The Scrotum and Testes (see also pp. 173-180)
The rather pendulous scrotum of the dog is globular and placed in a position intermediate between the perineum and the groin (Fig. 15.3/11). It is most easily inspected from behind, and because it is sparsely haired, its close molding on the testes is obvious.
A deep groove defines the boundary between the internal compartments occupied by the generally asymmetrical testes. The thin scrotal skin and underlying fasciae do not impede palpation, which normally allows recognition of the body and tail of the epididymis, the deferent duct, and the spermatic cord in addition to the testis itself. The scrotal skin of dogs is richly supplied with sweat glands. The scrotum of the cat is perineal, sessile, and commonly concealed by a dense covering of hair.The testes are relatively small in both species. They are carried horizontally in dogs but with their caudal extremities tipped toward the anus in cats. Each testis is roughly oval in outline, laterally compressed, and related to the epididymis along its dorsal (in cats, craniodorsal) margin. The head and tail of the epididymis adhere to the testis, but the body is partly free, creating a testicular bursa. The constituents of the compact spermatic cord disperse at the internal inguinal ring. Because of the very caudal position of the scrotum, the spermatic cord in the tom is unusually long. Perhaps that length explains why the cremaster muscle of the cat is very weak. The striated cremaster muscle originates from the iliac fascia on the ventral aspect of the psoas muscles just craniomedial to the caudal border of the internal oblique muscle, inserts on the internal spermatic fascia, and is innervated by the genitofemoral nerve.
» TABLE 15.2
Guide to The Aging of Dog Fetuses
From Evans HE, Sack WO: Prenatal development of domestic and laboratory animals: growth curves, external features and selected references, Anat Histol Embryol 2:11-45, 1973.
» TABLE 15.3
Guide to the Aging of Cat Fetuses
From Evans HE, Sack WO: Prenatal development of domestic and laboratory animals: growth curves, external features and selected references. Anat Histol Embryol 2:11-45, 1973.