Immunity acquired by natural means 449 



>zierzgowsky's experiment supplies no evidence against the passage 

 antitoxin through the placenta. 



In order to prove that the immunity against toxins may really 



acquired by the ovum, Dzierzgowsky ^ carried out a series of 



[periments with the eggs of fowls immunised against diphtheria 



)xin. The yolk of the egg, in accordance with the discovery made by 



Klemperer, contained antitoxin ; and this antitoxin passed into 



le blood of the hatched chickens. These facts, thougli in themselves 



bry interesting, cannot be used to refute the view that antitoxins 



iss through the mammalian placenta. It is true that this view is 



perhaps not yet completely proved, but it accords well with all the 



^nown facts. Thus, the frequent presence of diphtheria antitoxin 



the blood of new-born infants is explained much better on the 



jsumption that it passes through the placenta than that it is due 



an immunisation of the ovum surrounded, in the Graafian follicle, 



^y antitoxic fluid. It is difficult to conceive how this immunity could 



so fully retained during the nine months of pregnancy. 



In support of his interpretation of the phenomenon of immunity [471] 



ransmitted by the mother to her progeny Ehrlich invokes his 



jautiful discovery of the immunity conferred by the maternal milk. 



vaccinated female is capable of communicating to her young 



portion of the antibodies manufactured in her organism, not only 



)y the blood channels, but also, in certain cases, by the milk with 



which she feeds her young. 



The transmission of antitoxins by milk has been demonstrated by 

 Ehrlich, and this has since been confirmed by many observers (see 

 Chapter xii). When Ehrlich found that the immunity of the progeny 

 is retained for a longer time than is that which is conferred by in- 

 jections of antitoxic serum, he conceived the idea of investigating 

 whether the cause of more prolonged retention did not reside in 

 the transmission of the maternal antitoxin by the milk. With the 

 object of verifying this he took, at the moment when they had given 

 birth to young, unvaccinated mice and mice that had been vaccinated 

 against various toxins (ricin, abrin, tetanotoxin). He so changed the 

 progeny that the vaccinated mothers nourished the young born of the 

 normal mice, whilst the normal mothers suckled the ofi*spring of the 

 vaccinated mice. The result of these ingenious and delicate experi- 

 ments fully confirmed his anticipations. The vaccinated mice trans- 

 mitted their immunity not only to the young ones to which they had 

 1 Arch. d. jSci. bioL, St Petersbourg, 1901, t. vill, p. 421. 



29 



