670 BLOOD-VASCULAR SYSTEM OF THE HORSE 
(1) The umbilical artery is given off from the internal pudic about an inch 
(ea. 2-3 em.) from the origin of that vessel. It is a very large artery in the 
foetus, in which it curves downward and forward at the side of the bladder in the 
edge of the lateral umbilical fold of peritoneum, passes through the umbilical open- 
ing, becomes a component of the umbilical cord, and ramifies in the foetal placenta. 
After birth it extends only to the vertex of the bladder and is much reduced. Its 
lumen is almost obliterated and its wall is very thick, giving the vessel a cord-like 
character, hence it is commonly termed the round ligament of the bladder. It 
gives off small vesical branches (Aa. vesicales craniales) to the bladder, and twigs 
to the prostate and ductus deferens in the male. In the mare a small branch runs 
forward along the ureter into the broad ligament of the uterus. 
(2) The middle hemorrhoidal or vesico-prostatic artery (A. hxemorrhoidalis 
media) in the male arises usually near the prostate and runs backward lateral to 
the rectum. It supplies branches to the rectum, bladder, urethra, and accessory 
genital glands. In the female the homologous vessel is much larger and gives off 
the posterior uterine artery (A. 
uterina caudalis). This runs for- 
ward on the side of the vagina, to 
which it gives branches, and rami- 
fies on the body of the uterus, anas- 
tomosing with the anterior and 
middle uterine arteries. (In some 
cases this artery arises from the 
internal iliac or the umbilical.) 
(3) The perineal artery (A. 
perinei) is relatively small in the 
male. It ascends at the side of the 
anus, which it supphes, and gives 
twigs to the bulbocavernosus mus- 
cle and the skin of the perineum. — 
In the female it is large and is dis- 
tributed to the anus and vulva, and 
1, Dorso-lateral coccygeal vessels and nerve: 2, ventrolateral gives a large branch to the vestibu= 
coceygeal artery and nerve; 3, middle coceygeal artery; 4, sacro- lar bulb. 
-coccygeus dorsalis; 4’, sacro-coceygeus lateralis; 5, 5’, intertrans- (4) The artery of the bulb (A 
versales; 6, sacro-coccygeus ventralis; 7, recto-coccygeus; 8, 
coccygeal fascia; 9, fibro-cartilage between fourth and fifth bulbi urethre) may be regarded as | 
coceygeal vertebre. The veins are black. the direct continuation of the in- 
ternal pudic in the male. It lies 
at the side of the urethra above the ischial arch, dips under the bulbo-cavernosus 
muscle, and ramifies in the corpus cavernosum tes Before doing so it gives 
off a small branch which turns around the ischial arch to reach the dorsum penis, 
and anastomoses with the deep branch of the obturator. 
(4a) The artery of the clitoris (A. clitoridis) is the homologue in the female — 
of the preceding vessel, but is much smaller. It passes to the ventral surface of | 
the vulva with a branch of the pudie nerve, supplies the clitoris, and gives twigs to 
the vulva. 
3. The lateral sacral artery (A. sacralis lateralis) arises at the lumbo-sacral 
articulation (Fig. 576). It passes backward under the wing of the sacrum, then | 
along the pelvic surface of the bone below the ventral sacral foramina and the | 
| 
Fig. 579.—Cross-section or Tart or Horse, 
nerves emerging from them, and is continued by the lateral coccygeal artery. The | 
branches are as follows: 
(1) Spinal branches (Rami spinales) enter the vertebral canal through the | 
1 The obliteration in the adult extends a variable distance from the vesical end toward the 
origin, but usually involves completely only a small part. 
