NATURAL RESISTANCE 191 



Bearing this in mind, it seems likely that the in- 

 creased natural resistance of the young guinea pigs 

 discussed above must likewise be due to the passage 

 of the mothers' increased resistance to the offspring. 

 This conclusion does not controvert the generally ac- 

 cepted doctrine that acquired characters are non-in- 

 heritable, for it may be effectively explained on the 

 basis of the concept of anticytost. It will be recalled 

 that some evidence has been offered that the immuni- 

 zation procedure accomplishes its desired end by caus- 

 ing the elaboration of a specific anticytost. If the pla- 

 centa is permeable to anticytost, than the fetus may 

 acquire this substance by diffusion from the blood of 

 the mother. Consequently at birth the young animals 

 are endowed with a certain supply of anticytost which 

 offers them protection until such time as they become 

 able to develop anticytost of their own. 



Such a concept is in complete accord with the re- 

 sults of the experiments discussed above, and is in 

 agreement with the findings of Ehrlich (1891, 1892), 

 who found that when female mice were immunized 

 to the toxins ricin and abrin, their progeny possessed 

 a resistance to these substances which was greater than 

 that normally found in the offspring of non- 

 immunized mothers. 



Ehrlich further observed that the increased re- 

 sistance to ricin and abrin was transmitted to the off- 

 spring when only the mother was immunized to the 

 toxin, whereas immunization of the father alone did 

 not result in an increased resistance of the young to 

 these toxins. A similar finding is recorded by Behring 

 (1889) in the case of immunization to diphtheria 

 toxin. 



