THE PITUITARY BODY 



The oestrous cycles of the rat with intact ovaries may recur 

 normally. More often they become lengthened or disappear; 

 in the latter event, a period of prolonged dioestrus is later 

 succeeded by a period of prolonged oestrus. The following 

 are some of the ovarian changes which have been described: 

 growth of follicles, atresia of follicles, and formation of cor- 

 pora lutea or of corpus luteum cysts (4, 5, 7, 9, 10, 12, 14). 



7. 9 ^sT- In this type of experiment is found the best agree- 

 ment among different investigators as to the effects on the 

 female genital tract (i, 2, 3, 5, 7, 12, 15). Shortly after the 

 animals have been united (or after the castration of the male 

 if the rats were made parabiotic before gonadectomy) oestrus 

 appears in the female rat and persists, except for an occasion- 

 al short dioestrous stage, for weeks or months.^" The impor- 

 tant change in the ovaries is a marked growth of follicles 

 with the formation of follicular cysts. Atresia of follicles and 

 corpora lutea atretica have also been found in the ovaries of 

 the female parabiont. 



Experiments still more complex have also been undertaken. 

 In the experiments 9 c?", observations have been made either 

 after making the testes cryptorchid or after irradiating (X- 

 rays) the testes (Martins, 1930; Witschi, Levine, and Hill, 

 1932). Either treatment of the testes caused degeneration of 

 the germinal epithehum without appearing to impair the se- 

 cretory activity of the interstitial cells. The genital tract of 

 the female responded as in Experiment 7 ( 9 isf ); the response, 

 however, was less pronounced. In the experiment 9 9 , one 

 of the parabionts was subjected to X-ray irradiation of the 

 ovaries so that the oestrus cycles, if present, were abnormal; 

 the germ cells were destroyed by the irradiation. In the nor- 

 mal parabiont, prolonged oestrus and the formation of cystic 

 follicles in the ovary were observed — resembling the effects 



3° In the early period preceding oestrus, the ovaries may contain numerous cor- 

 porea lutea; the rat is then in dioestrus.'' 



[146] 



