Effect of Injections of Pituitary Whole Gland Extract on Immature Alligator

The efficacy of the anterior hypophysis in producing precocious development of the reproductive system in lower vertebrates has been shown by the recent studies of Burns and Buyse, 1 , 2 , 3 and Burns, 4 who used as subjects larvae and recently metamorphosed salamanders. Reptiles have rarely figured in pituitary investigations. Herlant 5 found that injections of anterior lobe extract caused a general hypertrophy of the reproductive system of Lacerta, Noble and Bradley 6 state that hypophysectomy delays moulting in Hemidactylus, Schaefer 7 reports testicular atresia in Thamnophilis following hypophysectomy, with a partial restoration of the testes to the normal condition following several hypophyseal implants, and Houssay 8 produced ovulation in a single female snake, Xenodon, after similar implantations. All of these experiments were carried out with mature animals.

In the present work, the immature alligator, Alligator mississipfiensis, was chosen for study. The average total length of the first group of animals used was 24 cm., and their approximate age at the beginning of the experiment was 4 months. Intraperitoneal injections into 10 animals of 0.5 cc. per animal of the Parke, Davis & Co. sheep whole gland alkaline aqueous extract were made 3 times a week, a similar group of 10 animals serving as controls. Gross examination after 6 weeks of injections, showed a great hypertrophy of the testes of the single male member of the experimental group. A slightly less, but still striking, hypertrophy of the gonads of the injected females was observed, together with lengthening and increased convolution of the oviducts. Due to lack of external evidences of sex in the immature animals, the ratio of males to females in this series was purely fortuitous, but a second series (see below) showed a preponderance of male animals, thus approximately equalizing the total number of males and females in the two series.