The class of medicines which particularly tone up a weak and relaxed stomach are the simple vegetable bitters. Such are quassia, columbo, gentian, and some others. Simple bitters we call these, because they have no other very positive quality except the bitter taste, and no marked effect upon the human system except as tonics to the stomach. (In large draughts their infusions or " teas " will act as emetics.)

There are some bitters which have other very important actions. Quinia is one, got from Peruvian bark; it acts powerfully on the nervous system, and is the special remedy for malarial fevers. The same bark contains also cinchonia, and several other more or less bitter tonic and nervine " alkaloids," as the chemists name them.

Nux Vomica is a very powerful bitter nervine tonic. Out of it is obtained strychnia, one of the deadliest of poisons, but also one of the most valuable of medicines, when used with judgment, care, and skill. With this information, we may venture to add that the tincture of nux vomica, in ten-drop doses, twice or thrice daily, is one of the most effective of all the stomachic bitters, in cases of continued weakness of digestion, with flatulence.

These bitters generally improve the appetite, which is almost always poor when the stomach is otherwise weak. For the same end, as appetizers, mineral acids are useful; dilute aromatic sulphuric acid, for example, under the common name of elixir of vitriol, and chlorohydric acid, formerly, and sometimes now, called hydrocholoric, or muriatic acid. Nitromuriatic acid adds a special tendency to act upon the liver. One or other of these acids, and most of all the last named, is often given to the subjects of prolonged indigestion-, along with the vegetable bitters.