appropriate treatment, but to insure a cure +prolonged and most thoroughgoing treatment is imperative. The symptoms +disappear so completely after a short period of treatment that it is very +difficult to persuade the average patient that he is not yet cured. Two +years at least are none too short a period of treatment, yet the majority +of patients, fully convinced that they are merely being exploited by the +physician as a source of revenue, drift away at the end of a few months. +As a matter of fact, however, the germs usually persist long after the +obvious symptoms of the disease have disappeared, and in consequence many +of the most serious results of syphilis may not manifest themselves for a +period of perhaps ten, twenty or thirty years. + +=Some of the Effects.--=It is now known that _paresis_, also termed +general paralysis or softening of the brain, is probably invariably due to +syphilis. The work of Flexner and Noguchi on _paresis_ and _tabes +dorsalis_ show that always in such afflictions the tissues of the central +nervous system have been invaded by the parasite. The original infection, +however, may have occurred so long before as to have been almost forgotten +by the patient. Thus many an apparently robust man is stricken down in the +prime of life. Earlier and prolonged treatment would in all probability +have eradicated the germs and thus prevented the mental breakdown, which +can not be cured by any known treatment. Postmortem examination always +shows that the _Treponema_ has wrought wide-spread damage in the brain. +The frequency of paresis may be realized when one learns that in some +regions it is responsible for about one-fifth of all cases of insanity +sent to hospitals for the insane. It ranks next to the highest as a cause +of insanity. Statistics show that in the state of New York more deaths +result annually from paresis than from smallpox, tetanus, malaria, +dysentery and rabies all combined. + +In some cases the disease attacks the membranes of the brain and the small +blood vessels giving rise to a still different type of mental disorder. +Practically all patients with _locomotor ataxia_ owe their condition to an +antecedent syphilis. Moreover it is one of the important causes of +_arterio-sclerosis_, or hardening of the blood vessels, and is also a +prominent factor in certain forms of heart-disease, as well as by no means +an unimportant cause of blindness in children. + +As to specific cases of the effects of this disease on descendants the +literature of the subject is crowded full. While it is needless to conduct +the reader through a chamber of horrors by reviewing clinical cases, it is +desirable to point out in a general way some of the effects. Doctor George +H. Kirby, director of Clinical Psychiatry, Manhattan State Hospital, says: + + "We find that when either the father or the mother suffers from + paresis that many other members of the family may be infected with + syphilis, and furthermore, we find that a large number of children in + these families are feeble-minded, nervous, or in other ways abnormal. + Doctor Plant examined a group of 100 children, the offspring of cases + of paresis, and found that 45 per cent. were plainly damaged mentally + or physically, or in both fields; the blood test showed that one-third + of these 100 children had the syphilitic poison in their systems. + + "Another investigator found in a group of 139 children, the + descendants of parents who had syphilitic nervous disease, that over + 25 per cent. were definitely feeble-minded or affected with some + serious nervous disorders. + + "Other studies indicate that there exists a close relation between + syphilis and many of the hitherto unexplained cases of + feeble-mindedness, including idiocy, imbecility, infantile paralysis, + and some forms of epilepsy. While the question is not yet settled, it + appears that syphilis is the real cause of many of these cases of + mental defect in children." + +Still other investigators give details of physical afflictions and +distortions, of suppressed development, of inordinate percentages of +stillbirths--perhaps the most merciful lot for the little victims--but +sufficient has been said to indicate the full horror of the situation. + +Goddard,[7] although not minimizing the terrible nature of the disease, +finds little evidence in his studies that syphilis in parents is a +specific cause of feeble-mindedness. + +=A Blood Test.--=Fortunately a delicate blood test known as the Wasserman +test has been discovered by means of which, through an examination of a +few drops of blood, any trace of syphilitic poison which exists in the +body may usually be detected. This is true even though the individual may +at the time show no visible symptoms of syphilis. The test is therefore of +great value in detecting the latent germs of syphilis in individuals who +have apparently been cured, and also often in making an early diagnosis of +paresis. The Wasserman test, however, is reliable only in the hands of a +skilled operator. It may occasionally give a positive reaction when +syphilis does not exist and on the contrary a negative when it is present. +The _luetin_ test is also now applied by some specialists, but is too new +a test to have come into general use. It works on the same principle as +the tuberculin test for tuberculosis. Some army physicians now also give +what is termed a provocative Wasserman. That is, in a suspicious case +which gives only negative results by an ordinary Wasserman, they can get, +if syphilis really exists, a positive reaction after giving small doses of +potassium iodide or salvarsan. + +It should be well understood by every one that syphilis is usually curable +provided the patient is given modern scientific treatment by a _competent_ +physician. I emphasize competent because there are so many quacks in this +field that one undergoing treatment can not be too careful in assuring +himself of the competency of the physician. In even a case of long +standing, where the symptoms have been in abeyance for a number of years, +the disease can be cured provided it has not developed into an active +cerebro-spinal type, and even the latter can be much benefited by proper +treatment. The great danger of the cerebro-spinal type is that it will +result in paresis or locomotor ataxia. + +As long as the blood of a patient shows a _positive_ Wasserman reaction, +marriage should certainly not be consummated. If after a proper course of +treatment by a well-informed physician, the patient shows a _negative_ +Wasserman when tested by a competent examiner, he probably would not +infect his wife or offspring, although prudence would require that he wait +at least six months or a year before marriage, and marrying then only if +later tests remain negative. + +The only way for a patient to be sure that he is not harboring the +cerebro-spinal form would be to have a spinal puncture made and the +cerebro-spinal fluid examined. While the cerebro-spinal phase often does +not occur until long after the primary infection, cases are known in which +it has appeared within a few weeks. Evidence that the central nervous +system is frequently invaded early in the course of the disease is +increasing. Marriage of an individual suffering from the cerebro-spinal +form should not take place, since such a one is almost sure to become a +burden on the family or the state. + +=Many Syphilitics Are Married.--=It may seem to some that in a treatise on +being well-born the subject of syphilis might be ignored as not being +especially pertinent, but the supposition that no considerable percentage +of syphilitics marry is not borne out by the facts. Seventy-five per cent. +of men with insanity due to syphilis who are admitted to hospitals are +married. The insanity in such cases is mainly the result of infections in +earlier years, often long before marriage. While syphilis, strictly +speaking, is not inherited, that is, does not become part and parcel of +the germ-plasm, still the frequency of its direct transmission to +offspring is so appalling that the outcome, as far as the immediate child +is concerned, is quite as disastrous as the most thoroughgoing real +inheritance could be. + +=Why Permit Conditions to Continue as They Are?--=When one faces the +easily ascertained facts regarding venereal disease, it seems incredible +that we, an intelligent people, can go on complacently handing our +daughters and sisters over to the surgeon's knife and a life of personal +misery, and even in not a few instances to become mothers of incurably +defective children, yet the dire fact confronts us that we do. We can no +longer excuse ourselves on the plea of ignorance, for the grisly record +may now be read in many medical and not a few popular treatises, and we +find the theme entering even into the modern drama, as witness Brieux's +_Damaged Goods_. Further indifference to these conditions can only be +attributed to culpable apathy or prudery. + +The extreme dangers to which parents are subjecting their daughters if +they do not demand a clean bill of health on the part of their prospective +husbands are obvious. Fathers and mothers perfectly willing to inquire +into their future son-in-law's social connections, his income, securities, +or business chances become strangely "modest" when it comes to determining +whether he is physically fit for marriage. + +One great cause of ignorance in the past was the prudish taboo against +frank discussions of venereal diseases which has thrown the veil of +silence about the subject. To-day, however, it is coming to be recognized +that these maladies are diseases and not a standard of social propriety, +and that like most other diseases the surest way to secure prevention and +gradual eradication is through the enlightenment of the public. They are +prevalent in all classes of society. Moreover, it must not be forgotten +that there is no form of venereal disease which may not be innocently +acquired. Even where acquired through transgression of moral law an +ignorant attitude toward the sexual instinct is often at the bottom of the +difficulty. + +=Medical Inspection Before Marriage.--=Ante-nuptial medical inspection is +certainly as necessary to the welfare of society as the certification of +age and of the single state now required by law. No one objects to a +medical examination pertaining to venereal and other diseases when it +comes to taking out a life insurance policy, and why there should be any +more objection to it as a preliminary to marriage is a mystery. A few +states already have compulsory ante-nuptial medical inspection. The laws +have been enacted too recently to judge adequately of their working. There +has been much debate in Wisconsin as to whether their law (Chapter 738, +Laws of 1913), which went into effect January 1, 1914, is constitutional +and whether it requires a Wasserman test. The Wisconsin law applies to +males only. The Supreme Court of the state has declared it constitutional +and that its requirement of "the application of the recognized clinical +and laboratory tests of scientific search" involves only such examination +as the ordinary licensed physician is equipped to make and can reasonably +be expected to make for three dollars, the maximum fee specified in the +law. + +A number of the physicians of the state are still dissatisfied with the +wording, although most do not oppose the principle of the law. Many +believe that it should apply to the women as well as to the men, and +others feel that the law should be extended to cover still other kinds of +marital unfitness. Most of the practitioners with whom I have discussed +the matter appreciate the motive underlying the law and are endeavoring to +make it successful. + +The general public of the state as a whole seems to be in favor of the +provision. At least one hears much favorable comment and little +dissension among those who understand its purpose. The very controversy +over it which sprang up after its passage proved to be of great benefit in +the education of the public regarding the necessity of such measures. Such +physicians as I have been able to question report that the candidates for +marriage rarely object to the requirement, but on the contrary strongly +favor it. Especially where they have suffered from venereal disease +earlier in life most are eager to know their condition and to have medical +advice. To my own mind this last fact is the most significant of all, as +it will give every candidate for marriage a chance to know the truth. Most +men are not so much brutal or vicious as ignorant in such matters. The +vast majority of those unfit for marriage as a consequence of venereal +disease will, when they realize the danger their condition imposes on wife +and children, take every possible means to put themselves into proper +condition. + +Desirable as the Wasserman test may be, it requires special laboratory +facilities and equipment as well as a specially trained examiner to make +it a reliable test. Moreover it can not be given by the general +practitioner for the very moderate fee that must obtain in a pre-nuptial +examination compelled by law. If it or the serum test for gonorrhea are to +be applied then the legislative body of the state will find it necessary +to establish a special public laboratory or laboratories for their +application. This, however, is not a matter of particular difficulty and +would be capital well invested in any state. + +=The Perils of Venereal Disease Must Be Prevented at Any Cost.--=However, +no matter what the cost may be to the state, no matter what the exaction +from the individual, the grave perils of venereal disease to society +_must_ be prevented. We owe it to the cause of humanity that there be +fewer victims born into a world of eternal night, that from a parentage of +polluted blood there spring no longer hosts of children with feeble +misshapen bodies or with tarnished intellects, death-marked at the door of +life. + +=Bad Environment Can Wreck Good Germ-Plasm.--=In conclusion it is evident +from our discussion of prenatal influences that not all of being well-born +is concerned with heredity in its proper sense, since the unborn young may +be influenced either directly or indirectly by environmental conditions +which are in no sense products of heredity, although as far as the +immediate child is concerned the result may be quite as disastrous where +the influence is a baneful one. As to the production of beneficial +prenatal effects, while parents can do nothing toward modifying favorably +such qualities as are predetermined in their germ-plasm, nevertheless they +must come to realize that bad environment can wreck good germ-plasm. They +can see to it that they keep themselves in good physical condition by +wholesome temperate living, and thereby insure as far as possible healthy +germ-cells for the conception and good nutrition for the sustenance of +their progeny. Their one sacred obligation to the immortal germ-plasm of +which they are the trustees is to see that they hand it on with its +maximal possibilities undimmed by innutrition, poisons or vice. + + + + +CHAPTER VII + +RESPONSIBILITY FOR CONDUCT + + +Since both physical and mental attributes are unquestionably inherited, it +becomes a matter of importance to inquire into the nature of the entity we +call personality. To what extent is human conduct a product of parentage? +Although apparently free agents are we in reality only by infinitely +subtle indirections making the responses, forming the habits, establishing +the characters which result merely from the blind impulsions of an +inherent constitution? If so, who is praiseworthy, who blameworthy? Are +men + + "But helpless pieces of the Game He plays + Upon this chequer-board of Nights and Days." + +=All Mental Process Accompanied by Neural Process.--=Whatever the ultimate +decision of psychologists may be regarding the relation of mind to the +sensory and nervous mechanism of man it is certain that there is so close +an association between them that the least alteration in the mechanism +means a parallel effect in the mind, or in the words of Huxley, "every +psychosis is definitely correlated with a neurosis." The rind or _cortex_ +of gray matter which constitutes the surface of the large cerebral +hemispheres of the human brain is regarded as the seat of consciousness. +The development of the mental powers in the infant is dependent on the +development of the elements of this cortical substance and the waning of +the mental faculties in old age goes hand in hand with its atrophy. +Abnormal arrangements, injuries or omissions in it mean mental +unsoundness. How the activity of the structural mechanism gives a reaction +in consciousness is not understood, but we know that in the living being +the two phenomena are inseparably linked. Whether we accept the hypothesis +that consciousness is an actual product of the structural mechanism or the +hypothesis that the latter is only an instrument for the manifestations as +consciousness of an outside force or entity, just as the telegraphic +instrument manifests the existence of electricity, is neither here nor +there for our purposes. On either supposition the degree and manner of +expression are determined by the structure of the mechanism. Our main +problem is to decide as nearly as possible how much of the mechanism is +rigidly inherited, how much is at birth largely undestined, so that its +ultimate outcome is in part a product of the forces which play upon it, or +in other words of education and training. + +=Gradation in Nervous Response from Lower Organisms to Man.--=To +comprehend fully the basic nature of human neural responses one must seek +the roots in the behavior of lower organisms. For there is found in a +simpler form many of the fundamental activities and the first dim gropings +which emerge in man as memory, reason and will. As we ascend the scale of +animal life we find a continuous advance in neural complexity and nervous +response that in many respects grades up closely to the human type. + +A windmill or a weather-vane points toward the source of the wind, +obviously not because either exercises any special choice in the matter, +but because it is constructed on such lines of symmetry that when the wind +strikes it, if it slants the slightest to left or right, the more exposed +surface receives the greatest pressure and thus swings the body back into +the line of least resistance. + +=Behavior of Many Animals Often an Automatic Adjustment to Simple External +Agents.--=It is a far cry, of course, from the responses of such a machine +as a windmill to the responses of even the simplest living thing, but in +spite of the broad gap between the two, there is much reason to believe +that the behavior of many living organisms is due in a marked degree to +the directive effects of comparatively simple external factors rather than +to the complex internal volitions the casual observer is likely to +attribute to them. + +=Tropisms.--=It is a marked characteristic of all living protoplasm that +it has the power of responding to external stimuli. This power of response +is termed _excitability_ or _irritability_. In describing the motor +responses of living organisms to stimuli resulting from a change in +surroundings the term _tropism_ (Gr. _Trope_, turning) is frequently used +and the kind of stimulus is indicated by a prefix. Thus the term +phototropism means a turning or _orientation_ brought about by means of +light. An organism which reacts by a movement toward the source of light +is said to be _positively phototropic_, one which moves away from it, +_negatively phototropic_. By using such a neutral terminology the +physiologist avoids implying that necessarily "likes" or "dislikes" or any +other psychic reaction enter into the movements. + +Several kinds of tropisms are recognized, such as _phototropism_ or +_heliotropism_, reaction to light; _thermotropism_, reaction to heat; +_electrotropism_ or _galvanotropism_, to electric current; _geotropism_, +to gravity; _chemotropism_, to a chemical; _rheotropism_, to current; +_thigmotropism_ or _stereotropism_, to contact; and _chromotropism_, to +color. + +=Many Animals Show Tropic Responses.--=Many of the lower animals seem to +have their movements determined more or less mechanically by the action of +such external factors, some being positively, others negatively responsive +to a given kind of stimulus, or the same individual may be at one time +positive, at another negative, according to modifying conditions to be +mentioned presently. + +In plants and in simpler lower animals there is no special nervous system. +The responses of these organisms depend on the general irritability of +their constituent protoplasm. In other animals a nervous system is +developed, crude and diffuse in lower forms, extremely delicate, complex +and definitely ordered in higher forms. But it should be borne in mind +that nerve protoplasm possesses only in high degree a capacity for +irritability, conduction, etc., that is common to all living substance. In +keeping with other "physiological divisions of labor" or specialization +which mark the increasing complexity of animals, this enormously enhanced +sensitivity and conductivity of certain tissues have come about, and they +have become set apart for these special functions. In higher animals, +therefore, the tropisms where operative must act more or less through the +agency of the nervous system instead of directly through the general +protoplasm of the organism. + +=Certain Apparently Complex Volitions Probably Only Tropisms.--=Where +nervous systems enter into tropic responses there must be specific +sensibility of certain nerve terminations (i. e., sense organs) at the +surface of the body. These sensory or receiving nerves connect through the +central system with corresponding motor nerves which in turn supply +certain specific muscles through the contraction of which the organism is +as surely and as mechanically oriented as in the simpler cases. For +example, if light is the stimulating agent, when it strikes a positively +phototropic animal, if the latter is not already oriented, the eyes or +other nerve terminations sensitive to light transmit an impulse through +the central nervous system to certain muscles causing them to increase +their tension and thereby swing the animal around with its head toward the +light. Progressive movements which the organism then makes must carry it +toward the source of light. Thus it is not "love of light" that draws the +moth into the flame but the mechanical steering of the body toward the +source of light through the stimulations produced by the light waves. It +is chemotropism, not solicitude for its offspring, which drives the flesh +fly to lay its eggs on decaying meat. And it is stereotropism and not a +desire for concealment which impels certain animals such as many worms +and insects to get into a close contact with solid bodies, or in other +words to "hide" themselves in burrows and crevices. + +=Complicating Factors.--=However, beautifully as these theories of +tropisms work out in a broad general way, there are various additional +factors entering which must be reckoned with, and these become more +numerous and of more consequence as the organism becomes more complex. In +the first place certain internal conditions must be considered. Living +matter is characterized by its instability. There are continual synthetic +and disruptive processes in progress which the physiologist terms +metabolic changes. The very "life" of such matter seems to be the +manifestation of such changes. Concerning what the ultimate source of +these changes is, whether or not indirectly they may be referred to +external conditions as seems probable to many biologists, no one so far +has ever given a convincing, positive answer. It is sufficient for our +purposes to know that they may have set up certain internal stimuli which +may modify the behavior of the organism in which they reside, and that the +"physiological state" of the organism at the time of external or internal +stimulation will condition the response. This physiological condition may +be dependent on the general metabolic equilibrium of the animal, or on the +extent of previous stimulation by means of the same or different agents. +Thus the organism may not always react in the same way to the same +stimulus. + +The intensity of the stimulation and change in the intensity of the +stimulation, are also factors to be reckoned with. Moreover, it must be +taken into account that a given organism is often operating under the +control of more than one external influence. For example, swarm spores in +a dish of water which at a given temperature are positively phototropic, +that is, gather at the side of the dish toward the light, may, if the +temperature of the water is raised or in case of marine forms if the +salinity is increased, become negatively phototropic. Sometimes two or +more forms of stimuli may cooperate in bringing about certain behavior as, +for instance, in the reaction of the earthworm to a suitable habitat, +through a combination of chemical and contact stimuli. On the other hand, +two different stimuli may interfere with each other; for example, the +usual phototropic responses of certain animals do not manifest themselves +when they are mating or feeding. In short, anything that alters the +physiological state of the organism may cause it to react in a different +manner. And thus with the interplay of shifting external agents and +variable internal state the bounds of behavior on these purely mechanical +bases become considerably extended. + +=Many Tropic Responses Apparently Purposeful.--=The query arises as to why +if these responses are mechanical they are so often apparently purposive; +that is, why do they so often subserve some useful end for the animal? +While they do not always work out to the animal's benefit, as for instance +in the case of the moth and the light or under many other conditions that +can be devised experimentally, as a matter of fact under normal natural +conditions they are on the whole useful to the organism, carrying it +into suitable surroundings of food, lessened danger, temperature, and the +like. + +The probabilities are that in their first origin the reactions were not +purposive. However, if any proved harmful they would result in the +extermination of their possessors and hence of that particular strain of +individuals. Those types that happened to have useful reactions would be +left and in course of time as the process of eliminating the others went +on, would become the prevailing types. Any organism which the useful +reaction had preserved would tend to hand it down to the succeeding +generation where again it would be the conserver of those individuals +which possessed it in sufficient degree. + +=Authorities Not Agreed on Details of Tropic Responses.--=Although all the +foremost modern students of animal behavior accept as facts the more or +less mechanical orienting effects of external stimuli, there is by no +means unanimity of opinion regarding details. Some stress as the directive +factor the continuous action of the stimulating agent on sensitive tissues +symmetrically situated. Others would maintain that it is the time rate of +change in the intensity of the stimulating agent, or that the factor is +different in different cases. Some make much of an automatic sort of +"trial and error" system by which certain organisms test out an inimical +environment until the path of least irritation is hit upon as the way to +safety. The field is a broad one and to get at the finer shades of +distinction the reader will have to refer to the works of such +authorities as Loeb, Jennings, Holmes and Mast. + +=Tropisms Grade Into Reflex Actions and Instincts.--=The tropisms in many +cases become indistinguishable from _reflex actions_ and these in turn +grade up into the _instincts_ of animals. The latter may be looked on as +but subtler and more involved reactions made possible through a more +intricate structural organization. As might be expected of instincts, the +feature of utility is more in evidence than in simpler tropisms because +they have become of proportionately greater magnitude, but the same +fundamental mechanism is apparently at bottom of both. It has already been +seen how the "instinct" of the blow-fly to lay its egg on meat is +interpretable as a chemotropic response. Thus no elaborate psychic +mechanism is necessary in such behavior. + +=Instincts.--=In the typical instinct there is a series of "chain +reflexes" in which one step determines the next until mechanically the +whole gamut of changes is run to the last step. It is characteristic of a +purely instinctive act that an animal performs it without practise, +without instruction, and without reason. Moreover, all of the same kind of +animals tend to perform the act in the same way. But with instincts, as +with tropisms, the physiological state of the organism must be regarded. +For instance, the instinctive reactions of an animal sated with food or +hungry will be different. + +=Adjustability of Instincts Opens the Way for Intelligent Behavior.--=As +we progress in the scale of animal life this adjustability of instincts +to new conditions comes more into evidence. While prescribed in the main +by internal impulse the carrying out of the action is capable of some +adaptability to circumstances. And in proportion as this adaptability +releases the organism from a blind rigid working-out of a predetermined +end, there is opened up the possibility of intelligent behavior; that is, +of modification of the instinctive behavior by individually acquired +experience. + +While the generation of instinctive impulses still occurs it is left more +for individual experience to teach discrimination between ends. But we can +not escape a fundamental structural mechanism, for with this new capacity +of educability must come new structural mechanisms in the nervous system +and this must be as faithfully reproduced in each individual as is the +basis for any other nervous response. How low in the scale of animal life +animals can profit from their experiences to the extent that their future +conduct is conditioned thereby is not known. Some would place it as far +back as the protozoa, others would not. Where such modification of +behavior is possible there must be some mechanism for the storage of +impressions in the form of what we term _memory_. + +=Modification of Habits Possible in Lower Animals.--=Among invertebrates +such animals as crayfish will acquire new habits, or rather will modify +old ones. Even as lowly an organism as the starfish can have changes of +habit thrust on it. When a starfish is placed upon its back it rights +itself by means of its arms or rays. Professor Jennings found that in a +given individual the tendency was always to employ certain rays for this +rather than others. However, by preventing the use of the rays customarily +employed, he found that the animal would use a different pair and that +ultimately in this way it could be trained into the habit of using this +pair of rays even when restrained in no way. One starfish which was given +one hundred eighty such lessons in eighteen days after an interval of +seven days still retained the new habit; young individuals were found to +be more easily trained than old ones. + +=Some Lower Vertebrates Profit by Experience.--=Among vertebrates it is +known that those as low in organization as fish will profit by experience. +They will learn to come for food at a regular time and apparently learn +more or less to appreciate the presence of certain obstacles with which +they have had unsatisfactory experiences. Professor Sanford sums up what +he believes are the limitations of the piscine mental organization as +follows: "No fish is ever conscious of himself; he never thinks of himself +as doing this or that, or feeling in this way or that way. The whole +direction of the mind is outward. He has no language and so can not think +in verbal terms; he never names anything; he never talks to himself; as +Huxley says of the crayfish, he 'has nothing to say to himself or any one +else.' He does not reflect; he makes no generalizations. All his thinking +is in the present and in concrete terms. He has no voluntary attention, no +volition in the true sense, no self-control." + +=Rational Behavior.--=Finally, however, out of these first dull +glimmerings of intelligence as exemplified in the higher invertebrates +and the lower vertebrates, which can modify behavior as the result of +experience, come the still higher factors so dominant in man, of +_rational_ behavior. This higher mental process can realize the end to be +reached and can deliberate on the means to be employed. By means of his +_reason_ man can overcome difficulties in advance by "thinking" out +suitable schemes of action. Some naturalists believe that man stands alone +in possessing the power to reason, although others believe that some of +the other mammals, notably the other primates, possess the same attribute +although in a much less degree. + +=Conceptual Thought Probably an Outgrowth of Simpler Psychic States.--=Is +the capacity for such conceptual thought, however, which appears as the +final efflorescence of complex neural activity something entirely new? +Most students of comparative psychology maintain that it is not. Just as +one kind of an instinct frequently grows out of another, so has this grown +out of the complex of _psychic_ states which preceded it. It apparently is +the product of the increasing awareness on the part of animals of their +neural processes and the outcome of these processes, which becomes more +and more prominent as we ascend the scale of animal life. With the advent +of associative memory the mind comes more and more to deal with attributes +of objects instead of merely with each single concrete object as it +presents itself, and these attributes being common to many objects, come +to represent definite ideas which can be manipulated by the mind. +Language, of course, has been an indispensable aid to man in this regard, +for words become descriptions of facts and symbols of concepts, and +thereby allow of abstract thought. + +=The Capacity for Alternative Action in High Animals Renders Possible More +Than One Form of Behavior.--=With this modification of instinct by +experience made possible, there comes at the same time, of course, the +capacity for a rational instead of a purely instinctive behavior. This +very capacity for alternative action opens up many new possibilities of +behavior and together with the well-known fixative effects of habit, also +the opportunity of permanently establishing certain ones. Thus it is +obvious that a behavior toward which in a strict sense there can not be +said to have been an original specific tendency, can be developed. What +was present in the first place was only a general possibility of the +development of any one of several types of behavior. The final choice of +the alternatives together with repetition makes it the habitual behavior +of the individual. Of course it can be urged that if the selection of the +type of behavior is left to the individual then the latter will operate +automatically toward the various impulsions of its neural make-up and one +path will be followed because of stronger inclination in that direction, +so that the whole procedure is in the end the mere operation of an +automaton. But however this may be in the individual left to itself, the +fact is in man that the young individual is never left to itself and in +the nature of things can not be, so that without entering into this +troubled pool of controversy regarding freedom of the will, I wish merely +to point out that the possibility of more than one form of behavior +exists and that if one is more desirable than the others then this one can +be chosen by the ones responsible for the training of the young individual +and clenched fast by the agency of habit. + +Intelligence, reason and habits, however, no less than instincts and +tropism must have neural as well as psychical existence and we can not +escape therefore the underlying mechanism. + +=The Elemental Units of the Nervous System Are the Same in Lower and +Higher Animals.