314 PHILOSOPHY OF ZOOLOGY. 
ing it for the particular parts,—depositing it where want- 
ed,—and removing those portions which have become su- 
perfluous. 
CHAP. XII. 
DicEstTivE SYSTEM. 
In treating of the appetites, as occupying a conspicuous 
place among the active powers, we had occasion to deline- 
ate the characters of the instinct for food. In this place, 
we have to investigate those organs over which this instinct 
presides, and the important purposes which they serve in 
the animal economy. 
Every one knows, that the sensation of hunger is felt 
when the stomach is empty, but the nature of the connec- 
tion between these circumstances has not been satisfactorily 
explained. Some have ascribed the feeling to the fatigue 
of the muscular fibre from the stomach being contracted, 
and others to the friction of the rugze of its internal cover- 
ing, while there have not been wanting many who refer it 
to the stimulus of the accumulated gastric juice, or to the 
acrimony of that fluid, arismg from its unusual detention. 
But the total absence of proof in support of any of these 
opinions, renders it unnecessary to enter upon their ex- 
amination. | 
Many circumstances, however, are known, which promote 
hunger, especially exercise, cold air applied to the skin, and 
cold, acid, or astringent fluids mtroduced into the stomach. 
Inactivity, warm covering, the attention diverted, and 
warm fluids, have a tendency to allay the sensation*. But 
“ These facts serve to explain the circumstance of the inhabitants of 
warm countries making use of food highly seasoned with hot spices, while 
