Appetite (Lat. appetitus, from appeto, 'I desire') is generally used of the natural desire for food experienced in health. Its causes are two: (1) A condition of the stomach, not yet accurately understood, relieved by taking food; (2) A condition of the system, not relieved till the products of digestion begin to be absorbed into the blood. These are usually present together, but either may act without the other. The stomach-condition is that in which the organ is in the most favourable state for digestion, and tends to recur at the habitual meal-hours; but often passes off if eating be long deferred, though the need and craving of the system for food remains. Hence the importance of taking food at regular hours. Too free indulgence of a naturally large appetite frequently leads to indigestion and ill-health, especial in persons of sedentary habits. This danger is much less if the food be eaten slowly and thoroughly masticated; for in that case the digestion of the food first taken has advanced so far before the close of the meal, as to appease the system-appetite. Habitual stimulation of the appetite, especially by the pernicious practice of taking alcohol before meals, leads to equally injurious results.
Alteration of the appetite is perhaps the most common of all the symptoms of disease. Occasionally it is increased. Morbid Appetites may consist of a desire which is, in character, natural and necessary to the animal economy, but becomes unhealthy when excessive and irresistible. Of this, the hunger which attends marasmus, and the thirst which attends diabetes, may be cited as illustrations. They may consist, further, in a craving for articles or objects not in reality deleterious or detrimental, but which do not constitute the ordinary gratification of the appetite, such as the desire for chalk and lime experienced by chlorotic and hysterical women. They may, thirdly, consist in the longings, often complicated with delusions, felt by pregnant women and others, which are injurious, repugnant to nature, and revolting. Georget gives an instance where a wife coveted the shoulder of her husband, killed him in order to obtain the morsel, and salted the body in order to prolong the hideous cannibalism. In such a case, the gross longing may be said to constitute the disease; but there are others in which it is one of many symptoms demonstrating the degradation of the mind under general disease, as when the insane devour garbage and excrement, or swallow grass, hair, stones.
Much more frequently the appetite is diminished, and accordingly medicines which increase the appetite and improve the digestion are often necessary. The chief of these stomachic tonics are—vegetable bitters, as quinine, hop, gentian; dilute mineral acids; salts of iron; pepsin and other digestive agents prepared from the organs of the lower animals. See DIET, DIGESTION, DYSPEPSIA, FOOD; cf. also THIRST.