PREHENSION OF SOLIDS -AND LIQUIDS. 137 



are small compound follicles called the glands of Brunn ; 

 and throughout the whole of the intestine are simple, blind 

 follicles, called the follicles of Lieberktihn. These glandu- 

 lar organs secrete the intestinal juice. As the food passes 

 from the stomach into the intestine, it imbibes the bile and 

 pancreatic juice, which are poured into the duodenum, as 

 well as the intestinal juice. 



Between the mucous membrane of the small intestine 

 and the peritoneum are two layers of unstriped muscular 

 fibres ; by the progressive peristaltic action of which, the 

 food is passed slowly on toward the large intestine. The 

 alimentary principles, liquefied and prepared by digestion, 

 are gradually absorbed by the blood-vessels of the intestinal 

 mucous membrane, and by the lacteals. 



The indigestible residue of the food is passed by peris- 

 taltic action into the large intestine. This portion of the ali- 

 mentary canal is from four to six feet in length ; and, like the 

 small intestine, has a peritoneal, mucous, and muscular coat. 

 Under ordinary conditions the large intestine is not con- 

 cerned in digestion. It simply retains the residue of food, 

 with certain excrementitious substances, until its contents 

 are expelled by the act of defecation. 



Prehension of Solids and Liquids. 



The different modes of prehension form a very interest- 

 ing part of the physiology of digestion in the inferior ani- 

 mals; but in the human subject, the process is so simple 

 and well known that it demands nothing more than a pass- 

 ing mention. The mechanism of sucking in the infant and 

 of drinking is a little more complicated. In sucking, the lips 

 are closed around the nipple, the velum pendulum palati is 

 applied to the back of the tongue so as to close the buccal 

 cavity posteriorly, and the tongue, acting as a piston, pro- 

 duces a tendency to a vacuum in the mouth, by which the 

 liquids are drawn in with considerable force. This may be 

 done independently of the act of respiration, which is neces- 



