Male Genital Organs of the Pig

The scrotum is situated a short distance from the anus, and is not so sharply defined from the surrounding parts as in the other animals.

The testicles are very large and are soft in texture. Their long axis is almost vertical, the free border being posterior and the tail of the epididymis dorsal. The mediastinum testis is well developed. The epididymis is closely attached to the testicle and the tunica vaginalis; the tail is specially large.

The spermatic cord is necessarily very long (20 to 25 cm. in a boar of medium size). The vas deferens in its testicular part is flexuous, and is closely attached to the tunica vaginalis; it forms no ampullæ. The cremaster externus is well developed, and extends to about the middle of the scrotal part of the tunic.

The vesiculæ seminales are exceedingly large, and extend into the abdominal cavity. They are three-sided pyramidal masses, are in apposition with each other medially, and cover the posterior part of the bladder and the ureters, the vasa deferentia, the body of the prostate, and the anterior part of the urethra. They are pale pink in color, distinctly lobulated and glandular in structure, and contain large alveoli, but no central cavity. There are two excretory ducts which open into the urethra close to the vasa deferentia; the two ducts frequently unite.

In the adult boar the vesiculæ are about five to six inches (ca. 12 to 15 cm.) long, two to three inches (ca. 5 to 8 cm.) wide, and one and a half to two inches (ca. 4 to 5 cm.) thick; they weigh about 6 to 8 ounces each.

The prostate consists of two parts, as in the ox. The body is about an inch (2.5 cm.) wide, and embraces the neck of the bladder and the urethra at their junction dorsally and laterally. It is concealed by the vesiculæ seminales. The pars disseminata forms a layer which surrounds the pelvic part of the urethra, and is covered by the urethral muscle.

The uterus masculinus is small.

The bulbo-urethral (Cowper’s) glands are very large and dense. They are somewhat cylindrical, and lie on either side of and upon the posterior two-thirds of the pelvic urethra. In a large boar they are about five inches (ca. 12 cm.) in length and an inch or more (ca. 2.5 to 3 cm.) in diameter. They are partially covered with a layer of striated muscle (M. ischio-glandularis), and have a lobulated surface. Each gland has a large excretory duct which leaves at the posterior extremity, perforates the dorsal wall of the urethra at the ischial arch, and opens in a cul-de-sac covered by a fold of mucous membrane.

It is to be noted that these accessory glands are very small in animals which have been castrated early.

The penis resembles in general that of the ox. The sigmoid flexure is, however, prescrotal. The anterior portion has no glans, and is spirally twisted, especially in erection. The urethral orifice is slit-like and is situated ventro-laterally, close to the pointed extremity. The penis in the adult boar measures about 18 to 20 inches (ca. 45 to 50 cm.) in length. Its muscles resemble those of the bull; the bulbo-cavernosus is very strong but short.

The prepuce has a narrow orifice, around which there are a number of stiff hairs. The cavity is partially divided by a circular fold into a posterior narrow portion and a much wider anterior portion. The lining membrane of the posterior part is papillated, and is in close contact with the penis. In the dorsal wall of the wide part there is a circular opening which leads into a cul-de-sac, the preputial diverticulum. This pouch is ovoid in form (when distended), and varies greatly in size in different subjects. It extends for the most part backward over the narrow part of the prepuce. Its cavity is partially divided by a narrow median septum. It contains usually decomposing urine and macerated epithelium, which have a characteristic and very unpleasant odor. Concrements have been found in it.

Oehmke found that a cast of the pouch in a Yorkshire boar weighing about 500 pounds measured 9 cm. in length, 12½ cm. in breadth, and 6 cm. in height. The opening into the prepuce will admit two fingers in the adult, but is ordinarily closed by folds of the lining membrane. The sac is much smaller in animals which were castrated young, and the opening is vertical and further back; in them it is often empty or contains only a little clear urine. The pouch is covered by a layer of striped muscle which is mainly derived from the homologue of the protractor of the prepuce of ruminants.

The urethra has a very long pelvic portion (ca. 15 to 18 cm. long in the adult); it is inclosed (with the pars disseminata of the prostate) by a thick urethral muscle. There is a distinct bulb at the root of the penis. The penile part is of small caliber, and is surrounded by erectile tissue which, however, does not extend to the extremity of the penis.