178 HUMAN PHYSIOLOGY 



large and small applied to the intestine have reference to 

 the diameter, not the length. 



The colon ascends on the right side of the body until 

 it is overhung by the liver, then crosses to the left just 

 below the stomach, and finally comes down on the left 

 side for a certain distance. Turning toward the back 

 it curves around to the mid-line, forming a segment 

 known as the sigmoid flexure. From this the rectum 



FIG. 39. This is an entirely schematic section across the human body 

 in the mid-abdominal region: S indicates the spine; K, the kidneys; P 

 is the peritoneum, the lining of the abdominal wall. It is prolonged 

 from the back to form the mesentery (M), which extends to and around 

 the loop of intestine (/) . The large unoccupied space shown does not 

 really exist, for successive portions of the alimentary canal together 

 with other organs completely fill the cavity. 



descends in front of the lower bones of the spine and 

 reaches the anus. A rough diagram of the colon re- 

 sembles a question mark. 



When the abdominal cavity is opened the first im- 

 pression is that the intestine lies loosely within like a 

 coil of rope. But if a loop is chosen at random and 

 lifted from its place a clear, glistening sheet of tissue is 

 found attached to it. This is the mesentery and it can 

 be followed to an attachment to the dorsal body wall. 



