494 



THE MALE GENITAL ORGANS OF THE HORSE 





about two inches (ca. 5 cm.) in length, and an inch or more (ca. 3 cm.) in width. 

 In the gelding they are about the size of an average hazel nut. 



Structure. — They resemble the prostate in general structure, but the inter- 

 stitial tissue is much less abundant, especially in regard to its muscular elements. 

 In the peripheral part there are striped muscle-fibers. Each gland has six to 

 eight excretory ducts (Ductus excretorii) which open into the urethra on a series 

 of small ])apilla3 behind the prostatic ducts and close to the median plane. The 

 blood-supply comes from the internal pudic artery. 



THE PENIS 



The penis, the male organ of copulation, is composed essentially of erectile 

 tissue, and incloses the extrapelvic part of the urethra. It extends from the ischial 

 arch forward between the thighs on to the umbilical region of the abdominal wall. 

 It is supported by the fascia penis and the skin, and its prescrotal portion is situated 



Deep artery {from internal pudic) 



Dorsal artery {from Corona (jlandis 



- external pudic) Collum (jlandis 



Proc. dorsalis gland is 



Ure- 

 -thrat 

 process 



Retractor penis muscle 



Fig. .395. — Penis op Horse, Later.\l View. 



in a cutaneous pouch, the prepuce or sheath. It is cylindrical in form, but much 

 compressed laterally in the greater part of its extent. 



In the quiescent state it is about 20 inches (ca. 50 cm.) long; of this, about 6 to 8 inches 

 (ca. 15 to 20 cm.) is free in the prepuce. In erection it increases 50 per cent, or more in length. 



It may be divided into a root, a body, and a terminal enlargement, the glans. 



The root (Radix penis) is attached to the lateral parts of the ischial arch by 

 two crura, which converge and unite below the arch (Fig. 452). The urethra passes 

 over the ischial arch between the crura, and curves forward to become incorpor- 

 ated with the penis. 



The body (Corpus penis) begins at the junction of the crura and constitutes 

 the bulk of the organ. At its origin it is attached to the symphysis ischii by two 

 strong flat bands, the suspensory ligaments of the penis (Ligamenta suspensoria 

 penis), which blend with the tendon of origin of the graciles muscles (Figs. 451, 

 456). This part of the penis is flattened laterally for the most part, but becomes 

 rounded and smaller anteriorly. It presents four surfaces. The dorsal surface or 

 dorsum penis, is narrow and rounded; on it are the dorsal arteries and nerves 

 of the penis and a rich venous plexus. The ventral or urethral surface (Facies 

 urethralis) is rounded, and along it runs the urethra, embedded in the deep 

 urethral groove of the corpus cavernosum. The lateral surfaces are high and 

 flattened, except anteriorly, where they are lower and rounded. 