--=It is interesting to note that the fundamental neural +mechanism which underlies the mental processes of higher animals is not +essentially different from that which serves in lower forms. Although as +animals become more complex their nervous systems have become +proportionately larger and incomparably more intricate, still all the +changes have been rung on the same basic neural unit, the _neuron_ or +nerve-cell (Fig. 32_A_, p. 209). The higher nervous system differs from +the lower in the number, in the specializations and in the associations of +these units rather than in possessing something of entirely different +elemental structure. + +=Neuron Theory.--=According to the prevailing modern conception the entire +nervous system is made up of a series of units called _neurons_. Each +neuron is a single cell with all its processes. The latter consists +typically of short branching processes on the one hand, known as +_dendrites_, and of a single process on the other, known as the _axon_, +which extends from the cell to become a nerve fiber (Fig. 32, p. 209). The +various neurons, with possibly a few exceptions, are not anatomically +continuous but contiguous. They communicate with one another apparently by +contact only. The axon of each neuron ends in an elaborate series of fine +branchings which lie in contact with the dendrites of another neuron, or +in some cases with the body of the other cell (Fig. 32, p. 209). Thus the +nervous impulse passes from one neuron to the other at these points of +contact. An impulse is supposed to travel normally only in one direction +through a neuron, the dendrites being the receiving and the axon the +discharging terminals. There are various types of neurons. Some, +particularly within the brain, have their main processes so provided with +branches and brushes that they may come into physiological connection with +a number of other neurons. + + +[Illustration: FIG. 32 + +A--Diagram to illustrate neurons and their method of connection; _a_, +axon; _d_, dendrite; _s_, synapse. To simplify the diagram the medullary +sheathes of such fibers as would have them have been omitted. The arrows +indicate the direction in which the impulse travels. The lower series +shows diagrammatically how from the same neuron in the cortex two +subordinate neurons may be affected, the one excited to cause contraction +of a certain group of muscle fibers, the other inhibited so that the +antagonistic fibers may relax and thus not hinder the movement of a given +part. + +B--Section of a region of the cerebral cortex (after Cajal). The cells +have been blackened with chrome-silver and are much less highly magnified +than the diagrams in A. The numerals refer to certain characteristic +layers of the cortex in this region.] + + +=Establishment of Pathways Through the Nervous System.--=It is believed +that more or less resistance to transmission of stimuli prevails at the +point of contact (_synapse_) between two neurons but that this resistance +is lessened by repetition of conduction. The frequent traversing of a +given pathway by similar impulses finally results in an automatic +occurrence of the transmission, or, in other words, the action becomes +habitual. Education consists largely in establishing such routes through +the nervous tissue. Because of the greater plasticity of the neural +mechanism in youth it is easier to open up and fix pathways of conduction +than in later years. Moreover the earlier established lines of conduction +become the more permanent. + +=Characteristic Arrangements of Nerve Cells Are as Subject to Inheritance +as Other Structures of the Body.--=That the main features of the nervous +system are inherited becomes obvious when we see that each kind of animal +has its own distinctive numbers, arrangements and proportions of the +various neural units. In man, for example, there are certain +characteristics, types and groupings of nerve-cells which are reproduced +generation after generation with remarkable fidelity. This means that in +so far as these represent the mental make-up of the individual, his +mentality is continuously linked with others which have gone before. The +new-born child has all the nerve-cells in its brain that it will ever have +but the ultimate linkages of the finer connectives between them, or at +least the pathways of travel, remain in large measure to be made. + +As we have already seen, the cerebral cortex is the seat of the chief +mental faculties of man or at least of the highest of these. Professor +Lloyd Morgan, one of our greatest authorities on comparative psychology, +is inclined to believe that the instincts are located in the subcortical +material. In any event, the inheritance of mental ability resolves itself +into the inheritance of a certain cerebral mechanism. + +=Different Parts of the Cortex Yield Different Reactions.--=The cerebral +cortex, however, is not functionally homogeneous throughout. Certain +regions have been shown to be motor, others sensory, and moreover, these +regions are apparently further specialized so that a given one of them is +associated with a specific type of sensory or motor response, not merely +with responses in general. Thus by injuring one of the sensory areas we +might destroy vision but not other sensations, or by stimulating one of +the motor centers we would get a response in a corresponding motor organ +but not in all such organs. Likewise, it is probable that still different +areas, the so-called "association areas," relatively of much greater +development in man than in any other animal, are the regions in which +various perceptions and conceptions are synthesized and formed into +organized knowledge. Here also are engendered the volitions which when +flashed through the motor centers become expressed in activity or +behavior. + +It seems highly probable that just as the sensory and motor areas differ +in kind from one another, so we must suppose there are qualitative +differences in various parts of the association areas so that the +different parts give different reactions in consciousness; that is, each +special mental ability of the individual is more or less centered in a +special part of the cortex. And just as there may be variations in other +structures of the organism so there may be variations in these areas. The +"gifted" person in some one direction, whether it be in mathematics, +music, painting, or what not, is on this hypothesis one who has that +particular area of his brain which forms the basis for the talent in +question more highly developed than it is in the average individual. And +since such talents are handed down to descendants, this can only mean that +a similar grouping of the neurons in the region in question has occurred. + +=Skill Acquired in One Special Branch of Learning Probably Not Transferred +to Another Branch.--=Such a differential arrangement of the +brain-mechanism which presumably underlies the various mental abilities +would lead to the inference that skill in one special branch of learning, +in so far as it involves only certain centers of the cortex, would not be +transferred to another branch based on different neural pathways and +centers. Development of historical knowledge, for example, would not +enhance one's mathematical ability, or vice versa. The testimony of +various psychologists bears out this idea. In so far as certain factors of +training, such as habits of industry, concentration, etc., are common to +the study of either mathematics or history, the good effects of either +discipline will probably be much the same, but the identity of effect +vanishes as soon as the intrinsic characteristics of the subjects +themselves are involved. + +Just how far we are warranted, however, in carrying this idea of localized +functions as regards the association areas is a moot question. Our present +attitude regarding the specificity of such localizations is largely a +matter of inference based on analogy to conditions which obtain in other +and better known parts of the brain, together with the indubitable +differences in inborn abilities which exist between individuals. Some few +brain physiologists maintain that the whole cortex operates more or less +as a unit in all of the higher psychical activities. + +=Preponderance of Cortex in Highest Animals.--=One of the most interesting +conditions in the nervous system of the highest types of animals is the +way in which the cortex has outrun the other parts of the brain in size +and complexity and has come to dominate the organism more and more both +directly and indirectly. Aside from the proportionately greater increase +in size of the cortex, there is an abundance of anatomical evidence of +this altered and probably altering system of control in man and the higher +apes. This is well illustrated in the fiber tracts (nerve bundles) of the +spinal cord. + +=More Long Fiber Tracts in the Spinal Cord of Man.--=The spinal cord +although having many nerve centers of its own is also in great part a +large cable for conducting enormous numbers of fibers from one part of the +cord to another, or to and from the brain. In man and the higher apes a +considerably larger percentage of the total area of the cord is given up +to the long fiber tracts from the brain to the body than in lower +vertebrates. This progressive increase in long fiber tracts in the higher +anthropoids probably marks more and more domination of the body by the +higher brain centers and correspondingly less by the direct activity of +the cord and by the lower brain centers. However, even in man, many of the +simpler reflexes of the body still have their centers in the spinal cord. + +=Special Fiber Tracts in the Cord of Man and Higher Apes.--=There are +certain special tracts of the cord that are particularly interesting in +connection with the increasing domination of the brain over the body, +namely, the _pyramidal tracts_. These were the latest tracts to appear in +the animal kingdom and are apparently the latest to become functional in +the individual. It is believed that the development of the medullary +substance (an enveloping sheath) of the common medullated nerve fiber +marks the time of entrance of the fiber into activity and it is a +significant fact that the formation of this sheath occurs last of all in +the fibers of the pyramidal tracts, where it does not appear till after +birth. These tracts convey impulses from the brain to the body. They +consist of two sets of tracts, in fact, one the crossed, the other the +direct. As an anomaly, probably arising most frequently from instrumental +injury at birth, the pyramidal tracts fail to develop normally, with the +distressing result that the infant, although possessing perfectly normal +brain activity and normal spinal cord reflexes, is unable to exercise +voluntary control of the body. In other words the condition, like +hare-lip, is one of suppressed development. At least this seems to be the +most plausible explanation of what is known as _Little's disease_. Such +unfortunates usually die early although they may survive for a few years. + +The direct pyramidal tracts occur only in man and man-like apes. They vary +considerably in extent in different individuals. They originate in nests +of characteristic large cells located in the cerebral cortex and are +regarded as paths, though not the only ones, through which volitional +impulses are conveyed from the brain. They seem to control certain of the +finer and more delicate movements of the body. + +=Great Complexity in Associations and More Neurons in the Brain of Man +Than of Other Animals.--=It has already been noted that as animals stand +higher in the scale of life while the general plan of their neural +elements remain the same, there is increasing complexity in the number and +connections of the neurons. The number of processes on individual +nerve-cells is also greater. There is in fact much greater complexity in +the number of processes and the inter-connections of the neural cells +than in the numbers of the cells themselves. This would seem to indicate +that the greater mental activities of higher animals depend more on +richness in complex associations than on mere increase in number of +neurons. The latter, however, is by no means unimportant as may be seen in +man, for instance, in whom it is estimated that the cerebral cortex, that +is, that part of his brain in which his more complex mental processes +transpire, contains some nine billion more nerve cells than does the +corresponding region of the brain of an anthropoid ape. + +Of especial significance in the psychic make-up of man is his vastly +increased capacity for inhibition. Although not possessed by all men in +equal measure and not entirely wanting in lower animals it is a +distinctive feature in all human conduct. Much of any child's education, +particularly as it pertains to behavior, must be concerned with training +in the exercise of proper inhibitions. He must learn to suppress certain +primitive types of reaction in favor of higher ones. This applies not only +to motor activities but to trains of thought as well. The essence of +self-control consists mainly in ability to substitute for one impulse or +idea other compensating ones. And the secret of concentration lies in +being able to banish irrelevant ideas and focus on the central thought. + +=The Nervous System in the Main Already Staged at the Time of Birth for +the Part It Must Play.--=It is clear from what is known of its anatomy +that in the main the central nervous system is framed to respond in +certain set ways, that there are determinative elements in it which +control or determine the responses, and therefore the behavior of the +body. The same evidence shows also, however, in the incompleteness of many +of the associations, that while the stage is all set and some of the main +features of the performance are determined at the time of birth, +considerable yet remains to be done toward fitting the parts together and +working up the detail. Just exactly what and how much is rigidly +determined no one knows. + +=Many Pathways of Conduction Not Established at Birth.--=As we have +already seen the evidence is that many of the neural pathways are not yet +fully established at birth, and there is some indication that routes once +opened may be altered. To what degree this has bearing on behavior is +still unknown, but since neurologists attribute so much importance to the +richness and the associations of the cell-outgrowths, it is evident that +this increase in the number of pathways after birth with possible +alternatives of connections may be a very important factor in the +modification of behavior. Yet, on the other hand, we are completely in the +dark as to what extent these later associations are predetermined in the +earlier cells. + +=The Extent of the Zone That Can Be Modified Is Unknown.--=There is little +doubt that many of the paths of action are already firmly established. +Others, although not irrevocably fixed, offer the least resistance and +would "naturally" be taken if not counteracted or modified by the more or +less artificial development and fixation of other paths through +cultivation and habit. Yet others perhaps are largely neutral; they still +await the initial decisive push which "choice" or external environment may +mete out to them. As trainers of youth all that is left that we can do is +to attempt to develop in certain ways the elements of this indefinite, +impressible zone. Unfortunately, we must labor in the dark to a great +extent as we have all too little indication of which the malleable factors +of intellect and conduct are. We can only infer from long, intelligent and +sympathetic observation of children in successive stages of their +development. It is only by having clearly in mind the nature of our +problem that our conclusions will finally come to be of enhanced practical +value in the training of children. Observation to the present time clearly +indicates that many children are strongly predisposed this way or that "as +the sparks fly upward." + +This is a point too frequently overlooked by educators. They are often +unduly actuated by the other piece of the truth that, "as the twig is bent +the tree inclines." They sometimes fail to realize that after all the tree +remains the same kind of a tree. If an apple tree, while it may be bent +from the normal path of development, it can not produce other fruit than +apples. Just how much the destiny of man can be influenced by training and +the exercise of his own will power is the fundamental question not only of +pedagogy but of ethics as well. For if man's rational judgments are +markedly conditioned by his neural make-up then the volitional judgments +which underlie conduct are likewise conditioned since they are +inextricably intermingled with his reason. We must believe that to a +considerable extent emotional expression, as well as other mental +functions, is due to hereditary dispositions of the neurons in the +various parts of the brain. + +=Various Possibilities of Reaction in the Child.--=Despite the innate +predeterminations of the tree, it is nevertheless our province to see that +the twig _is_ bent, but our work can only be done with due intelligence +when we recognize something of the limitations of our material. Of the +various possibilities of reaction we must see that certain desirable ones +are realized, even, in some cases, if only to have others thereby +excluded. It is a commonplace of psychology that all cerebral excitations, +no matter what the origin, must vent themselves in some way and if this +expression is not directed into proper channels it will very likely find +improper ones. We must see that the young wearer of the coat of +undetermined capacities gets it set by repeated performance into the +habitual wrinkles of normal social conduct. For it is a trite observation +that when habits are once well established it requires tremendous efforts +to do otherwise than as they dictate. There is not the least doubt that +some of our subjects will respond much more readily to training in certain +directions of habitual reactions than others, but we have always the +consolatory knowledge that no matter how difficult the art may be at +first, repetition reduces the difficulty. + +While much of any youth's character must be determined by external forces +brought to bear upon it, the ultimate climax of our effort and measure of +our success will be the extent to which we have engendered in him the +capacity for initiating and carrying out through his own volition those +impulsions and inhibitions which tend to the highest good of humanity. + +=Probable Origin of Altruistic Human Conduct.--=Those phases of human +conduct which find expression in consideration for others seem no less +than other mental attributes to have their origin in certain fundamental +instincts. Altruistic conduct, in last analysis, apparently resolves +itself back largely to certain very fundamental impulsions, namely those +which arise out of certain obligations for the welfare of others which are +necessarily associated with the marital, parental and filial relations +that must exist where the young require post-natal care. Looked at from +the standpoint of natural selection, this would come about as a mere +matter of survival value. Where the young, as in man, are helpless for a +long period of time, more opportunity would be afforded for the +development of both conjugal and filial affection. The sympathetic +emotions once established in such family relations would partly through +habit, partly through community of interest, readily become extended to +clan or tribe and as a final consummation to all mankind. + +=Training in Motive Necessary.--=In the training of children, then, we +must recognize first of all that there are decided inclinations or bents +which, as long as they are not anti-social in nature, must be respected if +not always encouraged. While it is necessary to utilize these as much as +possible in their training still we must bear in mind that although it is +natural for a child to follow certain interests, the fact remains that as +regards social worth these natural interests may not be the most valuable. +When this is true we must strive to develop others which will compel +attention and thus become impelling factors in conduct. Where certain +fundamental impulsions run contrary to the common welfare it is necessary +to practise the child in the setting up of inhibitions or counter-impulses +until this becomes habitual. He must be led to construct a protective +mantle of appropriate scruples, doubts and fears. It is all important to +get the proper motives for action to prevail in his mind. + +=Actual Practise in Carrying Out Projects Is All Important.--=But on the +other hand it is equally important to see that the action is effectively +carried out. In the matter of self-discipline, particularly, we may have +many ideal impulses and realize that they should prevail over certain of +our natural propensities, but unless we put forth effort to overcome the +propensities our ideal impulses are of no avail. The world has many such +moral paralytics to-day who can not seize their "languor as it were a +curling snake and cast it off." It is training in this very overcoming of +reluctance, in this putting forth of actual effort toward worthy ends +instead of merely memorizing precepts about the desirability of such +accomplishments, that is so sadly lacking in our school and home life +to-day. We prate of the importance of self-control, we say with our lips +that the way to learn to do is by doing, we proclaim that it is more vital +to instil good mental and physical habits into our pupils than to stock +them with information, we preach that mere fact training is as conducive +to making a first-class rascal as an upright man, yet we jog on +complacently in the well-beaten ruts of memory routine which require the +memorizing of symbols rather than real understanding. We seldom require +that our protégés make intelligent judgments based on evidence, we rarely +exact of them decisions in matters of ethics, and almost never demand that +they put their knowledge into efficient accomplishment. It can not be too +strongly urged that we need less of formulæ learned by heart, less dead +erudition pigeonholed in the brain like so many foreign bodies, and vastly +more assimilation of knowledge into the living personality of the +individual. + +Where in school or home to-day do we find provision for such training? Our +tendency is, in fact, just the opposite. According to the modern code, as +it works out in many instances at least, the child must be taught through +play. Though it is a truism that he who has not learned obedience can +never be master of himself, the child of to-day must not be made to obey +but be wheedled into changing his mind. If a given subject of study proves +distasteful to him, the fault is the teacher's for not making it +interesting, for he must always be led on by the thrill of fascination. In +other words, the child must not only be allowed but be encouraged to take +the path of least resistance. His own pleasure is to be the standard of +his actions. Let no stern demands of duty interfere! + +Is it any wonder that the products of such tutelage come into the +activities of life self-indulgent and undisciplined, and although often +recognizing our private and public shame in business, politics and +conduct, still remain supine, evasive of the unpleasantness or hardships +of reform, or inefficient or unwilling in accomplishing unselfish ends? + +=Interest and Difficulty Both Essential.--=The writer does not wish to be +understood as minimizing the importance of interest on the part of the +child in what he is doing. Interest is undeniably the open sesame to +desirable mental development; but what he does protest against is that not +uncommon interpretation of interest which deems it necessary to eschew +most serious consideration of a subject and evade such parts as present +difficulties. Certainly if there is any fact that stands out prominently +in human experience it is the fact that nothing conduces to the +development of moral stamina so much as the overcoming of difficulties, +particularly distasteful difficulties. + +=Conduct Developed Through Actual Performance.--=Self-control and the will +to do can be trained and crystallized into habit as well as can any other +activity. It is a fact that one well grounded in morals by habit will +successfully resist subconscious impulsions to wrongdoing even when +suggested in the hypnotic state. Conduct is largely a matter of growth +through actual performance. For proper guidance of this growth there must, +of course, be high ideals around which the feelings are led to cluster and +by which they gradually come to be controlled. + +=Construction of Ideals.--=The construction of such ideals through +example, through precept, through appeal and through actual practise in +self-denial and self-control on the part of the child, should be the +foremost duty of the parent or teacher. Above all it should be remembered +that imitation of teacher, of parents, of companions, is more of a factor +than intellect in the moral action of children. At present educationally +we are in a fever for vocational training, for "practical" work, and in +general for all things conducive to coaching our pupils in how to make a +living, yet commendable as all this may be, is it not of even more +fundamental importance to train them how to live? + +=The Realization of Certain Possibilities of the Germ Rather Than Others +Is Subject to Control.--=It may be said in a sense that there exists +potentially in any germ all the things that can possibly come out of it +under any obtainable conditions of environment. The very initiation of a +given mode of expression by some environmental factor, however, often +mutually excludes many of the others. We get a given average result +ordinarily because development normally takes place in a given average +environment. + +As may be easily shown by experiment, this is manifest even in the +instincts of lower animals. In the young the various instincts do not come +into expression at the same time, and it not infrequently happens that if +one of the earlier instincts becomes operative toward certain objects or +situations, later instincts will have a wholly different relation toward +these objects or situations than they would otherwise have had. As a +result the whole life conduct of the animal is markedly modified. For +example, young animals immediately after birth have no instinct of fear. +They do, however, have a strong instinct to attach themselves to some +moving thing and follow it. The utility of such an instinct, as for +instance in the case of young chickens, is obvious. The object of +attachment is usually the parent, but man may take the place of a parent +and the young animal will fearlessly follow him about. However if the +young animal has had no experience with man during its earliest infancy a +later instinct, that of fear or wildness, will have come into play and it +will flee from him. It is clear, therefore, that by familiarizing the +young animal with man before its instinct of fear has come to expression, +certain habitual reactions are set up in it which inhibit or limit the +application of its instinct of wildness as regards man. In other words, +the whole course of its life has been altered by this simple experience. +The same principle applies in even greater degree to the young of man. + +We have seen in a former chapter that what in the ordinary course of +nature was "predestined" to become one individual nevertheless contained +the possibility of becoming four or more if the environing conditions were +made such as to bring about a separation of the cleavage blastomeres. Or a +fish egg that contained the possibility of becoming a normal two-eyed form +also contained the possibility of becoming a one-eyed form and could be +made to do so by certain unusual modifications of the conditions under +which it develops. However we must not be led so far by the plausibility +of this comparison that we are misled, for the fact is that we are not +creating anything new by these environmental upheavals, but are mainly +altering features that already exist. Beyond doubt the nature of the +material is of greater import in the specificity of the outcome than are +the external forces brought to play on it. The only point I wish to make +is that even what seem ordinarily to be predestined ends can be altered +by environment, and that the probabilities are that certain features are +relatively indifferent at their inception, the environmental factor adding +the final touch of specificity. And our common experience in education +would indicate that the same is true of mental conditions, including +behavior. The actual appearance of a particular trait is not necessarily +always a matter of an initial trend, but may be due merely to the fact +that its development is possible under certain conditions of environment +and that these conditions have prevailed in the given instance. And even +where there is a specific bent it may be arrested through the awakening of +a contrary impulse, or, on the other hand, its exercise may prevent the +engendering of the opposite impulse. + +=Our Duty to Afford the Opportunity and Provide the Proper Stimuli for the +Development of Good Traits.--=It is clearly our duty to see that the +expression of good traits is made possible. We must throw a sheltering +screen of social environment around the young individual which will fend +off wrong forms of incitement and chances for harmful expression, and we +must provide proper stimuli and afford opportunity for development of +proper modes of expression. We must not forget that a normal instinct +denied a legitimate outlet will not infrequently find an illegitimate one. +Above all we must not forget the vital importance of establishing correct +habits nor the possibility of even replacing undesirable ones by good +ones. If training can redirect the machine-like behavior of as lowly a +creature as the starfish into new courses, why should we be so willing as +some of our genetists would seem to be to throw up our hands and admit +failure in the case of man before we have even made a rational attempt to +correct the evils in question? Even in lowly organisms we have seen that +behavior is not only the result of an innate constitution but also of the +degree and kind of stimulations to which it has been subjected. + +If the individual himself has not the initiative or will to make the +attempt to set up proper or corrective habits, or to cultivate the +necessary specific inhibitors, then all the more is it our duty to see +that he is led by suggestion and drill into the proper routine of +activities for their establishment. For if the individual with +propensities toward moral obliquity is to be saved to society it must be +through the stereotyping effects of good habits. + +=Moral Responsibility.--=Beyond question different men have different +degrees of capacity for mental and moral training. All can not be held +equally responsible ethically, but the lowermost limit of obligatory +response to social and ethical demands necessary to rank one as within the +pale of normal conduct is at such a level that any one not an actual +defective can in a reasonably wholesome environment surmount it. All +normal men are responsible for their conduct. + + + + +CHAPTER VIII + +MENTAL AND NERVOUS DEFECTS + + +Some of the most important and serious problems which confront humanity +to-day lie in the realm of mental and neural maladjustments. For human +progress and social welfare are in last analysis based fundamentally on +the results of normal reactions of human nervous systems. Any serious +derangement of the latter may, and in certain cases must, lead to more or +less disaster for the individual and disorder for society of which he is a +unit. So appalling has the number of neuropathic subjects become in modern +times that the matter may well cause even the most thoughtless citizen to +pause and consider. + +=Prevalence of Insanity.--=As to the prevalence of insanity, one learns +from recent charts prepared by a member of the National Committee for +Mental Hygiene that in 1910 we had more insane (187,454) in our +institutions than there were students (184,712) in all our colleges and +universities in the United States, or officers and enlisted men (142,695) +in our combined United States army, navy and marine corps; further, the +yearly cost ($32,804,450) of caring for these insane is greater than the +annual cost of construction ($32,520,100) on such a stupendous undertaking +as the Panama Canal. In New York over twenty per cent. of the revenues of +the state go to support the insane. Doctor Lewellys F. Barker, President +of the National Committee for Mental Hygiene, says: "It is calculated that +some 250,000 people in the United States are insane. One of every five men +discharged from the United States army for disability is discharged +because of insanity, 60 per cent. of the cases being _dementia precox_." + +Even in individual states with exceptionally large university populations +we still find these outnumbered by those of the insane. Thus in Wisconsin +by 1914 the state university had attained a population of about 4,700 +students resident at the university during the regular school year, and of +approximately 6,000 attending during some part of the year, but the number +of insane under restraint in public institutions in the state June 20, +1912, was 6,851, with an additional 1,284 on parole. This does not include +the insane in various private sanatoria, and moreover a considerable +greater number of patients had been treated in these public institutions +than were resident there June twentieth. + +To make such comparisons complete one should, of course, know the average +length of residence of students in college, and of insane patients in +institutions. No accurate data on this point are at hand. The average +period of residence in hospitals for the acutely insane is doubtless +considerably shorter than the average period of attendance of students in +college, while on the other hand the average period of residence of +inmates in asylums for chronic insane is probably considerably longer. For +example, the Wisconsin State Hospital for the Insane reports a total of +1,224 patients under treatment, but an average population at any one time +of only 622 during the year 1911, and the Northern Hospital for the +Insane, a total of 1,194, with a daily average of 613 during the same +period. The combined thirty-four county asylums in Wisconsin, for chronic +insane, had a total population of 5,384 during the year 1911, with a loss +of 517, or approximately 10 per cent. During 1912 the figures for these +same institutions run 5,758 and 742 respectively, or a loss of over 12.5 +per cent. The conditions in other states are probably much the same. + +In other representative states we find the number of insane in public +institutions as follows: California, 7,909; Michigan, 7,703; Minnesota, +5,329; Pennsylvania, 16,992. Epileptics are estimated by alienists to be +about equal in number to the insane, feeble-minded to be more numerous. +The estimate that in the United States there are 300,000 feeble-minded is +probably a minimal figure. + +=Imperfect Adjustments of the Brain Mechanism Often Inheritable.