ILIAC YEIXS PORTAL SYSTEM. 479 



to its muscular coat, but they are particularly rich towards the base of the 

 organ, and are there closely connected with the prostatic and hajmorrhoidal 

 plexuses in the male, and with the vaginal plexus in the female. 



The prostatic plexus receives two large vessels, one at each side, the divi- 

 sions of the dorsal vein of the penis. These, coursing downwards and 

 backwards on the sides of the prostate gland, expand into a close network 

 at the base of the gland, which is quite encircled by it. 



The hcemorrhoidal plexus consists of enlarged and. copiously anastomosing 

 veins in the walls of the lower part of the rectum, immediately underneath 

 the mucous membrane. From it proceed superior, middle, and inferior 

 hsemorrhoidal veins accompanying the arteries of the same name, and it 

 communicates freely with the plexuses in front of it. The superior 

 hsemorrhoidal vein being a branch belonging to the portal system, the 

 hsemorrhoidal plexus forms a very direct communication between the portal 

 and general venous systems. 



The vaginal plexus surrounding the vagina, principally in its lower part, 

 communicates freely with the hsemorrhoidal and vesical plexuses. 



The uterine plexus pours its blood in greatest part into the ovarian veins, 

 and is not considerable except in pregnancy. 



The dorsal vein of the penis commences by branches which issue from the 

 glans penis, and form in the first instance two veins, one at each side of the 

 middle line, in the dorsal groove of the penis. These receive branches from 

 the spongy body of the penis, and some superficial veins which accompany 

 the external pudic arteries, and, proceeding backwards, unite and form a 

 short trunk which enters the pelvis beneath the subpubic ligament. Here 

 it divides into two branches, which are directed obliquely downwards over 

 the prostate and the neck of the bladder, and are united with the prostatic 

 plexus. 



COMMON ILIAC VEIN. 



The common iliac vein is formed by the confluence of the external and 

 internal iliac veins. Extending from the sacro-iliac articulation upwards to 

 near the junction of the fifth with the fourth lumbar vertebra, at a point 

 a little to the right of the middle line, the two common iliac veins unite to 

 form the lower or ascending vena cava. The right vein is shorter than the 

 left, and is nearly vertical in its direction. The right vein is placed 

 behind, and then to the outer side of its artery ; whilst the left vein is to 

 the inner side of the left common iliac artery, and then passes behind the 

 right. These veins are destitute of valves. 



PORTAL SYSTEM OF VEINS. 



The portal vein differs from other veins of the body in being subdivided 

 into branches at both its extremities. The branches of origin, by the 

 union of which it may be said to be formed, are the veins of the chylo- 

 poietic viscera, viz., the stomach, intestine, pancreas, and spleen; the 

 other branches, or those of distribution, ramifying after the manner of an 

 artery in the substance of the liver, convey to the capillaries of that organ 

 the blood collected in the main trunk. This blood, together with that of 

 the hepatic artery, after having served for the secretion of the bile and the 

 nourishment of the liver, is withdrawn from that organ by the hepatic veins, 

 and carried by them into the vena cava inferior. 



The PORTAL VEIN or VENA FOOTS: is about three inches in length. 

 Commencing at the junction of the splenic and superior mesenteric veins, it 



