Being Well-Born: An Introduction to Eugenics

by Michael F. Guyer

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.