46 THE SMALL INTESTINES. 



very movable. This last piece, notwithstanding its exterior 

 uniformity, is considered as forming two parts. The upper- 

 most two-fifths form one part, which is called Jejunum ; and 

 the remainder is . called Ileum. The Great Intestine com- 

 mences in the lower part of the right side of the abdomen, and 

 after proceeding up that side, crosses over to the left, along 

 which it descends to the lower part again, when by a peculiar 

 flexure it proceeds to the centre of the posterior margin of the 

 pelvis, from which it passes down to the anus. A short portion 

 of this intestine, which is below its junction with the ileum, is 

 called Cfficum ; the part which proceeds from this, round the 

 abdomen, is called Colon ; and the portion which is in the 

 pelvis is called Rectum. 



Of the Small Intestines. 



Previous to the description of the small intestines, it is neces- 

 sary to observe, that the Mesocolon, or process of the peritoneum 

 connected to the transverse portion of the colon, forms a kind of 

 movable and incomplete septum, which divides the abdomen 

 into an upper and lower apartment. Above this septum are 

 the stomach, the commencement of the duodenum, the liver, 

 and the spleen ; below it, that portion of the small intes- 

 tine which is called jejunum and ileum, makes its appearance 

 The portion of the intestine which passes from the stomach to 

 the jejunum, and is called Duodenum, is so much involved by 

 the mesocolon, that the greatest part of it cannot be seen without 

 dissecting the mesocolon from its connection with the back of 

 the abdomen. For the duodenum proceeds backwards from 

 the pylorus, and passing down behind the peritoneum, enters 

 a vacant space between the two lamina of the mesocolon ; it 

 proceeds for some distance in this space, and then emerges on 

 the lower side of the mesocolon. Here the duodenum termi- 

 nates, and the small intestine then is invested by the peritoneum 

 in such a manner as to form the mesentery, which continues 

 with it throughout its whole course to the great intestine. This 

 portion of the intestine although very uniform in its exterior 

 appearance, as has been observed before, is divided into Jeju- 



