NUTRITION PROPER. 



321 



backbone, and by the other to the whole length of the 

 intestine, following all its complex windings. This is 

 called the mesentery (Fig. 205). From this arrangement 



Fig. 205. — Small intestines attached to the mesentery. 



it follows that the intestines are nowhere more than six 

 inches away from the great vessels lying along the 

 backbone. 



Peritonceum. — It may seem paradoxical, but is never- 

 theless in some sense true, that the intestines, and in- 

 deed all the abdominal viscera, are outside the abdomi- 

 nal cavity. The whole abdominal cavity (vc, Fig. 206) 

 is lined with smooth, shining, serous membrane called 

 the peritonceum (per). This, on reaching the backbone, 

 is reflected forward as a double membrane, the mesen- 

 tery, and then over the intestine as its investing coat. 

 If this serous membrane could be dissected off com- 

 pletely it would form a complete sac without opening. 



