Abstract
SUMMARY: Experimental unilateral cryptorchidism in the rat is accompanied by compensatory changes in the scrotal testis. These changes include hypertrophy of germ cells unaccompanied by hyperplasia, and hyperplasia and hypertrophy of Leydig cells. It is postulated that these changes are due to increased secretion of both follicle-stimulating hormone and interstitial cell-stimulating hormone by the adenohypophysis; this opinion is borne out to some extent by the histological changes in this organ, in which the presence of increased numbers of peripheral and central castration cells indicates increased secretion of gonadotrophins.