NATURAL RESISTANCE 189 



During the course of the experiment both groups of 

 animals and their offspring were kept under identical 

 conditions in the laboratory and were given the same 



rations. 



Following the birth of the young, the following dif- 

 ferences were noted: The litters of the immunized 

 mothers were larger than those of the controls, and 

 the young were more active and took to the breast 

 more rapidly than did those of the non-immunized 

 mothers. In a few instances, some of the latter died 

 shortly after birth from what appeared to be acute 

 inanition. This difference in appetite became much 

 more marked a month after birth, when the animals 

 born of immunized mothers showed the voracious 

 appetite common to healthy young animals, while the 

 members of the control group showed much less inter- 

 est in food. 



The difference in food intake was shown by the fact 

 that one month after birth the average weight of the 

 young of the immunized mothers was 60 grams greater 

 than the average weight of the young born of the con- 

 trol group, whereas after the lapse of two months the 

 difference in weight averaged 80 grams. Again, a dis- 

 tinct difference was noticeable in the appearance of 

 the fur, that of the control group appearing rough, 

 while that of the members of the other group was 

 sleek and glossy, an indication of better health. Dur- 

 ing this period a distinct difference in natural re- 

 sistance was evidenced by the fact that several of the 

 young in the control group succumbed to respiratory 

 disturbances which caused their death, whereas none 

 of the animals born of the immunized mothers suf- 

 fered from this cause or from any other. In other 



