THE POSTEEWE AOETA. 529 



the substance of the mesentery, and joins the first artery belonging to the left 

 fasciculus of the great meseiiteric, after furnishing some twigs to the 

 pancreas, and numerous branches to the duodenum. 



In terminating the description of the right gastro-omental artery, it may 

 be remarked that the stomach, owing to the anastomoses uniting that vessel 

 with the artery of the left side, is suspended, as it were, in a vertical arterial 

 circle, formed by the splenic and left gastro-omental arteries on the one 

 part, and the hepatic and right gastro-omental arteries on the other a circle 

 whose concavity sends out on the stomach a great number of divisions, 

 which communicate with the arterial ramuscules proper to that viscus. 



3. Great Mesenteric Artery. (Fig. 271.) 



The great mesenteric artery, which almost entirely supplies the intestinal 

 mass with blood, is as remarkable for its volume as for its complicated 

 distribution. This complexity, together with that of the intestine itself, 

 gives rise to some difficulty in the study of this vessel ; but this may be 

 averted by adopting the mode of description, as simple as it is methodical, 

 resorted to in his lectures by M. Lecoq. 



The great mesenteric arises at a right angle from the abdominal aorta, 

 at the renal arteries, and at 2 or 2^ inches behind the cceliac trunk, from 

 which it is separated by the pancreas ; it is directed immediately downwards, 

 enlaced by the anastomosing nervous branches of the solar plexus, and divides, 

 after a course of from 1 to 1 J l inches, into three fasciculi of branches, wliich 

 are distinguished as left, right, and anterior. The left fasciculus goes to the 

 small intestine ; the right is distributed to the terminal portion of that intes- 

 tine, to the caecum, and to the first portion of the loop or flexure formed by 

 the large colon ; the anterior is carried to the second portion of that flexure, 

 and to the origin of the small colon. The order in which these three fasci- 

 culi have been indicated will also be that followed in their description ; it 

 has, as will be observed, the advantage of recalling to the memory the 

 regular succession of the various parts of the intestine, and consequently 

 the passage of the food in this important portion of the digestive canal. 



A. ARTERIES OF THE LEFT FASCICULUS (Fig. 271, 2). These arteries 

 number from fifteen to twenty, and are named the ARTERIES OF THE SMALL 

 INTESTINE (vasa intestini tennis),, because of their destination. All spring at 

 once from the great meseiiteric artery, either separately, or several in 

 common, and pass between the two layers of the mesentery to gain the 

 intestine. Before reaching the small curvature of that viscus, each divides 

 into two branches, which go to meet corresponding branches from the 

 neighbouring arteries, and to anastomose with them by inosculation ; from 

 this arrangement results a series of uninterrupted arterial arches, whose 

 convexity is downwards, and which exist for the whole length of the intestine 

 opposite, and in proximity to, its concavity. From the convexity of these 

 arches emanate a multitude of branches that arrive at the inner curvature 

 of the intestine, and whose divisions pass to each of the faces of that viscus to 

 rejoin and anastomose on its great curvature. These divisions are situated be- 

 neath the peritoneum or in the muscular layer, and send the majority of their 

 ramuscules to the mucous tunic, which is therefore distinguished by its great 

 vascularity : a feature common to all the hollow organs in the abdominal cavity. 



1 This trunk of the great mesenteric is usually, in the old horses killed for dissec- 

 tion, the seat of a more or less voluminous aneurism, which sometimes extends to the 

 arterial tube placed at the origin of the branches of the right fasciculus, and it is not 

 unfrequentiy met with in one or ihe other section of the great mesenteric artery. 



