Immunity acquired ~by natural means 449 



Dzierzgowsky's experiment supplies no evidence against the passage 

 of antitoxin through the placenta. 



In order to prove that the immunity against toxins may really 

 be acquired by the ovum, Dzierzgowsky 1 carried out a series of 

 experiments with the eggs of fowls immunised against diphtheria 

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

 F. Klemperer, contained antitoxin ; and this antitoxin passed into 

 the blood of the hatched chickens. These facts, though in themselves 

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

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

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

 known facts. Thus, the frequent presence of diphtheria antitoxin 

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

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

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

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

 be so fully retained during the nine months of pregnancy. 



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

 transmitted by the mother to her progeny Ehrlich invokes his 

 beautiful discovery of the immunity conferred by the maternal milk. 

 A vaccinated female is capable of communicating to her young 

 a portion of the antibodies manufactured in her organism, not only 

 by 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 xn). 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 offspring 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. tici. biol., St Tetersbourg, 1901, t. Viil, p. 421. 



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