FUNCTIONAL ASPECTS

The size of the accessory glands is related to the large volume of the ejaculate, at least 200 mL. Despite their great size, the vesicular and bulbourethral glands together contribute rather less than half the seminal fluid; the bulk is provided by the prostate and urethral glands.

During erection the blood pressure in the cavernous spaces rises sharply, straightening the sigmoid flexure and increasing the length of the penis by about a quarter. The single longitudinal twist of the shaft increases to six turns, while the corkscrew spiral of the free part becomes much more pronounced. During coitus, a slow process that may last for as long as 30 minutes, the boar is said to “soak” because of the absence of obvious activity on his part. However, forward and backward twisting movements of the penis do occur under the influence of the retractor muscle. There is no substance to the persistent belief that the prominences of the cervical mucosa form a canal with a left-hand thread matching that of the spiraled end of

Figure 35-10 Prepuce and preputial diverticulum. A, In situ, schematic, craniolateral view. B, Ventral view. C, Dorsal view. 1, Cranial preputial muscle, in A cut at both ends; 2, preputial orifice; 3, orifice between prepuce and diverticulum;

4, 4', wide cranial and narrow caudal parts of preputial cavity;

5, preputial diverticulum; 6, penis; 7, medial surface of right hock; 8, umbilicus; 9, cutaneous trunci; 10, pectoralis profun­dus; 11, preputial fat.

the penis. The end of the penis is considered to almost enter the uterus.