578 GENITAL ORGANS OF THE STALLION 
THE VESICULZ SEMINALES 
The vesicula seminales (Fig. 517) are two elongated and somewhat piriform 
sacs, which lie on each side of the posterior part of the dorsal surface of the blad- 
der. They are partly enclosed in 
the genital fold, and are related to 
the rectum dorsally. Their long axes 
are parallel with the ductus def- 
erentes and converge posteriorly. 
Each consists of a rounded blind 
end, the fundus; a middle, slightly 
narrower part, the body; and a pos- 
terior constricted part, the neck or 
duct. 
In the stallion they are about 
six to eight inches (ca. 15 to 20 em.) 
long, and their greatest diameter is 
about two inches (ca. 5 cm.); in 
the gelding they are usually much 
smaller.! 
The vesiculie are chiefly retro- 
peritoneal, but the fundus extends 
forward into the genital fold and 
hence has a serous covering. The 
excretory duct (Ductus excretorius) 
dips under the prostate, and opens 
in common with or alongside of the 
ductus deferens in a pouch of the 
mucous membrane on the side of 
the colliculus seminalis. 
Structure.—The wall, exclusive 
of the partial serous coat, consists 
of a fibrous adventitia, a middle 
muscular coat, and a mucous lining. 
The muscular coat is thickest at the 
fundus, and consists of two planes 
of longitudinal fibers with a circular 
layer between them. The mucous 
membrane is thin, and is arranged 
in numerous folds and projections 
which form a network; the spaces 
so enclosed present the openings of 
Fic. 517.—IntTernat GENITAL ORGANS OF STALLION; DoRSAL 
VIEW. 
On left side urethral muscle has been removed over bulbo- tubulo-alveolar glands. The epithe- 
urethral gland. Cornua of uterus masculinus are indicated in lium is columnar. The blood-supply 
genital fold. The posterior limit of the peritoneum is shown 
is deriv ic 
but not marked. 1, Round ligament of bladder; 2, lateral liga- 1S deriv ed from the internal pud 
ment of bladder; 3, bulbo-urethral gland. artery. 
THE PROSTATE 
The prostate (Prostata) is a lobulated gland which lies on the neck of the 
bladder and the beginning of the urethra, ventral to the rectum. It consists of 
1Sometimes one or both of the vesicule are very large in the gelding. The writer has seen 
four cases in the dissecting room, three of which were bilateral, the other unilateral. The vesicula 
resembled the urinary bladder in appearance and contained about a quart of thick, amber-colored 
secretion. 
