These are substances that are employed to give a bitter taste, the object of their administration being to improve the appetite. When the appetite is below normal, a strong stimulation of the taste-buds will often restore it; and substances with a bitter taste that is not otherwise disagreeable tend to act as stimulants to the taste-buds.

That appetite is important for digestion has been demonstrated by Pawlow and his followers. They discoveredthat the stomach of a hungry dog would secrete gastric juice if he saw or smelled food, even though there was no food in the stomach. This is known as the "appetite" or "psychic" gastric juice.

They also found that some foods would not digest at all, - for example, white of egg, - if they were put in the empty stomach without arousing the appetite, as through a fistula while the animal slept. That is, they were incapable, by direct action on the stomach wall, of inducing the stomach to secrete. But Pawlow noted further that, on showing the dog food, the appetite juice would form and would act on the egg-albumin; and that the products of this primary digestion would then stimulate the stomach wall and induce the secretion which continued the digestion. Hence the appetite juice is of great importance in starting digestion; and since the formation of the appetite juice is favored by bitters, these may be considered aids to digestion in atonic cases.

Moorhead, 1901, found that in normal dogs bitters had no effect or were depressing, while in cachectic dogs they distinctly stimulated appetite, and the secretion of gastric juice. Barisoff gave tincture of gentian to a dog with the end of the severed esophagus opening outside so that substances swallowed did not reach the stomach. He followed this with a meal, and found the average amount of gastric juice increased over 30 per cent. by the bitter. An excess of bitter checked the secretion. Carlson's experiments with normal humans and dogs showed increased appetite, but an inhibition of the hunger contractions. He thinks that the effect of a bitter is purely psychic.

The bitter effect on appetite is solely the local one on the taste-buds, so it is not obtained if the bitter is hidden, as in capsules or gelatin-coated pills, or if it is disguised by sweetening agents or flavors. It requires for its development that the bitter shall be taken just preceding the usual time for eating; that is, from ten to twenty minutes before. If the appetite is already normal, the bitter may not increase it, and may even lessen it. If the stomach and bowels are deranged, a bitter may nauseate.

The bitters are classed as the simple bitters, which have no effect on taste other than bitterness, and the aromatic bitters, which, in addition to the bitter principle, contain a volatile oil or resinous aromatic.

The simple bitters are: barberry (berberis), calumba, con-durango, dandelion (taraxacum), gentian, and quassia. These may be used in the form of an infusion, dose, 1/2 ounce (15 c.c.), or tincture, dose, 1 dram (4 c.c.), diluted to give a bitter drink. The powerful pharmacologic drugs, nux vomica, with its alkaloid, strychnine, and cinchona, with its alkaloid, quinine, are often employed also as simple bitters. Quassia-cups are used in some households. They are turned out of quassia wood and impart an intense bitterness to water allowed to stand in the cup for fifteen minutes. The cups retain their power for a long time. Infusion of quassia is also employed as a bitter, as an enema for pin-worms, and as an insecticide in agriculture.

Orexine hydrochloride and tannate, bitter, crystalline bodies, are also used in dose of 5 grains (0.3 gm.). They are soluble in about 15 parts of water.

The aromatic bitters are: wormwood or vermouth (absinthium), chamomile (anthemis), German chamomile (matricaria), bitter orange-peel, and serpentaria.

There are two aromatic bitter tinctures which are favorite appetizers, viz., compound tincture of gentian (tinctura gentianae composita), made of gentian, cardamom, and bitter orange-peel, dose, 1 dram (4 c.c.), and compound tincture of cinchona (tinctura cinchonae composita), made of red cinchona, serpentaria, and bitter orange-peel, dose, 1 dram (4 c.c.).