232 ANATOMY OF THE ABDOMEN. 



want of food does not dissipate immediately the strength ; 

 but the body can for some space support itself, and desire, 

 though felt before, be actually forgotten ; thus the inani- 

 tion of a hunter long employed in reaching a distant 

 cover is no bar to his after-exertions in the chase. The 

 moment he hears the well-known sound, he receives a 

 temporary supply of nervous energy ; which acting on his 

 irritability, produces renewed muscular exertions : but the 

 chase over, a double prostration is the consequence ; for the 

 nervous impulse being expended, it often happens that the 

 stomach is sympathetic with the general frame, and the 

 horse becomes " too tired to eat." 



Thirst differs from hunger principally by its impelling us 

 to receive liquids instead of solids. The instinct, which is 

 independent of reason and superior to the will, calls for 

 fluids often not required for repair : it is true perspiration 

 will produce thirst ; and that diuretics will do the same, 

 but these are artiflcial not natural causes. Drink is also 

 instinctively sought for no cause save that of fickle appetite, 

 induced by long indulgence, which cannot be reckoned 

 among life's necessities. Stimulated, therefore, by the 

 sensations of hunger and thirst, animals seek for matters to 

 which they are instinctively directed by their senses of smell 

 and taste. 



The mastication, insalivation, and deglutition of the food 

 have already been noticed. To the saliva, however, by no 

 means is usually given its full merit as an important agent 

 in the digestive process. When we consider the quantity 

 secreted, the chemical nature of the fluid, its remarkable 

 affinity for oxygen, and that a complete mastication inva- 

 riably produces a direct change in the qualities of the food, 

 it would be most unphilosophical to regard it as a mere 

 diluent. The masticated aliments received into the stomach 

 become subjected to the further action of the gastric fluid, 

 the produce of the secreting surface of the villous division 

 of the stomach. The true gastric juice is possessed of a 

 solvent power, which is shown in a remarkable manner by 

 the food being dissolved by its action. 



The ordinary process is after this fashion with the horse. 

 The masticated vegetable matter is first deposited in the 

 cuticular cavity of the stomach ; whence it is propelled for- 



