e 
GENITAL ORGANS OF THE BULL 589 
The prostate is pale yellow in color, and consists of two parts, which are, how- 
ever, continuous with each other. The body (Corpus prostate) is a small mass 
which stretches across the dorsal surface of the neck of the bladder and the origin 
of the urethra. It measures about an inch and a half (ca. 3.5 to 4 cm.) transversely, 
and about half an inch (ca. 1 to 1.5 em.) in width and thickness. The pars dis- 
seminata surrounds the pelvic part of the urethra; dorsally it forms a layer about 
half an inch (ca. 10 to 12 mm.) thick, but ventrally it is quite thin (ca. 2 mm.). 
It is concealed by the urethral muscle and its aponeurosis; hence it often escapes 
notice, but is very evident on cross-section (Fig. 525). It has a branched tubular 
structure, and the interlobular tissue contains a large amount of unstriped muscle. 
The prostatic ducts open into the urethra in rows, two of which are between two 
folds of the mucous membrane that proceed backward from the colliculus seminalis; 
two other series occur on either side, lateral to the folds. 
The uterus masculinus appears to be absent usually. Ellenberger states that 
it opens between the ejaculatory orifices, while Martin says that it usually has two 
orifices at the colliculus, but that it often unites with the ductus deferens. 
The bulbo-urethral glands are somewhat smaller than in the stallion. They 
are liable to escape notice, since they are covered by a thick layer of dense fibrous 
tissue and also partially by the bulbo-cavernosus muscle. Each has a single duct 
which opens into the urethra under cover of a fold of the mucous membrane. 
The penis is cylindrical, and is longer and of very much smaller diameter than 
in the horse. Just behind the scrotum it forms an S-shaped curve, the sigmoid 
flexure; thus about one foot of the penis is folded up when it is fully retracted. 
The flexure is effaced during erection. The glans penis is about three inches (ca. 
8 cm.) in length. It is flattened dorso-ventrally, and its extremity is pomted and 
twisted. The external urethral orifice is situated at the end of a groove formed 
by this twist; it is only large enough to admit a probe of medium size. Even in 
the non-erect state the penis is remarkably dense and firm. The tunica albuginea 
is very thick, and encloses the urethra; it is composed of dense white fibrous tissue. 
In the first part, as far as the first curve, there is a thick median septum penis. 
Beyond this there is a central axial band of dense fibrous tissue from which numerous 
strong trabecule radiate. The erectile tissue is small in amount, except in the root, 
so that the organ undergoes very little enlargement in erection, the chief effect 
being increased rigidity. The walls of the cavernous spaces are fibro-elastic, not 
muscular. 
The length of the penis in the adult is about three feet (ca. 90 cm.). The crura are flattened 
laterally; they contain a well-developed corpus cavernosum and numerous helicine arteries, some 
of which open directly into the cavernous spaces. The suspensory ligaments are attached to the 
ventral ridge on the symphysis pelvis. The body is somewhat flattened dorso-ventrally beyond 
the first curve. The extremity of the glans is unsymmetrical, the urethral orifice being situated 
ventro-laterally. The glans contains only a thin superficial stratum of erectile tissue, and hence 
undergoes little enlargement in erection. In the body of the penis there is a longitudinal vein on 
either side in the ventral part of the corpus cavernosum. 
The bulbo-cavernosus muscle presents several remarkable features. It is for 
the greater part an inch or more (ca. 3 em.) in thickness, but its length is only 
six to eight inches (15 to 20 em.). It is covered by a strong aponeurosis, and is 
divided by a median raphé into two lateral halves, except at its origin. It 
diminishes in size from behind forward, and its anterior extremity is pointed.t 
The ischio-cavernosus muscle resembles in general that of the horse, but is 
flattened laterally. It is covered by a tight aponeurosis. 
The retractor penis muscle resembles that of the horse in origin. Its two parts 
1TIn the sheep and sometimes in the ox there is a m. ischio-bulbosus which consists of fibers 
that extend across the initial part of the bulbo-cavernosus. Fibers which extend from the ischial 
arch over the bulbourethral gland form the m. ischio-glandularis. A urethro-cavernosus muscle 
is sometimes present; it consists of fibers which arise on the urethra near the origin of the bulbo- 
cavernosus and end on the latter and the ischio-cavernosus. 
