Familiarity with the following definitions is essential to a correct understanding of a treatise on Materia Medica.

Acid

A compound composed of hydrogen with an electronegative element or group of elements and possessing the following properties: It contains hydrogen that can be replaced by a metal or base to form a salt; it changes the color of litmus from blue to red; it has (when soluble in water) an acid or sour taste. Examples: Sulphuric acid, hydrochloric acid, citric acid.

Acetum. Acet. Vinegar

The vinegars are solutions of medicinal substances in diluted acetic acid. There is one official vinegar. They are seldom prescribed.

Alcohol

As a class name it means a hydrocarbon radical in combination with the radical OH. As a name for a definite substance it means ethyl alcohol.

Aldehyde

A compound intermediate between an alcohol and acid. A hydrocarbon radical in combination with the radical COH. Example: Acetic aldehyde.

Alkali

A metallic oxide (except ammonia) that has the property of combining with an acid to form a salt, or with an oil to form soap. Examples: Caustic soda, caustic potash.

Alkaloid

A basic substance, usually the active principle of a plant, and composed of carbon, hydrogen, nitrogen, and, usually, oxygen. Examples: Quinine, morphine, strychnine.

Alterative

An agent that will restore deranged nutritive processes. Examples: Corrosive mercuric chloride, calomel, arsenic trioxide, and potassium iodide are usually placed in this class.

Anaphrodisiac

An agent that will depress the sexual function. Examples: Bromides, opium, monobromated camphor.

Anesthetic

An agent that will produce insensibility to pain or touch. According to action, they are subdivided as general and local. Examples: General-ether, chloroform, ethyl chloride. Local-cocaine, novocaine, phenol.

Anodyne or Analgesic

An agent that will relieve pain. Examples: Morphine, codeine, acetylsalicylic acid.

Antacid

An agent that will neutralize acidity. Examples: Magnesium oxide, sodium bicarbonate.

Anthelmintic

An agent used in the treatment for intestinal worms. Examples: Santonin, phenyl salicylate, thymol.

Antiemetic

An agent that will prevent or arrest vomiting. Examples: Cocaine, peppermint, bismuth subnitrate, cerium oxalate.

Antigalactagogue

An agent that lessens the secretion of milk. Belladonna, probably all hydragogue purgatives.

Antilithic

An agent that prevents the formation or favors the removal of stones or calculi in the urinary or biliary tracts. Examples: Lithium citrate, hexamethylenamine, alkaline waters, and glycerin are usually placed in this class.

Antimalarial

An agent that will prevent or relieve malaria. Examples: Quinine, arsenic.

Antiphlogistic

An agent that tends to relieve inflammation. Examples: Cataplasma of kaolin, ichthyol.