174 THE ACTION OF THE LIVING CELL 



month, however, distinct differences in egg produc- 

 tivity became apparent in the various flocks. While 

 the control birds reached and maintained an egg pro- 

 duction of about 30%, the immunized birds showed 

 a marked increase in the rate of egg production, attain- 

 ing 60% at the end of the seventh month ; whereas the 

 members of flock B which had received the cytost in- 

 jections every week throughout the period of observa- 

 tion, after the fourth month suffered a rapid decline 

 in egg production, which fell almost to zero after the 

 seventh month. (Turck, 1923.) The results of these 

 experiments are represented graphically in figure 13. 



These experiments with chickens recall those made 

 with the cats, wherein it was found that although a few 

 doses of cytost appeared to be distinctly beneficial to 

 the animals, a long continued series of injections ulti- 

 mately led to retrogression and pathological changes. 

 It may reasonably be assumed that the diminished egg 

 production observed in flock B is due to the produc- 

 tion of circulatory disturbances and consequent tis- 

 sue damage similar to that found in cats when treated 

 in the same manner. 



When attempts are made to breed cats under labora- 

 tory conditions it has been frequently observed that 

 the kittens born are sickly and survive but a short time. 

 Further, as we have shown previously (page 87), 

 when apparently healthy cats are placed in cages con- 

 taminated with cytost, the animals rapidly develop 

 respiratory disturbances, involvement of the lungs, 

 and frequently pneumonia. Hence when one allows 

 pregnant cats to give birth to kittens in cages con- 

 taminated with cytost, or places the newly born kit- 

 tens in such cages, the young animals are subjected to 



