156 



Physiology. 



INTESTINE 



ABDOMINAL CAVITY 



this enters the larger intestine. The intestine is held 

 in place by the mesentery, a thin fold of transparent 



membrane folded closely 

 around it, and supported 

 from the back wall of 

 the abdominal cavity. 

 Between the two layers 

 of the mesentery are the 

 branches of the artery 

 supplying the walls of 

 the intestines, and the 

 veins that convey the ab- 

 sorbed food from the 

 intestine to the liver. 



Fig. 66. Cross-section of Abdomen. 



The Mouth. The 



pupil should carefully examine his own mouth by means 

 of a mirror. We are apt to think of the mouth as a cavity 

 of considerable size, as indeed it is when fully opened; 

 but we are not so likely to think how completely the cavity 

 disappears when the mouth is closed. If one notes the 

 sensations from the mouth when it is closed, he will per- 

 ceive that the tongue almost entirely fills the space, touch- 

 ing the roof of the mouth, and the teeth in front and at 

 the sides. 



The Tongue. The tongue consists chiefly of muscles, 

 running in different directions, thus giving it a variety of 

 motions. The tongue is the chief organ of taste, and is 

 therefore (with the sense of smell) the gate-keeper of the 

 digestive tube. The tongue has also a keen sense of 

 touch, and so is useful in detecting and removing any 

 food particles that may remain on the teeth after eating. 

 During mastication the tongue, with the lips and cheeks, 



