The hepatic artery passes forwards and to the right under the lobulus Spigelii to the neck of the gall-bladder. In this part of its course it gives a few twigs to the gastro-hepatic omen tum and the inferior surface of the liver ; when it reaches the pylorus, it gives two considerable branches called the pyloric and the right gastro epiploic. The pyloric passes from right to left along the lesser arch of the stomach, where it meets the coronary with which it anastomoses, sending several branches over the anterior and posterior surfaces of the stomach to anastomose with the right gastro-epiploic artery. The right gastro-epiploic artery, much larger than the pyloric, arises after that vessel ; it passes down wards behind the pylorus, and arrives at the greater arch of the stomach, along which it courses from right to left and anastomoses with the left gastro-epiploic. While passing behind the pylorus, it gives several branches to the pancreas and duodenum, one of which, somewhat larger than the rest, called pancreatico duodenalis, lies concealed between the duo denum and head of the pancreas, and anasto moses with the branches which the pancreas receives from the superior mesenteric. As the gastro-epiploic artery courses along the greater arch of the stomach, it gives off numerous branches, some of which ascend on the anterior and posterior surfaces of the stomach, and anastomose with the coronary and pyloric ; others descend in the anterior layer of the great omentum : some branches from these ascend in the posterior layer of this fold of membrane until they reach the arch of the colon, where they anastomose with the colic branches of the superior mesenteric.
After having given off these branches, the hepatic artery ascends towards the right within the capsule of Glisson, in front of the vena porta, and to the left of the ductus communis choledochus. Having reached the transverse fissure of the liver, it divides into the right and left hepatic arteries which enter the liver by divisions corresponding to those of the vena porta, the right branch having previously given off the cystic artery, which arises opposite the junction of the cystic and common hepatic ducts, attaches itself to the neck of the gall bladder, and soon divides into two branches, one of which ramifies over the inferior surface of that reservoir, while the other sinks between the liver and the gall-bladder. For further particulars relating to the hepatic artery vide LIVER.
The splenic is the largest of the three branches of the coeliac. Immediately after its origin it passes with numerous contortions to the left, behind the stomach and along the superior border of the pancreas to the fissure of the spleen. In this course if gives off pancreatic. branches (pancreatic& magnet et parvx), which anastomose with the pancreatic branches of the right gastro-epiploic. It gives a large branch, the left gastro-epiploic, which some times arises from one of the branches in which the splenic terminates. This branch passes onwards to the left until it reaches the greater arch of the stomach, along which it descends, passes to the right until it meets the right gastro-epiploic, with which it anastomoses. In its course it gives off, like the right gastro epiploic, superior branches, which pass over the anterior and posterior surfaces of the sto mach to anastomose with the branches of the coronary and inferior branches which descend in the great omentum, where they have a simi lar distribution with the descending branches of the right gastro-epiploic : near the fissure of the spleen, the splenic artery divides into five or six branches, which anastomose by arches, and enter the substance of that organ. Before
entering the substance of the spleen these branches give off large vessels, called vasa brevia, which bend to the right, and are dis tributed to the great extremity of the stomach, spreading over its anterior and posterior sur faces, where they anastomose with branches of the coronary and right gastro-epiploic.
The superior mesenteric artery, often larger than the coeliac, arises from the aorta imme diately after the coeliac ; sometimes from a trunk common to both vessels, as in the tortoise. This artery is at first concealed by the pancreas, it descends perpendicularly behind that gland and crossing the termination of the duodenum arrives at the root of the mesentery, between the two layers of which it descends. In the middle of this fold of the peritoneum it forms a considerable curve, the convexity of which is to the left, and directs its course towards the ter mination of the small intestine in the right iliac region, forming near its termination a second curve, the concavity of which is to the left. Near its origin this artery gives some branches to the duodenum and pancreas, by means of which it anastomoses with the branches of the hepatic and splenic sent to these organs : in the mesentery it sends off from its left side the arteries of the small intestines, and from its right the arteries which it supplies to the great intestine.
Arteries of the small intestines.—These .arise from the left side of the superior mesenteric, varying in number from fifteen to twenty ; the superior are longer and larger, those which succeed them appear to diminish progressively in length and size, they all advance between the two layers of the mesentery to the concave side of the intestine ; at a certain distance from their origin they divide into secondary branches which diverge from each other at acute angles ; these secondary branches subdivide into still smaller branches, which, diverging in a similar manner, form arches of anastomoses with cor responding branches of the adjoining arteries ; the .convexities of these arches are all turned towards the intestine, and from them numerous branches arise, which, by dividing and anasto mosing like the larger trunks, form a second series of smaller arches ; other branches arising from the convexities of these arches divide and anastomose to form still smaller and more numerous arches ; thus we have three, some times four, and occasionally five series of arches, formed by the subdivisions of these arteries before they reach the intestine, and presenting in the mesentery a network with large meshes. From the convexities of the extreme arches which form the outer border of this network, thousands of small arteries pass in a straight direction to the tube of the intes tine ; these form two series, an anterior and a posterior, which apply themselves to the oppo site surfaces of the intestine, and anastomose with each other on its convex border. The detailed description of their further distribution will come under consideration in the article INTESTINAL CANAL.