VESICLE GROWTH AND IMPLANTATION 125 



young suckling suggests that definite quantities of necessary 

 substances are withdrawn from the uterus as the result of 

 mammary gland activity. 



Teel (1926) found that the daily injection of a NaOH 

 extract of the anterior hypophysis delayed implantation in 

 rats when injections were begun on the day of mating. 

 Injections on days 1 to 6 caused delayed implantation with 

 parturition occurring in normal fashion but several days 



4 5 6 7 8 9 10 11 

 NUMBER OF YOUNG SUCKLED 



12 13 14 



Fig. 33. Showing the relationship between the degree of delay of pregnancy 

 and the number of suckling young. (From the Anatomical Record.) 



after term; injections on days 1 to 12 also caused delayed 

 implantation but a definite interference in the birth mecha- 

 nism so that only one of a series of females produced normal 

 hving young in a late parturition; injections over a longer 

 period resulted not only in delayed implantation but also 

 in stillbirths 5 to 7 days after normal term. The impairment 

 of the birth mechanism can therefore be avoided by early 

 injection and is presumably a phenomenon distinct from 

 that of delayed implantation. The inhibition of parturition 

 can be caused not only by alkaline pituitary extracts (Evans 

 and Simpson, 19296; Snyder, 1934) but also by corpus 



