Drugs and other curative agents assist in the readjustment or correction of disturbed functions, as in the use of digitalis or of laxatives; in the limitation of the growth of pathogenic organisms within the body, as with quinine, methenamine, emetine or arsphenamine; or by supplying a deficiency in substances necessary to life or growth, such as thyroid substance, insulin or vitamins.
Knowledge of the use of drugs and other remedies in the treatment of disease is the result of centuries of observation and study and is undergoing now, as in the past, a continuous process of revision. Some drugs have reached what seems to be a permanent place in the Pharmacopeia through years of clinical observation; cinchona, digitalis and mercury come to mind. Some, previously misused and discarded, such as antimony, recently have been revived as new methods of use have been devised. The active principles of herbs and drugs