Being Well Born Part 9

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 const.i.tutional 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 const.i.tutionally 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 p.r.o.nounced 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 a.s.sociated typical disease generation after generation as long as the children follow the calling of their parents. The common misconception that deformities or postures a.s.sociated 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 s.e.x-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 const.i.tutional 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-gla.s.ses but not with eye-gla.s.ses 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 a.s.sociation 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 cla.s.s 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 const.i.tutional resistance. Some are predisposed to be non-resistant and hence succ.u.mb.

The work of Karl Pearson[5] and other recent researches forcibly indicate that hereditary const.i.tutional 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 const.i.tutional 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 p.r.o.ne 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 a.s.sociation of the two s.e.xes in special schools and inst.i.tutions 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.--=s.p.a.ce 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 acc.u.mulation 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 t.i.ttle 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 inst.i.tutions 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 a.n.a.lysis 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 mult.i.tude 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 a.s.sociated 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 ill.u.s.tration of how certain c.u.mulative 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 cla.s.s of cases. The sixth cla.s.s 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.