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 prostatas) 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 cm.) in width and thickness. The pars dis- 

 seminata surrounds the pelvic part of the urethra; dorsallyit 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 colli cuius seminalis; 

 two other series occur on either side, lateral to the folds. 



The uterus masculinus appears to be absent usually. EUenberger 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 

 flexxxre ; 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 pointed 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 septimi penis. 

 Bej^ond this there is a central axial band of dense fibrous tissue from which numerous 

 strong trabeculae radiate. The erectile tissue is small in amount, except in the root, 

 so that the organ undergoes very httle 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 httle 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 cm.) in thickness, but its length is only 

 six to eight inches (15 to 20 cm.). It is covered by a strong aponeurosis, and is 

 divided by a median raphe into two lateral halves, except at its origin. It 

 diminishes in size from behind forward, and its anterior extremity is pointed.^ 



The ischio-cavemosus 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 



^ In 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-cavemosus 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-cavemosus. 



