82 THE HUMAN BODY. 



marked enlargements. The coscum is its upper portion, of a, 

 larger calibre than the ileum, and separated from it by the 

 ileo-c&cal valve, a fold of the internal membranes designed to 

 prevent the reflux of fluids. It opens into the ileum, not at 

 its extremity, but by a lateral orifice; below this orifice, it 

 forms a sort of ampulla, terminated by the appendix vermi- 

 formis. The ccecum is followed by the colon, from which it 

 is separated only by an artificial division. It is the largest 

 and longest portion of the large intestine; it forms a curve 

 called the arch of the colon, and is divided into the ascending, 

 transverse, and descending colon, to which succeeds the rectum, 

 the extremity of the intestinal canal. 



The total length of the intestine is about nine yards. It 

 occupies a large portion of the abdomen, in which it is folded 

 in numerous convolutions. 



The peritoneum (peri, around; teinein, to stretch) enve- 

 lops the intestinal canal, attaches it to the vertebral column 

 by a double membranous fold, called the mesentery, and par- 

 tially covers it by a floating fold or epiploon. Imagine a 

 membrane doubled back so as to form a long broad fold. 

 At the bottom of and within this fold lies the intestine, which 

 we may suppose to be stretched in a straight line. The 

 membrane adheres closely to three-quarters of the surface 

 of the intestine, and then folds back on itself. The two 

 leaves of this peritoneal covering are united by cellular 

 tissue, which permits their separation by distension of the 

 intestines. If now we pucker the fold at its root, the 

 border which contains the intestine will form numerous 

 sinuosities, and this is really the arrangement of the intes- 

 tinal convolutions. In the region of the colon, the fold 

 formed by the peritoneum is very much broader, the in- 

 testine lies in the middle of its breadth, and the rest falls 

 like a veil in front of the intestinal mass, and rises to the 

 stomach, which it partially covers as well as the liver and 

 spleen. This moving veil is the epiploon (epi, upon; pleo, I 

 float). That part of the fold behind the intestine fastens it- 

 self to the front of the vertebral column, and takes the name 

 of mesentery (niesos, middle, and mteron, intestine). 



The mucous membrane. This membrane is to the cavities 



