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 cubie 
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 papillze 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 preserotal portion is situated 
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 em.) 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) 
external pudic) Collum glandis 
Proc. dorsalis glandis 
‘ 
cavernos um 
q 
wi 
Nail 
Retractor penis muscle 
Fie. 518.—Pents oF Horse; LaTerat VIEw. 
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 ef the penis (Corpus penis) 
begins at the junction of the erura 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 
Dorsal artery (from Corona glandis 