--=The +outside layer or "cortex" of the brain is the region in which the more +complicated adjustments occur, especially such as pertain to human +behavior, and inasmuch as this portion of the brain is extremely complex +and delicate in its mechanism, it is peculiarly liable to derangements +which, even when slight, may have far-reaching effects. + +This brain-mechanism is as much a product of ancestry as is any other +structure of the body, and it is obvious therefore that imperfect +adjustments of its structure must be as subject to the laws of +inheritance as are other malformations of the body. And just as with +other defects, mental disorders may thus flow from pre-existing ancestral +maladjustment of the nervous system or from immediate causes thrust upon +it, such as syphilis, alcoholism, degeneration of the blood vessels and +traumata. Or, in other words, the mechanism of mentality may be faulty +from the beginning, or it may be made faulty by bad environmental +conditions. + +The records of the inheritance of insanity, imbecility, feeble-mindedness +and other forms of nervous and mental defects are truly startling. Active +researches in this field have been in progress now for several years, and +as each new set of investigations comes in the tale is always the same. It +is questionable if there is a single genuine case on record where a normal +child has been born from a union of two imbeciles. Yet the universal +tendency is for defective to mate with defective. Davenport gives a list +of examples, beginning with such a one as this: "A feeble-minded man of +thirty-eight has a delicate wife who in twenty years has borne him +nineteen defective children." Little wonder, in the light of such facts as +these, that the number of degenerates is rapidly increasing in what are +called civilized countries. + +=Many Mental Defectives Married.--=But, it may be urged, these are +exceptional cases, there is surely no considerable number of mental +defectives who are married. Let us look at the available facts. In Great +Britain in 1901, of 60,000 known feeble-minded, imbeciles and idiots, +19,000 were married, and in the same year, of 117,000 lunatics, 47,000 +were married; that is, a sum-total of 66,000 mentally defective +individuals were legally multiplying, or had had the opportunity to +multiply their kind, to say nothing of the unmarried who were known to +have produced children. + +In the state of Wisconsin I note from the tenth biennial report of the +Board of Control that of 574 patients admitted to the Northern Hospital +for the Insane during the year from July 1, 1908, to June 30, 1909, 274 +were married and 29 others were known to have been married; this is a +total of 303 out of 574, considerably over half. At the Wisconsin State +Hospital for the Insane we find the conditions are no better, for out of +499 admitted in the year 1909-10, 208 were married and 65 others had at +some time been married, or a total of 273 out of 499. There is every +reason to believe that conditions are approximately similar in other +states. + +=Disproportionate Increase in the Number of Mental Defectives.--=Writing +of conditions in England the Commissioners in Lunacy state in their +fifty-fourth report that now (1901) there is one officially known lunatic +to 301.32 individuals of population, whereas in 1859 there was only one to +536 individuals of population. In Great Britain, taking into account +mental defectives of all kinds, the 1901 census showed a total of 485,507, +or 1:85 of total population. Rentoul estimates that 1:50 would be nearer +the truth because of the fact that the number of officially known mental +defectives is much less than the actual number. The conditions in Ireland +are even more impressive, for in 1851 there was one known lunatic to 657 +individuals of population; in 1871, one to 328, and in 1901 one to 178. +When all allowance is made in these statistics for the greater accuracy of +recent enumeration, and for other modifying influences, such as migration, +we are still forced to believe that an alarming increase in insanity is in +progress and that society is woefully derelict in permitting the marriage +of such unfortunates. + +A census of the insane under public care in Wisconsin June 30, 1910, not +counting the paroled, shows 6,537, or one to each 357 of population, since +the population of the state was then 2,333,860. If, however, we should add +the number of insane in private sanatoria and the number unconfined the +proportion of normal individuals would be very much reduced. + +In the United States as a whole, while I know of no data giving the number +of married insane, it is estimated that at least one-fourth of the insane +are not in asylums or hospitals. In all states the number of insane in +state institutions (there are no available records of most private +institutions) is rapidly increasing. According to the special census of +1903 covering a period of fourteen years, during which the general +population increased thirty per cent., the number of insane in +institutions increased one hundred per cent. This is due doubtless in part +to the fact that because of better facilities for keeping them a +proportionately greater number of insane are being sent to state hospitals +than in former years. Moreover, improved sanitation has cut down the +death-rate in asylums. The increase is in such vastly greater proportion +than the increase in general population, however, that it seems impossible +to attribute it wholly to the greater accuracy of recent enumerations and +the increasing custom of confining the insane in asylums. This is a matter +that demands our gravest attention and one that should be investigated +with the greatest thoroughness. One of the most disquieting facts in the +situation in most states is that many patients--an average of +approximately one thousand a year, in Wisconsin for example--are on parole +subject to recall. This means that although it is recognized that these +patients are likely to have to be returned to the asylum or hospital, +little or no restraint in the meantime is placed on their marital +relations.[8] + +=Protests Voiced by Alienists.--=Is it any wonder under the circumstances +that we find Doctor Charles Gorst, superintendent at the Mendota Hospital, +voicing in his 1910 report the following vigorous protest--and certainly +such men as he are in the best position to know. He says: "No one doubts +for a moment that defective mental conditions are transmitted from parent +to child as surely as the physical defects and deformities. Every one +knows that it is common for defectives to be attracted to each other and +marry, and that the defects of both parents are liable to be transmitted +to the children. It is also true that there are more children born in such +families; and for that reason the percentage of defectives is continually +on the increase. The report of the state of Illinois shows the increase to +be alarming, and many other states are no better. It is absolutely wicked +that the persons suffering from periodical insanity should be allowed to +return to their homes to propagate and scatter their children about the +state as dependents." + +=Examples of Hereditary Feeble-Mindedness.--=No one can look at the +remarkable series of charts and records brought together by Doctor Goddard +of the institution at Vineland, New Jersey, and by other directors of +similar institutions, and doubt for an instant the inheritability of +feeble-mindedness and allied defects. In some instances the family history +has been followed back as far as five generations, and it is always the +same dire sequence of insanity, idiocy, epilepsy or feeble-mindedness, +from generation to generation. For example, Fig. 33, p. 236, is one of +Doctor Goddard's charts. It shows thirteen descendants of a supposedly +normal father (possibly a carrier) and a feeble-minded mother, of whom +seven were feeble-minded, the others dying in infancy. The mother herself +was one of seven feeble-minded children, who were in turn the descendants +of feeble-minded parents, of whom the woman had five feeble-minded +brothers and sisters. In Fig. 34, p. 237, he shows mental defects running +through four generations. Fig. 35, p. 238, is a remarkable exhibit which, +starting in the fifth generation back with a feeble-minded, alcoholic +man--the mental condition of his wife being unknown--shows that in every +generation down to and including the present there has been nothing but +feeble-minded (or worse) offspring, leaving out of account two unknown +and a number who died in infancy without revealing their mental condition. +This is true notwithstanding the fact that in the course of the various +generations there had been several matings with apparently normal +individuals. The new blood, however, instead of redeeming the tainted +stock, itself became vitiated. The numerous specific cases of inheritance +of family traits reviewed in recent books or in special reports of trained +workers give us abundant confirmatory evidence of the inevitable +inheritance of various nervous and mental defects. + + +[Illustration: FIG. 33 + +Inheritance of feeble-mindedness (after Goddard): squares represent males, +circles females; F, feeble-minded; N, normal; E, epileptic; I, insane; C, +criminal; T, tuberculous; d. inf., died in infancy; the hand shows the +individual from whom the record was traced back; small black circle +indicates miscarriage.] + + +=Difficult to Secure Accurate Data.--=It is obvious, of course, that in +tabulations such as these there may lurk considerable margins of error. +Notwithstanding our Binet-Simon and other tests for feeble-mindedness, for +example, there is yet much to be desired in the way of accuracy. Many +cases just bordering normality are by no means easy to decide. Then again +in most human records, when one gets back beyond the third or, at most, +the fourth generation, the investigator has to depend on the hearsay +evidence of relatives, friends or neighbors, and how vague this generally +is can only be appreciated by those who have themselves tried to collect +such data. But in spite of all the difficulties, there is little doubt +that the more carefully prepared records are sufficiently accurate to +establish the fact beyond dispute that defective tends in large measure to +breed defective. + + +[Illustration: FIG. 34 + +Inheritance of feeble-mindedness (after Goddard); symbols same as in Fig. +33, p. 236.] + + +One serious drawback in making a study of the inheritability of insanity +and other nervous disorders is that so far we have dealt mainly with mass +effects rather than specific neuroses. But even when the latter is +attempted we are confronted by the fact that there are various +intergradations of the recognized types of defect, that because of +varying degrees of defect in the same type a standard is hard to +establish, and above all that what appears as a specific mental malady in +one individual may crop out in his descendants in an entirely different +guise. Moreover, not only the predisposition of the individual, but age +and precipitative cause enter as factors in determining the ultimate +symptoms. + + +[Illustration: FIG. 35 + +Inheritance of feeble-mindedness (after Goddard); symbols same as in Fig. +33, p. 236.] + + +=Feeble-Mindedness and Insanity Not the Same.--=Authorities make a sharp +distinction between insanities on the one hand and feeble-mindedness on +the other. According to Goddard, not only is there no close relationship +between the two conditions, but in reality they stand at opposite ends of +the psychical scale. In general, insanity is a degenerative process, +whereas feeble-mindedness is an arrest of development. In the first case +the victim loses part of the mentality he once had, in the second he stops +short of normal development. + +=Many Types of Insanity.--=The commonest manifestations of insanity are +undue depression, apathy, excitement, instability, obsessions, +hallucinations and delusions. Some mental disorders are associated with +recognizable structural changes in the nervous system, but the structural +basis of many is not known. + +In general there is more doubt about the inheritability of some of the +insanities than about cases of mental deficiency. The term insanity is +merely a loose descriptive one, and we shall gain little definite +knowledge about the inheritance of such maladies until we study each +separate insane diathesis specifically. Psychiatrists recognize many +different forms of insanity, some of them very distinct from others and +the product of unrelated underlying causes. Often it is only a question of +degree or sometimes a matter of chance as to whether a given individual is +certified as insane or not. A neuropathic person who manifests certain +anti-social activities is sure to be classed as insane, whereas another +individual with the same diathesis in a less degree might pass +unrecognized. It is almost impossible in some instances to tell just where +the border-line between a neuropathic and a normal constitution lies. Many +of the idiosyncrasies of the insane, indeed, are merely exaggerations of +characteristics seen in normal people. Recent studies of the psychology of +the insane show that most of their hallucinations and delusions are +closely related to some previous mental experience they had before +becoming insane. And it has been found that the surest means toward +removing the obsessions of the patient in curable cases is to ferret out +these earlier experiences and correct the wrong impressions regarding +them. Again, certain forms of insanity do not become manifest except as +special reactions to particular environmental conditions, and if these +conditions do not happen to occur, then the neuropathic constitution +though existing would not be revealed. Certain critical periods of life +such as puberty, pregnancy and the close of sexual life are particularly +likely to test out the mentally unstable, although such individuals may +have maintained normal mental balance up to the crisis in question. + +=Not All Insanities of the Same Eugenical Significance.--=Of the various +kinds of insanity some seem to be of much greater eugenical significance +than others, not only because they are strongly heritable, but also +because of the periodicity of the attacks. The patient may be repeatedly +in and out of the asylum and in his sane intervals wholly unrestrained as +far as propagating his kind is concerned. _Manic depressive_ psychoses and +_dementia precox_ in the order named represented the largest number of +admissions to the Wisconsin State Hospital for the Insane in 1911 and +1912, and both of these very frequently have a hereditary basis. Fig. 36, +a chart showing the insanity in a local family as worked out by one of my +pupils, is a good example of a recurrent type. The father (Fig. 36, p. +241) was about eighty-two years old when the record was made. His memory +was poor and he could not talk connectedly, although this was possibly +attributable to old age rather than to insanity. His brother, written to +in Ireland, stated that to his knowledge there had never been insanity in +his side of the family. The mother (2) was insane at nine, again at +twenty-nine and again at thirty-six. In her later life she has been in the +Mendota Hospital for the Insane five times and in the County Asylum twice. +The eldest daughter (3) has been in the State Asylum five times and is now +at home. The next daughter (4) spent five months in the asylum in 1885. +Another daughter (5) likewise spent a short period in the asylum. Two sons +(6, 7) have each spent two periods in the asylum, and a third son (8) has +had an attack of insanity. The youngest child died at the age of three. +Thus of the eight adult children six have been insane at some time. The +cases in this family seem all to be instances of manic-depressive +insanity. + + +[Illustration: FIG. 36 + +Inheritance of insanity in the L---- family. See text for description.] + + +=A Neuropathic Constitution May Express Itself Differently Under Different +Conditions.--=Some of the difficulties of getting genealogies of specific +forms of insanity are obvious from the following quotations chosen from +the works of eminent psychiatrists. Kraepelin, for instance, expresses the +opinion that: "The psychopathic charge of a family may reveal itself not +only by the appearance of mental disorders but also by other forms of +manifestation. Here belong before all, those diverse slighter deviations +from mental health which go to make up the borderland of insanity: +nervousness, states of anxiety and compulsion, constitutional depressions, +slight hysterical disorders and forms of feeble-mindedness, tics; also odd +characters, peculiarities in mode of living, criminal tendencies, lack of +self-control, intemperance, love of adventure, mendacity, suicide on an +inner basis." + +From the volume of Church and Peterson on _Nervous and Mental Diseases_ a +further confirmatory opinion may be cited: "In determining the factor of +heredity we must not be content with ascertaining the existence of +psychoses in the ascendants, but must seek, by careful interrogation of +various members of the family, for some of the hereditary equivalents, +such as epilepsy, chorea, hysteria, neurasthenia, somnambulism, migraine, +organic diseases of the central nervous system, criminal tendencies, +eccentricities of character, drunkenness, etc., for these equivalents are +interchangeable from one generation to another, and are simply evidence of +instability of the nervous system. It is the unstable nervous organization +that is inherited, not a particular neurosis or psychosis, and it must be +our aim in the investigation of the progenitors to discover the evidence +of this." + +=Certain Forms of Insanity, But Not All, Seem to Behave as Mendelian +Recessives.--=A number of psychiatrists and investigators of the +inheritance of insanities (Rudin, Lunborg, Davenport, Rosanoff, Jolly), +although working independently and in different countries, concur in the +opinion that manic-depressive insanity, dementia precox and allied +psychopathic conditions tend to occur after the manner of a Mendelian +recessive. On the other hand such maladies as Huntington's chorea are +transmitted as a dominant and in all probability at least half of the +children of an afflicted individual will inherit and manifest the defect. +As to inheritance of various other psychoses we have too few accurately +charted pedigrees for most types to make very positive statements about +their degree or manner of inheritance. Little can be said beyond the +statement that there is a decided tendency for various forms to recur in +offspring. Where more than one case of insanity occurs in a given family +or stock it is strong presumptive evidence that a hereditary defect is at +the bottom of it. As Doctor Wilmarth says, "Mental accident may occur in +any family, but it is rarely a second case occurs unless there is a +tendency to nerve degeneracy." For example, of 818 insane at the Wisconsin +State Hospital for the Insane during the biennium 1909-10, 187, or +practically one-fourth were positively known to have insane relatives. Of +these, 24 had insane fathers, 31 insane mothers, 30 insane brothers, 23 +insane sisters, 25 insane uncles, 21 insane aunts, and 21 insane cousins. +Where definite information could be obtained it was found that of the +5,700 admissions of insane patients to the New York state hospitals +during the year ending September 30, 1911, 27.7 per cent. of the cases +showed a history of insanity in the family and an additional 22.9 per +cent. showed a history of alcoholism, nervous diseases and the like. + +=Grades of Feeble-Mindedness.--=As to the various grades of +feeble-mindedness, while no sharp lines of demarcation can be drawn, a +rough and ready test usually applied is the relative ability of such +subnormal individuals to take care of themselves. In all, the conditions +exist from birth or shortly after. _Idiots_ are such defective individuals +as are unable to take care of themselves even to the matter of guarding +against common physical dangers. Their mentality does not progress beyond +that of a two-year-old child. _Imbeciles_ can take care of themselves in +the cruder physical ways, but are unable to earn their living. Their +mental age ranges from three to seven years inclusive. _Morons_, or the +"feeble-minded" in a more specific usage of the term, can under proper +direction become more or less self-supporting but they are as a rule +incapable of undertaking affairs which demand judgment or involve +unrestricted competition with normal individuals. Their intelligence +ranges with that of normal children from seven to twelve years of age. The +last class grades up insensibly into the shiftless, ne'er-do-well types +which exist in every community. It is the hordes of the feeble-minded in +the restricted sense that afford our most serious problems to-day. The +idiot and the imbecile are usually early and easily recognized and are +kept more or less under restraint, but the higher grades of feeble-minded, +the so-called moron type, can be detected often only by carefully devised +tests. + +=About Two-Thirds of the Feeble-Minded Have Inherited Their +Condition.--=Concerning the various types of feeble-mindedness there is +strong evidence that heredity is a factor of greater magnitude than in +most insanities. All facts point to the conclusion that most mental +deficiency is strongly inheritable and that the majority of our defectives +of this type come from degenerate stocks. Practically all specialists at +the heads of asylums and homes for the mentally deficient concur in the +opinion that about two-thirds of the cases are hereditary. For example, +Doctor Alfred Wilmarth, superintendent of the Wisconsin Home for +Feeble-minded, says: "My own observations, and those of others in this +country and Europe, would indicate that at least two-thirds of the +feeble-minded have defective relatives." + +In his study of two thousand children tested by the Binet measuring scale +for intelligence, Doctor Henry H. Goddard, director of the Department of +Research at the Training School for Feeble-minded at Vineland, N. J., +remarks concerning heredity of feeble-mindedness: "But we now know that +sixty-five per cent. of these children have inherited the condition, and +that if they grow up and marry they will transmit the same condition to +their offspring. Indeed, we know that this class of people is increasing +at an enormous rate in every community and unless we do something to stop +this great stream of bad protoplasm we shall some day be swamped in a sea +of degeneracy." + +E. R. Johnstone, superintendent of the training school at Vineland, N. +J., in a recent bulletin remarks concerning feeble-minded and epileptics, +"We are now convinced that from sixty to eighty per cent. of the cases are +hereditary." + +Again, we find Doctor A. C. Rogers, superintendent of a school for +feeble-minded in Minnesota, saying, "We have no survey of mentality in +this country except in very small areas, but probably about sixty-five per +cent. of the feeble-minded children that we know of are feeble-minded from +heredity; that is, they come from families in which there is much +feeble-mindedness, usually associated with various neuroses or psychosis. +There are about thirty-five per cent. approximately that are acquired +cases. These cases develop from various things. Full development may be +prevented during gestation, or early childhood, or early adolescence, but +these acquired cases are entirely distinct from the hereditary ones." + +In a recent paper Doctor Martin W. Barr, chief physician for the +Pennsylvania Training School for Feeble-minded Children, says: "In my +individual study of 4,050 cases of imbecility, I find 2,651, or 65.34 per +cent., caused by malign heredities; and of these 1,030, or 25.43 per +cent., are due to direct inheritance of idiocy; and 280, or 6.91 per +cent., to insanity." From these figures it will be seen that Doctors Barr, +Goddard, Wilmarth, Johnstone and Rogers all agree in their estimates; +namely, that two-thirds of our imbeciles are so through inheritance. + +=Some Results of Non-Restraint of the Feeble-minded.--=The following +excerpt from a paper by Doctor Barr, is a fair sample of what happens +when such defective individuals are not restrained from propagating their +kind: + + "My own study and observation alone, of over 4,000 degenerates, shows + such examples as: A man 38 years of age, the father of 19 defective + children, all living, he and his wife both under par mentally; as was + another couple, with 9 imbecile children; an idiot woman with 7 idiot + children. A forcible instance is that of a man with two daughters and + one illegitimate grandchild, all feeble-minded.... I could name a + family, one of the proudest in the land, where there are five + children, an aunt and two uncles, all feeble-minded. + + "Yet another, which in seven generations numbering some 138 + individuals, records 10 still-born children (premature births), 16 + insane, 7 imbeciles, 3 epileptics and 32 with mental peculiarities so + pronounced as to occasion remark. Of the 138 there remain 80 + apparently normal, who are nevertheless hopeless slaves of a neurotic + heredity, direct or collateral. + + "In a study of 15 imbecile girls, 3 were recognized prostitutes, 9 had + each 1 illegitimate child (2 being the result of incestuous + intercourse with brothers); 1 had 2; 2 epileptics had, the one 3, and + the other 4 idiot children. + + "Four feeble-minded women had 40 illegitimate children. + + "A feeble-minded woman living in an almshouse since early childhood, + allowed to go out to service periodically, had given birth to six + illegitimate children, all inheriting her defect. + + "An imbecile drunkard is the father of three feeble-minded children. + The daughter, seduced before the age of sixteen, gave birth to an + idiot child; one son is a harmless imbecile, but the other is a moral + imbecile, a sexual pervert, a thief on the streets, and a pyromaniac, + firing in sheer wantonness a large mill property. + + "Another shows the entire family for three generations below normal. + Father, mother, mother's sister, and father's uncle, all imbecile. + Five children feeble-minded. One girl had a proposal of marriage, and + one boy is married to a feeble-minded girl. + + "One insane woman, whose brother and sister committed suicide, had + five sons. The oldest, feeble-minded, a drunkard and hobo, had one + son, a criminal. The second son, insane, had three imbecile children. + The third, an insane epileptic, had three imbecile sons, one of whom + was an epileptic. The fourth son was insane. The fifth, apparently + normal, had a morally imbecile son and an epileptic daughter." + +Yet striking as is the inheritance of these maladies, Doctor Barr points +out that of the 10,000 known cases of feeble-mindedness in Pennsylvania, +only 3,500 are sequestrated. This leaves a balance in that state of 6,500 +totally irresponsible individuals to work havoc in society by producing +their kind. + +=Inheritance Not a Factor in Some Cases of Mental Deficiency.--=On the +other hand as our data show, there remain about one-third of the mentally +deficient type to be accounted for on other than a basis of heredity. As +already noted, some of these are doubtless the product of suppressions of +normal development by various extraneous factors operating before or +shortly after birth. There is one class particularly, estimated by some +authorities as constituting as high as thirty per cent. of the +feeble-minded which is unusually puzzling. These are the so-called +mongolians. The name is given because the features of such individuals +bear more or less resemblance to those of some of the Mongolian races. The +defect does not seem to be hereditary although it is usually congenital. +It appears to be due to something which interferes with prenatal +development. Whatever the conditions, whether lack of nutrition in the +mother, alcoholic or other poisoning, the cases seem to be as hopelessly +incurable as are the hereditary forms. From the social standpoint, of +course, such individuals are in their immediate generation, as incompetent +or as dangerous to society as those suffering from the more surely known +hereditary forms of mental defect. + +=Epileptics.--=Although epileptics are not classed as imbeciles +ordinarily, as a matter of fact no sharp distinction can be drawn between +the two classes. Doctor Wilmarth says, "Epilepsy and mental deficiency are +as closely related as branches on the same tree.... Over one-half and +perhaps two-thirds of all feeble-minded are subject to convulsive seizures +at some period of their lives, and we are never surprised at the +appearance of epilepsy in any feeble-minded person. On the other hand, so +small a percentage of epileptics maintain normal mental actions as hardly +to be worth consideration ... even those who retain a normal mind in the +early stages of the diseases almost infallibly become imperfect later." +How slight a chance the epileptic has of ever becoming normal may be +inferred from a statement made by Doctor Frank Billings in a paper read +before the Illinois State Medical Society in 1909 to the effect that "ten +per cent. or more can be cured by proper care." + +According to the estimates of "The Committee of Fifty" in the state of +Illinois, who have been agitating for the establishment of a colony for +epileptics, there are 10,000 of these unfortunates in that state. The +consensus of opinion of experienced workers in various states is that +there is about one epileptic to each three hundred fifty to five hundred +inhabitants. + +=In Heredity Conditions of Feeble-Mindedness Are Probably Recessive to +Normal Condition.--=As to the mode of inheritance of the various forms of +feeble-mindedness, the evidence points to such defects in the main as +being recessive. However, no particular grade can be picked out and shown +to be a pure recessive. For instance, the children of two epileptics will +be defective but it is impossible to predict always whether the defect +will appear as epilepsy or feeble-mindedness. This is doubtless due to the +fact that mental deficiencies even of the inheritable type are not all due +to the same specific cause, and in many cases the individual is defective +in more than one direction. If one or more of a great number of units +which are necessary for complete mental development are lacking, obviously +mental deficiency will result. In other words, feeble-mindedness and +allied disorders may not be definite characters, but simply evidences of +the fact that the nervous system has not developed all factors necessary +for normal mental coordination. Goddard, however, one of our best +authorities on the heredity of feeble-mindedness, is inclined to regard +the condition as a unit character, "due either to the presence of +something which acts as an inhibitor, or due to the absence of some +stimulus which sends the normal brain on to further development." + +Supposing nervous defects finding expression in feeble-mindedness, +epilepsy and related conditions, to act as a Mendelian recessive, then the +marriage of one such defective with another should yield only mentally +enfeebled offspring. How nearly this expectation may be realized is seen +from the following examples. + +In an extensive study[9] of feeble-mindedness, just from the press, Doctor +Henry H. Goddard points out that of 482 children with both parents +feeble-minded all but six were feeble-minded. Even the exceptions may be +apparent rather than real as there is possibility of mistake in judging +the condition of the parents or of the children themselves. Moreover, with +the feeble-minded one is not always sure of the paternity of a child, as +is instanced by Doctor Goddard in a case quoted from Doctor Emerick in +which of twelve children in a white family with both father and mother +feeble-minded ten were feeble-minded and two were not, but these two were +_mulatto_ children. + +In a paper by Weeks (_The Inheritance of Epilepsy_), in part an extension +of an earlier joint paper by Davenport and Weeks, is recorded among others +a study of twenty-seven fraternities in which both parents were either +epileptic or feeble-minded. Of the 28 progeny, 19 lived long enough to +reveal their mental state. Of these 3 were feeble-minded, 8 epileptic and +8, from parents who developed epilepsy late in life, were what Doctor +Weeks terms "tainted." In 15 fraternities in which one parent was +epileptic and the other feeble-minded he found there had been 81 +conceptions. Of these 7 were too young to classify and 19 had died before +fourteen years of age. Of the remaining 55, 28 were epileptic, 26 +feeble-minded, and 1 insane. Again, in 9 families in which the parents +were both feeble-minded, of the 38 surviving offspring who were old enough +to classify, 7 were epileptic, 29 feeble-minded, and 2 drunkards. In 5 +families where one parent was insane and the other epileptic or +feeble-minded, 5 children died before the age of fourteen, the condition +of 2 was unknown, 2 were epileptic, 4 feeble-minded, 1 insane, 8 tainted, +and 7 seemingly normal. Regarding the latter Doctor Weeks says they came +from two families where in one case the father's insanity seemed to be +traumatic and in the other alcoholic. + +In a few cases where the defect in one parent has apparently been of a +type different from the defect of the other parent a "normal" child was +produced. That is, presumably each parent carried normality in the trait +defective in the other so that the child became simplex with reference to +each defect. Davenport points out that not infrequently two deaf-mutes +whose defects are due to different causes may have normal children. + +In general, however, the reasonable expectation is that where two +feeble-minded individuals marry, a very common occurrence, the children +will all show mental deficiency. A mating between a feeble-minded person +and one of perfectly normal stock will apparently result in normal +children although they will be carriers. There is some evidence, however, +that such carriers may occasionally show "taints" of abnormality in the +form of migraine (nervous sick headache), alcoholism, queerness, violent +temper, etc. Thus according to the studies of Doctor Weeks, "In 50 matings +where at least one parent is migrainous, there were 350 conceptions, of +which number enough is known of 212 to classify 55, or 26 per cent., as +epileptic; 12, or 6 per cent., as feeble-minded, with the others tainted +or normal. In the 131 matings where at least one parent is alcoholic, +there were 845 conceptions. Of the 494 classified, 151, or 31 per cent., +were epileptic; 54, or 11 per cent., feeble-minded, with the balance +tainted or normal." Marriage between two carriers will cause the defect to +reappear in active form in approximately 25 per cent. of the offspring and +50 per cent. will continue to be carriers. + +=Many Apparently Normal People Really Carriers of Neuropathic +Defects.