Iletin and Reproduction 



245 



most ovulations are successfully suppressed by subcutaneous in- 

 jections of quantities of insulin which -certainly leave the birds 

 feeding and mating normally, and which do not affect the body 

 weight more adversely (average initial weight = 176g.) than 

 do some other tested tissue extracts which do not suppress 

 ovulation. This depression (12g.) is also not more than the 

 maximum normal seasonal variation. 



TABLE I. 



Ovulations suppressed in ring doves during one month by subcutaneous injec- 

 tions with one-sixth unit iletin twice daily. 



Bird No. 



Loss in weight 



(grams). 



Number of 

 Expected. 



ovulations. 

 Kealized. 



1 



11 



6 



0 



2 



13 



6 



0 



3 



4 



6 



2 



4 



1(3 



4 



0 



5 



14 



4 



2 



6 



14 



4 



0 



7 



13 





0 



8 



14 



t 



0 



9 



15 



2 



0 



10 



7 



2 



0 



Total or Average- 



12 



42 



4 



Table 1 indicates that not more , than one-tenth of the ex- 

 pected number of ovulations are realized under the dosage se- 

 lected. The indicated number of suppressed ovulations is, how- 

 ever, somewhat too high since only one of the 10 birds used 

 was given blank injections during the control period (upon 

 which the ovulation rate is calculated). Much earlier experience 

 with blank injections and with injections of other tissue ex- 

 tracts shows that this treatment alone appreciably reduces the 

 ovulation rate. It seems certain, however, that the ovulations 

 actually suppressed were equal to more than one-half the num- 

 ber indicated in the table. Only very tame doves were used in 

 this study. 



In addition to the data of the table it has been found that 

 this dosage usually does not prevent the ovulation of an egg 

 which is within 48 hours of ovulation at the time of beginning 

 the injections. Again, five birds killed or opened for inspec- 

 tion at three to twenty days after beginning injection showed 

 three cases of degenerating (larger) ova, and two cases in 

 which no ovum has been able to pass into the final stage of 



