Abstract
Few experiments have been done which give evidence concerning differences in gonad-stimulating potency of the amphibian pituitary of the two sexes, either in the normal animal or after castration. Although Bardeen 1 reported no difference in pituitaries of males and females of Rana pipiens, Rugh 2 discovered that in this species the pituitary of the female is twice as potent as that of the male, and Rostand 3 has found a similar condition in Rana temporaria and R. esculenta. Using toad material (Bufo arenarum), Houssay, Giusti and Lascano-Gonzalez 4 observed no marked variation in potency of the pituitaries of the normal male, castrated male, normal female, and spawning female, and Novelli 5 was unable to demonstrate any difference in pituitaries of males of this species castrated for 30, 60, and 90 days as compared with those of the normal animal.
The criterion by which potency has usually been estimated is the ovulation (or egg-laying) induced in females in the non-breeding season judged by (1) the number of animals ovulating (or depositing eggs) in a definite time or (2) the number of grafts necessary to cause ovulation (or egg-laying) in a series consisting of a definite number of animals. The speed of the extra-seasonal ovulatory response is dependent on (1) the temperature 6 and (2) the period in the interbreeding season in which the tests are being made. 7
Using Triturus viridescens in the non-breeding season (October through early March), the gonad-stimulating potency of anterior pituitaries of normal males and females and of those castrated for 4 days (Series II), 4 weeks (Series I) and 95 to 100 days (Series III) was judged by the average number of grafts (one P.A. daily, intramuscularly) necessary to cause egg-laying in a series of 15 normal females (Table I).
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