--=There is considerable evidence that many apparently normal +individuals of our average population are in reality carriers of some form +of neuropathic defect, some authorities placing the proportion +provisionally at over thirty per cent. This being true, then it is easy to +explain the apparently unaccountable appearance of epilepsy, +feeble-mindedness, or similar defects among the children of what pass for +normal stocks. The probabilities are that in many cases it means simply +that the parents of the defective children have been carriers. + +As to the contention that in preventing the propagation of the +feeble-minded we may be depriving the world of geniuses, Doctor Goddard +remarks: "It is a significant fact that in our three hundred family +histories totaling 11,389 individuals not a single genius has been found. +Not only are there no geniuses but the fact can not be too strongly +emphasized that even the people who are considered normal ... are not as a +rule people of average intelligence...." However, between insanity and +genius he finds more kindred spirit. + +=Tests for Mental Deficiency.--=As to tests for mental deficiency, the one +commonly meted out to victims in the every-day world is the +social-economic one of survival in the competitions of life. The mentally +deficient fail. Although often unrecognized as feeble-minded they drift +through life social and economical derelicts who have to be supported by +the community. + +Of laboratory tests many have been devised. While all yet leave much to be +desired, still through their application the majority of mental defectives +can be detected. Fairly accurate standards of normality have been +established from which the relative degree of "backwardness" can be +determined. We have just awakened to the importance of detecting +defectives early in life, hence many of our tests have been planned with +reference to children. They are based not so much on training or conscious +learning as on fundamental processes which develop at certain ages in +children. Another impetus toward securing adequate criteria of mental +deficiency has been the crying need of having some easily applied standard +for detecting the very large numbers of defective immigrants who are +continually seeking to enter the United States. + +Most of the methods consist of "performance" tests which are planned to +test the powers of perception, concentration, application, ingenuity and +education of the subject. Previous environment, education and the +difficulties under which the subject may be laboring at the time of the +test must, of course, be taken into account. It is particularly difficult +to get adequate tests for the immigrant which will enable one to +distinguish between ignorance, stupidity, fear and temporary psychic +depression on the one hand, and congenital mental deficiency on the other. + +Perhaps the most successful single set of tests for mental deficiency is +that known as the Binet-Simon Scale. From an examination of large numbers +of French school children Binet constructed a scale of tests of increasing +complexity accurately graded to age and previous training of the average +normal child. In the Binet-Simon system tests are given for each age from +three years to thirteen. When a child successfully passes the tests for +his age he is classed as normal. If he succeeds only in tests which +normally are those given for a child a year younger then he is backward to +the extent of one year. Similarly he may show by these graded tests that +he is backward to the extent of two years, three years and so on. If a +child is more than three years backward according to the test he is +regarded as mentally defective. Various corrections and adjustments of the +original scale have been worked out to allow for unevenness in mental +development. On the whole the scheme works out satisfactorily when applied +by one skilled in its use. The attitude of the examiner, however, is of so +great importance that the tests are of less value in the hand of +inexperienced workers. A revision of the scale to adapt it better to +American children has recently been made by Doctor Goddard.[10] Besides +the Binet-Simon tests various performance tests, standardized for children +of different ages, such as Seguin's form board, Healy's pictorial +completion test, Fernald's construction puzzle, the Rossolimo test, De +Sanctis test, etc., are used by different investigators. Questions +designed to reveal moral tone are also employed. Doctor Howard A. Knox, +assistant surgeon United States Public Health Service, in a recent +article[11] gives an interesting account of the tests applied to determine +the exact mentality of immigrants entering the United States together with +a brief review of various tests. A full account and discussion of the +various tests for the mentally subnormal will be found in a recent +publication by Doctor William Healy,[12] director of the Juvenile +Psychopathic Institute, Chicago. + +=The Backward Child in School.--=It is only in recent times that we have +come to realize the seriousness of the problem which the backward child +presents in our schools. It is of the utmost importance to discover early +in school life which of the backward children owe their condition to +adenoids, defective sight or hearing, poor nutrition, imperfect +circulation, or other remediable defects, and which are the victims of +innate mental deficiency. The treatment of the individual must be very +different in the two cases. In the one the condition can be cured by +proper manipulations or other treatments; in the other it can only be +ameliorated. All school children who are two or three years below grade +should be rigidly inspected by the medical examiner. + +From a study of about two thousand children comprising the first five +grades of an entire public school system Goddard found that eighteen per +cent. were definitely "backward." Of these between two and three per cent. +were actually feeble-minded, the condition in the remaining fifteen per +cent. being presumably capable of correction. Other similar surveys have +given practically the same results. + +=The Exceptionally Able Child Likely to Be Neglected.--=However, while we +must not forget that it is important to recognize backward children and to +see that they are segregated into small groups which are not required to +do the full amount of work in regular time, it is equally urgent to see +that the unusually bright individual is also given opportunity to advance +more rapidly than the rank and file. Only too often the holding back of a +child in school leads to lack of interest and habits of mental laziness, +and sometimes to truancy and incorrigibility. The general attempt in our +graded schools to keep all children close to the average is to be strongly +condemned. + +=Cost of Caring for Our Mentally Disordered.--=Doctor Charles L. Dana, +member of the National Committee for Mental Hygiene, estimated in 1904 +that the actual cost of caring for feeble-minded and insane in the +United States amounted to sixty million dollars, to which should be added +the corresponding loss in industrial activity on the part of the +afflicted,--at least twenty million dollars more, and he figures that the +amount was increasing at the rate of four per cent. per annum. Many +investigators concur in the opinion that our insane and feeble-minded +alone cost us far above one hundred million dollars. Adding to this +economic burden the cost of our delinquents and criminals the total +expense becomes stupendous. And when we consider still further the even +greater burden of suffering of the unfortunates themselves and the sorrows +of those to whom they are dear, a burden not measurable in money, the +feeling that something must be done to relieve the situation becomes +overpowering. + +=Importance of Rigid Segregation of Feeble-Minded.--=As regards the really +feeble-minded little can be done beyond making them as happy as possible +and developing the limited gifts they have been given by nature. Their +teaching must be in the main concrete and simple. At the age of puberty it +is imperative to see that the sexes are separated and kept under +sufficient permanent supervision to prevent all possibility of +procreation. There is neither economic nor common sense in even allowing +the remotest chance of such occurrences as the following: "This is the +case of a feeble-minded and epileptic woman who had six children by +various persons while an inmate of a county poor house. One child at the +age of eighteen died in the almshouse, two died in infancy, one was +epileptic (the son of a man with a criminal record) and two who are now +living in the almshouse are feeble-minded, one being the son of a negro." +Again, we find a superintendent of an English almshouse reporting that one +hundred and two out of one hundred and five children born there in five +years were feeble-minded. + +As conditions are to-day every institution for the feeble-minded has a +long waiting list and the same is true of most asylums for the insane. +Instead of providing the prolonged care necessary for such patients, +institutions are forced to discharge many prematurely in order to make +room for more urgent cases. + +=Importance of Early Diagnosis of Insanity.--=In insanities, even when of +hereditary origin, there is much hope in certain cases of greatly +benefiting the individual, though a permanent cure, or at least the +establishment of procreative fitness may be impossible. It is extremely +important that the public realize how much can be done through early +examination and advice in such mental afflictions. Most of the insane who +recover usually do so within a few months of their first alienation, hence +the importance of losing no time in detecting the condition and securing +early treatment. It is now well known that many cases of chronic insanity +may be measurably improved under the care of a psychiatrist by systematic +re-education, especially in industrial lines. But how little of this may +be expected at the hands of the untrained custodians who "feed" the +inmates of our county almshouses, to which in many states the chronic +insane are entrusted, is obvious. + +=All Insane Should Be Passed Upon by Competent Psychiatrists.--=The +atrocious system of turning the chronic insane over to county poorhouses +manned by supervisors whose chief qualification for the position has not +infrequently been the lowness of their bid for boarding and caring for the +inmates, can not be too strongly condemned. Incredible as it may seem, in +some states the court can on its own judgment send patients directly to +these institutions without first submitting them to the study of expert +physicians in the state hospital for the insane. The viciousness of such +procedure is evident when one realizes that often careful scrutiny on the +part of the very best experts, extending over a considerable period of +time, is required before the true condition of the patient can be +determined. Recently a psychiatrist of high standing, who was gathering +data on county asylums for a national organization, informed the writer +that beyond the shadow of a doubt he had come across case after case in +county asylums which would have been curable under proper treatment. + +Here again the responsibility in last analysis must rest upon us as +citizens, for it is largely through our intelligent demands as voters that +conditions will be improved and competent experts be put in charge of +county asylums as well as of the state hospitals for the acutely insane. + +=Some Insanities Not of Hereditary Origin.--=Some alienists believe that +self-poisoning known as _auto-intoxication_, due to improper elimination +of poisons generated through faulty digestion or metabolism, if of long +standing, may be not only a contributory but a more or less direct cause +of insanity. About twenty per cent. of insanities of men living in cities +and about fifteen per cent. of those living in the country seem to be +directly related to the intemperate use of alcohol. The corresponding +figures for women are seven per cent. and one per cent. respectively. +General paresis or softening of the brain is probably invariably preceded +by syphilis. About twenty-two and five-tenths per cent. of the first +admissions to hospitals for the insane from city-dwelling men, and eight +per cent. from men living in the country in the state of New York are +cases of this kind of insanity. The corresponding figures for women are +five and five-tenths per cent. and two and five-tenths per cent. +respectively. + +=Importance of Heredity in Insanity Not Appreciated.--=We have already +seen that heredity plays an important part in insanities. There can be +little doubt that the tendency is to under-estimate rather than +over-estimate its importance. Many cases said to be "caused" by mental +strain such as those occasioned by domestic infelicities, business +reverses and the like should in all probability be fundamentally +attributed to something far more deep-seated than the more obvious cause. +In many such instances there is little doubt that an inherent weakness in +mental make-up exists which predisposes the individual toward mental +breakdown. This is more apparent when one recalls that there are thousands +of other individuals who undergo equally great or greater calamities +without loss of mental balance. There are well-recognized types of mental +disposition which later contribute to corresponding forms of insanity. In +many instances the final catastrophe may be averted if the "peculiar" +individual can be kept in good health and guided into right habits of +thought. Undoubtedly certain infectious diseases, arterio sclerosis, +various poisons in the blood, child-birth, and similar influences often +enter as important contributory factors. In all cases of cure, however, we +must face the fact that under existing conditions these mentally restored +individuals are released into society without let or hindrance as regards +their marital relations. + + + + +CHAPTER IX + +CRIME AND DELINQUENCY + + +=The Relative Importance of Heredity and Environment in This Field +Uncertain.--=The whole question of crime and delinquency is a highly +complex one. Here, perhaps, more than in any other phase of race +betterment we find the greatest difficulty in separating the effects of +hereditary predisposition from the results of unfavorable environment. +While there is no longer a reasonable doubt about such nervous disorders +as epilepsy, feeble-mindedness and certain forms of insanity being rooted +largely in ancestral taints, the degree to which crime or delinquency is +based on heredity is far more questionable. Every student of genetics +knows that we may have dwarf plants because the constitution of the germ +is of a nature to produce only such individuals, or we may have dwarfed +plants because of adverse conditions of soil and lack of an opportunity to +climb or rise to their full capacity. Bateson pertinently remarks, "The +stick will not make the dwarf pea climb, though without it the tall can +never rise. Education, sanitation, and the rest are but the giving or +withholding of opportunity." The important sociological question for us to +determine is which of these lowly peas of the human family are really +dwarfs and which are dwarfed simply because the stick of opportunity on +which to climb is lacking. + +Beyond doubt a considerable portion of crime and degeneracy is due in +large measure to innate inclination, but with just as little doubt much is +the effect mainly of vicious habits acquired through an unwholesome +environment. A normal appetite or impulse may be given a pathological +trend by bad influences. And one has to reckon, moreover, with degrees of +hereditary aptitude to crime. Just what is the measure of normality? To +what extent by developing to their highest point certain inhibitive or +opposing tendencies, can we counteract certain inherent proclivities for +wrong-doing? By what means shall we sift the congenital defectives from +the victims of suppressed opportunities? These and kindred questions +confront us at the very outset of our studies of crime and delinquency. It +is obvious that although we may institute the strictest elimination of the +socially unfit, unless we can provide a wholesome environment for the fit, +lapses into unfitness are sure to recur. + +=Feeble-Mindedness Often a Factor.--=The conviction is steadily growing +among students of human heredity that a considerable amount of crime, +gross immorality and degeneracy is due at bottom to feeble-mindedness and +that, therefore, if we can once eliminate feeble-mindedness, these vicious +accompaniments will at the same time in equal measure disappear. Goddard, +for example, one of our authorities on the inheritance of +feeble-mindedness, is convinced that a large proportion of the delinquent +girls who fill our reformatories are actually feeble-minded. They are +often the higher grade or moron type, and their mental condition remains +unsuspected because they have never been thoroughly tested in this +respect. + +=Many Delinquent Girls Mentally Deficient.--=According to Havelock Ellis, +2,500 of some 15,000 women who passed through Magdalen homes in England +were definitely feeble-minded and were known to have added a thousand +illegitimate children to the population. + +The preliminary reports of the so-called white slave investigations now in +progress in New York City classes 25 per cent. of these unfortunate women +as mentally incapable of taking care of themselves. Other investigations +indicate that from 40 to 60 per cent. of this class of women are +defectives. For example, from the report of the Massachusetts "Commission +for the Investigation of the White Slave Traffic, So-Called," one reads: +"Of 300 prostitutes, 154, or 51 per cent., were feeble-minded. All +doubtful cases were recorded as normal. The mental defect of these 154 +women was so pronounced and evident as to warrant the legal commitment of +each one as a feeble-minded person or as a defective delinquent.... The +135 women designated as normal, as a class were of distinctly inferior +intelligence. More time for study of these women, more complete histories +of their life in the community, and opportunity for more elaborate +psychological tests might verify the belief of the examiners that many of +them were also feeble-minded or insane." + +The data from some of our public reformatories, industrial schools and +state homes for delinquent girls, are very instructive in this respect. +Reports from a number of such institutions show that many of their inmates +are mentally subnormal. The proportions range from thirty-three per cent. +in the New Jersey Reformatory at Rahway to eighty-nine per cent. in the +institution at Geneva, Illinois. + +=Institutional Figures Misleading.--=However, significant as are these +figures from institutions for delinquents, one should not be misled by +them. They are undoubtedly not representative of offenders in general, but +of a selected group of the most hopeless cases. In the first place the +more capable individuals escape the dragnet which lands the defective +delinquents in an institution, and furthermore, because of liberal systems +of probation, only the more incorrigible or the very stupid make up the +bulk of the population of such places. Miss Augusta F. Bronner, assistant +director of the Psychopathic Institute of the Juvenile Court of Chicago, +from a careful study of five hundred and five cases of delinquent boys and +girls in the Detention Home, chosen with as little selection as possible, +finds the proportion of mentally subnormal among them to be less than ten +per cent. + +=Many Prisoners Mentally Subnormal.--=Doctor Walter S. Fernald, of the +Massachusetts School for Feeble-minded, estimates that "at least 25 per +cent. of the inmates of our penal institutions are mentally defective." +Among the various available estimates at hand this seems to be a fairly +conservative approximation. Hastings H. Hart points out that this +calculation of 25 per cent. means that there are 20,000 adult defective +delinquents in prison, and 6,000 youths in juvenile reformatories, or a +total of 26,000 in custody in the United States. + +=The Inhibitions Necessary to Social Welfare Not Well Established in +All.--=But let us look at this matter of delinquency a little more in +detail. In common with other living creatures mankind has two strongly +predominating instincts without which there can be no prolonged individual +or racial existence, namely, the self-preservative and the reproductive. +Says Schiller: "While philosophers are disputing about the government of +the world, Hunger and Love are performing the task." Under +self-preservative would be included everything pertaining to food, +property and self-protection. In addition, however, man, together with +certain other social animals, has developed a third set of activities or +instincts--an impulsion toward the preservation of the community to which +he belongs--and so far has this evolved in his case that it outranks in +importance the other two. For the highest accomplishments and ideals of +the race are in last analysis expressions of this social instinct. But +with this system of mutual help comes the necessity of certain restraints, +because for society to exist its members must impose upon themselves, or +have imposed upon them, certain inhibitions of their self-preservative and +reproductive instincts. + +Being a late acquisition of the race and less firmly ingrained, the social +instinct is not well established in all individuals. Some have it +sufficiently strong to exercise of their own accord the necessary +inhibitions of other instincts. Experience has shown that others, either +through a lack or through a wrong cultivation of it, can not or will not +do so unaided. For the latter, society has instituted certain conventions +and the criminal law whereby through a system of restraints and +punishments such an individual is held in check either by actual physical +restraint of his property or person or through the powerfully inhibitive +factors of shame or fear. Man as a normal member of society must +constantly take heed of the physical, intellectual or moral danger the +exercise of a given feeling, action or procedure on his part will bring to +humanity, and govern himself accordingly. + +But it is in just these very inhibitions that mental defectives are +lacking. They are almost invariably anti-social types because they are +unable to establish the personal abstentions which are necessary for the +good of the community. While in the individual of innate normal mentality +anti-social traits may have developed because of improper training or +surroundings, in mentally defective types some factor or factors necessary +to normality have been left out of their make-up and as a result they are +often wholly lacking in social instincts or have these so feebly developed +that education and exhortations toward social ideals are fruitless. We can +not appeal successfully if there is nothing to appeal to; we can not +develop something out of nothing. + +=The High-Grade Moron a Difficult Problem.--=One great difficulty in +identifying the high-grade morons who are a bountiful source of our +criminals is our almost universal failure to recognize that a memory test +alone is not sufficient to determine the mental responsibility of an +individual. Not only memory, but judgment, will-power and perhaps, also, +to a lesser degree, the powers of attention and concentration are all +indispensable elements in the make-up of a normal individual. There are +cases on record of imbeciles with prodigious memories, yet hopelessly +incapable of caring for themselves or of respecting the rights of others. +In fact certain types of morons, usually cunning, often prepossessing and +superficially clever, are characterized by good memories and will +_moralize_ volubly, although their wills are too weak to inhibit impulses +when they face temptation. It is obvious that just in proportion as the +intelligence of the high-grade degenerate approaches normality and yet +remains abnormal, the more dangerous he may become to society. + +=Degenerate Strains.--=A number of family records are now available which +show convincing evidence of the hereditary nature of a degeneracy which +finds expression in pauperism, immorality and crime. + +As has already been pointed out, there is reason to believe that much of +this is based in some degree on feeble-mindedness. One of the most +remarkable of these is the recent study on degeneracy by Goddard as set +forth in his book called _The Kallikak Family_. The record is that of six +generations of descendants from an original progenitor to whom the +fictitious name of Kallikak has been assigned. This individual, descended +from good stock, before his marriage met a feeble-minded girl by whom he +became the father of a feeble-minded son. Later he married a normal woman +by whom he had normal children. Thus from one normal father have sprung +two lines of progeny, one vitiated with feeble-mindedness, the other +normal. The comparison may be readily made by drawing up in parallel +columns the data as follows: + + LINE A LINE B + + In five generations 480 direct In five generations 496 descendants + descendants from a normal father from the same normal father as in + father and a feeble-minded Line A and a normal mother have the + mother have been accounted for following record: + as follows: + + 143 known to be feeble-minded. All but one of normal mentality. + + 291 mental status unknown or Two men known to be alcoholic. + doubtful. + + 36 illegitimate. One case of religious mania. + + 33 sexually immoral, mostly Among the rest have been found + prostitutes. nothing but good representative + citizenship, numbering doctors, + 24 confirmed alcoholics. lawyers, educators, judges, + traders, etc. + + 3 epileptics. No epileptics or criminals. + + 82 died in infancy. Only fifteen children died in + infancy. + + 3 criminals. + + 8 keepers of disreputable houses. + + 46 only ones known to ben ormal. + +Certainly there is abundant food for thought in these two records. + +If we take still other families of criminal or degenerate antecedents the +same multiplication of viciousness, as a rule, is in evidence. Thus, +_Margaret, the Mother of Criminals_, has left a progeny of some 700 +paupers, prostitutes and criminals, some of the women bearing as many as +twenty children. The famous Jukes family, so often cited, with its 310 +professional paupers, 300 deaths in infancy, 440 physical wrecks from +debauchery, 50 prostitutes, 60 habitual thieves, 7 murderers, and 130 +other convicts out of a total 1,200 descendants who have been identified, +has alone cost the state of New York $1,250,000 in the care of its +criminal, defective and immoral progeny. + +Another family record, the Zeros, reported by Poellman, of Bonn, starts +with a female confirmed drunkard. In six generations of her descendants, +totaling 800 people, Poellman found 102 professional beggars, 107 +illegitimates, 181 prostitutes, 54 in almshouse, 76 convicted of serious +crime, 7 of murder, and costing some $1,206,000. Or we might cite the +so-called _Tribe of Ishmael_, the progeny of a neurotic man and a +half-breed woman. They have spread their ill-favored spawn over various of +the central states in a veritable flood of imbecility and petty crime. And +to these families may be added the records of _The Hill Folk_, _The +Pineys_, or others of the several recent studies of degenerate strains. +All bear the same message of rapidly multiplying degeneracy. + +=Intensification of Defects by Inbreeding.--=Most of these regional +surveys that are now in progress show that there is particular danger in a +population becoming broken up into small communities and isolated. Under +such conditions there is a pronounced tendency to intermarry, and if +deterioration is already present in the stock such communities become +centers of marked degeneracy. The situation is well exemplified in the +following excerpt from Davenport: + + "I have been going over the records of one family in New York, the + so-called Nam family. There were 55 per cent. consanguineous matings, + marriage between cousins, in one generation, and, owing to the fact + that the strain was already loaded with defects, we can see how these + defects were concentrated by these cousin marriages, so that about 90 + per cent. of the strain is feeble-minded. There were fully 90 per + cent. of the men who are unable to resist the lure of liquor. + One-fourth of the children are born illegitimates. Infanticides, + incest, murder, harlotry, are all over the chart. This is a highly + inbred community, keeping a nearly pure strain of social defects, and + the cost to the community has been a million and a half on a fair way + of figuring, not directly in the care, but indirectly in the damage + they have done. These constitute a rural community. Out of this + community we can trace those who have gone to the cities and become + murderers, prostitutes and thieves. They are not confined to one + state; they spread out over the country. One branch of the family came + to the state of Minnesota. We sent to one of Doctor Rogers' trained + field workers to learn whether she had ever heard of this family, and + received a reply that the family was well known to social workers in + the state of Minnesota. These strains of degenerates are not local + matters at all; they are matters of national interest." + +Concerning crime and delinquency, we find that all evidence tends to show +that an alarming increase is in progress although satisfactory data are +hard to obtain. It is certain that there is a tremendously +disproportionate increase in the number of prisoners in recent years +compared with general population, for while the total population has +increased three and one-half fold, the prison element has increased +fifteen fold. According to Wier, in this country there are four and +one-half times as many murders for every million of our population to-day +as there were twenty years ago. + +It may be urged that this increase in prison population is not a +disproportionate increase in the number of defectives or criminals, but +only an increase in the number sent to prison, and this is probably a +partial truth--but when we recall such pedigree as those of the Nams, the +defective line of Kallikaks and other known unsound strains, he must be +hopeful indeed who can find much consolation in this supposition. In any +event, no such uncertainty exists regarding the number of murders and +homicides, since these have in all probability been as fully recorded in +the past as at present. + +=Vicious Surroundings Not a Sufficient Explanation in Degenerate +Stocks.--=It is sometimes urged that we are not dealing in such cases with +degenerate strains, but merely with unfortunate individuals who have been +subjected to pernicious surroundings from the beginning. And it can not be +denied that parents who are mentally defective, dissipated or syphilitic +afford most noxious developmental and environmental conditions for their +children. But when one notes how intimately the moral degeneracy in such +stocks is bound up with some degree of feeble-mindedness, he is strongly +skeptical toward the sufficiency of such an interpretation, although +environment undoubtedly intensifies the results. Concerning this point +Davenport says: + + "We have certain methods of testing whether it is bad environment or + bad breeding which produced these people. Some of the children have + been taken at an early age and 'placed out'. We have traced their + subsequent history. In most cases they have turned out quite as bad as + those who have remained at home. In a few cases they have turned out + well, but it is also true that some of the children who remained at + home in bad environment have turned out well." + +And to Davenport's testimony may we add that of Doctor Wilmarth, who, +speaking of children at the home for feeble-minded, says: + + "In no place is this subject of the power of heredity in relation to + environment so easily studied as among our children. A group of many + little children came to us from the state school, being untrainable + there. They have had with us the same teaching and the same + companionship. Each one has lived, eaten and slept among the others, + and, so far as we know, with but one exception, those of vicious + parentage have turned instinctively to vicious traits by preference, + while those of simple but honest stock do evil things only under + strong temptation, and do not persist in them after the wrong is + pointed out." + +=By No Means All Delinquents Are Defectives.--=One must not overlook the +fact, however, that _delinquent_ and _defective_ are by no means +synonymous terms, and that many delinquents are with little doubt the +product of adverse social circumstances. + +The recent careful work of Doctor William Healy[13] in connection with the +juvenile delinquents of Chicago shows convincingly that the underlying +causations of delinquency are many. Such factors as immorality or constant +quarreling of parents, bad companions, lack of parental control, defective +sense organs, debilitating habits, lack of healthy mental interests and a +host of other environmental factors are not infrequently sufficient in +themselves to develop delinquency in the absence of inherited deficiency. +The present-day efforts of the student of heredity should not be +misunderstood. They are not attempts to make all delinquents out +defectives, but rather to determine what percentage of delinquents may be +legitimately reckoned as defective and to make the facts known. Since +there is no longer any reasonable doubt that, to express it in the mildest +terms, an amount of delinquency far from negligible is due in great +measure to congenital omissions or propensities, then the sooner the +public learns this the better, for we may then set about supplementing our +present efforts at race betterment through external improvement by +devising means of cleansing the fountain source as well. + +It can scarcely be doubted that the average man differs little if any in +inherent personality and capacity from many a criminal who is such by +occasion rather than by undue predisposition. Who can truthfully answer +how many individuals there are who are not potentially criminals to some +extent, given sufficient evocative conditions of ignorance, vice, adverse +economic pressure and undue temptation? + + "Virtue itself turns vice, being misapplied." + +=No Special Inheritable Crime-Factor.--=The main difficulty in trying to +find a hereditary basis for crime lies in the multiplicity of things crime +may be. The individual impulsions which lead to certain offenses may be +utterly different from those which conduce to others. Undoubtedly many +inborn tendencies which are perfectly normal or neutral in themselves may +be warped by circumstances into the commission of what are classified as +crimes. The moral man may have the same desire for a thing that the +criminal does, but when he finds that this desire can only be gratified by +injury to others, he inhibits it because of his repugnance to such injury. +The criminal makes no such inhibition. + +In general, crime means an offense of some kind against person, property +or state. But a biological analysis of it, could it be made, would require +among other things knowledge of crime in terms of motive or lack of +motive, whether the act was intended to benefit the perpetrator, some +other person, or even the race or state; whether the offense was one of +dishonesty, of cupidity, of lust, or of violence against another. + +As a matter of fact no satisfactory classification of crime can be made +since so many factors enter and in such varying degrees. Most +classifications made in our legal codes are a hodge-podge based on a +mixture of motive on the part of the participant, degree of turpitude +involved, nature and extent of the injury inflicted, and the object +against which the offense was perpetrated, whether an individual, society +or the state. Moreover, it must not be forgotten that in many instances +what was crime in the past is no longer so, and vice versa many things +which are regarded as criminal to-day were not considered so in the past. +So the futility of seeking a specific inherent propensity for "crime" is +manifest. How, for instance, in terms of hereditary determiners shall we +draw the fine lines of distinction among those who bribe legislators and +legal officials, those who are avaricious and dishonest in the world of +trade, and those who are wilfully obtuse in providing proper safeguards +for employees? + +=What Is Meant by a Born Criminal?