576 



PHYSIOLOGY OF GONADS 



Progesterone, in contrast with estrogen, 

 does not produce rapid growth of the vagi- 

 nal epithelium but at the same time it is 

 not without an effect. The vaginal epithe- 

 lium, weeks or months after castration, has 

 relatively few papillae projecting from its 

 basal border into the underlying stroma. 

 When progesterone is given, this condition 

 is changed but not in a spectacular way. 

 There is very slow growth without cornifica- 

 tion. The epithelium remains thin but the 

 papillae become more numerous. These are 

 mostly small epithelial buds which tend to 

 remain solid but may show enlargement of 

 the cells in their centers. 



When estrogen and progesterone are given 

 concurrently, the effects of estrogen on the 

 vaginal mucosa are modified. If an estrogen 

 treatment has continued for a sufficient time 

 to produce full cornification and then pro- 

 gesterone is added, the first indication of an 

 inhibition of estrogen is a decrease in mi- 

 totic activity. This is followed by a con- 

 tinuation of cornification and loss of cells 

 faster than they are replaced ; consequently, 

 most of the functionalis is lost and the epi- 

 thelium becomes thinner. There is also a 

 noticeable decrease in the intensity of corni- 

 fication, which in the monkey is never as 

 pronounced as in rodents, and under these 

 conditions is quite incomplete, each cell re- 

 taining a conspicuous nucleus. Partly corni- 

 fied cells may be present for several weeks 



.-•^ss;^ 



4* ' V ^ § 



Fig. 9.22. ^^•tgi^al epithelium of a pregnant mon- 

 key showing condition on the 154th day of gesta- 

 tion. (From Carnegie Institution, No. C713.) 



when both estrogen and progesterone are 

 given, but eventually they almost entirely 

 disappear and the epithelium attains a con- 

 dition resembling that of late pregnancy. 



The inhibitory effect of progesterone on 

 the action of estrogen is shown perhaps even 

 better when a castrated monkey having a 

 fully involuted reproductive tract is first 

 given progesterone for a few days and then 

 (>strogen is added to the treatment, or when 

 injections of the two hormones are started 

 at the same time. In such experiments es- 

 trogen has little effect on the vaginal mucosa 

 even in doses that would produce marked 

 cornification if given alone. These observa- 

 tions show that a fully cornified vaginal 

 epithelium cannot be produced or main- 

 tained by estrogen when an effective dosage 

 of progesterone is included in the treatment 

 (Hisaw, Greep and Fevold, 1937). 



Estrogens and progesterone are the domi- 

 nant hormones of gestation and their simul- 

 taneous action is reflected by the changes 

 in the vaginal epithelium. The fully corni- 

 fied vagina, present at the time of ovulation, 

 is gradually modified as pregnancy pro- 

 gresses into a condition strikingly like that 

 seen in experiments when estrogen and pro- 

 gesterone are given concurrently. In late 

 pregnancy the most striking feature of the 

 thin, uncornified epithelium is the presence 

 of numerous epithelial buds extending 

 deeply into the underlying stroma. They 

 may branch and rebranch and along their 

 course there is conspicuous enlargement of 

 the more centrally situated cells among 

 which cavities ai^pear, enlarge, and join 

 each other (Fig. 9.22). It seems quite prob- 

 able that this process may be of considerable 

 importance in increasing the diameter of 

 the vagina. 



VIII. Sexual Skin 



A so-called sexual skin is jiresent in most 

 catarrhine monkeys, is not found in platyr- 

 iliine monkeys, and among the anthropoids 

 occurs regularly only in the chimpanzee 

 I l^]ckstein and Zuckcrman, 1956). Changes 

 in the sexual skin during the menstrual cy- 

 cle have been observed most extensively in 

 the monkey (Macaca), the baboon (Papio), 

 and the chimpanzee (Pan). The sexual skin 

 of t!ie baboon and chimpanzee undergo jiro- 



