xi .] THE A L I MEN TARY S YSTEM. 433 



LESSON XL 



THE ALIMENTARY SYSTEM. 



1. THE ALIMENTARY SYSTEM of man has been in great 

 part described in the Sixth Lesson of " Elementary Phy- 

 siology," 13 22. Here, however, a certain amount of 

 recapitulation seems necessary for clearness. 



This system begins, as all know, at the mouth, which is 

 furnished with lips and a tongue, and which opens behind 

 into the swallow (or pharynx), which, by means of the gullet 

 (or oesophagus), leads down into the stomach, from which a 

 long and very tortuous canal (the intestine) continues onwards 

 to the termination of the alimentary tube or cavity. 



The alimentary tube, from the lips downwards, has 

 various fluids poured into it in different parts of its course, 

 and these fluids are secreted (i.e. extracted from the blood) 

 by certain organs termed glands. 



Thus spittle is poured into the mouth by " salivary 

 glands." " Gastric glands " supply their secretion, the gastric 

 juice, to the stomach. A second set of spittle glands, the 

 pancreas, pour the fluid they form into the intestine ; and 

 that vast organ, the liver, also pours into the alimentary canal 

 its special formation, the bile. As has been already said, 

 peculiar lymphatic vessels the lacteals collect nutritive 

 fluid from the alimentary canal and convey it into the blood. 



All the alimentary organs below the diaphragm namely the 

 stomach, intestines, liver, and pancreas are invested by a 

 fold of delicate serous membrane, which also lines the inner 

 wall of the whole abdominal cavity, thus forming a very large 

 sac, folded in an exceedingly complex manner and contain- 

 ing a serous fluid. This complex serous sac, by which the 

 viscera are attached (as in a sling) to the front wall of the 

 vertebral column, is called the peritoneum. 



2. The MOUTH of man has been described in 13 of the 



F F 