--=All we can do is to fall back on the +assurance that any act directly or indirectly injurious to society is an +offense, and that those offenders who are congenitally unable to +distinguish between what is generally accepted as right and wrong, or who +if recognizing this are nevertheless uncontrollably impelled toward or are +unable to refrain from anti-social acts because of some inherent condition +of intellectual or volitional make-up, may be legitimately classed as +individuals born with an aptitude for crime and social transgressions. In +such individuals the natural mental make-up is lacking in some of its +necessary elements so that memory, judgment, or will-power are not up to +the minimum that is necessary for the establishment of proper conduct. In +some cases, apparently, this lack finds expression in almost any kind of +vice or crime into which circumstances happen to lead the individual. In +others, however, there seem to be tendencies toward the commission of +certain types of crime or vice. Certain family strains are characterized +by petty thieving, others by deeds of violence, and still others by sexual +offenses. Certain types of mental defect are closely associated with +certain crimes. Thus sufferers from incipient paresis seem particularly +prone to commit assaults and larceny; epileptics, crimes of brutality and +violence. + +=The Epileptic Criminal Especially Dangerous.--=One of the characteristics +of epilepsy, indeed, emphasized by various psychiatrists, is that +frequently it leads to loss of those forms of self-restraint which are +absolutely indispensable to morality and the safety of society. Cruelty, +atrocious sexual offenses and other vicious crimes are the result. It is a +noteworthy fact, moreover, that often in the milder forms of affliction, +where instead of well-marked convulsions only momentary lapses of +consciousness occur, the greatest amount of mental and moral deterioration +and fluctuation is sometimes found. + +The situation as regards the epileptic is well presented by Doctor William +Healy, Director of the Juvenile Psycopathic Institute of Chicago, in an +article entitled "Epilepsy and Crime; the Cost", in the _Illinois Medical +Journal_, November, 1912. He says: + + "In the work of our institute,[14] which represents the most + thoroughgoing research into the genetics of criminalism ever + undertaken in this country, we have with the help of parents and + others carefully studied nearly 1,000 young repeated offenders. We + have found that no less than 7-1/2 per cent. of these are ordinary + epileptics, and we have reason to suspect others. This by no means + represents the total number of epileptics seen in connection with + juvenile court work, where, of course, first offenders as well as + large numbers of dependents are seen. In addition to my above + enumeration, other cases seen by the Detention Home physicians and + myself amount up to many scores of cases. If one remembers that it is + ordinarily calculated that one person in every 500 is epileptic, the + significance of this high criminal percentage is clear, and the + practical bearing of it is still further accentuated by the fact that + some of the worst repeaters are epileptics, and that many of the + gravest crimes are committed by those unfortunates. The connection + between epilepsy and crime has everywhere been recognized by students + of the subject, but it apparently needs constant emphasis in order + that common sense steps may be taken toward guardianship of these who + suffer from a disease which wreaks such extravagant vengeance on + society." + +=Mental Disorders Most Frequently Associated With Crime.--=Doctor Charles +Mercier, an English authority on crime and insanity, in enumerating the +mental disorders most frequently associated with crime, places the +insanity of drunkenness first. Any one who will take the trouble to verify +the facts in his own community will find that a large percentage, +frequently considerably over half, of the arrests made by the police are +for acts committed while the offender was more or less under the influence +of alcohol. Next to drunkenness among mental disorders which lead to crime +Doctor Mercier places feeble-mindedness. Next to feeble-mindedness comes +epilepsy; then paranoia or systematized delusion; next paresis; and lastly +melancholia. + +Paranoics are peculiar in that they are particularly apt to attack persons +of prominence. Highly egotistical, they almost invariably believe +themselves or some one or some cause dear to them, the subject of a plot, +perhaps to rob them, to torture them, to steal their inventions or +literary productions, or to persecute them in some way. Two if not three +of our murdered presidents owe their assassinations to paranoics. Many +rulers have been attacked and some killed by such insane individuals. Most +of the "cranks" who write threatening letters are lunatics of this type. + +Of the kinds of mental unsoundness known to be inheritable which are of +special significance from the standpoint of crime and delinquency +undoubtedly feeble-mindedness ranks first. We have already seen that as +our methods for detecting the higher grades of feeble-mindedness become +more accurate we disclose in border-line cases a veritable hot-bed of +mental incapacity suitable for the engendering of the criminal and the +vicious. Here in addition to some of the more pronounced criminal types +belong hosts of our chronic petty offenders, our sexually vicious and our +"won't-works". One interesting outcome of a recent investigation into the +army of unemployed in England was the discovery of the general unfitness +of these unemployed. In our own country the habitually unemployed are so +not because of lack of work, but largely because it is unprofitable to +employ them. + +=The Bearing of Immigration on Crime and Delinquency.--=Perhaps in no +field more than this of crime and delinquency, especially in so far as it +is based on innate deficiency, does the gravity of the immigration +question impress itself on us. How stupendous this problem[15] has become +may be realized from the fact that according to the census of 1910, +13,345,545, or one out of seven of the inhabitants of the United States, +were foreign born. And if we add to these the 18,897,837 of whom one or +both parents were of foreign birth, we reach the astonishing total of over +32,000,000, or more than one-third of our total population, who are +foreign born, or who have one or both parents of foreign birth. + +During the decade from 1900 to 1910, 8,500,000 foreigners came to the +United States, of whom 5,250,000 remained to make a permanent home. This +shows how rapidly our whole population might be radically changed. In +recent years the source of our immigrants has shifted proportionately from +northwestern Europe to southern and eastern Europe (Italy, Austria-Hungary +and Russia), and whether for weal or woe this new blood must inevitably +leave its impress upon us. Does it not behoove us then to seek with +anxious eyes some knowledge of these invading hordes with whom we are to +mingle our life-blood? + +Even the most superficial examination may well cause us grave concern. We +find that in one year (1908) at Ellis Island alone, 3,741 paupers, 2,900 +persons with contagious disease, 184 insane, 121 feeble-minded, 136 +criminals, 124 prostitutes and 65 idiots were denied entrance, and yet, +according to the estimate of Doctor F. K. Sprague, of the United States +Public Health Service, probably only about 5 per cent of the mentally +deficient and 25 per cent. of those who will become insane have been +detected. When confronted by such data we can begin to realize what we are +facing. Others estimate that from 6 to 7 per cent. of the immigrants who +are now arriving are feeble-minded. We learn further that recently while +the foreign-born population of New York state was about 30 per cent., the +foreign-born population of the insane hospitals of the state was over 43 +per cent., and at one time approximately 65 per cent. for New York City. +In one year (1908) 84 per cent. of the patients in Bellevue Hospital, New +York City, were of foreign parentage. Paresis, which probably always has +syphilis as its antecedent, is proportionately twice as prevalent among +foreigners as among natives in New York City. + +But from the standpoint of inheritance, however great the danger may be +from classifiable defectives, it is probably far greater from that much +larger class of aliens we are now receiving with open arms who are below +the mental and physical average of their own countries. Moreover, with our +present system of inspection there is no way of detecting the grades of +feeble-mindedness above idiocy and imbecility in the great numbers of +foreign children under five when brought in, who are beginning to show up +in alarming numbers in the schools of some of our larger cities. About +thirty per cent. of the annual increment of our population is due to +immigration and not to births; and once in our country the alien far +outbreeds the native stock, with relatively little increase in death-rate, +thus making a double contribution to the increase of population. When we +take all these facts into consideration it certainly is high time that we +arouse from our self-complacent attitude and consider the whole question +of immigration most earnestly. + +In spite of the fact that many individuals are caught in the net of +inspection at our portals, it is clear that still more rigid rejection[16] +is imperative. The inspectors at our various ports are doing the best +they can under the circumstances, but there are at present too few of them +and they are too restricted in their powers to meet the situation +satisfactorily. Moreover, when at one of our ports in one year (1910), of +1,483 immigrants certified by the inspecting surgeons as unfit to land +because of serious mental or physical defects, 1,370 were landed anyway, +it is evident that there is a strong and reprehensible pull somewhere to +evade the obvious intent of the law. + +It remains for us as a people to decide whether we shall continue to let +the large employers of cheap labor, the railroad and steamship agents and +brokers, who care nothing about the innate fitness of the immigrants they +bring, determine the character of our future population, or whether we +shall insist on a proper regulation of this flood so that we may receive +only an honest, intelligent, industrious and healthy stock. To continue to +absorb these aliens with as little selection as we now do is nothing short +of criminal carelessness. Let us not be deceived by the promptings of a +misguided sentiment, "The voice is Jacob's voice, but the hands are the +hands of Esau." The voice is Jacob's voice, nor should this voice of the +easily persuaded, the sentimentalist, the interested organization to which +the relatives of the defective alien belong, or any other pressure move us +from our obvious duty of refusing to fasten upon this country an incubus +of degeneracy for which we as a nation are in no way responsible. + +To render us safe we should not only have more carefully drawn laws and +more rigid selection at our ports of entry, but we should if possible +also know the stock from which our future citizens come. This is +peculiarly desirable for such defects as feeble-mindedness and various +other mental imperfections, some of which require prolonged observation +for detection. Davenport estimates that it is wholly within the realm of +possibility and good business sense to maintain a corps of trained +inspectors abroad in the chief centers from which our immigrants come who +shall certify the desirable applicants. He makes the point that the +national expense would be far less than the cost of maintaining the army +of defectives we are now admitting to our own country, many of whom almost +immediately become public charges, to say nothing of the hordes of +carriers who though normal themselves, will transmit undesirable traits. + +=Sexual Vice.--=As to sexual vice, the skein is indeed a tangled one. +Since nine-tenths of the difficulty centers in a lack of self-restraint, +and inasmuch as the mating instinct is one of the strongest that tugs at +the flesh of humanity, it is obvious that those by nature deficient in +volitional control will almost without exception give way to the call. So +as might be expected the hordes of our feeble-minded and epileptic are +always a source of grave danger in this respect. However, the mentally +enfeebled are by no means the only offenders; indeed, they are probably +not the majority. The true situation is finally dawning on society and the +reformer's call for instruction in "sex-hygiene" resounds through the +land. The whole matter is one of the most perplexing and momentous that +confronts us to-day. + +=The Question of School Instruction in Sex-Hygiene.--=While the writer +does not for an instant underestimate the gravity of the situation, and +has only contempt for the nonsense that is palmed off on children about +their origin, or the indelicate self-consciousness which puts under the +ban the discussion of so serious a problem by adults, still he is not +convinced that the universal teaching of the subject to children in +schools by the average teacher, as advocated by some, is to be the +solution of the matter or is even a wise attempt at solution. Yet he +freely admits that he is possibly overfearful of the effects of the +undesirable features of such instruction. True it is that all children do +learn, frequently at an astonishingly early age, about sex, and their +knowledge is usually of an undesirable kind from unreliable and often +vicious sources, and it is equally true that parents, either through +ignorance or prudery, generally can not be depended on to give the child +necessary instruction. But before entering on a wide-spread campaign of +undiluted sex-instruction in schools might it not be more prudent to make +an attempt toward reaching fathers and mothers and convincing them of the +necessity of dealing more frankly and intelligently with their children +regarding sex? + +Even to the novice in psychology the powerful nature of suggestion is +known, and with this knowledge before us, is it not wiser to strive in the +main to keep the child's mind off of sex rather than specifically to focus +it on it by special convocations and discourse? If our psychology means +anything, then the worst possible thing we can do for a child is to make +him unduly sex-conscious. Something might be done profitably perhaps in +schools in an unobtrusive way by specially gifted persons, but the +self-conscious way in which most teachers go about topics of sex is +certainly not reassuring to the thoughtful observer as regards the benefit +derived from such instruction. The one evident method of accomplishing +wholesome sex-instruction in schools, devoid of all possibility of +undesirable suggestion and sex-consciousness, is in the form of biological +work where plants and animals are studied in all their relations, the +subject of propagation being taken up in as matter-of-fact a way as the +functioning of any other organ system of plants or animals. In such a +course, long before the subject of sex in higher animals need be +approached the pupil will have developed an attitude of mind which will +lead him to see nothing unusual or suggestive in the function of sex no +matter where it may be found. Incidentally, inasmuch as the manner in +which germs affect living organisms should be studied in such a course +anyway, it would be a simple matter to give all necessary information +about the dangers of infection from venereal diseases. + +=Mere Knowledge Not the Crux of the Sex Problem.--=However, desirable as +correct knowledge about sex is, knowledge alone is not the crux of the sex +problem. The moral dangers and abuses that we are trying to circumvent lie +rather in the realm of the emotions than that of the intellect. The +problem must be solved from a broader foundation than mere information. +The all-important consideration is the early establishment of general +habits of self-control so that these may become incorporated in the +nervous organization of the child and become inhibitory anchors against +passions and temptation. Children must be taught to suppress the present +impulse, to sacrifice the immediate pleasure for the more distant or +permanent good. They must be practised in calling up feelings that will +counteract other promptings which if followed blindly are inimical to +social welfare. Their control must come from within not as a matter of +external compulsion. That way character lies. + +So in viewing the problem of sexual hygiene the writer feels that our +attempts toward damming the torrents in the adolescent by a belated effort +at verbal instruction on sex-hygiene is at best only a palliative or an +attempt to cure the symptoms of a more deeply-seated, organic, social +malady. The treatment should have been in progress long before in the form +of training in self-control, and in the inculcation of the sense of +dignity and self-respect which springs from the individual's consciousness +of being, not a slave to his desires, but his own master. This, together +with the judicious schooling of boys in a greater chivalry and respect for +womanhood, and of girls in the necessity of meriting such esteem, will, in +my estimation, carry us further than formal courses in sex-hygiene. + +=Early Training in Self-Restraint an Important Preventive of Crime and +Delinquency.--=As to crime and delinquency in general, it is evident that +the same early training in self-restraint is a most important factor of +prevention. A wise warden in charge of a large prison says, "Most of these +men are here because they have not learned sufficiently the lesson of +self-control." This is the age of preventive medicine, why not also of +preventive crime and delinquency? Instead of confining our practise to +punishing offenders, necessary as this may be under the present +conditions, why not strive more to prevent the commission of offenses? As +far as normal individuals are concerned much can be done by early +cultivation in self-discipline and through the establishment of moral +backbone by training in the overcoming of difficulties. Much, very much, +also remains to be done in the correction of wrong social conditions. + +=Unpardonable to Permit Delinquent Defectives to Multiply Their Kind.--=As +for our mental defectives and moral imbeciles, knowing now how strongly +hereditary the underlying factors of these conditions are, and with no +preventive or curative agents in sight, to let them produce progeny, is +clearly unpardonable. + + + + +CHAPTER X + +RACE BETTERMENT THROUGH HEREDITY + + +Most of us have heard in one form or another the fairy story of the youth +on adventure bent, who was captured by the giant and under dire penalty in +case of failure was set the task of sweeping out the giant's stable before +sundown. The peculiarity of this stable, it will be recalled, was that, as +fast as the refuse was swept out at the door an even greater quantity +poured in through the windows so that the sweeper, just in proportion to +his zeal, became more and more encumbered with his burden. + +=A Questionable Form of Charity.--=Though we smile at the childishness of +this legend, are we not as a civilized people attempting through our +charities a feat parallel to that of this unfortunate youth? We foster and +favor our social wastage with the inevitable result that it runs riot +under our sheltering hand and deluges us with an ever accumulating flood +of its like. For are we not constantly building more asylums, sanitaria +and prisons, to preserve more unfit, to produce more defectives, to +require still greater numbers of asylums, sanitaria and prisons, to +preserve more unfit, and so on in unending progression? + +At nearly every period of history there have been certain individuals who +have seen the necessity of a state eliminating its supply of defectives. + +=Past Protests.--=For instance, we find the importance of this strongly +urged by Plato. After pointing out the fact that the shepherd, in order to +maintain the standard of his flocks, bred only from the best individuals, +as did likewise the huntsman with his dogs and horses, and the fancier +with his various pets, Plato went on to show the danger to the state of +allowing the constantly increasing body of defectives and degenerates to +multiply their kind. Repeated expression of the same idea has occurred +from time to time during the succeeding centuries. + +Little heed was paid to these remonstrances, however, with the result that +is known to us all. To-day, "the glory that was Greece and the grandeur +that was Rome" is still sung by the poet, but the original nations +themselves have long since passed into the night. + +=An Increasing Flood of Defectives.--=Strive to ignore the unpleasant +facts as we may, we have to admit that the same problem of what the human +harvest shall be is with us in grave form to-day. The alarming phase of +the situation, however, lies in the fact that we are facing an ever +increasing flood of social wastage. + +But _why_ this increase of defectives? It can not be attributed to +oppression, to grinding poverty, or to decline in attention to our sick +and needy, for never was prosperity greater, never were charities more +flourishing, never such activity in the search for palliatives and cures. +The simple fact is that we are breeding our defectives. The human harvest +like the grain harvest is based fundamentally on heritage. And to get a +better crop of human beings, we must, as with other crops, weed out bad +strains. + +To whatever source of information we turn the facts are essentially the +same. Abroad we find that in England, for example, the ratio of defectives +to normals more than doubled between 1764 and 1896. At home, from the +investigation of Davenport and Weeks we learn that in the state of New +Jersey the number of epileptics doubles every thirty years. And other +investigators estimate that the fecundity of mental defectives in general +is about twice as great as that of the average of our population. In a +recent report of the New York State Board of Charities we read, "There are +about thirty thousand feeble-minded persons in the state of New York, of +whom four thousand are intermittently sequestered while twenty-six +thousand who are a menace to society are at liberty and may produce the +unfit." And a passage from the last Massachusetts report reads as follows: +"We have been obliged to refuse a very large number of applicants for the +admission of feeble-minded women--many of whom have given birth to one or +more children. The prolific progeny of these women almost without +exception are public charges from the date of their birth." + +How fertile defective types may be is shown by a passage in one of Doctor +Wilmarth's papers which runs as follows: "One feeble-minded woman, now +removed from this state, had by different men eighteen children in +nineteen years, she alleges." In a letter Doctor Wilmarth tells me that +the birth of the twenty-third child of this woman has just been +announced! In one English workhouse Potts reports sixteen feeble-minded +women who have produced one hundred sixteen mentally defective children, +and Branthwaite ninety-two female habitual drunkards who have had eight +hundred fifty babies. If we include the two million individuals cared for +annually in various institutional homes, hospitals and dispensaries as +dependents, the estimated total of insane, feeble-minded, epileptic, deaf +and dumb, criminals, juvenile delinquents, paupers and other dependents in +the United States in 1910 was approximately three million, or one in every +thirty of our population! With the higher fertility of certain of these +classes and with only a small percentage under custodial care where will +it all end? Is it not time for us to waken from our lethargy and stem this +tide of national deterioration? + +=Natural Elimination of Defectives Done Away With.--=With our improved +methods of sanitation and care of the sick, the pauper and the defective, +these classes have been freed from the stress of an environment that under +natural conditions would have resulted in their premature death and +consequent infertility. Or in the terminology of the biologist, we have +done away with the factor of _natural selection_, the factor which in +state of nature keeps all races purged of the unfit, the ill-adapted. With +this restraining, and purifying influence removed, however, the weakling, +the defective, may arrive at maturity and commingle his blood with that of +the strong, with the inevitable result that the general vigor of the +progeny from generation to generation is sapped and progressively +undermined. Thus we are confronted by the stubborn fact that through +present humanitarian methods we are driving the race toward decadence. + +=Why Not Prevent Our Social Maladies?--=Now there is no reasonable person, +I think, who will not admit that the motives underlying our modern +altruistic practises are the noblest fruitage of our slow upward struggle +from the brute to man. As humane beings, we can not cast aside these +principles and return to the painful and pitiless method of nature which +would leave the sick and the defective alone to perish miserably; the +sacrifice would be too great. + +Is there then no escape from this dilemma? To this query the modern +student of heredity answers yes; let us but add more wisdom to our charity +and the enigma is solved. We need no sacrifice of pity but rather an +expansion of it. Let us but extend our vision from immediate suffering to +the prospective suffering of the countless unborn descendants of our +present unfit and ask ourselves the question, why should they be born? Why +not prevent our social maladies instead of waiting to cure them? This is +the province of eugenics. + +=Eugenics Defined.--=The term Eugenics was coined in 1883 by Francis +Galton in his book entitled _Inquiries Into Human Faculties_, and we may +therefore look to him for a satisfactory definition. He says, "Eugenics is +the study of the agencies under social control, that may improve or impair +the racial qualities of future generations, either physically or +mentally." And again, "I take Eugenics very seriously, feeling that its +principles ought to become one of the dominant motives in a civilized +nation, much as if they were one of its religious tenets.... Man is gifted +with pity and other kindly feelings, but he also has the power of +preventing many kinds of suffering. I conceive it to fall well within his +province to replace natural selection by other processes that are more +merciful and not less effective. This is precisely the aim of Eugenics. +Its first object is to check the birth-rate of the unfit instead of +allowing them to come into being, though doomed in large numbers to perish +prematurely. The second object is the improvement of the race by +furthering the productivity of the fit, by early marriages and the +healthful rearing of their children." + +=Improved Environment Alone Will Not Cure Racial Degeneracy.--=While many +an enthusiastic humanitarian is laboring under the assumption that if we +can improve external conditions human deficiencies will disappear, the +student of heredity realizes that this is in large part a delusion unless +we can secure an accompanying improvement in intrinsic qualities of the +human species itself through the suitable mating of individuals. Just as +the intelligent farmer to-day demands selected seed as well as good soil +and proper cultivation, so one with the facts of heredity at hand would, +as he views social problems, urge the fundamental importance of having +selected stock with which to start. No shifts or shapings of environment +will ever enable men to "gather grapes of thorns or figs of thistles." + +=Heredity and Environment.--=To wrangle over the question of which is the +more important, heredity or environment, is about as idle a proceeding as +to argue which is the more important, the stomach or something to put in +the stomach. Man would soon come to grief without either. So, too, the +question of human development is not one of heredity alone nor of +environment alone; both are necessary and must work hand in hand. Dormant +capacities must have proper environment to call them forth, but on the +other hand no kind of environment can evoke responses if some degree of +aptitude is not present. + +Professor Thorndike undertook experiments with groups of school children +of high and of low initial ability respectively to determine whether equal +opportunity or equal special training would produce an equalizing effect +in easily alterable traits such as rapidity in addition and the like. +Without exception he found that at the end of such experiments, although +both groups had improved, the superior individuals were farther ahead than +ever, that equality of opportunity and training had widened rather than +narrowed the gap between the two classes. Others who have made special +studies on the causes of individual differences have come to the same +conclusion; namely, that individuals differ widely by original nature and +that similarity in conditions of nurture and training will not avail in +deleting these differences. + +Galton and others, from extensive studies based on English sources, have +shown that notable achievements have run in certain families to a degree +that is inexplicable on the basis of opportunity alone; it can be fully +accounted for only by attributing much to superior inborn capacity. Doctor +Woods has shown much the same thing for certain families in America. +Schuster and Elderton have proved that there is a high degree of +similarity in scholastic standing between fathers and sons in Oxford. +Professor Pearson's measurements of mental characters in brothers and +sisters while at school show a high degree of innate resemblance in many +cases and certain cases of decided contrast. Where contrasts exist in +certain families they remain unreduced in spite of the similarity of +environment, thus proving that environment is less operative in the final +intellectual establishment of such individuals than are their inborn +aptitudes. Even in twins, as both Galton and Thorndike have shown, there +is no tendency for similar education, home life and the like to render +those originally different any more similar with advancing years. + +Professor Karl Pearson has done more perhaps than any other individual +toward attempting actually to measure the relative strength of heredity +and environment. Numerous statistical measurements lead him to conclude +that it is a conservative estimate to regard heredity as at least five or +ten times as important as environment in the development of the +individual. A vigorous defense by him of this position will be found in +_Biometrika_ for April, 1914. + +=Inter-Racial Marriage.--=Some of the dangers of racial deterioration +which threaten us because of our laxity regarding immigration have already +been indicated. It is high time that we give this whole question the most +serious consideration of which we are capable. From the rate at which +immigrants are increasing it is obvious that our very life-blood is at +stake. For our own protection we must face the question of what types or +races should be ruled out. Aside from the dangers which lie in the +defective or unsuccessful types already discussed in Chapter IX, many +students of heredity feel that there is great hazard in the mongrelizing +of distinctly unrelated races no matter how superior the original strains +may be. Unfortunately there is a great lack of reliable data on this +point. The mulatto of our own country, the Eurasians in India and the +mixed races of South America are, according to the testimony of many +observers, eloquent arguments against such hybridization. Agassiz remarked +on this point as follows: + + "Let any one who doubts the evil of the mixture of races and who is + inclined from mistaken philanthropy to break down all barriers between + them come to Brazil. He can not deny the deterioration consequent upon + the amalgamation of races, more wide-spread here than in any other + country in the world, and which is rapidly effacing the best qualities + of the white man, the Indian, and the negro, leaving a mongrel + nondescript type deficient in physical and mental energy." + +Of the American mulatto one not infrequently meets with the assertion that +he is on the average inferior mentally, morally and physically to either +the white or the negro race. Thus Doctor J. B. Taylor[17] states that, +"It is demonstrated by well-attested facts that these hybrids of black and +white are vastly more susceptible to certain infections; their moral as +well as physical stamina is lower than that of either original race." +Others would deny that conclusive evidence to this effect exists. However, +it is certain that under existing social conditions in our own country +only the most worthless and vicious of the white race will tend in any +considerable numbers to mate with the negro and the result can not but +mean deterioration on the whole for either race. + +There is certainly not one iota of evidence that the crossing of any two +widely different human races will yield superior offspring in any respect +and there are many indications that such intermixture lowers the average +of the population. Our evidence derived from plant and animal breeding is +also against pronounced crosses. The inferiority of the mongrel is +universally recognized. No sane farmer, for example, would seek to improve +his Jerseys or his Herefords by crossing one with the other. It is true +that in pure breeds of plants and animals we sometimes venture on a cross +to introduce some new desirable character but we follow up such mixture by +a rigid selection in which is eliminated all but the rare individuals +having the desired characteristics, and we continue this elimination +generation after generation to fix our characters again. It is obvious +that no such selection as this would be possible among the progeny of +human crosses. + +It clearly becomes our duty then to determine as accurately as possible +the degree of non-relationship between races it is inadvisable to +transcend in inter-racial marriages. We are certainly taking great risks +in accepting in any considerable numbers those races we can not assimilate +to advantage into our own stock. + +=War.--=The deteriorating effect of war on national physique and vigor has +been so frequently cited by eugenists[18] and is so obvious as scarcely to +require further comment. It should be pointed out, however, that where, as +is the case at present in Great Britain, armies are assembled from +volunteers, instead of by conscription, there is the greatest danger from +the eugenic standpoint, since not only physical but moral qualities are +involved. For it is the brave, the generous, the individual with a high +sense of duty who goes forward to the slaughter leaving the cowardly, the +selfish or the indifferent to father the race. With the awful deadliness +of modern warfare upon exhibition before our very eyes to-day, the extreme +seriousness of such selective action must be evident to every thoughtful +person. + +=Human Conservation.