AORTA. 



195 



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 cceliac. 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 (pancreatictE magn<e et parva), 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 thecreliac ; 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. 



Colic arteries. The superior mesenteric 

 sends off three, sometimes only two, branches 

 from its concavity, called right colic arteries, dis- 

 tinguished as superior or colica media, middle or 

 colica dextra, and inferior or ileo-colic ; when 

 there are but two, the superior and middle form 

 but a single trunk; the inferior is generally 

 distinct. 



The right superior colic or colica media arises 

 a few inches distant from the origin of the supe- 

 rior mesenteric; it passes forwards between the 

 layers of the meso-colon towards the middle of 

 the transverse colon, and divides into a right 



o 2 



