no 



Source o£ Equine Gonadotroph in 



injections were made on three consecutive days with autopsy 1 20 hours after 

 the initial injection. This is an arbitrary procedure,— attempting to make the 

 assays as comparable as possible to those of the other tissues. Inasmuch as the 

 nature of the gonadotrophic response of pituitary tissue differs from blood 

 and embryonic tissues, it is impossible to make a direct comparison. For ex- 

 ample, 64 mg. of fresh pituitary tissue of mare 4 gave an average ovarian 

 weight of 14.5 mg., in a group of four rats and there was no evidence of develop- 



TABLE 1 



Amount of Gonadotrophin (I.U. per gm.) in Fresh Tissues and in Endometrial-Cup 



Secretion of Pregnant Mares 



• The assay of pituitaries is not in terms of I.U. but on an arbitrary basis. See text for details. 



ment either of the ovaries or of the accessory reproductive organs, while 128 

 mg. gave an average ovarian weight of 38.2 mg. with estrous uteri and vaginal 

 smears in all animals. With mare serum one regularly obtains a clearcut 

 ovarian and accessory organ response with one-sixth of the dose necessary to 

 produce ovaries weighing 38 mg. 



Gonadotrophin m Various Tissues. Table 1 gives the amount of gonado- 

 trophin per gram of fresh tissue. The endometrial cups contain 50 to 900 times 

 more hormone per gram than the chorion and 17 to 260 times more than the 

 endometrium between the cups. The endometrial-cup secretion contains 10 

 to 35 times more hormone per gram than do the endometrial cups. The slight 

 activity of the chorion could easily be explained by the adherence of a small 

 amount of this secretion to it. 



Table 2 gives the total amount of gonadotrophin in various tissues. One 

 endometrial cup with the chorion attached was saved for histological study 

 in each case and this was not taken into account in the computation. Thus, 

 the figures on the amount of hormone in the endometrial cups, endometrial- 

 cup secretion, and chorion are somewhat low— approximately 1-5 per cent of 

 the total tissue was saved for histological study. 



