Page:A manual of pharmacology and its applications to therapeutics and toxicology (1922).djvu/18

 Definitions.—Pharmacognosy deals with the origin and the anatomic and chemic structure of crude drugs.

Materia Medica is an older, obsolescent title, which was used to include also the actions, uses and dosage. Organic Materia Medica is limited to the drugs derived directly from the vegetable and animal kingdoms. Importance of Pharmacognosy.—An accurate knowledge of this branch is necessary to the pharmacist to insure the quality of his wares. It is much less important to the physician. However, it is useful to know the appearance, odor, taste, solubility, and perhaps the origin, at least of the more important drugs. Vegetable Drugs.—The crude organic drugs are derived mainly from plant, either wild or cultivated; collected at the proper season to insure the maximum activity; and properly dried or otherwise prepared.

Parts Used.—The active principles are often diffused throughout the plant; but they are generally more abundant in one particular part, which is then used. The parts are designated by their usual botanic names. The following are the most important, with some characteristic examples. Root (Radix).—The underground part of the plant, generally devoid of chlorophyl (green coloring matter), and which does not produce leaves {Dandelion, Belladonna, Ipecac, Rhubarb).

Tuberous Roots.—Roots swollen with accumulation of reserve food material (Sweet Potato, Aconite, Jalap), They are often called tubers; but true tubers (Potato) are similar formations on rhizomes. Corm.—A thickened underground stem (Colchicum).

Bulb.—Very fleshy, closely crowded leaves, enfolding the underground base of the stem (Onion, Squills).

Rhizome.—Underground stems which bear leaves (Podophyllum, Hydrastis. Ginger, Aspidium). Wood (Lignum).—The wood of trees, in fragments, chips or coarse powder (Quassia, Hematoxylon. Sandalwood).

Bark (Cortex).—The outer layer of the stem (Cinchona, Cascara, Wild Cherry), or of the root (Sassafras, Cotton-root). Sometimes only the inner bark is collected (Ceylon Cinnamon, Elm).

Leaves (Folia).—Digitalis, Uva Ursi, Belladonna, Senna. Herb (Herba or Species).—The smaller leafy and flowering or fruiting stems (Peppermint, Cannabis Indica, Savin).