GONADOTROPIC SUBSTANCES 



color, and there appeared uterine bleeding from a "resting" 

 ("interval") mucous membrane, which might persist for days 

 if injections of prolan were continued. The most striking 

 ovarian changes in immature monkeys consisted of atresia of 

 larger foUicles with luteinization of the theca interna; cor- 

 pora lutea atretica were thus formed. As a result of 

 changes in smaller follicles a different type of atretic corpus 

 luteum was produced. Extensive hyalinization of smaller fol- 

 licles was frequently observed. No follicular growth or effect 



Fig. 36. — The effect of prolan and of anterior-pituitary extract on the ovary of 

 the immature monkey {Macaca mulatta). From Engle (1933). Left: Ovary of a 

 monkey receiving prolan; there is extensive hyalinization of small follicles. Right: 

 Ovary of a monkey receiving anterior pituitary extract; there is marked stimulation 

 of follicle growth. 



on the sexual skin appeared. Bleeding from an "interval" 

 mucosa might also set in and persist during the period of in- 

 jection. Similar changes were produced in older monkeys. 

 Engle also was unable to cause ovulation in immature mon- 

 keys by injecting prolan intravenously (3,000-9,900 rat-units 

 in 4 days). The changes observed depended upon the age of 

 the monkey, but were essentially similar to those already de- 

 scribed. However, he brought about a more extensive forma- 

 tion of corpora lutea atretica by first injecting anterior-lobe 

 extract subcutaneously to produce a growth of follicles; he then 



[197] 