--=We talk much in recent years of _conservation_; but +what are our forests and frontiers, our minerals and our waterways, +compared with our national health and life-blood? No farmer would think of +setting aside a diseased or physically defective _animal_ for breeding +purposes, yet the same man together with the majority of mankind is wholly +oblivious to similar faults when it comes to the mating of human beings. +But is it not as important to look to fitness in man as in Poland China +hogs or Holstein cows? Certainly the various strains are as marked and +breed as true in the human family as in our live stock. Why face +complacently in our own families what we would not tolerate in our +piggery? + +From the expenditure of comparatively small sums in studying the +inheritance of various qualities in wheat, corn and other grain, +improvements based on the laws of genetics have been secured which are +enormously increasing our agricultural output and thereby adding to our +national wealth. But if it costs relatively little to discover and +conserve millions of dollars' worth of hereditary qualities in our plants +and animals, what are we to think of ourselves, an intelligent people who, +knowing that "every good tree bringeth forth good fruit, but a corrupt +tree bringeth forth evil fruit," still go on placidly permitting the +production of defectives and delinquents? Can we continue to drink the +sluggish blood of the pauper and the imbecile into our veins and hope to +escape unscathed? + +We are all familiar with the fate of Babylon, Assyria, Persia, Egypt and +Rome. Why not America? Certainly we have no pledge of special immunity +from Divine Powers. If so, what then is the meaning of our 366 hospitals +for insane which cost us annually $21,000,000; our 63 institutions for +feeble-minded costing us over $5,000,000; our 1,300 prisons maintained at +a cost of more than $13,000,000; our 1,500 hospitals whose annual +maintenance requires at least $30,000,000; our 115 schools or homes for +deaf and dumb; our 2,500 almshouses with an annual expense account of +$20,000,000 and our 1,200 refuge homes costing annually several millions +of dollars more? To say that we spend annually over $100,000,000 on the +custody of insane, feeble-minded, paupers, epileptics, deaf, blind and +other charges is expressing the situation very conservatively. + +=Kindness in the Long Run.--=There is no one I think who will not admit +that the sympathy and charity of the human heart are its noblest virtues. +But we must face the problem of what is kindness in the long run. Havelock +Ellis well says, "The superficially sympathetic man flings a coin to the +beggar; the more deeply sympathetic man builds an almshouse for him so +that he need no longer beg; but perhaps the most radically sympathetic of +all is the man who arranges that the beggar shall not be born." + +What shall we do? + +=The Problem Has Two Phases.--=For an intelligent consideration of the +problem one must recognize at the outset that it has two distinct phases; +namely, (1) a selective union of the fittest, or in other words, a +conscious attempt to breed a superior race; and (2) the elimination of the +obviously unfit by preventing their reproduction, with the purpose of +purifying the present race. It is evident at a glance that these are two +essentially distinct problems although the practise of either method could +result in racial improvement. The first is sometimes spoken of as +_positive_ or _constructive eugenics_, the second as _negative_ or +_restrictive eugenics_. + +=Constructive Eugenics Must Be Based on Education.--=As to the first +phase, direct selection for superiority, the campaign must, in the very +nature of things, be one of education. With the necessary knowledge of the +facts in mind, the awakening conscience of the individual together with +an enlightened public opinion will form the safest guide. Increasing +popular comprehension of the inevitable nature of human inheritance must +engender a sense of responsibility as to the positive eugenic fitness of a +contemplated marriage. The growth of this sentiment will doubtless be +slow, and properly so, for as yet we have but half-lights on what are the +most desirable types of humanity. No one can say what the highest type of +man should be, but almost any one can readily pick out types which +certainly should _not_ be. + +=Inferior Increasing More Rapidly Than Superior Stocks.--=Modern +eugenists, although realizing that the constructive phase is of great +importance, are making no attempt to map out any fixed mode of procedure +for it beyond pointing out the desirability of larger families among the +better classes. The need for individuals of superior physical, mental and +moral qualities to multiply is so obvious as scarcely to require comment. +Yet the fact is that judging from all appearances these are the very ones +who have the lowest birth-rate. Eugenics is mainly concerned with the +relative rates of increase of the various classes, not with mere fertility +in itself. And the actual increase must be measured in terms of the extent +to which birth-rate exceeds death-rate. If a high birth-rate is +accompanied by a high death-rate then it is not especially significant in +increasing a given class as a whole. All available evidence points to the +fact that to-day the lower strata of society are far outbreeding the +middle and higher, with an almost negligible difference in death-rate, and +just in the measure that these lower strata are innately inferior just in +that degree must the race deteriorate. The seriousness of the whole +situation as it exists to-day hinges, therefore, on the extent to which +the lower strata are inferior to those above them. + +=An Unselected Population May Contain Much Valuable Material.--=In +evaluating these lower strata a matter of very great importance is whether +the population is a selected or an unselected one. If the population has +been long resident in a given region and has had fairly good opportunity +for education then we will find in the lower reaches a larger percentage +of sedimentation made up of the worthless and inferior stocks. If, +however, a continual fomentation and geographical shifting of the +population is in progress as in parts of America, or if adequate +educational opportunities are lacking, as in some parts of Russia, the +poor and less well-to-do classes may contain, no one can tell how much, +relatively valuable stock. + +Forel remarks on this point as follows: + + "If we compare the nature of delinquents, abandoned children, + vagabonds, etc., in a country where little or nothing has been done + for the people (Russia, Galicia, Vienna, etc.), with that of the same + individuals in Switzerland, for example, where much has already been + done for the poor, we find this result: In Switzerland, these + individuals are nearly all tainted with alcoholism, or pathological + heredity; they consist of alcoholics, incorrigibles, and congenital + decadents, and education can do little for them because nearly all + those who have a better hereditary foundation have been able to earn + their living by honest work. In Russia, Galicia, and even in Vienna, + we are, on the contrary, astonished to see how many honest natures + there are among the disinherited when they are provided with work and + education." + +=The Lack of Criteria for Judging Fitness.--=Barring the untold hordes of +actual defectives who have gravitated into this lower stratum, there are +few positive criteria by which we can measure the real fitness of the +remainder. Before we can set out on a campaign of positive eugenics we +must have some standard by which to steer, and it would be a rash advocate +indeed who would assert that class distinction alone, or even success as +measured by public opinion to-day should be our whole criterion of +fitness. Shall we measure fitness in terms of how successfully one can +acquire worldly goods, or in other words, by the property test, or what +shall be our standard? + +=The College Graduate.--=Many of our modern critiques of the birth-rate +situation make much of the fact that our college graduates as a group are +scarcely reproducing themselves. According to Davenport, Bryn Mawr College +between 1888 and 1913 has graduated 1,193 bachelors of arts, but these +women have produced up to January, 1913, only 263 girls to take their +place in the next generation. He also points out that statistics on some +of the graduate classes of Harvard of twenty years ago or earlier show +that they are little more than maintaining themselves; thus one class of +328 graduates twenty years later had produced 195 sons, and in another +case a class of 278 individuals had produced, twenty-five years later, 141 +sons. Relatively similar statistics can be cited for other eastern +colleges. + +All such cases of college graduates cited as especially deplorable +declines in birth-rate are based on the assumption that these individuals +are a particularly superior stock.[19] But one might question this premise +as a generalization. It may or may not be true. Are they superior or have +they had mainly a combination of luck and incentive, luck in that their +parents had sufficient means, acquired possibly through their own +superiority, possibly not, to send them to college, and incentive derived +from a fortunate environment which awakened a desire in them--or in their +parents for them--for college education? Is the woolly-witted son of +opulence, so abundant in our colleges to-day, who is boosted through by +hook or by crook, of superior eugenical value to the alert eager boy--and +his name is legion--destined for economic reasons to go to work at or +before the completion of his high-school course, perhaps because of the +very fact of an unlimited fecundity in his own family which necessitates +his help for the general support? + +When one first learns of the declining birth-rate among college women and +men he feels appalled, but immediately the question flashes up, if this is +_the_ superior stock, and up to date it has died out or is dying out +rapidly, whence then this ever augmenting rush of young folk who fairly +deluge our universities and colleges to-day? Does it not rather point to +the fact that in our own country at least, the man who will and can take +a college education successfully is not so much the product of breeding +from college men, but of a prosperity which leaves a sufficient surplus in +the family exchequer to enable sons and daughters to go to college, and is +it not reasonable to suppose that there is yet an abundant stock back of +these who similarly await but the golden touch of opportunity? When we +consider such men as Carlyle, Lincoln and a host of others who were not +the sons of collegians, although we may be university pedigreed ourselves +we can not but feel doubtful of the validity of a premise which takes a +college stock unqualifiedly as having any considerable monopoly of innate +superiority. After all, college can mean little more than opportunity, and +the obtaining of such opportunity in this world of economic maladjustments +and accidents of social position is too largely a matter of chance, at +least in America, to stamp the possessors of these advantages, on this +criterion alone, as of inborn superiority. Undoubtedly much that is +intrinsically good now slumbers in the lower strata of society because of +lack of favorable environment to call forth the latent possibilities. + +=Native Ability, Independence and Energy Eugenically Desirable.--=Although +we can not sift out with certainty the superior from the inferior in our +normal population by the property test or the educational standard alone, +it is undoubtedly true that, on the whole, native ability, independence +and energy are present to a higher degree in our well-to-do and prosperous +families than in the stocks which merely hold their own or which +gradually decline, and there is no gainsaying the fact that in so far as +the lower classes are where they are through actual deficiency--and there +are enormous numbers in this category--they threaten our very existence as +a race. It is imperative that the great middle class in particular +establish in some way a selective birth-rate, by increased fertility on +their own part, and diminished fecundity on the part of inferior stocks, +which will offset or more than offset the disproportionate increase of the +socially unfit. + +=Four Children to Each Marriage Required to Maintain a Stock.--=It is +estimated that under present conditions an average of at least four +children should be born to each marriage if a stock is to maintain its +numbers undiminished. Some of our most valuable strains are falling far +short of this average. In a statistical table on the relative fertility of +different stocks, prepared by Pearson, we find the mentally defective, +criminal, deaf-mute and degenerate stocks heading the list with averages +ranging from five to seven children per family, while the American +graduate (based on Harvard statistics) and the English intellectual types +average less than two children per marriage. While the death-rate is +higher in the undesirable classes mentioned, it is by no means enough +higher to compensate for the difference in birth-rates. Thus while certain +very desirable types are not maintaining themselves genetically, other +extremely undesirable ones are rapidly more than replacing themselves. +Investigations made by Heron in London show that this condition as regards +English desirables did not exist sixty years ago; then the richer a +community was in professional men and well-to-do families, the higher was +the birth-rate. + +=Factors Contributing to Low Birth-Rate in Desirable Strains.--=Most +students of the subject believe that the fecundity of much of the best +blood in our country has reached such a low ebb as to threaten the whole +fabric of our commonwealth. How to correct this is the pressing problem to +which no one has found a solution. However much one may deplore it the +fact remains that always in the history of the civilized world with the +rise of material conditions in any class of a population there has come an +accompanying limitation of child-birth. Explain this as we may in modern +times--whether as an awakened individualism which looks only to the +immediate interest of the individual as against the ultimate interest of +the race, or a desire for luxuries or for a better opportunity for smaller +numbers of children, or as a determined effort of the wage earner to +better his conditions, or to the feminist movement with its accompaniment +of a greater personal freedom of married women and the recognition of the +fact that marriage and child-bearing are often bars to employment, or to +general increasing pressure of economic burdens--in brief whatever the +cause or causes, there is no denying the fact of a diminishing birth-rate +among our abler men and women. Moreover, no amount of coaxing, cajoling or +dire prophecy seems to avail in altering the conditions. Various partial +remedies, many of them of questionable practicability, have been proposed, +but so far there has been no far-reaching effort made to put any of them +into effect. It has been suggested that society return to the simple life +so that our young folk may marry earlier and live more easily on limited +means, but so far few volunteers have appeared to lead the procession. +While there is no doubt that present economic conditions tend to penalize +parenthood, the simple life will not return for the mere asking. It has +been pointed out that the father is in unfair competition with the +bachelor and is also unfairly taxed in comparison, and some would +therefore tax unmarried men more heavily. Others would pay a direct bounty +on reproduction, but it is probable that such rewards would merely +stimulate families of the lower types to increased fruitfulness. And so +one panacea after another may be weighed and found wanting. + +=The Educated Public Must Be Made to Realize the Situation.--=It seems +probable that the most success will be met with through the slow and +unspectacular methods of education. The necessity of the situation must be +driven home so that it becomes part and parcel of the collective +intelligence of the educated public. Different ideals of life will have to +be established in the young. If knowledge of the facts of heredity is +thoroughly disseminated among the people and ideals regarding parenthood +are fostered, then much will have been accomplished by the psychic power +of suggestion alone toward the end desired. + +=Utilization of Family Pride as a Basis for Constructive Eugenics.--=There +are few more powerful incentives to make the best of one's abilities, or +few greater deterrents from vice than family pride; and there is no +reason why this same sentiment may not be aroused in behalf of unborn +generations. The sentiment of caste or aristocracy in some form is well +nigh universal in mankind. The family of Mr. A came over in the Mayflower +and is therefore worlds above the family of Mr. B, who arrived fifty years +later. Mr. X's income is $5,000 a year, Mr. Y's only $1,500. The poor +family in the front suite of the tenement regards itself as far superior +to the one in the rear. Among criminals the professional house-breaker +feels himself to be of higher caste than the sneak-thief, and in turn is +surpassed by the bank-burglar. Even in the insane asylum the feeling is +rampant. With such a wide-spread tendency for a foundation the creation of +a sentiment of eugenic aristocracy is by no means a visionary undertaking. + +=The Tendency for Like to Marry Like.--=Even now there is a decided though +unconscious tendency for like to marry like and thus create particular +strains. We have lines, for instance, which produce notably families of +scholars, others which yield mainly statesmen, and still other strains of +inventors, of financiers, of naval men, of soldiers, and of actors +respectively. And there is little doubt that people, with the facts of +inheritance of ability once before them, will be led to act more or less +in accordance with their knowledge. On the other hand, due apparently to +the same unconscious tendency for like to marry like, we find produced +criminalistic, feeble-minded, deaf-mute and tubercular stocks. The first +type of family is often termed _aristogenic_ and the second or defective +type, _cacogenic_. + +=Public Opinion as an Incentive to Action.--=Much of our social conduct is +the result of the pressure of public opinion, yet so accustomed are we to +this that we ordinarily do not feel it as a hardship. There is little +doubt that similarly the more wholesome attitude toward parenthood +advocated by the eugenist would be taken as a matter of course, once the +idea became prevalent. It would come to be one of those socially +preconceived ideas which are as much actualities and which become +unconscious guides to action no less certainly than do the more obvious +personal habits of the individual. And just in the degree that we as a +race get the "feeling" that intellect, morals and skill are highly +desirable attributes in marriage selection, just in that degree will one's +affections in their earlier stages gravitate toward individuals who +possess such qualities in high degree. In the main, those stocks which +have shown by ancestral as well as personal achievement their superiority +will tend to insure most certainly a continuation of this superiority in +offspring. + +=Choosing a Marriage Mate Means Choosing a Parent.--=Although marriages, +as all young folks know, are made in Heaven, it is interesting to see what +a vast number of these foreordained matches coincide with propinquity in +college, in church, or in the same social set. Moreover, children are born +here on earth. The one thing of all things that the eugenist desires is +for these young folk to get a clear-eyed vision of the fact that in +choosing a marriage mate they are also choosing the future father or +mother of their children with all that this implies. + +=The Best Eugenic Marriage Also a Love Match.--=A few recent writers, who +show an utter misconception of what the aim of modern eugenics is, have +raised the cry of give us the old-fashioned love match instead of the +eugenic marriage, as if the eugenist's ideal of moral cleanliness, freedom +from transmissible physical taints or mental enfeeblement, and an attitude +of special approval toward marriages which bring together individuals of +more than average mental or spiritual endowment, had anything in it that +was inimical to love. No one better than he realizes the sordid depths to +which marital relations devoid of mutual affection and regard must reach. +Certainly there is nothing in the eugenic ideal when its full import is +understood that can shock the sensibilities of the most delicate-minded. +Indeed it is people of fine susceptibilities who will be the first to feel +repugnance toward a marriage which means mental or physical deterioration +of their own blood. + +=Good Traits No Less Than Bad Ones Inherited.--=An inspection of such +charts as those shown in Figs. 37, 38 and 39, pp. 313, 314, 316--and an +abundance of such encouraging records may now be found--reassures us in +our convictions that good traits are no less inheritable than bad ones. +And what any healthy, mentally well-endowed person may be depriving the +world of if he or she declines to enter into a fruitful marriage can not +be better exemplified than in the following excerpt from Davenport: + + "Many a man at the opening of his life work vows, as Judge John Lowell + of the middle of the eighteenth century did, as he was being graduated + from Harvard College, that he will never marry. But nature was too + strong for John Lowell and he married three times, and among his + descendants was the director of a great astronomical observatory, the + president of Harvard College, a principal founder and promoter of the + Massachusetts General Hospital and the Boston Atheneum; the founder of + the city of Lowell and its cotton mills; the founder of the Lowell + Institute at Boston; the beloved General Charles Russell Lowell and + his brother, James, both of whom fell in the Civil War, and James + Russell Lowell, poet, professor and ambassador; besides brilliant + lawyers and men entrusted with large interests as executors of + estates. Do you think John Lowell would have taken that vow could he + have foreseen the future?" + + +[Illustration: FIG. 37 + +Pedigree of family with artistic (dark upper section), literary (dark +right section) and musical (dark left section) ability (from Davenport).] + + +=The Elimination of the Grossly Unfit Urgent.--=But even if, under present +conditions of partial knowledge and lack of an adequate standard, the +constructive phase of eugenics must be left in the main to the awakening +conscience of the individual as humanity improves in general +enlightenment, the second phase, the elimination of the grossly unfit is +one of the greatest social obligations that confronts us to-day. For if +there is an alarming amount of mental impairment in civilized nations, and +if the problems of pauperism, inebriety, prostitution and criminality are +closely interwoven with the problems of mental unsoundness, as we have +every reason to believe from available data, then any means which will +operate toward securing normally functioning brains will at the same time +operate toward diminishing, defects and delinquencies. And inasmuch as a +considerable proportion of defects, both mental and physical, are +inheritable, it is obvious that if we can diminish the number of children +born into the world with defective brains or bodies we have made a long +stride in the right direction. + + +[Illustration: FIG. 38 + +Inheritance of ability (from Kellicott after Whetham).] + + +=Suggested Remedies.--=But how go about it? Various schemes have been +proposed, of which the chief are as follows: + + 1. Laws restricting marriage. + + 2. Systems of mating with the purpose of covering up and gradually + diluting out defective traits. + + 3. Segregation during the reproductive period. + + 4. Sterilization. + + 5. Education in the principles of eugenics. + +=Inefficacy of Laws Which Forbid Marriage of Mental Defectives.--=The +utter inefficacy of the first proposition, namely the enactment of laws +restricting marriage, at least as regards the socially unfit whose +condition is based on impaired mentality, has been demonstrated time and +again. If they are forbidden marriage, they merely have children without +getting married. Most states have laws to prevent the marriage of such +individuals but these laws are almost wholly ineffective in preventing +procreation on their part. We might as well recognize once for all that in +such cases nothing short of close custodial care or sterilization will +accomplish the end desired. + +As to the second proposition, systems of mating with the purpose of +covering up and gradually diluting out defective traits, this has been +shown to be possible with certain types of defectives. Whether it is +desirable or not is a different question. + + +[Illustration: FIG. 39 + +Inheritance of ability (chart condensed and incomplete) in three markedly +able families (from Kellicott after Whetham): + +1, Charles Darwin; 2, his cousin, Francis Galton, founder of the modern +eugenic movement.] + + +=Systems of Mating Impracticable in the Main.--=By systems of mating, it +should be said, is not meant the arbitrary marrying of two individuals +willy-nilly, but rather it is the prevention from marriage of two +individuals having similar defects. In general the facts at our command +indicate that in the majority of cases the offspring from a marriage of an +insane, feeble-minded or epileptic person with a normal individual free +from all neuropathic taints are normal or at most show but slight effects +of the taint. But what normal individual would knowingly marry into such a +stock? With few exceptions such traits where inheritable are apparently +negative, that is, not represented by some positive abnormal factor but +due to the lack of some element or elements necessary to the proper +working of the normal brain. In the offspring of such a union the +necessary missing factors are supplied by the normal parent. Or in +Mendelian phraseology, the defective traits are recessive and are +dominated by the normality of the other parent. Such offspring, however, +while apparently normal of body are not normal of germ-plasm, inasmuch as +half of their germ-cells will carry the abnormality of the defective +parent as earlier explained (page 119) under Mendelism. We have already +seen (page 119) how by continually marrying into strong strains the +liability to recessive defect can be diluted out until the descendants are +no more likely to have defective children than are members of our ordinary +population. If, however, as is estimated in Bulletin No. 5 of the +_Eugenics Record Office_, about thirty per cent. of our general population +already carry recessive neuropathic taints, it certainly is a hazardous +proceeding to attempt thus to breed out nervous defects unless one is +absolutely sure of the normality of the strain into which it is proposed +to marry. The great difficulty is in determining whether or not there is a +defective ancestry in a given stock. We have at present no criteria for +identifying normal individuals who have defective germ-plasm. As a +practical test, however, if no defect has appeared in the stock for three +or four generations back, the marriage would be relatively as safe as are +the marriages of our average population to-day. + +=Corrective Mating Presupposes Knowledge of Eugenics.--=But such a scheme +of corrective mating presupposes a relatively high degree of intelligence +and judgment on the part of the participants, and this is just what we do +not have and in the nature of things can not get, in the types of +feeble-minded, epileptic and degenerate strains we are striving to +eliminate. All our evidence shows that when unrestricted there is a marked +tendency for feeble-minded to mate with feeble-minded, degenerate with +degenerate. About sixteen per cent. of the feeble-minded, in fact, come +from consanguineous marriages. If we try to legislate them into specific +types of marriage then we encounter the same futility pointed out under +our discussion of restrictive legislation, they will produce offspring +without the formality of marriage. + +In certain cases of insanity and in other than neuropathic defects one can +see how the system might be inaugurated with greater prospects of success, +but even then a knowledge of the principles of eugenics would be necessary +to the participants, or in other words we could only accomplish our end +through our fifth proposition, education. + +=Segregation Has Many Advocates.--=As to the third proposition, +segregation during the reproductive period, this seems to have a larger +number of advocates than any other coercive measure. While on theoretical +grounds it is plausible enough, when we face the actual putting of the +method into practise we are confronted by the fact that tremendous sums of +money would be required to sequestrate and maintain colonies or industrial +refuges. + +When one realizes that no state now provides for more than a small +minority of its defectives, and knowing also of the pressure that must be +brought to bear on legislatures to secure sufficient funds to provide for +these cases of extremest urgency, one can not be overly optimistic about +the practicability of extensive sequestration. + +E. R. Johnstone, the superintendent of a large training school for +feeble-minded in New Jersey, points out that no state in the Union is +providing for many more than one-tenth of her feeble-minded and +epileptics. If his estimate is true, to place in institutions, treat and +train all its feeble-minded and epileptics would even now almost swamp any +state treasury. But what _will_ it be in the future if we permit this +unrestricted nine-tenths to go on and multiply their kind? + +Leaving out of account the enormous sums spent in private charities even +now from one-fifth to one-seventh the total public expenditures of almost +any one of our states is going to maintain its defectives, dependents and +criminals. From the 1912 report of the secretary of state, in the state of +Wisconsin, for instance, I learn that of the total expenses for 1912, +sixteen per cent. was for charitable and penal institutions. The situation +is even worse in some other states. Think of it! Think what a large total +of expense it becomes! And the expense is far secondary from the +humanitarian standpoint to the misery involved. + +In the _Survey_ of May 24, 1913, we find Mr. Hastings H. Hart, Director of +the Department of Child Helping of the Russell Sage Foundation, proposing +very specifically "a working program for the extinction of the defective +delinquent," which involves segregation during the reproductive period. He +gives the number of feeble-minded under public care as 20,000 in +institutions for the feeble-minded, 16,000 in almshouses, 5,000 in +hospitals for the insane, and 26,000 in prisons and reformatories, or a +total of 67,000 already under custodial care. And he asserts that as +nearly as can be judged, this is one-third of the feeble-minded persons in +the United States. + +Between this estimate that one-third of our feeble-minded are in +institutions and Doctor Johnstone's that we are not providing for many +more than one-tenth of our feeble-minded and epileptic, there is a wide +discrepancy, but I know of no accurate data[20] whereby the matter can be +settled definitely. One point of difference may be that Doctor Johnstone +specifically includes epileptics and another may be one of definition of +feeble-minded. However, supposing that we could get them all into +institutions, institutional care at present by no means also implies +prevention of propagation. It is not an unusual history of feeble-minded +women in our county poor-houses that they alternate between periods of +housework in some family and periods of residence in the almshouse, the +return to the latter being only too often to bear an additional child. + +Not a few students of the problem, however, advocate a rigid segregation +as the only reasonable preventive measure, no matter what the expense. +They point out that the cost is mounting up higher each year and that we +are only increasing it ultimately by procrastination. They urge, moreover, +that when counting the cost of the segregation of the feeble-minded we +should bear in mind also that we are reducing the expenses of our other +charity and penal institutions, since much of degeneracy, pauperism and +petty criminality centers in mental enfeeblement. Some believe that +colonies can be established which are in considerable measure +self-supporting. Doctor Johnstone, for instance, although his estimates of +the number of feeble-minded and epileptic is one of the highest, sketches +out in a recent paper (in _Pediatrics_, August, 1912) a plan which he +considers feasible. + +But what assurance have we that we can prevent the production of +defectives by segregation? In reply may be cited a recent experiment on an +extensive scale. Cretinism is a condition due to disease of the thyroid +glands. It is characterized by goiter, marked deformities and imbecility. +It is hereditary and has been very prevalent in certain valleys of +southern Switzerland and northern Italy. Cretin mated with cretin and +consequently a large new supply was constantly produced. In recent years +in certain communities the sexes have been segregated (see _Eugenic +Review_, 1910, Jordan) with the result that in such places cretinism has +about disappeared. + +Coming now to the fourth solution proposed, namely, sterilization,[21] let +us consider some of its alleged advantages and disadvantages. + +=Sterilization.--=First of all, since there is some considerable popular +misunderstanding on the subject, it should be made plain that by +sterilization is not necessarily, nor in fact generally, meant +asexualization, or the removal of the reproductive glands. On the +contrary, in the male, sterilization is ordinarily accomplished by an +operation known as _vasectomy_, in which a small piece of each sperm duct +is removed. Such reports on it as I have found indicate that it is a +comparatively simple minor operation which involves no special +inconvenience or hardship on the subject beyond the deprivation of +offspring. In fact, according to Doctor Sharp's report, in the majority of +cases where it has been put into practise the patient has usually +submitted voluntarily after having the details of the situation explained +to him and has often advised fellow delinquents to do likewise. + +Even should later developments show that a mistake had been made, in all +probability the matter could be remedied by a second operation in which +the cut ends of the ducts can be reunited. This has been accomplished +experimentally in dogs, and furthermore, in men rendered sterile by +occlusion of the duct through inflammatory diseases, the sterility has +been remedied by removing the blocked area and reuniting the ends of the +duct on either side. + +In women the corresponding operation--a section of the oviduct--is termed +_salpingectomy_. Here, however, the operation is a more serious one as it +usually involves opening the abdominal cavity and the accompanying hazard +of infection, a danger sufficiently great that it is safe to say that the +operation will be resorted to more rarely than vasectomy in man. + +=As a Eugenic Measure.