THE ILIAC VEINS. 851 
Sciatic Veins (vv. glutaez inferiores).—The venze comites of the sciatic artery com- 
mence in the subcutaneous tissues on the back of the thigh ; they ascend with the sciatic 
artery, and pass deeply into the buttock beneath the gluteus maximus, where they receive 
humerous tributaries from the surrounding muscles. Entering the pelvis through the 
great sciatic foramen, they unite into a single vessel, which terminates in the lower and 
anteri ior part of the internal iliac vein below the termination of the obturator vein. 
Gluteal Veins (vv. glutaeze superiores).—The ven comites of the gluteal artery are 
formed by tributaries which issue from the muscles of the buttock. They accompany 
the artery through the great sciatic foramen, and terminate in the internal iliac vein ; 
they frequently unite together before reaching their termination. 
‘Internal Pudic Veins.—The venie comites of the internal pudic artery commence 
by tributaries which,emerge from the corpus cavernosum of the penis (vv. profundee penis) 
or clitoris (vv. profundee clitoridis). They follow the course of the internal pudic artery, 
and usually join together into a single vessel (v. pudenda interna) which terminates in 
the internal iliac vein. As tributaries they receive the veins from the bulb, the superficial 
perineal and inferior hemorrhoidal veins (vy. hemorrhoidales inferiores), and veins from 
the muscles of the buttock. 
The inferior hemorrhoidal veins, which commence in the substance of the external 
sphincter of the anus and in the walls of the anal canal, anastomose with the middle and 
superior hemorrhoidal veins, and consequently connect the portal and vena caval systems 
together. 
The intra-pelvic tributaries of the internal iliac vein are either (a) parietal or 
(>) visceral; the former comprises the lateral sacral veins, the latter includes the 
efferent vessels from the plexuses around the several pelvic viscera. 
(a) Parietal: Lateral sacral veins (vv. sacrales laterales) accompany the corre- 
sponding arteries, and terminate on each side in the inner and back part of the internal 
iliac vein. 
(4) Visceral tributaries are derived from the rectum and from the plexuses associated 
with the uterus, vagina, bladder, and prostate. They include the middle hemorrhoidal, 
the uterine, the vaginal, and the vesical veins. 
The middle hemorrhoidal veins (vv. hemorrhoidales mediales) are very irregular ; 
sometimes they cannot be distinguished. When present they are formed by tributaries 
which commence in the submucous tissue of the rectum, where they communicate with 
the superior and inferior hemorrhoidal veins; they pass through ‘the muscular coat, 
and fuse together to form two middle hzmorrhoidal veins, right and left, each of 
which runs outwards beneath the peritoneum, on the upper surface of the levator ani, 
to terminate in the internal iliac vein. In the male each middle hemorrhoidal vein 
receives tributaries from the seminal vesicle and vas deferens of its own side. 
Uterine Plexuses and Veins.—The uterine plexuses lie along the lateral borders 
of the uterus; they receive tributaries, which are entirely devoid of valves, from the 
uterus, and they communicate above with the ovarian, and below with the vaginal 
plexuses. 
The uterine veins (vv. uterine), usually two on each side, issue from the lower parts 
of the uterine plexuses above their communications with the vaginal plexuses. At first 
the uterine veins on each side lie in the inner part of the base of the broad ligament 
above the lateral fornix of the vagina and the ureter ; they then pass backwards, accom- 
panying the corresponding artery, in a fold of peritoneum which lies between the back 
of the broad ligament and the recto-uterine fold; finally they ascend in the floor of the 
ovarian fossa, and terminate in the internal iliac vein. 
Vaginal Plexuses and Vaginal Veins.— The vaginal plexuses lie at the 
sides of the vagina. They receive tributaries from the walls of the vagina, and communi- 
cate above with the uterine plexuses, below with the veins of the bulb, in front with the 
vesical plexus, and behind with the veins which issue from the middle a lower parts of 
the hemorrhoidal plexus. A single vaginal vein issues from the upper part of the vaginal 
plexus on each side ; it accompanies the corresponding arteries, and terminates in the 
internal iliac vein. 
Superior Vesical Plexus.—The superior vesical plexus of veins lies on the outer 
surface of the muscular coat of the bladder at the fundus and the sides. It receives 
tributaries from the mucous and muscular walls, and its efferent vessels terminate in the 
prostatico-vesical plexus in the male, and in the inferior vesical plexus in the female. 
Prostatico-vesical Plexus.—This plexus is distributed round the prostate and the 
neck of the bladder, and is enclosed between the proper fibrous capsule of the prostate and 
its sheath of recto-vesical fascia. In front it receives the dorsal vein of the penis, which 
