THE GONADOTROPIC ACTIVITY OF THE ANTERIOR PITUITARY OF COCKERELS1

THE DETERMINATION of the gonadotropic activity of the anterior pituitary in the chick has been handicapped until recently because relatively large amounts of avian glandular substance were thought to be necessary to elicit responses in test animals. Recently, however, Jaap (1935), Meyer, Mellish, and Kupperman (1939), Phillips (1942) and Riley and Fraaps (1942), have developed techniques which make it possible to test individual glands. A sensitive test was reported in the two latter papers in which the growth of the vaginal epithelium of rat and mouse was utilized. This technique demonstrated that it was feasible to make a more detailed physiological study of the pituitary of the chick during the first few months after hatching. The time from hatching to 90 days of age is a period of great physiological change in White Leghorns as is evidenced by the fact that the anterior pituitary weight increases more than 9 times and the testicular weight more than 80 times during this interval, Brene-man (1944).