A bulk of studies on the assay of gonadotrophic hormone content of the anterior pituitary from the animals in various reproductive conditions has been done. Riley and Fraps(1942b) assayed pituitary glands from chickens in various reproductive stages, judging the gonadotrophic potency by the increment of uterine weights of immature mice, and concluded that glands from non-laying hens produced a greater gonad stimulating effect than did those from laying hens. A similar result was obtained by

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... lips(1942) in the gonadotrophic assay of the chicken pituitary using the histological changes of the vaginal epithelium of immature rats as an index of the gonadotrophic potency. On the other hand, it was reported that, in immature female chickens, the gametogenic components of the ovary were almost refractory to gonadotrophins of mammalian origin,but were capable of being stimulated by the avian gonadotrophin (Nalbandov and Card,1946; Das and Nalbandov, 1955), and that hypophysectomized male chickens were capable of responding to mammalian gonadotrophins for a very limited time, whereas sustained testicular growth and androgen secretion could be obtained by the injection of chicken pituitary (Nalbandov, Meyer and McShan, 1951). These results showed that there was a qualitative difference in the gonadotrophic complex of mammals and birds.