THE SCROTUM AND TESTES
The scrotum is perineal in position. The tail of the epididymis and the less salient associated pole of the testis point dorsocaudally by the anus and are readily palpable. The free border of the testis faces caudoven- trally, and the attached border is closely applied to the surface of the thigh (Figure 35-6).
It has been the established custom to castrate male pigs when they are 2 to 4 days old in the belief that this prevents the development of the taint that characterizes the flesh of boars. It is now increasingly appreciated, in some countries at least, that the taint does not appear until after the usual age at slaughter and that castration is therefore pointless. Both the open and closed methods of castration are used with young pigs. In the former, the tunica vaginalis is incised, the ligament joining it to the epididymis divided, and the cord severed. This is the method employed with old boars. In the closed method (Figure 35-7, B), the scrotum is opened, the tunica vaginalis is left intact but freed from attachments, and the cord is transected close to the external inguinal opening. The situation of the scrotum explains the unusual length of the cord.
In pigs, descent of the testis commences about the 60th day of gestation, and regression of the extraabdominal gubernaculum creates the conditions in which
Figure 35-6 Schema of the boar's reproductive organs. 1, Scrotum; 2, left testis; 3, tail of epididymis; 4, deferent duct; 5, bladder; 6, rudimentary teat; 7, vesicular gland covering the small body of the prostate; 8, bulbourethral gland; 9, prepuce; 10, penis; 11, preputial diverticulum; 12, right hip bone.
the testis is able to leave the inguinal canal by approximately the 90th day. After a period of uncertainty, when the testis may move back and forth between the canal and the groin, a permanent position in the scrotum is adopted by full term. Abnormalities of gubernacular development and regression are common. Both excessive swelling and delayed regression may widen the canal abnormally, allowing a loop of intestine to slip into the vaginal cavity and thus creating an indirect inguinal or, should it reach so far, scrotal hernia. Surgical correction of this defect is generally combined with castration by the closed method. (The inguinal hernias occasionally seen in young gilts are associated with abnormal genital tracts that resemble those of bovine freemartins.)