PROBLEMS OF HEKEDITY — APEET. 403 



is, then, the result of a gross, anatomical malformation. All family 

 diseases thus have for their origin an hereditary malformation, though 

 often it is not so easily revealed and is discovered only by micro- 

 scopically examining the inmost of the tissues. But in either case 

 it is a question of the transmission of a special defect, and there is 

 nothing wonderful in the fact that it is transmitted according to the 

 same laAvs as physical peculiarities. 



There are other diseases inherited in an entirely different way. I 

 will commence with microbe diseases. In these diseases the aflfliction 

 which has stricken either the father or mother, or both, is transmitted 

 to the child through an entirely different process. It is really con- 

 tagion. In certain diseases the mother, carrying some deadly germ 

 (which she may or may not have received from the father of the 

 child), contaminates her child before its birth. That is most usually 

 the case on the average. I do not insist upon it. These cases are 

 known as '' heredity contagion.*' Oftener still, the child is born safe 

 and sound, and it is only during the course of the first months or the 

 first few years that it is contaminated by one or the other of its 

 parents. It is apparent that it does not seem to be more than pure 

 heredity. Tuberculosis is like that. You know how tuberculosis 

 appears to be inherited. In your Eed Cross dispensaries you find that 

 entire families are now and then decimated by tuberculosis; the 

 father or mother, or both, are ill with pulmonary tuberculosis; the 

 new-born children die of tuberculosis meningitis ; if they escape that, 

 they show signs toward the fifth, tenth, or twelfth year of " King's 

 evil," or tuberculosis of the glands ; of Pott's disease, osteotic tubercu- 

 losis of the vertebrae; of coxalgia, arthritic tuberculosis of the hip, 

 etc.; and at last, during their youth, they succumb to pulmonary 

 tuberculosis. Such facts are unfortunately reported each day, and 

 we understand how belief in the inheritance of tuberculosis has per- 

 meated the mind. In reality heredity here plays only a restricted 

 role, as I will show you. The great secret in its spread is contagion. 

 A proof of it is that the disease is communicated just as easily to 

 persons who live with a tuberculosis family, though they have no re- 

 lation to it. Sometimes it is neither the father nor the mother who 

 is the source of disease which has stricken their children successively, 

 but it may be a governess or a domestic affected with tuberculosis. I 

 once knew of a family free from tuberculosis where a young widow 

 returned to her father's home after having been married a year to a 

 tuberculosis husband, from whom she had caught the germ of the 

 disease; she communicated it to her two young brothers, who died, 

 and then to her mother, who at present alone survives her three chil- 

 dren. One could relate innumerable instances of this kind. I do not 

 wish to say that heredity has nothing to do with tuberculosis. It in- 

 fluences more or less a resistance to the disease. In some families we 



