THE GONADOTROPIC HORMONES 



Ian), especially toward the end of the second lunar month, 

 and thus possibly replaces the anterior pituitary. When ges- 

 tation is completed or fails because of fetal death, this hor- 

 mone is no longer secreted, either because the placenta, to- 

 gether with the other products of gestation, leaves the body 

 or because the placenta degenerates and is resorbed or re- 

 moved. 



Conditions in the pregnant mare appear to be different, al- 

 though the function of the gonadotropic hormone probably 

 is similar. The period of secretion is more sharply limited 

 (especially between the 40-80 days of gestation). The endo- 

 metrium as well as the chorionic epithelium secretes a hor- 

 mone which is far more complete in its gonadotropic effects 

 than is prolan. Whereas prolan is chiefly a hormone facilita- 

 ting the growth and function of lutein tissue in the ovary or 

 of the interstitial cells in the testis, the gonadotropic princi- 

 ple(s) of pregnant-mare serum resembles anterior pituitary 

 gonadotropic principles in respect of the adequacy and com- 

 pleteness of its effects. The chorionic-endometrial hormone 

 of the pregnant mare can maintain the gonads of hypophy- 

 sectomized male or female animals and therefore affects the 

 follicles, corpora lutea, and interstitial tissue of the ovary or 

 the interstitial cells and germinal epithelium of the testis. 

 Likewise this hormone stimulates the gonads of birds, where- 

 as prolan does not. Some believe that the hormone is a mix- 

 ture of gonadotropic principles. However, more evidence is 

 needed before this belief can be accepted. On the other hand, 

 prolan appears to be a single gonadotropic substance. 



In this chapter and in others which have preceded it, the 

 recent investigations of the effects of these hormones charac- 

 teristic of pregnancy are discussed. Neither hormone has 

 been isolated as a pure substance. If either is injected re- 

 peatedly, the gonadotropic effects disappear, and an as- 

 sociated production of "antihormone," which can be found 

 in the globulin fraction of serum, takes place. The hormone 

 of pregnant-mare serum appears to have much the greater 



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