586 GENITAL ORGANS OF THE BULL 



Except at its origin and termination the urethra is provided with a continuous 

 layer of striped muscle, placed outside of the erectile tissue. This is described as 

 consisting of two parts or muscles. 



(1) The urethral muscle (M. urethralis)i encloses the wide pelvic part of the 

 urethra, and covers the bulbo-urethral glands. It consists of longitudinal and 

 transverse fibers. It is a compressor of the pelvic part of the urethra and the bulbo- 

 urethral glands. Hy its forcible contraction it plays an important role in the ejacula- 

 tion of the seminal fluid, and also in evacuating the last of the urine in micturition. 



(2) The bulbo-cavemosus muscle (M. bulbocavernosus)^ is the continuation 

 of the urethral muscle on the extrapelvic part of the urethra; it extends from the 

 ischial arch to the glans penis. At the root of the penis it is the thickest, and 

 forms a complete layer of circular fibers which enclose the corpus cavernosum 

 urethras. Beyond this it diminishes very gradually in thickness, and consists of 

 fibers which arise on a median ventral raphe and curve around the corpus cavernosum 

 urethree to end on the tunica albuginea of the corpus cavernosum. Its action is to 

 empty the extrapelvic part of the urethra. 



The ischio-virethral muscles (Fig. 577) are small bands which arise on the 

 ischial arch and crura of the penis and pass forward to become lost on the ventral 

 layer of the urethral muscle. They may assist in erection of the penis by exerting 

 pressure on the dorsal veins. 



GENITAL ORGANS OF THE BULL 



The scrotum is situated somewhat further forward than in the horse. It is 

 ovoid, but compressed from before backward, is long and pendulous, and has a well- 

 marked neck when not contracted. The skin here is usually flesh-colored, but in 

 some breeds it is more or less pigmented; it is sparsely covered with short hairs. 

 Just in front of it are four (sometimes only two) rudimentary teats. 



The testicles are relatively larger than those of the horse, and have an elon- ■ 

 gated, oval outline. The long axis is vertical, the attached border being posterior. 

 The medial surface is somewhat flattened. A testicle of an adult bull measures on 

 the average about four or five inches (10 to 12 cm.) in length, exclusive of the epi- 

 didymis; ^^•ith the latter the length is about six inches (15 cm.). The width is 

 about two and a half to three inches (ca. 6 to 8 cm.), and the anterior-posterior 

 diameter about the same. The weight is about ten to twelve ounces (ca. 300 grams). 

 The tunica albuginea is thin; it contains many elastic fibers, but no unstriped 

 muscle. The parenchyma is yellowish in color. The mediastinum testis is an 

 axial strand of connective tissue (about 5 mm. in thickness), which descends from 

 the upper part of the attached border deeply into the gland. From it the chief 

 trabeculse radiate, but distinct interlobular septa are not present. The seminif- 

 erous tubules form in the mediastinum a network, the rete testis. The efferent 

 ducts from the rete, a dozen in number, leave at the upper end of the mediastinum. 



The epididymis is very closely attached to the testicle along the posterior 

 border of the latter. The head is long; it curves oyer the upper extremity and 

 about a third of the way down the anterior border of the testicle; it is covered by 

 an extension of the tunica albuginea. The body is very narrow, and lies along the 

 lateral part of the posterior border of the testicle, to which it is attached by a narrow 

 peritoneal fold. The tail is large and is closely attached at the lower extremity of 

 the testicle. 



The spermatic cord and the tunica vaginalis are much longer than in the horse; 



1 Formerl)' termed Wilson's muscle. ^ Formerly called the accelerator urinse. 



