580 



GENITAL ORGANS OF THE STALLION 



stitial tissue is much less abundant, and contains much less muscular tissue; hence 

 the lobulation is not very distinct. The parenchyma consists of large collecting 

 tubules, into which numerous side branches open; these are lined with cubic 

 epithelium. In the larger septa 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 papillae behind the prostatic ducts and close to the median plane 

 (Fig. 521). The blood-supply comes from the internal pudic artery which overlies 

 the gland. 



THE PENIS 



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

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

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

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

 in a cutaneous pouch, the prepuce or sheath. It is cjdindrical 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. 



Deep artery {from internal pudic) 



/l| Dorsal nrlenj {from Corona glandis 



fU external pudic) Colhnn glandis 



Pruc. dorsalis glandis 



Retractor penis muscle 



BODY 



Fig, 518. — Pexis of Hohse; Lateral View. 



Ure- 

 ''■' 1 ^MKIr -ihral 

 i" .- A '^M process 



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



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

 arch by two crura, which converge and unite below the arch (Fig. 577). The 

 urethra passes over the ischial arch between the crura, and curves sharply forward 

 to become incorporated with the penis. The body of the penis (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. 518, 576). This part of the penis is flattened 

 laterally for the most part, but becomes rounded and smaller anteriorly. It pre- 

 sents four surfaces. The dorsum penis is narrow and rounded; on it are the dorsal 

 arteries and nerves of the penis and a rich venous plexus. The urethral surface 

 (Facies urethralis) is ventral; it 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; they are 

 ■ covered to a large extent by a plexus of veins. 



The glans penis is the enlarged free end of the organ. Its anterior surface or 

 base is surrounded by a prominent, denticulated margin, the corona glandis. The 



