In treating of the appetites, as occupying a conspicuous place among the active powers, we had occasion to delineate 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 connection 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 rugae of its internal covering, 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, arising from its unusual detention. But the total absence of proof in support of any of these opinions, renders it unnecessary to enter upon their examination.

Many circumstances, however, are known, which promote hunger, especially exercise, cold air applied to the skin, and cold, acid, or astringent fluids introduced into the stomach. Inactivity, warm covering, the attention diverted, and warm fluids, have a tendency to allay the sensation. But whether these effects indicate the local state of the stomach as the cause of the sensation, or merely its connection with other circumstances, which give rise to the feeling, can scarcely be determined.