324 The Intestine 



column in coils contained within the mesentery, though the duodenum, 

 which lies at the root of the transverse mcso-colon, has no mesentery. 

 The ileum is recognised by the comparative thinness of its wall, for it 

 does not contain valvulas conniventes, which abound in the jejunum to 

 thicken its mucous coat and increase its physiological activity. There 

 is no definite limit between jejunum and ileum, but, for convenience, 

 the jejunum is considered as making about two-fifths of the entire 

 length of small bowel (jejunum, empty ; ileum, * tAe ti/, twisted). 



The duodenum is 10 in. long, and takes a horse-shoe bend 

 around the head of pancreas. 



The first part ascends from the pylorus to the neck of gall-bladder, 

 and is 2 in. long ; like the pyloric end of stomach, it is covered 

 front and back by peritoneum, and is comparatively movable. In 

 front of it are the liver and neck of gall-bladder ; behind it are the 

 vena portae, and the hepatic artery and duct. Below it is the head 

 of the pancreas. 



The second part is 3 in. long, and descends on the anterior 

 surface of the right kidney. In front of it is the ascending colon. 

 To the left is the head of the pancreas, the pancreatico-duodenal artery 

 lying in the crevice between them in front, and the common bile-duct 

 behind. This part is firmly fixed. 



The third part measures 5 in., and passes transversely across the 

 spine at the level of the second lumbar vertebra to end in the jejunum. 

 Behind it are the aorta, vena cava, thoracic duct, and crura of dia- 

 phragm. In front the superior mesenteric vessels descend to enter the 

 mesentery ; they come out from below the pancreas, which viscus lies 

 along the upper border of the third part of the duodenum. 



On account of the nearness of the gall-bladder, the duodenum is 

 usually stained by bile, and by this, when the 20 ft. of small in- 

 testines are removed at a post-mortem examination, the upper end 

 can be recognised at a glance. 



Like the rectum, the first part of the duodenum is entirely sur- 

 rounded by peritoneum, the second piece being covered only in front, 

 and the third part being destitute of a serous coat. 



The _;>/////; has a thick mucous coat, owing to the presence of the 

 valvulcE conniventes. The ileum is thin-walled (on account of the 

 comparative absence of the valvular), and is coiled chiefly in the right 

 iliac fossa, where it is about to end in the ciecum. 



Peyer's patches are oval collections of solitary glands in the ileum, 

 arranged along the aspect which is opposite to the attachment of the 

 mesentery. 



On account of the presence of the ileum in the right iliac fossa, the 

 physician gently presses his hand over that region to detect tender- 

 ness, and the gurgling of fluid, in enteric fever. When inflammation 

 extends to ulceration, fatal collapse and bloody stools may follow 

 the implication of a branch of artery, or perforation of the bowel may 



