24 ESSAY ON THE DESCRIPTIVE ANATOMY OF THE 
anastomosing on the corresponding surfaces with the colic 
arterial trunks. 
The two branches going to the colon extend, about parallel to 
each other, downwards and forwards and to the left, the one 
gaining the csecal end of the colon, whilst the other proceeds 
on to the hepatic flexure. Then these may be traced, the one 
backwards and the other forwards, relatively to the course of 
the gut, along its superior border, so as to reach the sigmoid 
flexure, where they mutually inosculate. From the mesenteric 
division going to the transverse colon, is a branch proceeding 
on to the single portion, which anastomoses posteriorly with the 
posterior mesenteric. This vessel divides first into two branches, 
i.e. an anterior colic and a posterior rectal one. The anterior 
colic branch is directed forwards and downwards between the 
layers of the mesocolon, and divides into four or five branches, 
which bifurcate and form arches, like the arteries of the small 
intestine, for the supply of the contiguous gut. The arteries 
of the rectum are sometimes spoken of as the haemorrhoidals, 
and these are distinguished as anterior, middle, and posterior. 
The anterior haemorrhoidals are formed by the hindermost branch 
of the posterior mesenteric artery, which, passing into the folds 
of the meso-rectum, supplies consecutive branches to the gut, 
till, posteriorly to the peritoneum where the arteries pierce the 
muscular coat, and, forming a network of vessels, anastomose 
with the middle haemorrhoidals, which are the ramifications of 
the internal pudic.* These inosculate with the posterior 
haemorrhoidals derived from the same source. The anus is, 
then, supplied with blood from the last named branches, as well 
as from perineal twigs of the external pudic. 
The veins of the intestine accompany the arteries, and are 
equally distributed. The posterior mesenteric vein is formed 
by similar divisions to those coming off from the posterior 
mesenteric artery, and then the main trunk extends forwards 
and enters the porta, near the termination of the splenic. At 
this spot the veins from the small intestine, as well as from the 
caecum and double flexures of the colon, also contribute to 
form the large portal trunk. 
The nerves of the intestines are derived from the solar plexus, 
and they are found in association with the arteries. The duo¬ 
denum also receives branches from the par vagum nerves, and the 
rectum and anus are supplied also by divisions of the two last 
sacral pairs. 
The lacteal and lymphatic vessels of the intestine are 
anatomically alike, and even physiologically they admit of 
* This artery sometimes, erroneously, goes by the name of its terminating 
branch—the artery of the bulb. 
