THE DUODENUM. 47 



num and lleum : the jejunum being the upper portion, which 

 begins at the mesocolon ; and the ileum the lower portion, which 

 opens into the great intestine. 



Of the Duodenum. 



The length of this intestine is equal to the breadth of twelve 

 fingers, and hence its name. It is very different from the rest 

 of the small intestine, not only as respects its position and 

 investment by the peritoneum, but on account of its connexion 

 with the liver and pancreas, by means of their excretory ducts 

 which open into it. From this connexion with these glands, 

 probably, all the peculiarities of its position are to be deduced. 



When the stomach is in its natural situation, the pylorus is at 

 some distance from the back of the abdomen. The duodenum 

 proceeds backwards from this point, and passes near the neck 

 of the gall bladder, being here connected with the small oment- 

 um ; it then curves downwards, and descends before the right 

 kidney, sometimes as low as the lower part of it; then it curves 

 again and passes over to the left : after it has arrived at the left 

 side of the spine, at the second or third lumbar vertebra, it 

 projects forwards and downwards to form the jejunum. The 

 only portion of this intestine which is movable, is that which 

 is in sight as it proceeds immediately from the pylorus, being 

 about an inch and a half, or two inches in length. The remain- 

 der is connected to the back of the abdomen, and lies between 

 the two lamina of the mesocolon. In its progress it passes 

 before the aorta and the vena cava, but the principal branch of 

 the vena portarum is before it. 



The duodenum is larger in diameter than any other part of 

 the small intestines, and has a stronger muscular coat. Its 

 general situation admits of great dilatation, and it has been 

 called a second stomaeh, (ventriculus succenturiatus.) Its 

 internal coat is strictly villous in the anatomical sense of the 

 word ; and its folds, the valvulae conniventes, begin at a small 

 distance from the pylorus. The orifices of many mucous ducts 

 are to be seen on its surface. It is supposed that some of these 

 are the terminations of ducts from ths glands of Brunner, which 



