NATURAL IMMUNITY 57 



acquired by an individual can be wholly or in part transmitted to 

 the offspring is an open question at present in the same state of 

 unclearness as are other questions relating to the transmissibility of 

 acquired characteristics. However this may be, there are a number 

 of facts available which indicate that inheritance plays an important 

 part. It is apparent in the case of many diseases afflicting human 

 beings that infection takes a milder course in those races among 

 which it has long been endemic whereas the same disease, suddenly 

 introduced among a new people, is relatively more severe and spreads 

 more rapidly. This seems to be the case with yellow fever and tuber- 

 culosis, and in measles and small-pox, too, the principle seems 

 to hold good. Syphilis when first described authentically as epi- 

 demically sweeping through Europe toward the close of the 15th 

 century appears to have been a far more acute and violent disease 

 than it is among us to-day. It may well be that this depends upon 

 a gradual elimination (elimination in this case, especially as far as 

 reproduction is concerned) of those individuals that are fortuitously 

 more susceptible and, by natural selection, a higher racial resistance 

 is gradually developed. Whether or not direct inheritance of the 

 individually acquired immunity can be considered at all as a con- 

 tributing factor is difficult to decide. That immunity can be trans- 

 mitted from mother to offspring was observed by Chauveau 7 as 

 early as 1888. Lambs thrown by anthrax-immune ewes possessed a 

 higher resistance against this infection than did the lambs of normal 

 ewes. The extensive experiments of Ehrlich, 8 carried out chiefly 

 upon mice with the vegetable poisons ricin and abrin, showed that in 

 these cases immunity may be transmitted from mother to offspring, 

 but depends upon a passive transfer of the specific antitoxins both 

 by the blood and the milk of the mother. The sperm of the father 

 did not seem to have anything to do with inherited resistance, since 

 no immunity followed in the offspring when immunized males were 

 paired with normal females. From the complete absence of im- 

 munity in the second generation (grandchildren) of the immunized 

 female, and from the short duration (2 to 3 months) of its per- 

 sistence, he concluded that the ovum itself had no influence, but that 

 the entire phenomenon was attributable to a passive transference of 

 antitoxins from mother to child during gestation and lactation. He 

 interpreted, in the same sense, Chauveau's anthrax experiments, and 

 similar experiments of Thomas 9 and Kitasato 10 with symptomatic 

 anthrax, suggesting that, here also, a transept of antibodies from 

 mother to offspring had taken place. The experiments of Ehrlich 

 permit of no doubt as to the validity of his conclusions. However, 



7 Chauveau. Ann. Pasteur, 1888. 



8 Ehrlich. Zeitschr. f. Hyg., 1892, Vol. 12. 



9 Thomas. Compt. rend, de I'acad. des sc., Vol. 94, cited by Ehrlich, loc. cit. 



10 Kitasato. Cited by Ehrlich, loc. cit. 



