NATURAL RESISTANCE 185 



decrease the tendency towards toxemia in the mother, 

 and hence the possibility of attendant damage to the 

 developing fetus, but, as shown in the experiments 

 with kittens in cytost-sprayed cages, the offspring will 

 be relatively more resistant to cytost than are the 

 young born of non-immunized mothers. That a course 

 of immunizing injections actually does decrease the 

 liability towards the toxemia of pregnancy follows 

 from the fact that the nausea and retching which fol- 

 low the intraperitoneal injection of small quantities 

 of cytost is not observed when a similar injection of 

 cytost is administered to pregnant female cats which 

 have been actively immunized by the procedure pre- 

 viously described. (Turck, 1921, 1923.) 



From a laboratory standpoint cats are not conven- 

 ient animals for investigations concerning breeding 

 activities, and it was exceptionally fortunate for the 

 writer that through the kindness of the late Dr. Edwin 

 J. Banzhof we were able to conduct such experiments 

 on a large number of guinea pigs used for breeding 

 purposes in the laboratories of the New York City 

 Department of Health. For a period of years it had 

 been observed by members of the Health Department 

 Laboratories that a large proportion of the breeding 

 stock died in pregnancy, and that the young, when 

 born, were often feeble and did not survive for long. 

 This situation occurred time and time again during 

 the winter months, although the animals were kept in 

 a warm, well-ventilated room. At first it was thought 

 that the unusually high mortality was due to some 

 infection, and attempts were made to combat the situ- 

 ation by sterilizing the cages and by transferring the 

 animals to other rooms. Such means, however, proved 



