The word prescription comes from the Latin pre and scribo, and means literally written before or that which is written before the application of the treatment. In its broadest sense it includes any instructions for the benefit of the patient. It is customary to speak of prescribing forced diet for one patient, of prescribing exercise for another, or the seashore or the mountains.

In its restricted meaning, as it will be employed in this work, a prescription is a written order from a doctor to a druggist for medicine for a patient. A layman may send a druggist a written order for a bottle of Compound Syrup of Pine; that would not be considered a prescription. A physician may send a nurse a written order to give the patient a dose of salts; that would not be a prescription. A physician may send a written order to a druggist to pay a patient a dollar on his account; not a prescription. A physician may send a druggist a written order for a pound of chloroform for his obstetrical case; not a prescription, as it is generally understood.