Digestion — The Mouth 105 



tiallj' or wholly performed for the animal in hay-cutters 

 and grain mills. However this may be accomplished, 

 it is an essential operation for two reasons, (1) it puts 

 the food in condition to be swallowed, and (2) fits it 

 for the prompt and efficient action of the several diges- 

 tive fluids. Dr}' whole hay or kernels of grain could 

 hardly be forced down the tube leading to the animal's 

 stomach. It is necessary for these materials to be 

 broken down and moistened in order that they may be 

 swallowed. Even if they could be conveyed to the 

 stomach in their natural condition the process of ren- 

 dering their constituents soluble would proceed very 

 slowly. Common experience teaches us how much 

 more quickly finely powdered sugar or salt will dis- 

 solve than the large crystals or lumps. The more 

 finely any solid is ground, the larger is the surface ex- 

 posed to the attack of the dissolving liquid, and this is 

 as true of foods as of sugar or salt. 



Prompt and rapid solution of food is essential, be- 

 cause if it is too long delayed, uncomfortable and in- 

 jurious fermentations are likely to set in, and because 

 of imperfect digestion, the final nutritive effect of the 

 ration may be diminished. For these reasons, animals 

 with diseased teeth, or those that have lost teeth, 

 make poor use of their food, and require an unneces- 

 sary amount to keep them in condition. These condi- 

 tions may often be a cause, especially with horses, of 

 disappointing results from an ordinarily sufficient ration. 



The teeth of our domestic animals differ somewhat 

 in number and arrangement. Authorities state the 

 following to be the usual number: 



