392 THE POPULAR SCIENCE MONTHLY. 



sitic or suspected to be so, like tuberculosis and cancer, appear 

 more frequently in the same families. The last coincidence may 

 be explained by the fact that the system of nerves regulating nu- 

 trition may, when its activity is weak, diminish the resistance of 

 the organism and favor the action of morbid agents. 



The question of morbid heredity is still more complicated by 

 the established facts that in a large number of tainted families 

 there exist individuals wholly exempt, while the exceptional 

 character of their cases can not be interpreted by the uncertain- 

 ties of paternity ; and that a considerable number of affectioDS 

 usually regarded as hereditary or peculiar to the family may 

 appear in a family independently of all heredity. Many diseases 

 are known that merit the title of family disorders and attack 

 several children of a single generation without its being possible 

 to find anything like them in either the paternal or the maternal 

 line. The persistence of healthy individuals in an unhealthy fam- 

 ily may be explained by atavism ; but the appearance of a family 

 disease without any resemblance among the ascendants consti- 

 tutes an exception to the laws of normal heredity. 



We are justified in charging certain toxic or infectious agents 

 with being capable of determining, by the influence they exercise 

 upon progenitors, the same morbid predispositions as heredity. 

 Thus, we can attribute to chronic alcoholism, to saturnism, to 

 morphinism, and to other habits of intoxication of parents a con- 

 siderable number of nervous affections and psychopathies which 

 are developed in the children at different ages, and confer upon 

 them characters quite different from the characters of their par- 

 ents. Acute transitory intoxications may have the same effect ; 

 and drunkenness of parents at the moment of conception or dur- 

 ing gestation has been charged with producing imbecility, idiocy, 

 epilepsy, and other diseases in the children. 



The effect of intoxication by drugs may likewise be induced by 

 emotional intoxication. The acute or chronic emotions of the 

 mother during gestation may undoubtedly have a noxious influ- 

 ence upon the child and determine troubles of development in it, 

 which may be manifested by anomalies of forms or by functional 

 troubles revealing anomalies of structure. Bad food or defective 

 hygiene, acting directly upon the nutrition of the mother, may 

 have the same effects. All these conditions, finally, may be ac- 

 cumulated under certain circumstances. 



In short, the predisposition to disease may be hereditary or con- 

 genital. Hereditary transmission is, however, not inevitable, and 

 most frequently it is due to very diverse conditions in the nutri- 

 tion of the progenitors. Some authors have associated the idea 

 of degeneration with that of heredity, and designate a whole 

 category of disorders under the name of hereditary degenerations ; 



