THE JEJUNO-ILEUM. 1649 



Blood-Vessels. Arteries. The duodenum, like the stomach, is attached to 

 that part of the original mesentery through which the branches of the cceliac axis 

 run. The stomach is supplied chiefly by the gastric and the splenic arteries, the 

 duodenum by the hepatic with the help of a recurrent branch from the superior 

 mesenteric. The hepatic artery gives off the pyloric, which sends some insignificant 

 twigs to the beginning of the duodenum, and the gastro-duodenal, 

 which runs on the left of the first part and sends off the superior FIG. 1402. 

 pancreatico-duodenal, which passes downward and to the left in the 

 concavity of the duodenum between it and the pancreas, lying 

 rather on the front of the duodenum, of which it is the chief artery. 

 The superior is met by the inferior pancreatico-duodenal artery, 

 which arises from the right side of the superior mesenteric and 

 descends along the right of the fourth part of the duodenum. The 

 superior mesenteric distributes one or two small twigs to the very 

 end of the duodenum. 



Veins. The pyloric vein, larger than the artery of the same Abnormal form 

 name, in conjunction with the superior pancreatico-duodenal, and course of duo- 



. ' , r i 1 1 ITI denum. (Schieffer- 



drains the greater part of the duodenum. 1 hey may open in com- decker.) 



mon or separately into the portal vein, and are in direct connection 



with the inferior pancreatico-duodenal, which opens into the superior mesenteric 



vein. 



The lymphatics pass to the pre-aortic lymph-nodes. 



The nerves of the duodenum, as are those supplying other parts of the small 

 intestine, are from the solar plexus. 



Variations. As already shown (page 1644), much variation exists in the shape of the 

 duodenum ; moreover, very extraordinary duodena sometimes occur. It is probable that these 

 are generally due to an over-long duodenum, which, after having completed the usual course, 

 describes one or more additional curves before reaching the duodeno-jejunal flexure. We 

 have seen a case in which the end of the V almost touched the pylorus and then, mounting still 

 higher, described a loop to the left behind the peritoneum. This occurred in a man with the 

 sigmoid flexure and rectum on the right. These cases usually are associated with other errors 

 of intestinal or peritoneal development. In the remarkable case of Schiefferdecker 1 (Fig. 1402) 

 there was a mesenterium commune. 



THE JEJUNO-ILEUM. 



The jejuno-ileum includes the remainder of the small intestine, which, disposed 

 in folds attached on one side to the mesentery, extends from the duodeno-jejunal fold 

 to the caecum, its length being, therefore, approximately 6.75 m. (nearly 22 ft.), of 

 which the first two-fifths are conventionally credited to the jejunum and the remain- 

 ing three-fifths to the ileum. It is a cylindrical tube continually decreasing in size. 

 The diameters are variously stated, Testut giving the mean diameter of the upper 

 part as from 2530 mm. and that of the lower as from 2025 mm. These latter figures 

 our own measurements confirm, since on thirty-seven inflated specimens of the lower 

 end the average diameter was 24 mm., the extremes being 17 and 37 mm. Chaput 

 and Lenoble* assert that the inferior circumference is reduced internally to 32 mm. 

 (on inflated specimens to 50 mm. ).by a valve near the caecum. This valve, which 

 we have found in about one-third of the cases, is remarkable in being always situ- 

 ated on the posterior aspect of the gut, generally at a sharp bend ; it often contains 

 a small artery, and is probably formed by the folding in of the muscular coat. Its 

 position is frequently near the point at which the ileum begins to lie against the 

 wall of the caecum, but it may be 2.5 cm. or more higher. The valve is sometimes 

 double, and varies in height from 2 mm. to i cm. We have not found, however, 

 that this fold is necessarily the narrowest point of this part of the gut. A piece of 

 the intestine from the upper part of the jejunum weighs more than one of equal area 

 from the lower part of the ileum, owing to the greater thickness of the walls of the 

 former and to the greater development of the valves in that part. The structure 

 of this part of the small intestine has already been described (page 1634). 



1 Arch, fur Anat. und Entwicklng., 1887. 



2 Bull. Soc. Anat. de Paris, 1894. 



104 



