FUNCTION AND STRUCTURE 



mentary canal. In some of the higher animals this is a 

 very complex organ. In the cow, one of the cud-chewing 

 mammals or ruminants, it consists of several distinct por- 

 tions, which differ among themselves very much (Fig. 30). 

 First, there is the mouth, or opening for the entrance of 

 the food. The mouth is sup- 

 plied with teeth for biting 

 off and chewing the food, 

 with a tongue for manipu- 

 lating it, and with taste pa- 

 pillae situated on the tongue 

 and palate for determining 

 the desirability of the food. 

 Into the mouth a peculiar 

 fluid (the saliva) is poured 

 by certain glands, organs ac- 

 cessory to the alimentary 

 canal. The herbage bitten 

 off, mixed with saliva, and 

 rolled by the tongue into a 

 ball, passes back through a 

 narrow tube, the oesophagus, 

 and into a sac called the ru- 

 men, or paunch. Here it 

 lies until the cow ceases for 

 the while to take in food, 

 when it passes back again 

 through the oesophagus and 

 into the mouth for mastica- 

 tion. After being masticated it again passes downward 

 through the oesophagus, and enters this time another sac 

 called the reticulum, lying next to the rumen. From here 

 it passes into another sac-like portion of the alimentary 

 canal called the omasum, where it is strained through 

 numerous leaf-like folds which line the walls of this part 

 of the canal. From here the food passes into a fourth 



FIG. 30. Alimentary canal of the ox 

 (after COLIN and MILLER), a, rumen 

 (left hemsiphere) ; 6, rumen (right hem- 

 isphere) ; c, insertion of oesophagus ; d, 

 reticulum ;' e, omasum ; f, abomasum ; 

 g, duodenum ; h and i, jejunum and 

 ileum ; j, caecum ; k, colon, with its 

 various convolutions ; I, rectum. 



