180 ANIMAL PHYSIOLOGY. [LESSON 51. 



a canal is formed which conducts to the third stomach, the omasum, 

 or many plies (d). 



LESSON LI. 



NUTKITION IN MAMMALIA, CONTINUED. 



783. This stomach is of much greater dimensions than the second, 

 and much longer than wide ; its interior consists of a vast number 

 of folds of a membrane, hence the word many plies, or folds, whereof 

 every alternate fold is large and deep, and the intermediate one short 

 and shallow. The food gets impacted closely within these folds, and, 

 from its appearance, no less than the quantity of moisture found always 

 in the membranous folds of this stomach, its function appears to be 

 to press the food, and absorb from it all extraneous moisture. The 

 effect of these folds is like that of a series of damp towels, and it is 

 quite remarkable how compact and comparatively dry the food be- 

 comes in the omasum. In due time it passes through an aperture of 

 communication into the abomasum, or reed, the fourth and last sto- 

 mach (e). 



784. Examined by the microscope, this is the only organ pos- 

 sessing a mucous membrane organized to secrete gastric juice and 

 mucus, and digestion of the food in this stomach appears to proceed 

 precisely on the same plan as in those animals possessing only one 

 stomach. These animals, therefore, in common with insects, possess 

 really but one digestive sac, all the others being auxiliary, and en- 

 dowed with functions extraneous to that of true digestion, but neces- 

 sary and essential, from the unmanageable nature of their food. The 

 duodenum is seen at/". 



785. In the Camels and Dromedaries, the second stomach be- 

 comes of great importance, as its cells are employed as a reservoir to 

 contain large quantities of water to supply its daily need when trav- 

 ersing the dreary and parched deserts, where no water can be found. 

 The surface of these cells (in them) is covered with a layer of muscu- 

 lar fibres, and the animal possesses the power of opening these aper- 

 tures, to admit a small supply of water only to escape, and closing 

 them again, as soon as its immediate want is supplied. So great is 

 their thrift and economy in this respect, that Camels have frequently 

 been known to travel for thirty days without water. 



786. The length of the intestinal canal is always great in vege- 



