SMALL INTESTINE. 6C7 



Vessels and Nerves. The arteries supplying the stomach are, the gastric, pyloric 

 and right gastro-epiploic branches of the hepatic, the left gastro-epiploic and vasa 

 brevia from the splenic. They supply the muscular coat, ramify in the submucous 

 coat, and are finally distributed to the mucous membrane. The veins accompany 

 the arteries, and terminate in the splenic and portal veins. The lymphatics are 

 numerous ; they consist of a superficial and deep set, which pass through the lym- 

 phatic glands found along the two curvatures of the organ. The nerves are, the 

 terminal branches of the right and left pneumogastric, the former being distributed 

 upon the back, and the latter upon the front part of the organ. Branches from 

 the sympathetic also supply the organ. 



THE SMALL INTESTINE. 



The Small Intestine is that part of the alimentary canal in which the chyme is 

 mixed with the bile, the pancreatic juice, and the secretions of the various glands 

 imbedded in the mucous membrane of the intestines, and where the separation of 

 the nutritive principles of the food, the chyle, is effected : this constitutes chyli- 

 fication. 



The small intestine is a convoluted tube, about twenty feet in length, which 

 gradually diminishes in size from its commencement to its termination. It is 

 contained in the central and lower parts of the abdominal and pelvic cavities, 

 surrounded above and at the sides by the large intestine ; in relation, in front, 

 with the great omentum and abdominal parietes ; and connected to the spine by 

 a fold of peritoneum, the mesentery. The small intestine is divisible into three 

 portions ; the duodenum, jejunum, and ileum. 



The duodenum has received its name from being about equal in length to the 

 breadth of twelve ringers (eight or ten inches.) It is the shortest, the widest, and 

 the most fixed part of the small intestine ; it has no mesentery, and is only partially 

 covered by the peritoneum. Its course presents a remarkable curve, somewhat 

 like a horseshoe in form ; the convexity being directed towards the right, and 

 the concavity to the left, embracing the head of the pancreas. Commencing at 

 the pylorus, it ascends obliquely upwards and backwards to the under surface of 

 the liver ; it then descends in front of the right kidney, and passes nearly trans- 

 versely across the front of the spine, terminating in the jejunum on the left side 

 of the second lumbar vertebra. Hence the duodenum has been divided into three 

 portions : ascending, descending, and transverse. 



The first or ascending portion, about two inches in length, is free, movable, 

 and nearly completely invested by the peritoneum. It is in relation, above and in 

 front, with the liver and neck of the gall-bladder ; behind, with the right border 

 of the lesser omentum, the hepatic artery and duct, and vena portee. This por- 

 tion of the intestine is usually found stained with bile, especially on its anterior 

 surface. 



The second or descending portion, about three inches in length, is firmly fixed 

 by the peritoneum and pancreas. It passes from the neck of the gall-bladder 

 vertically downwards, in front of the right kidney, as far as the third lumbar 

 vertebra. It is covered by peritoneum only on its anterior surface. It is in 

 relation, in front, with the right arch of the colon and mesocolon ; behind, with 

 the front of the right kidney ; at its inner side is the head of the pancreas, and the 

 common choledoch duct. The common bile and pancreatic ducts perforate the 

 inner side of this portion of the intestine obliquely, a little below its middle. 



The third or transverse portion, the longest and narrowest part of the duodenum, 

 passes across the front of the spine, ascending from the third to the second lumbar 

 vertebra, and terminating in the jejunum on the left side of this bone. In front, 

 it is covered by the descending layer of the transverse mesocolon, and crossed by 

 the superior mesenteric vessels ; behind, it rests upon the aorta, the vena cava, and 

 the crura of the Diaphragm ; above it is the lower border of the pancreas, the 

 superior mesenteric vessels passing forwards between the two. 



