Hcredil\- and 1\il)crciil()sis 



113 



the disease. Raymond Pearl adds that 

 "a tuherculous person, chosen at 

 random in the working population of 

 Baltimore, will have nearly six times 

 as many blood relatives tuberculous as 

 will a non-tuberculous person." 



Supi^lementinf^ these lines of investi- 

 gation, wliose extent and usefulness 

 has here hardly been hinted at. Dr. 

 Govaerts has made a more detailed 

 analysis of 214 families, representing 

 5,629 individuals, in which occurred 

 185 tuberculous matings and 29 non- 

 tuberculous matings. He calls "a tul)er- 

 culous mating one in which the father 

 or mother, one or both, are tuberculous 

 or whose fraternity and ancestry are 

 tuberculous. Non-tuberculous matings 

 are matings in which no member of the 

 family is tuberculous or lielongs to a 

 tuberculous stock." 



The individuals are classified in two 

 groups, "namely, close contact and non- 

 close contact with tuberculosis of the 

 lungs. Close contact means a close 

 contact with a case of tuberculosis of 

 the lungs during the whole or a part 

 of life ; non-close contact implies the 

 opposite." If infection is more impor- 

 tant than blood relationshij), then most 

 of the tuberculous individuals ought 

 to be discovered to have had close con- 

 tact, more or less prolonged, with some 

 diseased person. 



The op])Osite is the fact. The larger 

 number of the tuberculous ])ersons have 

 not been in close contact with a "case." 



On the other hand, when the material 

 is classified according to the amount of 

 tuberculosis in the ancestry, the fre- 

 quency of the disease among the chil- 

 dren is found to vary directly with its 

 frequency among their forebears. 



The unexpected result is developed 

 that the influence of the father, in 

 transmitting weakened resistance to the 

 disease, is greater than that of the 

 mother. "Wherever the paternal stock 

 alone is known to be tainted, more of 

 the children show active tuberculosis 

 than when the maternal alone is known 

 to be tainted." As the children are 

 much more closelv associated in dailv 



life with the mother than with the 

 father, and most of them have been 

 nourished by her milk in the first year 

 of life, this fact — if sul)stantiated — 

 tends still further to show the relatively 

 small importance of the mere matter 

 of contact or exposure. 



Dr. (jovaerts discusses somewhat 

 Aciguely the question whether the re- 

 sults of his studies indicate a sim])le 

 Mendelian form of inheritance. He 

 readies no conclusion, and his material 

 hardly lends itself to analysis on this 

 ])oint. 



( )utlining his own interpretation of 

 the results of his study. Dr. Govaerts 

 says : 



One cannot maintain that there can be 

 tuberculosis without infection, but various 

 considerations may still be urged to support 

 the view that different persons have the 

 power to resist the infection in different 

 degrees, and that in consumptive families a 

 lack of resisting power is transmitted from 

 gametes to children. The tubercle bacillus 

 is everywhere about us. Some people en- 

 tirely escape its attack, while in others the 

 disease may occur in such a slight form that 

 the person attacked recovers from it with- 

 out being aware that anything has been 

 wrong. 



Tuberculosis is not an inheritable charac- 

 ter in the sense in which eye color is in- 

 heritable. It belongs to a second kind of 

 heredity called indirect heredity. Infection 

 and immunity are causes, but they do not 

 exclude inheritance. Biologically speaking, 

 people inherit directly a constitutional make- 

 up, possibly functional, chemical, and struc- 

 tural, with a certain amount of power to 

 resist tuberculosis or other related diseases. 



From the social and eugenical point of 

 view it is very important that tuberculosis 

 is transmitted approximately in a Mendelian 

 sense. So it seems possible to establish some 

 principles based on the law of averages. 



From present knowledge no one is able 

 to give advice to normal (persons or one 

 apparently normal for a contemplated mar- 

 riage. Advice is possible only in extreme 

 cases and we need still more minute in- 

 vestigations and studies. Xevertheless, it 

 will be useful to dissuade marriage be- 

 tween two stocks in which the same de- 

 fect is apparent. In such stocks consan- 

 guineous marriages arc dangerous. A 

 tuberculous subject will find more advantage 

 for his progeny by marrying a person be- 

 longing to a resistant strain. Eugenical 

 marriages should be between normals and 

 those free from defects. 



Paul Popenoe. 



