STOMACH AND INTESTINE. 



341 



greater exactness, the three chief portions of 

 the duodenum may be described separately. 



The first portion is called the superior 

 transverse or hepatic. It is much the shorter 

 of the three, being scarcely two inches in 

 length. It lies solely in the right hypoclion- 

 drium ; and, near the neck of the gall-bladder, 

 terminates by bending downwards to merge 

 into the second portion. Like the stomach, 

 it is invested by peritoneum on both surfaces. 

 This membrane is derived from the gastric 

 omenta previously described; the extreme right 

 of the gastro-hepatic omentum being some- 

 times called the /ig'tiiieiifuw- hepatico-duodenale. 

 The latter fold of serous membrane also forms 

 the anterior boundary of the foramen of Wins- 

 low, or opening by which the general sac of the 

 serous membrane communicates with the bag 

 of the omentum ; and it contains the hepatic 

 duct and vessels. 



The above relations of this first portion of 

 the duodenum to the peritoneum confer upon 

 it a mobility which approaches that of the 

 stomach ; while its close proximity to the 

 gall-bladder explains that discoloration by bile 

 which is generally seen in the dead intestine, 

 as well as the adhesion and ulceration of its 

 parietes, which so frequently occur in the 

 course of disease of the liver or gall-bladder. 



The second, the descending or vertical por- 

 tion, which is rather less than three inches 

 long, passes downwards, and slightly inwards, 

 to the right side of the third lumbar vertebra. 

 Above it is the right lobe of the liver. In 

 front it is crossed by the right extremity of 

 the transverse colon. Behind it is the inner 

 border of the right kidney, together with a 

 variable extent of its anterior surface, and its 

 eniulgent vein. On its right side is the ter- 

 mination of the ascending colon. On its left 

 it is intimately connected^ with the head of 

 the pancreas. Every one of these anatomical 

 relations has more or less pathological im- 

 portance. 



The partial covering of peritoneum received 

 by this portion of the duodenum may be 

 traced, from the front of the great omentum, 

 to the anterior surface of the intestine ; and 

 around its external or right side, to the wall 

 of the abdomen. Here it is fixed to the right 

 kidney, by an attachment that is sometimes 

 termed the ligamentum duodeni renalc. The 

 posterior and left surfaces of the intestine, 

 which are devoid of this serous membrane, 

 are connected with the neighbouring organs 

 by a loose areolar tissue, that concedes to the 

 tube a considerable degree of distention and 

 movement. 



The third or inferior transverse portion is 

 about five inches in length. In its course 

 across the spine it lies upon the structures 

 already named. Above it is the lower border 

 of the pancreas. In front of it is the pos- 

 terior or attached border of the transverse 

 meso-colon, the superior lamina of which 

 covers it above, the inferior below, so as to 

 leave an uncovered space along the line of 

 their bifurcation. Anteriorly to this double 

 process of peritoneum, is the large and 



moveable transverse colon which it serves to 

 attach. And close to the commencement of 

 the mesentery the end of the duodenum is 

 crossed by the superior mesenteric artery and 

 nerves. 



Owing to this very partial covering of 

 serous membrane, the inferior transverse 

 portion of the duodenum is even less mobile 

 and dilatable than either of the preceding. 

 And, from the position of the pancreas above 

 the intestine, distention of the latter chiefly 

 affects its inferior surface, which may thus 

 be rendered so convex and bulging as to 

 cover the aorta to within a very short dis- 

 tance of its bifurcation. 



Hence the duodenum becomes most fixed 

 in the second and third divisions of its course. 

 Its fixation and curvature may together assist 

 in delaying the passage of its contents, and in 

 facilitating that admixture of the biliary and 

 pancreatic secretions to which its attachment 

 perhaps chiefly refers. Its use as a means 

 of fixing the stomach has already been suffi- 

 ciently alluded to. Its comparative immunity 

 from hernia is explained by its site. 



The jejunum and ileitm. Below the duo- 

 denum, the small intestine is loosely attached 

 to the posterior wall of the belly by means 

 of a double lamina of peritoneum which is 

 called the mesentery (/.te'iros middle, tvrepov 

 intestine.) Behind, this fold is fixed to the 

 cellular tissue that covers the aorta and vena 

 cava, by a line of attachment which is not 

 quite vertical, but descends from the end 

 of the duodenum to the commencement of 

 the ca2cum, passing very obliquely across the 

 spine from the left to the right side of the 

 lumbar vertebrae. In front, its two laminae 

 split to enclose the bowel, around which they 

 become continuous with each other. Its 

 antero-posterior depth between these spinal 

 and intestinal borders is about three or four 

 inches ; but tapers away suddenly at its com- 

 mencement and termination. We may, per- 

 haps, gain a better idea of the peculiar shape 

 of this process of peritoneum by imagining it 

 as a very obtuse triangle of some flexible 

 material. Such a triangle we may suppose 

 fixed to the spine by a truncated apex of 

 three inches in length. While its broad base, 

 which is about twenty feet long, is attached 

 to the intestine, where it is plaited so as to 

 occupy the least possible space. 



It is the extreme freedom of movement 

 which such a mode of attachment concedes 

 to the small intestine, that gives rise to the 

 convoluted appearance so characteristic of 

 this part of the tube. The exact figure of 

 these convolutions is probably never quite alike 

 at any two different times in the same indi- 

 vidual, being the conjoined result of the 

 muscular movements of the canal, the nature 

 and amount of its contents, the size of the 

 neighbouring viscera, and the state of the 

 abdominal parietes. The effect of dilatation 

 resembles that seen in some other parts of 

 the alimentary canal : namely, distention of 

 the tube always causes it to split up the 

 loosely connected laminse of peritoneum, and 



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