The Fibro-Muscular Scrotal Sac Under Normal and Experimental Conditions in an Annual Breeder (Citellus). ∗

Abstract

What causes the testis of an adult ground squirrel to ascend into the peritoneal cavity during the non-breeding period? Is decrease in testis-size a primary factor, or does the scrotum regress and force the testis to ascend? The scrota of 89 ground squirrels (Citellus tridecemlineatus) have been studied in an attempt to answer these questions. Details concerning the normal sexual cycle in the male are presented elsewhere. 1 , 2

The present report deals largely with the muscular pouch which incloses testis and epididymis, designated in this paper by the name “fibro-muscular scrotal sac” (Fig. 2). This sac is composed of the following layers: peritoneum, internal spermatic fascia, cremasteric skeletal muscle and external spermatic fascia (Figs. 1, 3). The fibromuscular sac of each animal was freed of its contents, severed at the inguinal ring (Fig. 3), weighed while fresh, fixed in Bouin's solution and sectioned at 6 micra for microscopical study.

The scrotal sac of prepuberal males undergoes a gradual increase in weight (Table I). The sacs of adults are large in males with large scrotal and spermatic testes, and are greatly reduced in size in animals having small, abdominal and aspermatic testes. Weight of paired sacs in males with spermatozoa ranged from 0.1212 to 0.5215 gm., yet this weight was slightly less than the average for males lacking spermatozoa in only 2 of 32 cases. The greatest weight of paired sacs in any aspermatic male was 0.2400 gm., and this is significantly less than the average weight for animals with spermatozoa. Data for individual animals indicate clearly that variations in sac weight lag behind variations in testis weight. The testis may be experimentally caused to remain spermatogenetically active within the scrotum during the non-breeding period by subjection of the animal to cold temperature and darkness 3 ; such males have large scrotal sacs.