--=Sterilization as a eugenic measure has many +advocates and perhaps more opponents; and among the latter, it must be +said, are many competent and thoughtful students of the subject who +recognize existing conditions and deplore their continuance as much as any +one. They maintain that while we may have to come to it as a last resort, +we are yet too ignorant of the actual effects of the operation, or are too +little informed on the inheritability of the specific traits we are trying +to eradicate, to launch forth on so radical a program. We must not forget +that when we put sterilization into effect we are going to have to deal +with individual cases, not general averages. + +=To What Conditions Applicable.--=And just here, it seems to me, is the +crux of the situation. When confronted by the defective individual, in a +practical case, just what criteria are we going to use to determine +whether this particular individual should be sterilized or not? Nearly all +of the twelve states which have sterilization laws specify insanity, +feeble-mindedness, epilepsy and criminality. + +=In Insanity.--=When it comes to insanity I strongly suspect that those +who have the selection of the examining board will have difficulty in +finding an alienist who is willing to take the responsibility of deciding +on just which insane individuals shall be operated on and which not. For +among the insane there are so many kinds and degrees of mental +unsoundness, and these are of such varying and as yet unknown eugenical +significance, that a positive decision is frequently out of the question. +Of the twenty-seven or more recognized forms of insanity who knows with +any considerable degree of certainty which are heritable, which not? Shall +we treat all manic-depressives alike? Shall we treat them as, for +instance, we would those suffering from dementia precox? Who will take the +responsibility of answering positively? Again, what shall we do in cases +of paresis, or general paralysis of the insane, an affliction which +probably invariably has syphilis as its antecedent? Yet it constitutes one +of the commonest forms of insanity found in asylums. Doctor George H. +Kirby, director of Clinical Psychiatry, Manhattan State Hospital, says +that with one exception there are more admissions of paretics to Manhattan +State Hospital than sufferers from any other form of mental disorder. He +continues, "We find that when either the father or the mother suffers from +paresis that many other members of the family may be infected with +syphilis, and furthermore, we find that a surprisingly large number of +children in these families are feeble-minded, nervous, or in other ways +abnormal." But here, it is clear, the patient has done the damage before +he reached the hospital, nor was it paresis as such that did the harm but +the syphilitic infection of which paresis itself was but the outcome. + +Certainly the one fact which stands out conspicuously when we face most +concrete cases, is that at present we need more urgently than +sterilization laws for the insane, exhaustive studies of the +inheritability of specific mental infirmities that we may know with some +degree of certainty which warrant sterilization. + +Yet on the other hand one of the most disquieting facts that confronts us +to-day is the large number of patients who are on parole from our +hospitals for the insane, subject to recall. What shall we do with them? +Shall we submit them to the tremendous hardship of still remaining under +custodial care although to all intents and purposes sane, or shall we make +their release contingent upon their submission to vasectomy or +salpingectomy? + +In a few cases such as Huntington's chorea (Figs. 26, 27, pp. 114, 115) we +can proceed with a fair degree of assurance, for we know that this +dreadful malady is transmitted as a positive trait and that in all +probability half of the children of an afflicted individual will inherit +the defect. Such patients, if they ever rally sufficiently temporarily to +leave the hospital, or where encountered outside the hospital should +certainly be restrained from procreation. It is questionable if even their +children, though apparently normal, should be allowed to have offspring, +for usually the disorder does not manifest itself until middle life and +then it is too late to try to prevent its transmission since the affected +individual has already probably married and had children. But Huntington's +chorea is a comparatively rare form of insanity, and one of only a few +about which our knowledge as regards its transmissibility is fairly +satisfactory. + +=In Feeble-Mindedness.--=When we come to institutions for the +feeble-minded, however, there seems to be much more unanimity of opinion +among physicians in charge of such institutions that sterilization would +be an effective and satisfactory disposition to make of many cases, if we +are to release the patients in question from custody. Unquestionably in +cases of imbecility it is easier than in insanities to pass conclusive +judgment on the inheritability of the condition in a large class of cases. +Practically all are agreed that either permanent custodial care through +the reproductive period or sterilization should be enforced. Some maintain +that such individuals should remain permanently in institutions anyway and +that therefore to sterilize them is needless, while others urge that if +sterilized many capable of making their own living could be freed and +allowed to do so. + +According to Goddard the feeble-minded woman is about three times as +likely to find a mate as a feeble-minded man, hence it would seem to be of +much greater importance to sterilize the woman than the man. + +Again it might be urged with much justification, that even though +sterilized, the feeble-minded individual because of lack of self-control +will transgress sexually and will thus certainly become a menace to +society in the spread of venereal diseases. If Mr. Hart's estimate is +anywhere near correct, that there are 60,000 feeble-minded women in the +United States of child-bearing age, and that 13,000 are already in +custody, then the task of getting all women of this class into custody is +not so insurmountable as would at first appear. + +=In Cases of Epilepsy.--=As to epilepsy, I find a very decided difference +of opinion among physicians. Some consider it, on account of its +apparently strong inheritability, together with the shocking crimes +perpetrated by epileptic criminal types, one of the most serious menaces, +while others point out that we know nothing of the real cause of epilepsy, +that there are all degrees and shades, that it is probably referable to +different causes in different cases and that no one is able to say what +the offspring of any given epileptic will be. + +As to criminal types, here again we face the difficulty of deciding any +particular case. Let us suppose that twenty-five per cent. of criminals +are mental defectives, how shall we sift them out from the seventy-five +per cent. who are supposed to be eugenically normal? Doubtless in many of +the twenty-five per cent. class, the indications of defective mentality +are sufficiently evident to prevent mistakes, but a considerable number of +uncertain status must also remain near the border-line. + +=Sterilization Laws.--=Although twelve of our states already have +sterilization laws, only two, Indiana and California, seem to have made +any active attempt to enforce them. The situation is too new yet in +Wisconsin, Michigan and Pennsylvania for these states to have shown what +they intend to do. Although the Indiana law says, "it shall be compulsory +for each and every institution" to maintain the practise, it has fallen +into disuse since 1911, presumably because the governor believed the law +unconstitutional. It is of interest to see the motive underlying the law +in various states. In the majority it is purely eugenic. In Connecticut it +is mainly eugenic though partly therapeutic. In California it is +apparently in part therapeutic, since it is stated as being for the +physical, mental or moral benefit of inmates of various state +institutions, and in part punitive and eugenic, since individuals twice +committed for sexual offenses or three times for other crimes are subject +to the operation. + +In Washington and Nevada the object is purely punitive, the persons +specified being habitual criminals and persons adjudged guilty of carnal +abuse of female persons under ten years of age, or of rape. In these +states also the court orders the operation instead of leaving it to the +decision of a board of medical experts. + +=Social Dangers in Vasectomy.--=It has been urged against vasectomy that +it will work untold harm because it relieves of the responsibility of a +probable parentage. This argument does not appeal to one as very weighty +as far as the imbecile or other degenerate is concerned, because one of +the very traits characteristic of such individuals is lack of any sense of +responsibility. By this same token, however, we have a very good argument +for sequestration as against sterilization, for the degenerate, even +though sterilized, will not be restrained sexually and will be likely to +disseminate venereal diseases or commit rape. Furthermore, there will be +the temptation to sterilize and liberate certain types that would +otherwise have been kept permanently in custody. + +=Our Present Knowledge Insufficient.--=When all is said and done, after we +take into account the meagerness of our present knowledge on the subject, +it is not to be wondered at that many thoughtful students of a +conservative turn of mind, feel that any considerable practise of +sterilization is premature. The problem has so many phases, and despite +occasional bits of positive knowledge, we are yet in such a sea of +ignorance regarding it, that in no field is the good Friar Laurence's +admonition of "wisely and slow; they stumble that run fast," needed more +at present than it is here. + +There is little doubt that in theory the feeble-minded and similar +defectives should be sent to institutions and kept there, but the +important practical question is, can this be done? We can have no final +answer until it is tried. While the initial expense would undoubtedly be +great, if we could keep our defectives from propagation for a single +generation we could very materially lessen their numbers and in succeeding +generations the expenses of their care would rapidly diminish. + +The one crying need that stands out most prominently in this whole field +is that of careful investigation of individual cases and specific types of +malady, together with an accurate census of conditions as a whole. Our +knowledge of individual malign heredities is too meager to carry us very +far at present. When we have found after adequate investigation in just +which specific types of defects heredity is an important factor--and we +shall undoubtedly find it to be one in many cases--then we can proceed +confidently with sterilization, if it will prove to be more practical and +desirable than sequestration. + +=Sterilization Laws on Trial.--=It will be of great interest and +instruction to see how extensively, in the various states which have +recently passed sterilization laws, the experts selected will find it +expedient to carry on sterilization, and what criteria they will use in +deciding on individual cases. That sterilization can be put into effect is +indisputable, as may be seen from the fact that several hundred operations +have been performed in Indiana. If the board on whom the decision depends +happens to be one which feels that many people are likely to distress +themselves unduly over the border-line cases, and overlook the fact that +there is always a goodly residue with which to proceed without great risk +of mistake, then we may expect to see a vigorous campaign inaugurated, and +those of us who are still undecided in the matter will have an opportunity +of learning more certainly the merits or the failings of the scheme. + +Certain married degenerate types would seem to be the ones most urgently +demanding attention. Having already begotten several defective children +and with nothing else in prospect but the production of the same kind, it +is difficult to see from any standpoint why a vasectomy on the male would +not be a merciful act. There are not a few such families where the father +is periodically in the hands of the law and yet not in permanent +restraint. Once in custody his release could be made contingent on +vasectomy. + +=An Educated Public Sentiment the Most Valuable Eugenic Agent.--=Coming +now to the last proposition, education of the public in the principles of +eugenics, this is the method calculated to be of more far-reaching service +than any other, in the negative as well as in the positive phases of +eugenics. Education is necessary before we can have effective restrictive +measures for the mentally incompetent established and enforced, and it is +also a prerequisite to intelligent procedure on the part of normal +individuals in considering their own fitness for marriage. + +Of greatest importance in preventing undesirable marriages, as far as +people of normal intelligence is concerned, will be the sentiment of +disapproval which will arise on the part of society itself when it becomes +really convinced that certain marriages are inimical to social welfare. +Public opinion is, in fact, one of the most potent influences in marital +affairs, simply because refusal to abide by the dictates of the community +means social ostracism. + +That social disapproval of certain unions can become a very real factor in +preventing such marriage is evinced on all sides by the numerous barriers +to marriage already in existence based on race, religious sect or social +status. Even in our much vaunted democracies one is looked down on who +marries "beneath" his or her social set. This sentiment of taboo, so +readily and often so senselessly cultivated in our present human society, +will inevitably spring up in consequence of a wide-spread knowledge of the +facts of human heredity. It is to such a growth, to the establishment of a +disapproval which is the product of its own sentiments rather than to +legislative enactments, that society must look for the greatest +furtherance of the eugenic program. + +Necessary as legal restraint is in certain cases, it must obviously be +restricted to only the most glaring defects. Moreover, legislation can not +run far in advance of public opinion. + +=The Question of Personal Liberty.--=It must be admitted that there is a +reluctance on the part of many even thoughtful individuals to the +application of methods which savor in any way of restraint. An objection +not infrequently urged by such persons against the application of certain +eugenic principles is that they demand an unwarranted curtailment of +personal liberty. + +To those who hoist the flag of personal liberty, it may fairly be asked, +how much personal liberty does the syphilitic accord his doomed and +suffering wife and children, or how much personal liberty is the portion +of the offspring of feeble-minded parents? Or, what quota of personal +liberty will accrue to the ill-fated descendants of the epileptic, the +habitual drunkard or criminal, the gross moral pervert, the congenially +deaf and dumb, or to even the progeny which may result from the union of +two well-established tubercular strains? + +We do not hesitate to send the pick of our stalwart healthy manhood to war +to be slaughtered by the thousands and tens of thousands when an affront +is offered to an abstraction which we term our national honor, and, +sublimely unconscious of the irony of it all, we throw ourselves into a +well-nigh hysterical frenzy of protest when it is proposed to stop the +breeding of defectives by infringing to a certain extent on their personal +liberties. + +Society has already found it necessary to suppress certain individuals +and yet we hear little complaint about loss of personal liberty in such +cases. But if it is necessary to restrain the man who would steal a purse +or a horse, is it not still more urgent to restrain one who would poison +the blood of a whole family or even of an entire stock for generations? +Surely there can be but one answer; society owes it to itself as a matter +of self-preservation to enforce the restraint of persons infected with +certain types of disease and of individuals possessing highly undesirable +inheritable traits, so that perpetuation of such defects is impossible. + +=Education of Women in Eugenics Needed.--=One of the most crying needs of +the present is the awakening and educating of women to the significance of +the known facts. For they are perhaps the greatest sufferers, and once +informed, as a mere matter of safety if for no other reason, they will see +the necessity of demanding a clean bill of health on the part of their +prospective mates. Furthermore in the last analysis woman is the decisive +factor in race betterment, for it is she who says the final yea or nay +which decides marriage and thus determines in large measure the qualities +which will be possessed by her children. Above all, young women must come +to realize that the fast or dissipated young man, no matter how +interestingly or romantically he may be depicted by the writer of fiction, +is in reality unsound physically, and is an actual and serious danger to +his future wife and children. + +=Much Yet to Be Done.--=But plain as is our duty regarding the application +of facts already known, when we consider that the student of heredity has +made only a beginning, it is equally evident that he must be urged on in +his quest for new facts, and the establishment of new principles. There is +imperative need to carry on proper experiments with plants and animals, to +collect necessary data regarding man, and for what is scarcely less +important, the publication of the facts already acquired so that the +public may be guided aright. + +Just at present it is of the utmost importance to secure more trustworthy +statistics in order that we may intelligently go about instituting +suitable restrictive measures for undesirable human strains. We must know +the exact number and kinds of feeble-minded, epileptic and insane in our +population, and we must have more insight into the personal status and +pedigrees of our delinquents and criminals. For purposes of rational +procedure such information is indispensable. Much can be done by +hospitals, "homes" and penal institutions by determining and recording +more accurately all obtainable facts regarding the ancestry of their +charges. Moreover, in such states as Wisconsin, where the state hospitals +for the insane have each an "after-care-agent," the duties of such +officers might well include the collection of more adequate data regarding +the hereditary aspects of their patient's condition. And lastly, if in +every census, whether state or national, it were made an important part of +the work to secure accurate vital statistics, particularly as they pertain +to human heredity, the contribution toward enabling us ultimately to +purge the blood of our nation of certain forms of suffering, degeneracy +and crime would be inestimably great. + +=A Working Program.--=And now after reviewing at some length various +aspects of man's hereditary and congenital endowment, the important +question arises as to whether it is possible, with the knowledge at +present available, to go ahead with a practical program which will insure +to the child of the future its right of rights, that of _being well-born_. +When one considers the matter it is evident that much can be done at once. +Most of the needs set forth in the preceding paragraph can clearly be met +in a fair degree by instituting the procedures indicated. + +One of the obvious duties in a restrictive way that confronts us right at +the start is the care and control of the feeble-minded and of the +defective delinquent in such a way as to prevent procreation. Much help +can be given also through intelligent agitation for the establishment of +colonies for epileptics and the higher grades of feeble-minded which can +be made in considerable measure self-supporting. A given colony must, of +course, be for one sex alone. Much can be done, furthermore, by putting +into operation, both in and out of institutions, effective systems of +registering births and deaths together with accompanying facts which may +prove of eugenical significance. + +Again, we should more surely identify and exclude undesirable immigrants +and also undertake thoroughgoing investigations to determine which races +we can not profitably assimilate into our own blood. + +Physicians should pay more attention to the hereditary and congenital +aspects of their cases and make it more a matter of conscience than they +do at present to advise patients with regard to marriage. Prenuptial +medical inspection should become the custom, if not by law at least as a +voluntary procedure. Every parent must come to realize the grave risk to +which he is subjecting his daughter if a guarantee of physical fitness, +even more than assurance of financial standing or social position, is not +forthcoming from her prospective mate. + +Wholly apart from the field of heredity though in a realm intimately +concerned with the birthright of the child, much practical good can be +accomplished by pondering the facts and the fictions of prenatal influence +and in the light of the knowledge thus gained, seeing that while foolish +and unnecessary worries are abolished, the conditions of health, nutrition +and occupation surrounding the expectant mother are the best obtainable. +It is the sacred duty of every individual, moreover, to see that the +maximal possibilities of his own germ-plasm are not lowered by vicious or +unwholesome living. + +As individuals we can cultivate a greater sense of responsibility +regarding marriage and parenthood in those for whose training we are +responsible. We can study this whole subject conscientiously, keep pace +with new knowledge and see that other people are likewise informed. In +showing an enlightened interest in the ideals of eugenics and a +sympathetic approval of wholesome marriages, a sentiment toward parenthood +will gradually arise which will make it seem more desirable to many worthy +people than it does at present. If we are of good stock ourselves we +should recognize that it is highly desirable that we give to the race at +least four children. On the other hand, if we come from a strain which is +eugenically undesirable we should with equal conscientiousness refrain +from contributing to human misery. For where serious obstacles to a union +exist, renunciation is certainly a higher manifestation of love than is +consummation of a marriage which will result in untold misery to the +object of the affections. As a matter of fact, with adequate preliminary +knowledge as to what actually constitutes a serious drawback to marriage, +where such really exists and is recognized by the associated individuals, +love of the kind that leads to marriage is not likely to arise. + +As has been suggested by various students of eugenics, it is even at +present perhaps not infeasible for earnest individuals to start in a quiet +way local centers for the keeping and filing of accurate records of their +family traits for the future use of their descendants. Such groups, +voluntary though they be, would soon acquire a degree of distinction that +would make other people of good endowments wish to join in and go on +record as eugenically desirable. + +Lastly, it should not be forgotten that good traits are inherited as +certainly as bad ones. Moreover, in the realm of human conduct, even +though the fundamental features of behavior are based on an inherited +organization, man is not always driven by an inexorable linkage of +inherited neutral units into only one line of conduct, since more or less +capacity for alternative action is also inherited. It is the personal +duty of every member of society to aid in affording the opportunity and +providing the proper stimuli to insure that out of the many possibilities +of behavior which exist in the young at birth, those forms are realized +which are best worth while to the individual and to society. And while we +recognize that improved environment alone can not correct human +deficiencies we must nevertheless not relax our efforts to get cleaner +foods, cleaner surroundings, cleaner politics and cleaner hearts. + +Why go on alleviating various kinds of misery that might equally well be +prevented? When one squarely faces the issue, surely the absurdity of our +present practises can not but be evident to even the most thoughtless. + +=Which Shall It Be?--=As a matter of social evolution, human homes +originated in the necessity of an abiding place for the nurture and +training of the young past their first period of helplessness. Well in the +foreground of the mental picture which arises when we hear the very word +_home_, are children. What shall the home of the future be with regard to +its most important assets, the children? Shall we as a people continue to +be confronted at every turn by the dull countenance of the imbecile, the +inevitable product of a bad parental mating; or the feeble body and the +clouded intellect of the child sprung from a parentage of polluted blood; +or the furtive cunning of the born criminal, the will-less mind of the +bred degenerate, or the shiftless spawn of the pauper? Or shall it be a +type with laughing face, with bounding muscles, with unclouded brain, +overflowing with health and happiness--in short, _the well-born child_? + +The answer is in our own hands. The fate of many future generations is +ours to determine and we are false to our trusteeship if we evade the +responsibility clearly laid before us. How conscientiously we heed known +facts, how actively we acquaint ourselves with new facts, and how +effectively we execute the obvious duties demanded by these facts, will +give us the answer. + + +THE END + + + + +GLOSSARY + + +ACQUIRED CHARACTERS, traits developed in the body through changes in +environment or function, in contra-distinction to those which have their +specific causes in the germ-cells. + +ADAPTATION (L. _ad_, to; _aptus_, fit), fitness to environment. + +ALBINISM (L. _albus_, white), a condition of deficiency in pigment. + +ALLELOMORPH (Gr. _allelon_, of one another; _morphe_, form), one of a pair +of alternate Mendelian characters. + +AMEBA (Gr. _amoibe_, change), a primitive single-celled animal. + +AMPHIBIAN (Gr. _amphi_, both; _bios_, life), capable of living both on +land and in water. + +ANTHROPOID (Gr. _anthropos_, man; _eidos_, form), man-like. + +ARISTOGENIC (Gr. _aristos_, best; _genesis_, origin), pertaining to the +genetically most desirable human strains. + +ASSOCIATION AREAS, those regions of the brain in which presumably the +higher mental processes are effected. + +ATAVISM (L. _ad_, before; _avus_, grandfather), a return in one or more +characters to an ancestral type. See p. 8 for restricted modern usage. + +ATROPHY (Gr. _a_, negative; _trophe_, nourishment), a wasting away of a +part of a living organism. + +AXON (Gr. _axon_, axis), the process from a nerve cell which becomes a +nerve fiber. + +BINET-SIMON SCALE, a series of tests graded to age and previous training +of the average normal child, much used in measuring mental deficiency. + +BIOLOGY (Gr. _bios_, life; _logos_, discourse), the study of life and of +living things. + +BIOMETRY (Gr. _bios_, life; _metron_, measure), the study of biological +problems by means of statistical methods. + +BLASTOMERE (Gr. _blastos_, germ; _meros_, part), one of the early cells +formed by the division of the ovum. + +BLASTOPHTHORIA (Gr. _blastos_, germ; _phtheiro_, destroy), deterioration +of the germ as the result of direct pathogenic or other disturbing agents. + +BLENDING INHERITANCE, inheritance in which the characters of the parents +seem to blend in the offspring. + +CACOGENIC (Gr. _kakos_, bad; _genesis_, origin), pertaining to genetically +undesirable human strains. + +CELL, the fundamental unit of structure in plants and animals. + +CENTROSOME (Gr. _kentron_, center; _soma_, body), a small body which +functions in indirect cell-division. + +CHARACTER, any distinguishing feature, trait or property of an organism. + +CHEMOTROPISM (chemical and tropism), defined, p. 198. + +CHROMATIN (Gr. _chroma_, color), deeply staining substance of the +cell-nucleus. + +CHROMOSOMES (Gr. _chroma_, color; _soma_, body), characteristic deeply +staining bodies, typically constant in number and appearance in each +species of animal or plant, which appear in the cell during indirect +division. + +CHROMOTROPISM (Gr. _chroma_, color; _trope_, turning), defined, p. 198. + +CLEAVAGE, the division of the egg-cell into many cells. + +CONGENITAL (L. _con_, together; _gigno_, bear), present at birth. + +CONJUGATION (L. _con_, together; _jugum_, yolk), the union of germ-cells +or unicellular individuals for reproduction. + +CONSTRUCTIVE (or positive) EUGENICS, a system of securing a superior race +through propagation of the fittest individuals. + +CORTEX (L. _cortex_, bark), the outer or investing layer of the brain. + +CYTOPLASM (Gr. _kytos_, cell; _plasso_, form), the protoplasm of the cell +outside of the nucleus. + +DALTONISM, the commonest form of color-blindness in which the affected +individual is unable to discriminate between red and green. + +DENDRITES (Gr. _dendron_, tree), branching processes which spring from +nerve-cells. + +DETERMINER (L. _determinare_, to determine), the distinctive cause or unit +in a germ-cell which determines the development of a particular character +in the individual derived from that cell. The terms _gene_ and _factor_ +are sometimes used as synonyms of determiner. + +DIHYBRIDS (L. _di_, two; _hybrida_, mongrel), the offspring of parents +differing in two characters. + +DIPLOID (Gr. _diploos_, double; _eidos_, form), the dual or somatic number +of chromosomes. + +DOMINANT CHARACTER (L. _dominare_, to be a master), a character from one +parent which manifests itself in offspring to the exclusion of a +contrasted character from the other parent. + +DROSOPHILA, a genus of fruit-flies of which there are several species. + +DUPLEX (L. _duo_, two; _plico_, fold), the condition in which a character +is represented by two determiners, one from each parent. + +ELECTROTROPISM (Gr. _electron_, amber; _trope_, turning), defined, p. 198. + +EMBRYO (Gr. _embryon_), the young organism in its earliest stages of +development. + +EMBRYOGENY (Gr. _embryon_; _genesis_, generation), the development of the +embryo. + +EUGENICS (Gr. _eugenes_, well-born), the science relating to improvement +of the human race through good breeding. + +FACTOR, the determiner of a particular hereditary character. + +FEEBLE-MINDEDNESS, deficiency in mental development. For grades, see p. +244. + +FERTILIZATION, union of the sexual cells. + +FETUS (L. _feuere_, to bring forth), the unborn young animal in its later +(after the second month in man) stages of development. + +FLAGELLUM (L. _flagellum_, little whip), a vibratile, thread-like organ of +locomotion. + +GAMETE (Gr. _gamos_, marriage), a mature germ-cell. + +GENETICS (Gr. _genesis_, origin), the science which deals with heredity +and the origin of individuals in general. + +GENOTYPE (Gr. _genea_, race; _typto_, strike), the germinal constitution +of an organism. + +GEOTROPISM (Gr. _ge_, earth; _trope_, turning), defined, p. 198. + +GERM-CELL, a reproductive cell. + +GERMINAL VARIATIONS, variations which owe their origin to some +modification in the germ-cells. + +GERM-PLASM, the material basis of inheritance. + +GONAD (Gr. _gonos_, generation), a germ-gland. + +HAPLOID (Gr. _haploos_, single; _eidos_, form), the single or reduced +number of chromosomes as found, for instance, in the mature germ-cells. + +HELIOTROPISM (Gr. _helios_, sun; _trope_, turning), defined, p. 198. + +HEREDITY (L. _heres_, heir), resemblance of individuals to their +progenitors based on community of origin. + +HERITAGE (L. _heres_, heir), all that is inherited by an individual. + +HETEROZYGOTE (Gr. _heteros_, other; _zygon_, yolk), an individual produced +through the union of germ-cells which are unlike in one or more +determiners. Adjective, _heterozygous_. + +HOMOZYGOTE (Gr. _homos_, same; _zygon_, yolk), an individual produced +through the union of germ-cells which are alike in determiners. Adjective, +_homozygous_. + +HYBRID (L. _hybrida_, mongrel), the offspring of parents which differ in +one or more characters. + +IDENTICAL TWINS, twins which show identical inborn characters, both having +come presumably from the same ovum. + +IDIOT (Gr. _idios_, peculiar, private), defined, p. 244. + +IMBECILE (L. _imbecillis_, weak), defined, p. 244. + +INHERITANCE (L. _in_, in; _heres_, heir), the sum of all characters which +are transmitted by the germ-cells from generation to generation. + +INHIBITOR (L. _in_, in; _habeo_, hold, have), that which checks or +restrains. + +INSTINCT (L. _in_, in; _stingno_, prick), defined, p. 203. + +INTRA-UTERINE (L. _intra_, within; _uterus_, the womb), within the womb. + +IRRITABILITY (L. _irrito_, excite), the property of responding to stimuli. + +LININ (L. _linum_, flax), filaments of the cell-nucleus not readily +stained by dyes. + +LUETIN TEST (L. _lues_, pest), a test for syphilis; see p. 188. + +MAMMALS (L. _mamma_, breast), warm-blooded, hairy animals which suckle +their young. + +MATURATION (L. _maturus_, ripe), the final stages in the development of +the sex-cells characterized by two divisions in one of which the number of +chromosomes is reduced by one-half. + +MENDELIAN, MENDELISM, referring to Mendel, the founder of a theory of +heredity. See p. 67. + +METAZOA (Gr. _meta_, over; _zoon_, animal), all animals higher than the +protozoa. + +MITOSIS (Gr. _mitos_, thread), indirect nuclear division, characterized by +the appearance of a fibrous spindle and a definite number of chromosomes. +The latter split to form daughter chromosomes which diverge to the poles +of the spindle to form parts of the new nuclei. + +MONGOLIAN, a type of feeble-minded individual, see p. 248. + +MONOHYBRID (Gr. _monos_, single; L. _hybrida_, mongrel), the offspring of +parents, differing in one character. + +MORON (Gr. _moros_, foolish), defined, p. 244. + +MUTATIONS (L. _mutare_, to change), abrupt, inheritable germinal +variations. Frequently though not necessarily they are changes of +considerable extent. + +NEURAL (Gr. _neuron_, nerve), pertaining to the nervous system. + +NEURON (Gr. _neuron_, nerve), a nerve-unit consisting of a nerve-cell with +branching processes called dendrites and an axon or axis cylinder process +which gives rise to a nerve fiber. + +NEUROPATHIC (Gr. _neuron_, nerve; _pathos_, suffering), relating to +disease of the nervous system. + +NUCLEOLUS (L. dim. of nucleus), a well-defined body found within the +nucleus of a cell. + +NUCLEUS (L. _nux_, a nut), the central organ of a cell. + +NULLIPLEX (L. _nullus_, not any; _plico_, fold), the condition in which no +determiners of a given character exist in a particular individual. + +OÖCYTE (Gr. _oon_, egg; _kytos_, cell), the ovarian egg in one stage of +development. + +OÖGENESIS (Gr. _oon_, egg; _genesis_, origin), the development of ova from +primitive sex-cells. + +OÖGONIUM (Gr. _oon_, egg; _gonos_, generation), a primordial egg-cell. + +OVARY (L. _ovum_, egg), the organ in which the egg-cells multiply and are +nourished. + +OVUM (L. _ovum_, an egg), the female sex cell. + +PARTHENOGENESIS (Gr. _parthenos_, virgin; _genesis_, origin), development +of an