SUPERIOR MESENTERIC. 501 



cceliac axis, and is remarkable for the extreme tortuosity of its course. It 

 passes horizontally to the left side behind the upper border of the pancreas, 

 accompanied by the splenic vein, which lies below it; and on arriving near the 

 spleen, divides into branches, some of which enter the hilum of that organ to 

 be distributed to its structure, whilst others are distributed to the great end of 

 the stomach. 



The branches of this vessel are 



Pancreaticae parvse. Gastric (vasa brevia). 



Pancreatica magna. Gastro-epiploica sinistra. 



The pancreatic are numerous small branches derived from the splenic as it 

 runs behind the upper border of the pancreas, supplying its middle and left 

 parts. One of these, larger than the rest, is given off from the splenic near 

 the left extremity of the pancreas ; it runs from left to right near the posterior 

 surface of the gland, following the course of the pancreatic duct, and is called 

 the pancreatica magna. These vessels anastomose with the pancreatic branches 

 of the pancreatico-duodenal arteries. 



The gastric (vasa brevia) consist of from five to seven small branches, which 

 arise either from the termination of the splenic artery, or from its terminal 

 branches; and passing from left to right, between the layers of the gastro- 

 splenic omentum, are distributed to the great curvature of the stomach; anas- 

 tomosing with branches of the gastric and gastro-epiploica sinistra arteries. 



The gastro-epiploica sinistra, the largest 'branch of the splenic, runs from left 

 to right along the great curvature of the stomach, between the layers of the 

 great omentum; and anastomoses with the gastro-epiploica dextra. In its course 

 it distributes several branches to the stomach, which ascend upon both surfaces: 

 others descend to supply the omentum. 



SUPEEIOR MESENTERIC ARTERY. (Fig. 292.) 



In order to expose this vessel, raise the great omentum and transverse colon, draw down the 

 small intestines, and cut through the peritoneum, where the transverse mesocolon and mesen- 

 tery join ; the artery will then be exposed, just as it issues from beneath the lower border of the 

 pancreas. 



The Superior Mesenteric Artery supplies the whole length of the small 

 intestine, except the first part of the duodenum ; it also supplies the cascum, 

 ascending and transverse colon ; it is a vessel of large size, arising from the 

 fore part of the aorta, about a quarter of an inch below the cceliac axis ; being 

 covered, at its origin, by the splenic vein and pancreas. It passes forwards, 

 between the pancreas and transverse portion of the duodenum, crosses in front 

 of this portion of the intestine, and descends between the layers of the mesen- 

 tery to the right iliac fossa, where it terminates, considerably diminished in 

 size. In its course it forms an arch, the convexity of which is directed for 

 wards and downwards to the left side, the concavity backwards and upwards to 

 the right. It is accompanied by the superior mesenteric vein, and is surrounded 

 by the superior mesenteric plexus of nerves. Its branches are the 



Inferior pancreatico-duodenal. Ileo-colic. 



Vasa intestini tenuis. Colica dextra. 



Colica media. 



The inferior pancreatico-duodenal is giyen off from the superior mesenteric 

 behind the pancreas, and is distributed to the head of the pancreas, and the 

 transverse and descending portions of the duodenum ; anastomosing with the 

 pancreatico-duodenal artery. 



The vasa intestini tenuis arise from the convex side of the superior mesenteric 

 artery. They are usually from twelve to fifteen in number, and are distributed 

 to the jejunum and ileum. They run parallel with one another between the 

 layers of the mesentery ; each vessel dividing into two branches, which unite 



