258 /. /. Christian 



responsible for the regulation of ACTH and TSH secretion (Laqueur et al., 

 1955; Greer, 1957; D'Angelo and Traum, 1958). In addition there are 

 neurogenic factors involved in ovulation which consist of adrenergic and 

 neurogenic components (Markee et al., 1952; Everett and Sawyer, 1953; 

 Nalbandov et al, 1955) and probably also in the milk let-down reflex 

 (Grosvenor and Turner, 1959a). Finally, as in other endocrine regulating 

 mechanisms, the level of circulating sex steroids seems to exert a regulating 

 effect on the release of the particular gonadotropin responsible for their 

 release (Selye, 1947; Sturgis, 1950; Byrnes and Shipley, 1950; Byrnes and 

 Meyer, 1951). Whether these steroids exert their effects on the hypothala- 

 mus or on the anterior pituitary itself is not known. In any event, with- 

 drawal of stimulation by the gonadotropins leads to atrophy of the gonads 

 and decline in the production of their respective steroids (Burrows, 1949). 

 The decline in the production of sex steroids is in turn followed by atrophy 

 of those accessory organs and secondary sex characteristics which depend 

 on the sex steroids for their activity and maintenance (Burrows, 1949). 



If a male animal is subjected to adverse circumstances for any length of 

 time, there is a marked decrease in spermatogenesis and a reduction in the 

 secretion of androgens as indicated by atrophy of the seminal vesicles, 

 prostate, and preputial glands (Christian, 1956; 1959b; Christian and 

 LeMunyan, 1958) . These changes may all be followed by the changes in 

 their weights, but weight changes should be assessed by appropriately 

 selected histologic examination of the organs. In young animals there may 

 be either a delay in the onset of puberty or a total suppression of the de- 

 velopment of puberty, as indicated by the development of spermatogenesis 

 and the sex accessories or, in the mouse, by a failure of the X-zone to 

 involute at the usual time (Christian, 1956, 1959a, b). If mature animals 

 are subjected to severe stimuli, there may be easily discernible degenerative 

 changes in the tubules of the testes and cells of the spermatogenic series. 



Changes in the female reproductive function are less easily seen than in 

 the male, as organ weights do not provide as useful a criterion of changes. 

 Nevertheless, changes in estrus are usually evident and can be detected by 

 vaginal perforation or by vaginal smears. Depending on the severity of the 

 inducing stimulus, estrus may be prolonged or totally suppressed. Uterine 

 weight may reflect reproductive suppression, and would be especially 

 valuable in demonstrating a delay in the onset of puberty in female animals. 

 In some circumstances there may be a total suppression of reproductive 

 activity. It is in actual reproductive performance that the effects of sup- 

 pression of the reproductive endocrine system becomes most evident. De- 

 pending on the severity of the stimulus and on the species involved, there 

 may be a complete failure to become pregnant, which may be due to a 

 failure of ovulation or a failure of the shed ova to implant in the uterus or, 