egg which has not united with a male gamete. + +PHENOTYPE (Gr. _phaino_, show; _typto_, strike), the existing type of +individual irrespective of hereditary possibilities which may reside in it +undeveloped. + +PHOTOTROPISM (Gr. _phos_, light; _trope_, turning), defined, p. 198. + +PLACENTA (L. _placenta_, a flat cake), the organ by which the fetus of the +higher mammals is attached to the uterine wall of the mother for purposes +of nourishment, respiration and excretion. In it the maternal and fetal +blood, although not intermingling, are brought into such close proximity +that an interchange of dissolved substances is possible. + +POLAR BODIES, the minute cells which are separated from the egg in its +maturation divisions. + +PRIMATE (L. _primus_, first), the highest order of animals, including +monkeys, apes and man. + +PRONUCLEUS, the nucleus of the mature ovum or sperm-cell. + +PROTOPLASM (Gr. _protos_, first; _plasma_, form), the essential living +substance. + +PROTOZOA (Gr. _protos_, first; _zoon_, animal), single-celled animals or +animals composed of cells not separable into different tissues. + +PSYCHICAL (Gr. _psyche_, the soul), pertaining to the mind. + +RECESSIVE CHARACTER (L. _recessus_, a going back), a character from one +parent which remains undeveloped in offspring when associated with the +corresponding dominant character from the other parent. + +REDUCTION DIVISION, a division of the maturing germ-cells in which the +dual or somatic (diploid) number of chromosomes is reduced to the single +(haploid) number. + +REFLEX ACTION (L. _re_, back; _flectere_, bend), an automatic response of +the nervous and motor mechanism of the body. + +RESTRICTIVE (or negative) EUGENICS, a system of improving the human race +by preventing reproduction of the unfit. + +REVERSION (L. _re_, back; _verto_, turn), the reappearance of ancestral +traits which have for some generations been in abeyance. + +RHEOTROPISM (Gr. _rheo_, to flow; _trope_, turning), defined, p. 198. + +SALPINGECTOMY (Gr. _salpinx_, trumpet; _ectome_, cutting out), removal of +part or all of a Fallopian tube (oviduct). + +SEGREGATION (L. _se_, aside; _grex_, flock), separation. + +SEX CHROMOSOME, a special chromosome which is supposed to be concerned in +the determination of sex. + +SEX-LINKED CHARACTERS, defined, p. 60. + +SIMIAN (L. _simia_, ape), ape-like. + +SIMPLEX (L. _sim_, same; _plico_, fold), the condition in which a +character is represented by a determiner from only one of the two parents. + +SOMA (Gr. _soma_, body), the body considered apart from the germ-cells. + +SPERMATID (Gr. _sperma_, seed), a cell resulting from the last division of +the germ-cell in spermatogenesis. It transforms into the spermatozoon. + +SPERMATOCYTES (Gr. _sperma_, seed; _kytos_, cell), cells concerned in the +maturation divisions of the male germ-cells. + +SPERMATOGENESIS (Gr. _sperma_, seed; _genesis_, origin), the development +of spermatozoa from primitive sex-cells. + +SPERMATOGONIUM (Gr. _sperma_, seed; _gonos_, generation), a primordial +sperm-cell. + +SPERMATOZOON (Gr. _sperma_, seed; _zoon_, animal), the functional male +sex-cell. + +SPINDLE, a fibrous organ formed in indirect cell-division. + +SPIREME (L. _spira_, coil), a characteristic stage preliminary to indirect +cell-division in which the chromatin material of the nucleus appears in +the form of a skein of filaments. + +STEREOTROPISM (Gr. _stereos_, solid; _trope_, turning), defined, p. 198. + +STERILIZATION (L. _sterilis_, barren), deprivation of reproductive power. +For methods, see p. 322. + +SYNAPSE (Gr. _syn_, together; _hapto_, unite), the coming in contact of +the processes of one nerve cell with the processes or body of another. + +SYNAPSIS (Gr. _syn_, together; _hapto_, unite), union of the chromosomes +in pairs preliminary to the reduction division. + +TELEGONY (Gr. _telegonos_, born far away), the supposed influence of an +earlier sire on offspring born later of the same mother to a different +sire. + +THERMOTROPISM (Gr. _thero_, heat; _trope_, turning), defined, p. 198. + +THIGMOTROPISM (Gr. _thigmo_, touch; _trope_, turning), defined, p. 198. + +TOXIN (Gr. _toxicon_, poison), poisonous compounds of animal, vegetable, +or bacterial origin. + +TROPISM (Gr. _trope_, turning), the automatic directing of an organism +toward or away from a source of stimulus. + +UNIT-CHARACTER, a character which behaves as an indivisible unit in +heredity. + +VASECTOMY (L. _vas_, vessel; _ektome_, cutting out), removal of a portion +of the vas deferens (duct for conveying spermatozoa). + +VESTIGEAL (L. _vestigium_, footstep), representing organs which existed +once in a more developed condition. + +VOLVOX (L. _volvo_, roll), a small fresh-water organism occurring in +spherical colonies. + +WASSERMAN REACTION, a test for syphilis, see p. 188. + +X-ELEMENT, same as sex-chromosome. + +ZYGOTE (Gr. _zygon_, yolk), the product of the union of two gametes. + + + + +REFERENCES FOR FURTHER READING AND STUDY + + +BATESON, W., 1909. _Mendel's Principles of Heredity._ Cambridge, The +University Press. The best technical account of Mendelism. It contains +also a translation of the original papers of Mendel. + +CASTLE, WILLIAM E., 1911. _Heredity._ New York, D. Appleton and Company. + +CASTLE, WILLIAM E.; COULTER, JOHN M.; DAVENPORT, CHARLES B.; EAST, EDWARD +M.; TOWER, WILLIAM L., 1912. _Heredity and Eugenics._ Chicago, The +University of Chicago Press. + +CONKLIN, EDWIN GRANT, 1915. _Heredity and Environment in the Development +of Men._ Princeton, Princeton University Press. + +DAVENPORT, CHARLES B., 1911. _Heredity in Relation to Eugenics._ New York, +Henry Holt and Company. + +DONCASTER, L., 1911. _Heredity in the Light of Recent Research._ +Cambridge, The University Press. + +DONCASTER, L., 1915. _The Determination of Sex._ Cambridge, The University +Press. + +ELLIS, HAVELOCK, 1912. _The Task of Social Hygiene._ New York, Houghton +Mifflin Company. + +GALTON, FRANCIS, 1869. _Hereditary Genius: an Inquiry Into Its Laws and +Consequences._ London, Macmillan and Company. + +GALTON, FRANCIS, 1889. _Natural Inheritance._ New York, The Macmillan +Company. + +GALTON, FRANCIS, 1895. _English Men of Science; Their Nature and Nurture._ +New York, D. Appleton and Company. + +GALTON, FRANCIS, and SCHUSTER, EDGAR, 1906. _Noteworthy Families_ (Modern +Science). London, J. Murray. + +GODDARD, HENRY HERBERT, 1912. _The Kallikak Family; a Study in the +Heredity of Feeble-mindedness._ New York, The Macmillan Company. + +GODDARD, HENRY HERBERT, 1914. _Feeble-mindedness; Its Causes and +Consequences._ New York, The Macmillan Company. + +HEALY, WILLIAM, 1915. _The Individual Delinquent._ Boston, Little, Brown +and Company. + +KELLICOTT, WILLIAM E., 1911. _The Social Direction of Human Evolution; an +Outline of the Science of Eugenics._ New York, D. Appleton and Company. + +MORGAN, THOMAS HUNT, 1913. _Heredity and Sex._ New York, Columbia +University Press. + +PUNNETT, R. C., 1911. _Mendelism._ New York, The Macmillan Company. The +best popular account of Mendelism. + +SALEEBY, CALEB WILLIAM, 1909. _Parenthood and Race Culture; an Outline of +Eugenics._ London, Cassell and Company. + +SCHUSTER, EDGAR, 1912. _Eugenics._ London, Collins Clear-Type Press. + +THOMSON, J. ARTHUR, 1908. _Heredity._ London, John Murray. + +WALTER, HERBERT EUGENE, 1913. _Genetics._ New York, The Macmillan Company. + +WHETHAM, W. C. D. and C. D., 1909. _The Family and the Nation._ London, +Longmans, Green and Company. + +WOODS, FREDERICK ADAMS, 1906. _Mental and Moral Heredity in Royalty._ New +York, Henry Holt and Company. + +VARIOUS AUTHORS, 1914. _Eugenics; Twelve University Lectures._ New York, +Dodd, Mead and Company. + +JOURNALS: + + _The Journal of Heredity._ The organ of the American Genetic + Association, Washington, D. C. + + _The Eugenics Review._ Issued at the University of London. + + _Memoirs and Bulletins_ published by the Eugenics Record Office, Cold + Spring Harbor, Long Island, N. Y. + +Every one interested in eugenics should be acquainted with the work of +this office. In its own words its functions are: + + 1. To serve eugenical interests in the capacity of repository and + clearing house. + + 2. To build up an analytical index of the traits of American families. + + 3. To train field workers to gather data of eugenical import. + + 4. To maintain a field force actually engaged in gathering such data. + + 5. To cooperate with other institutions and with persons concerned + with eugenical study. + + 6. To investigate the manner of inheritance of specific human traits. + + 7. To advise concerning the eugenical fitness of proposed marriages. + + 8. To publish results of researches. + + To such persons as will undertake to fill them out it furnishes free + in duplicate (one copy to be retained by the applicant) the following + blank schedules: 1. _Record of Family Traits._ 2. _Index to + Germ-plasm--A Parallel Family Record for Prospective Marriage Mates._ + 3. _Musical Talent._ 4. _Mathematical Talent._ 5. _Tuberculosis._ 6. + _Special Trait Chart._ 7. _Harelip and Cleft-palate._ + + _Publications of the Volta Bureau_ of Washington, D. C., an + institution given over entirely to data regarding deaf mutes. + + _Studies in National Deterioration._ The University of London. + + _Memoirs and Lectures_, from the Biometric Laboratory, University of + London. + + _Treasury of Human Inheritance_, a series of studies being issued from + the Eugenics Laboratory, University College, London. + + + + +INDEX + + + Ability: 118; + calculating, literary, musical, 120. + + Able child likely to be neglected, 257. + + Achondroplasy, 113. + + Acquired characters, inheritance of, 121. + + Adami, 164. + + Adaptations, establishment of, 140. + + Adaptive responses, 201. + + Agassiz, 297. + + Albinism, in man, 116. + + Alcohol: and crime, 279; + and degeneracy, 172, 179; + and germinal tissue, 172; + a poison, 168. + + Alcoholism: 101, 117, 167; + factors in, 180; + in lower animals, 173-178; + views regarding inheritance of, 169, 170, 172, 178, 179, 180. + + Alkaptonuria, 117. + + Allelomorph, 77. + + Alpine plants, non-inheritance of acquired characters, 131. + + Alternative action in behavior, 207. + + Altruism, possible origin of, 220. + + Ambystoma, 132. + + Ameba, 23, 24. + + Ancestors, number of, 4. + + Ancestry: a network, 3; + dual, 6; + in royalty, 5; + pride of, as a eugenic agent, 309. + + + Backward child, 256. + + Backwardness, importance of early determination, 256, 257. + + Bardeen, 126. + + Barker, 229. + + Barr, 246, 247, 248. + + Barrington, 179. + + Bateson, 77, 82. + + Bees, inheritance in, 136, 137. + + Behavior: lower animals, 197; + modifiability of, 200, 204-207, 217, 219, 224, 225, 337; + not wholly established by heredity, 217, 227; + rational, 205, 206; + various forms of, possible, 207, 219. + + Bell, 152. + + Bezzola, 170. + + Billings, 249. + + Binet-Simon test, 255. + + Biometry, 16. + + Birthmarks, 159, 160. + + Birth-rate: significance of, 302; + too low in desirable stocks, 302, 304, 305, 307. + + Blastomeres, 55. + + Blastophthoria, 163. + + Blended inheritance, 87, 92, 93. + + Blends, mistakes for, 91. + + Blindness, infantile, 183. + + Blistering, 113. + + Body: how built up from germ, 36; + duality of, 50. + + Brachydactylism, 107. + + Brain: in higher animals, 213; + mechanism, maladjustments of, 230. + + Branthwaite, 180, 292. + + Breeding, experiments, method of, 14, 15. + + Brewer, 142. + + Brieux, 101. + + Bronner, 266. + + Brown Sequard, 132, 133. + + + Cabot, 183. + + Cacogenic strains, 310. + + Cajal, 209. + + Cancer, 117, 154. + + Capsella, 131. + + Castle, 134. + + Cataract, presenile, 112. + + Cattle: horn characters, 79; + roan, 81. + + Cell: a unit of structure, 20; + diagram of, 21; + structure of, 20, 30. + + Cell-division: 31; + indirect (mitosis), 32; + meaning of indirect, 34. + + Cell-theory, 22. + + Cellular basis of heredity, 22. + + Ceni, 174. + + Centrosome, 31. + + Cerebral cortex, not functionally homogeneous, 211. + + Character: defined, 12; + dominant, 74; + recessive, 74. + + Characters: contrasted, 69; + determiners of, 13, 14; + independence of, 69; + inheritable and non-inheritable, 121, 122; + more than two pairs of, 87; + new combinations of, 82, 83, 84; + separable, 69; + symbols for, 78; + two pairs of, 82. + + Chauvin, 132. + + Chemotropism, 198. + + Childbirths, intervals between, 165. + + Children of the future: ours to determine quality of, 338, 339; + and home, 338. + + Cholera, 152. + + Chorea: 117; + Huntington's, 113-115, 243, 325. + + Chromatin, 31. + + Chromosome, 32. + + Chromosomes: individuality of, 39, 48; + determiners in, 94; + in germ and body cells, 40; + Mendelian factors and, 93; + number and appearance, 34, 41; + pairs of, 40, 93, 94; + significance of, in heredity, 35, 49, 50, 51, 53, 54. + + Chromotropism, 198. + + Church, 242. + + Cleavage, 36. + + Cleft-palate, 178. + + Cole, 166. + + College graduates and birth-rate, 304. + + Coloboma, 113. + + Color-blindness, 60-62. + + Conceptual thought, origin of, 206. + + Conduct: importance to young of practise, 221, 223; + hereditary predisposition and, 218, 337; + responsibility for, 195. + + Congenital traits, 123. + + Conjugation, 25. + + Consciousness, 206. + + Conservation: of superior strains, 157; + human, 299, 300. + + Constructive eugenics, 309. + + Corneal opacity, 113. + + Correns, 68. + + Cortex of brain, 195, 213. + + Cost, of caring for our disordered and delinquent, 257, 300. + + Cretins, effects of segregating the sexes, 321. + + Crime: and delinquency, 263, 287; + and feeble-mindedness, 264-270; + bearings of immigration on, 280; + classifications of, 276; + defined, 276; + heredity vs. environment in, 263; + increase in, 272; + mental disorders most frequently associated with, 279; + no specific hereditary factor for, 275. + + Criminal: the born, 277; + the epileptic, 277. + + Criminality, 117. + + Criss-cross inheritance, 61. + + Criteria for judging reproductive fitness, 304, 306. + + Cytoplasm: 30; + in heredity, 51. + + + Daltonism, 60. + + Dana, 257. + + Darwin, pedigree of, 316. + + Davenport, 92, 116, 231, 243, 257, 271, 273, 284, 291, 304, 312. + + Davis, 185. + + Deaf-mutism, 152, 153. + + Death, natural, 28. + + Decline of nations, 290, 300. + + Defective delinquent, should prevent procreation of, 335. + + Defectives: increase due to breeding, 290, 291; + natural elimination done away with among, 292; + unpardonable to let multiply, 288. + + Defects: breeding out, 118, 119; + mental and nervous, 228. + + Degenerate strains: 269; + not a product of surroundings, 273. + + Degenerates, sterilization of married, 330. + + Delinquency, causes of, 267, 274. + + Delinquents not all defectives, 274. + + Delinquent women and girls, many mentally defective, 265, 266. + + Dendrite, 208. + + De Sanctis, 256. + + Determiners: 13, 77; + different producing the same character, 88, 90; + segregation of, 84. + + Development: in higher organisms, 28; + suppressed, 9. + + De Vries, 68. + + Diabetes, 113. + + Difficulty, educational value of, 222, 223. + + Digital malformations, 107. + + Dihybrids, 82. + + Diploid number of chromosomes, 41, 43. + + Disease: defined, 146; + inheritance of, 98, 148; + predisposition to, 148; + reappearance of not necessarily inheritance, 146. + + Dominance: 74; + delayed, 81; + incomplete, 80, 100; + in human genealogies, 102; + in man, 99, 107. + + Don Carlos, number of ancestors, 5. + + Drosophila, 66. + + Duplex character, 80, 99. + + Dwarfing, by starvation, 130. + + Dwarfs, true, 117. + + + East, 91. + + Education: actual practise in carrying out projects important, 221; + affording opportunity for development of good traits, 226; + effects of not inherited, 142, 155; + establishing pathways through the nervous system, 210; + importance of difficulty in, 222, 223; + non-transference of skill acquired in one line to other lines, 213; + providing proper stimuli, 226; + training in motive necessary, 220; + value of interest in, 223. + + Egg, a cell, 22. + + Egg-cell and sperm-cell contrasted, 29. + + Elderton, 179, 296. + + Electrotropism, 198. + + Ellis, 265, 301. + + Embryo, relation to mother, 161. + + Embryogeny, 36. + + Emerick, 251. + + Environment: direct action on germ cells, 124, 125; + effects of faulty, 158; + in crime and delinquency, 263, 266, 273, 274. + + Epidermolysis, 113. + + Epilepsy: 101, 117, 242, 249, 251, 252, 253; + in guinea-pigs, 132; + relation to feeble-mindedness, 249. + + Epileptic, the criminal type, 277-279. + + Epileptics, number of, 230, 246, 250. + + Eugenic agent, educated public sentiment, 330. + + Eugenics: and education, 309; + and personal liberty, 332; + a working program of, 335; + constructive, based on education, 301; + defined, 293; + desirable traits, 306; + education of women in, 333; + influence of public opinion on, 331; + much yet to be done, 333, 334; + positive and negative, 301. + + Ewart, 10, 165. + + Exceptional child likely to be neglected, 257. + + Experimental breeding, method of, 15. + + External conditions, influences of, 130. + + Eye-color: 9, 103; + inheritance of, 104. + + Eye-defects, 108, 110. + + + Family pride and eugenics, 309. + + Farabee, 106. + + Fay, 153. + + Feeble-minded: prevention of procreation in, 258, 335; + results of non-restraint, 246. + + Feeble-mindedness: 101, 117; + and crime, 264-269, 279; + grades of, 244; + inheritance of, 245; + not insanity, 238; + relation of alcohol to, 169-172. + + Fernald, 256, 266. + + Fertilization, 26, 29, 47, 48. + + Fetus: poisoning of, 162; + relation to mother, 161. + + Fiber-tracts in man, 214. + + Fitness, criteria for judging, 304, 306. + + Flexner, 186. + + Forel, 169, 173, 303. + + Fowl, Andalusian, 69, 70, 71. + + Frederick the Great, number of ancestors, 5. + + Friedreich's disease, 117. + + Fruit-fly, 66. + + + Galton, 293, 295. + + Gamete, 28, 40. + + Gametes in dihybrids, 85. + + Gametic matings in man, 100. + + Geddes, 55. + + Genealogies, imperfect, 98. + + Genotype, 86. + + Geotropism, 198. + + Germ and body distinct, 37, 38. + + Germ: control of possibilities in, 224; + singleness of, 50. + + German emperor, number of ancestors, 5. + + Germ-cells: affected by poisons, 126; + changes in, 126, 127; + early set apart, 37; + question of effects of body on, 128, 135; + effects of external influences on, 124; + in Miastor, 37, 38; + metabolic changes in, 138; + origin of, 36, 37; + possibilities of development, 127; + two classes of, 71, 73. + + Germinal continuity, 39. + + Germinal variation and the origin of new characters: 138; + cases analyzed, 141; + sexual reproduction in relation to, 138. + + Germ-plasm and bad environment, 194. + + Gifted persons, 212. + + Glaucoma, 113. + + Goddard, 118, 171, 174, 188, 235, 238, 245, 250, 256, 257, 264, 269, 326. + + Gonads, transplantation of, 134. + + Gonorrhoea: seriousness of, 182; + prevalence, 183. + + Gorst, 234. + + Gout, 153, 234. + + Guinea-pigs: alcoholism in, 175; + Mendelism in, 75. + + Guyer, 59. + + + Habit, 219. + + Habits, modification of in lower animals, 204. + + Hair-color, 105. + + Hair shape, 105. + + Hamburger, 150. + + Handwriting, 120. + + Haploid number of chromosomes, 41, 43. + + Harelip, 178. + + Hart, 266, 319, 326. + + Healy, 256, 274, 278. + + Hearing, hardness of, 118. + + Heart disease, 154. + + Hegner, 27, 38. + + Heliotropism, 198. + + Helm, 109, 111. + + Hemophilia, 64. + + Hereditary character defined, 12. + + Hereditary mingling, mosaic rather than blend, 13. + + Hereditary transmission, laws of, 68. + + Heredity: and environment, 295; + dual ancestry in, 6; + defined, 1; + false, 163; + human, uncertainty of records, 98; + in protozoa, 22, 23; + in insanity, importance of, 261; + in sexually reproducing forms, 7; + in unicellular forms, 22, 23; + methods of study, 14, 15; + new discoveries in, 67; + not a blend, 13; + race betterment through, 289. + + Heritage, blood, 1. + + Heron, 307. + + Heterozygote: 80; + detection of, 80. + + Hill-folk, the, 271. + + Hodge, 175. + + Holmes, 203. + + Home, for children, 338. + + Homozygote, 80. + + Huntington's chorea, 113-115, 243, 325. + + Huxley, 195, 205. + + Hybrids: 52; + whites and negroes, 297, 298. + + Hypotrichosis, 113. + + Hysteria, 117. + + + Ichthyosis, 65. + + Ideals, importance of establishing in children, 223. + + Idiots, 244. + + Imbeciles, 244. + + Immigrants, duty of excluding undesirable, 335. + + Immigration: and mental unsoundness, 281, 282; + bearing on crime and delinquency, 280; + bearing on venereal diseases, 282; + importance of restricting, 283, 335. + + Immortality: of protozoa, 23; + of the race, 3. + + Immunity, artificial, not inherited, 155. + + Inbreeding, in defectives, 271. + + Individual, and race, 3. + + Inebriate women, offspring of, 168. + + Inebriety, constitutional, 180. + + Infant mortality, 149. + + Infection, prenatal, 147. + + Inheritance: and disease, 146; + blended, 87, 93; + of tendencies, 107. + + Inhibitions, 216. + + Inhibitors, 79. + + Insane, increase in numbers of, 233, 234. + + Insanity: 117; + certain forms recessive, 243; + eugenical significance of, 234, 235, 240; + importance of early diagnosis, 259; + some forms not hereditary, 260; + types of, 239; + prevalence in the United States, 228, 229. + + Insect colors, effect of temperature, 129. + + Instincts: 203; + adjustable, 203; + not inherited acquirements, 144; + origin of intelligent behavior from, 203, 204. + + Institutional figures misleading, 266. + + Intelligence, 205, 206. + + Intelligent behavior, opening up possibilities of, 204. + + Ireland, 171. + + Irritability, characteristics of living protoplasm, 197. + + + Jennings, 203, 204. + + Johnson, 305. + + Johnstone, 245, 319, 320, 321. + + Jolly, 243. + + Jordan, 4, 299. + + Jukes, 270. + + + Kallikak family, 269, 270. + + Kellicott, 314, 316. + + Kellogg, 299. + + Keratosis, 113. + + Kidney diseases, 154. + + Kirby, 187, 324. + + Knox, 256. + + Kraeplin, 242. + + + Laitinen, 174. + + Language, as mental aid, 206, 207. + + Lapsed intelligence, theory of, 145. + + Larval stages, susceptibility of, 128. + + Laws, sterilization, 323, 327, 329. + + Lead-poisoning: 163; + experiments on rabbits, 163. + + Lederbaur, 131. + + Legal restraint of defectives limited, 331. + + Lens: displaced, 113; + cataract, 112. + + Leprosy, 152. + + Leptinotarsa, production of variations in, 125. + + Linden, Countess von, 129. + + Linin, 31. + + Little's disease, 215. + + Locomotor ataxia, 187. + + Loeb, 62, 203. + + Longevity, 120. + + Lord Morton's mare, 10. + + Lorenz, 113, 114, 115. + + Low birth-rate, 308. + + Lowell, Judge John, 312. + + Luetin test, 188. + + Lunborg, 243. + + + MacDougal, 125. + + Margaret, Mother of Criminals, 270. + + Marriage: barriers to, 331; + inter-racial, 296; + medical inspection before, 191. + + Mast, 203. + + Maternal impressions, 159-160. + + Maturation: 39, 41, 43, 44; + parallel between egg and sperm-cell, 44, 46. + + Mechanical skill, 120. + + Mechanism of heredity, 22, 25, 26, 28, 29, 30, 35, 37, 40-54, 94, 95. + + Melancholia and crime, 279. + + Memory: 120, 204; + not a complete test of normality, 268, 269. + + Mendel: 68; + work on peas, 82. + + Mendelian factors and chromosomes: 93; + inheritance and man, 97; + principles, rediscovery of, 68; + ratio, cause of, 71. + + Mendelism, 67, 69. + + Mental and nervous defects, 228. + + Mental defective: defined, 255; + disproportionate increase in, 232; + numbers married, 231, 232; + inefficiency of marriage laws concerning, 315. + + Mental deficiency: not always inherited, 248; + tests for, 254, 255. + + Mental organization of lower vertebrates, 205. + + Mental process as neural process, 195. + + Mental unsoundness, 196. + + Mentality, inheritance of, 19. + + Mentally disordered, cost of caring for, 257, 258. + + Mercier, 279. + + Merriere's disease, 117. + + Metazoa, 28. + + Metz, 41. + + Mice, 78. + + Michigan, state report on mentally defective, 234. + + Migraine, 101. + + Mind, relation to brain, 195. + + Mitosis: 32, 33; + meaning of, 34, 37. + + Mjöen, 171. + + Modifiability of behavior, 200, 204, 205, 207, 217, 219, 224, 225, 337. + + Mongolians, 248. + + Moral responsibility, 227. + + Morgan, C. Lloyd, 146, 211. + + Morgan, T. H., 59, 66. + + Moron, 244, 268. + + Morons and crime, 268. + + Mosaic, heredity a, 13. + + Motherhood, safeguarding, 165. + + Motive, training in, 220. + + Mott, 150. + + Mulattoes, 92. + + Multiple sclerosis, 64, 117. + + Muscular atrophy: 113; + Gower's, 65. + + Musical ability, 120. + + Mutations: artificial production of, 125; + germinal, 125. + + Mutilations, non-inheritance of, 134. + + Myopia, 64. + + + Naegeli, 131. + + Nam family, 271. + + Natural selection partly done away with in human society, 292. + + Near-sightedness, 64. + + Nervous and mental diseases, 153. + + Nervous organization, inheritable, 242. + + Nervous response, in lower organisms, 196. + + Nervous system: mainly inherited, 210, 216; + establishment of pathways in, 210; + maladjustments of, 231; + special developments in man, 213, 214, 215; + units of, 208. + + Nervous systems of anthropoids, 214. + + Neural pathways, not all established at birth, 217. + + Neuritis optica, 65. + + Neurons, 208. + + Neuron theory, 208. + + Neuropathic constitution, expression of, 241. + + Neuropathic defects, carriers of, 253. + + Neuter insects, heredity in, 136, 137. + + New characters, origin of, 138. + + Newman, 56. + + Nicloux, 172. + + Night-blindness, 65. + + Nilsson-Ehle, 88, 89. + + Noguchi, 186. + + Nucleolus, 31. + + Nucleus, structure of, 31. + + Nulliplex character, 80, 100. + + + Obesity, 120, 154. + + Offspring: from one parent only, 5; + different from either parent, 12. + + Oöcyte, primary, secondary, 44. + + Oögenesis, 44. + + Oögonia, 44. + + Optic nerve, atrophy of, 64. + + Organs, formation of, 36. + + Origin of sex cells, 12, 36. + + Ovaries, transplantation of, 134. + + Ovum, 26, 40. + + + Paralysis, general, 186. + + Paranoia, 279. + + Parent-body and germ distinct, 12. + + Parenthood, cultivation of wholesome sentiment toward, 336. + + Paresis: 186; + and crime, 279. + + Parthenogenesis, 6. + + Patterson, 56. + + Paul, 163. + + Pearson, 150, 151, 179, 296, 307. + + Peas, 68, 82. + + Performance tests, 256. + + Peron, 133. + + Personality determined by heredity, 2, 195. + + Peterson, 242. + + Phenotype, 86. + + Phillips, 134, 135. + + Phototropism, 198. + + Pinard, 165. + + Pineys, the, 271. + + Plato, 290. + + Poellman, 271. + + Polar bodies, 44, 45. + + Polydactyly, 108. + + Potato-beetle, production of variations in, 125. + + Potts, 292. + + Predisposition to disease, 148. + + Pregnancy, neglect of mothers during, 165. + + Prenatal care: 336; + infection, 147; + influence, 11, 159, 162. + + Prenuptial medical inspection desirable, 336. + + Presence and absence theory: 78; + formulæ for man, 99. + + Primrose, experiments on, 125. + + Principles, Mendelian, 68. + + Prisoners, many mentally subnormal, 266. + + Pronucleus, 47. + + Protective coloration, not of somatic origin, 135, 136. + + Protoplasm, germinal, 39. + + Psychical development, 196, 203, 205, 206, 213, 215. + + Pyramidal tracts, 214. + + + Quagga hybrid, 10. + + + Race amalgamation: 297, 298; + deterioration, in a selected population, 303. + + Racial degeneracy, not curable by improved environment alone, 294. + + Ratio: the 1:2:1, 73; + the 3:1, 77; + the 9:3:3:1, 85; + the 27:9:9:9:3:3:3:1, 87; + the 15:1, 88; + the 63:1, 90. + + Rational behavior, 205, 206. + + Reason, 206. + + Recessiveness: 74; + in man, 115. + + Records of family traits desirable, 337. + + Reduction division, 41, 42. + + Reflexes, 203. + + Regression, law of, 17. + + Renault, 172. + + Rentoul, 232. + + Reproduction: asexual, 6, 26; + sexual, 26; + sexual and variation, 139. + + Reproductive cells, 27, 28, 29. + + Responsibility for conduct, 195. + + Rest, importance of, in pregnancy, 165. + + Reversion: 7, 8; + and atavism, 8; + in guinea-chicken hybrids, 8. + + Rheotropism, 198. + + Rheumatism, 154. + + Ritter, 143. + + Rogers, 246, 272. + + Romanes, 133. + + Rosanoff, 243. + + Rossolimo, 256. + + Rudin, 243. + + + Salpingectomy, 322. + + Sanford, 205. + + St. Vitus' dance, 117. + + Schulze, 24. + + Schuster, 296. + + Sclerosis, multiple, 64, 117. + + Segregation: in dihybrids, 84; + Mendelian, 69, 70, 75; + of defectives, 318. + + Seguin, 256. + + Self-control, importance of, 221, 267, 268, 284, 286, 287. + + Sex: and chromosomes, 59; + and heredity, 53; + cells of Volvox, 25; + chromosome, 57, 58; + determination, 55; + differentiation and X-element, 60; + evolution of, 25-30; + hygiene, question of school instruction in, 285; + in certain insects, 56; + linked characters, 60, 65; + not a necessary factor in heredity, 6; + problem, knowledge alone not sufficient, 286. + + Sexual vice, 284. + + Sharp, 322. + + Simplex character, 80, 99. + + Skill, non-transference in brain, 212, 213. + + Skin, color of, 92. + + Smallpox, 152. + + Social maladies, prevention of, 293. + + Softening of the brain, 186. + + Soma, 28. + + Spermatid, 43. + + Spermatocyte, primary, secondary, 43. + + Spermatogenesis, 42. + + Spermatogonium, 43. + + Spermatazoon: 26, 40; + a cell, 22; + formation of, 43; + structure of, 43. + + Spindle, in cell-division, 32. + + Spottedness of hair-coat, 113. + + Sprague, 281, 305. + + Starfish, training a, 204. + + Statistical methods, 15. + + Statistics, trustworthy needed, 334. + + Stature, inheritance of, 17. + + Stereotropism, 198. + + Sterility, 182. + + Sterilization: 322; + in epilepsy, 326; + laws, 323; + laws, on trial, 329; + laws, states having, 327. + + Stevens, 41. + + Stockard, 174-178. + + Strength, muscular, 120. + + Stripes, reversionary, 8. + + Stutzman, 305. + + Sullivan, 168. + + Superior strains, conservation of, 157. + + Synapse, 210. + + Synapsis, 41, 42. + + Syndactyly, 65, 108, 111. + + Syphilis: 184-190; + and prostitutes, 185; + cerebro-spinal form, 189-190; + prenuptial inspection for, 190-192; + prevalence, 186; + stages of, 185; + tests for, 188. + + Syphilitics: children of, 187, 188; + married, 190. + + + Tabes dorsalis, 186. + + Taints, 101. + + Talent, inheritance of, 212. + + Taylor, 297. + + Telegony, alleged cases of, 10. + + Temperament, inheritance of, 19. + + Thermotropism, 198. + + Thigmotropism, 198. + + Third generation, segregation in, 69. + + Thomsen's disease, 118. + + Thomson, 55. + + Thorndike, 296. + + Tower, 125. + + Training of children: and heredity, 218; + faults in, 221, 222. + + Transmission, not necessarily inheritance, 163. + + Tredgold, 170. + + Treponema pallidum, 185. + + Tribe of Ishmael, 271. + + Tropic responses: often purposeful, 201; + uncertainties in, 202. + + Tropisms: 197; + complications in, 200; + in plants and animals, 198; + relations to reflex actions and instincts, 203. + + Tschermak, 68. + + Tuberculosis, 118, 148-160, 162. + + Twins: identical, 55; + sex of, 55. + + Typhoid, 152. + + + Unemployed, frequently morons, 280. + + Unfit, elimination of, urgent, 313. + + Unit-character: 12; + inheritance of, 13. + + Unicellular organisms: 21; + inheritance in, 22, 23. + + Use and disuse, 122. + + + Van Ingen, 167. + + Vasectomy, 322. + + Venereal disease, 182. + + Virchow, 147. + + Voison, 133. + + Volitions as tropisms, 199. + + Volvox, 25, 26, 27. + + + War, eugenical effects of, 299. + + Wasserman, provocative, 189. + + Wasserman test, 188, 189. + + Webbed digits, 65. + + Weeks, 251, 252, 253, 291. + + West, 167. + + Wheat, 75, 81, 88. + + Whetham, 314, 316. + + Whitman, 145. + + Wilmarth, 243, 245, 274, 291. + + Wilson, 59, 62, 94, 95. + + Woods, 296. + + + X-element, 57, 58. + + + Zebra hybrids, 10. + + Zeros, the, 271. + + Zygote: 26, 27; + chromosomes of, 40. + + + + +FOOTNOTES: + +[1] The reader desiring more detailed information will find fuller +discussions in the following: + +Wilson, E. B.: _Recent Researches on the Determination and Heredity of +Sex_. Science, January 8, 1909. + +Wilson, E. B.: _The Chromosomes in Relation to the Determination of Sex_. +Science Progress, April, 1910. + +Guyer, M. F.: _Recent Progress in Some Lines of Cytology_. Transactions of +the American Microscopical Society, April, 1911. + +Morgan, T. H.: _Heredity and Sex_. Columbia University Press, 1913. + +[2] A translation of Mendel's original papers will be found in _Mendel's +Principles of Heredity_, by W. Bateson. + +[3] _Heredity of Skin Color in Negro and White Crosses_: Publication No. +188, of the _Carnegie Institution of Washington_. + +[4] Whitman, C. O.: _Animal Behavior, Biological Lectures_, Marine +Biological Laboratory, 1898. + +[5] _The Fight Against Tuberculosis and the Death Rate from Phthisis_, +London, Dulau & Co., 1911. + +[6] Forel, August: _The Sexual Question_, p. 268. + +[7] Loc. cit. p. 251. + +[8] In this connection it is instructive to note from a Michigan state +report, just off the press, that, among 4,917 insane individuals +concerning whom satisfactory information was obtained, 65.4 per cent. "had +among their ancestors or family such hereditary influences as insanity, +apoplexy or paralysis, psychopathic abnormalities or alcoholism." See +_Report of the Commission to Investigate the Extent of Feeble-mindedness, +Epilepsy, Insanity and Other Conditions of Mental Defectiveness in +Michigan_. Wynkoop Hollenbeck Crawford Co., State Printers, Lansing, +Michigan, 1915. + +[9] _Feeble-mindedness; Its Causes and Consequences_, by Henry H. Goddard, +The Macmillan Company, 1914. + +[10] _The Binet-Simon Measuring Scale for Intelligence_, by Henry H. +Goddard, 1911. The Training School, Vineland, N. J. Price 15 cents. + +[11] "Tests for Mental Defects," by Howard A. Knox, _Journal of Heredity_, +March, 1914. See also Knox: _Journal of the American Medical Association_, +1914. + +[12] _The Individual Delinquent_, by William Healy, M. D. Little, Brown & +Co., Boston. + +[13] _The Individual Delinquent_, by William Healy, M. D. Little, Brown & +Co., Boston. + +[14] The Psycopathic Laboratory in connection with the Juvenile Court of +Chicago. + +[15] See "The Foreign Born in the United States." _The National Geographic +Magazine_, September, 1914. + +[16] See First Report of the Committee of the Eugenic Section of the +American Breeders' Association, "On Immigration", _American Breeders' +Magazine_, Vol. III, No. 4, 1912. Also Second Report of same, _The Journal +of Heredity_, July, 1914. + +[17] "The Negro and His Health Problems," _Medical Record_, September 12, +1912. + +[18] See D. S. Jordan, _The Human Harvest_, or V. L. Kellogg, _Eugenics +and Militarism_. + +[19] For arguments indicating the superior eugenical fitness of college +graduates see "Wellesley's Birth-Rate," by Roswell H. Johnson and Bertha +Stutzman, _The Journal of Heredity_, June, 1915. See also, "Education and +Race Suicide," by Robert J. Sprague, _ibid._, April, 1915. + +[20] Since the present manuscript went to press an excellent government +report (_Insane and Feeble-Minded in Institutions in 1910_, Department of +Commerce, Bureau of the Census, 1914, Washington, D. C.) has appeared. In +it one finds the estimate that not over one-tenth of our feeble-minded are +being cared for in special institutions. + +[21] For summaries of existing sterilization laws and statements of the +issues involved see (1) _The Legal, Legislative, and Administrative +Aspects of Sterilisation_, Bulletin 10B, February 3, 1914, Eugenics Record +Office, Cold Spring Harbor, N. Y.; (2) _Sterilisation of Criminals_, +Report of Committee H of the American Institute of Criminal Law and +Criminology, Bulletin No. XV, September, 1914. + + + + +Transcriber's Notes: + +Passages in italics are indicated by _italics_. + +Passages in bold are indicated by =bold=. + +Superscripted characters are indicated by ^{superscript}. + +Subscripted characters are indicated by _{subscript}. + +The original text contains a few letters with diacritical marks that are +not represented in this text version. + +The original text contains male and female symbols. 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