60 NUTRITIONAL PHYSIOLOGY 



gall-bladder when it is full may send a considerable amount 

 of bile at one time into the intestine. The relation of the 

 gall-bladder to the liver is like that of the urinary bladder 

 to the kidneys, at least to the extent that its existence 

 makes possible a continuous production of the secretion 

 with an intermittent emptying. It has been shown, how- 

 ever, that the bile is concentrated and otherwise modified 



Fig. 11. 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 unoc- 

 cupied space shown does not really exist, for successive portions of 

 the alimentary canal together with other organs completely fill the 

 cavity. 



during its stay in the gall-bladder. The urine does not 

 change its character distinctly while it is in storage. 



When the abdominal wall of an animal is cut through 

 and laid back from the organs within, one's first impression 

 is that the viscera are lying unattached in the cavity. 

 They are, in fact, not adherent to the ventral or lateral 

 portions of the wall. But if we take a loop of the_small 

 intestine at random and attempt to lift it from its resting- 

 place, we find it attached to the middle of the back by a 

 tough, transparent membrane, the mesentery. In the 



