A prescription (L. prae, for; scriba, I write) is an order on the pharmacist to furnish the patient a single remedy or a combination of remedies made into the form desired by the physician. All prescriptions are, then, simple if containing but one drug preparation, and compound if containing more than one.

The first element of correctness in prescription-writing consists in so forming the prescription that the pharmacist will, without question, understand it as the physician does. Any chance of a wrong interpretation by the pharmacist must be carefully guarded against.

The names of drugs in prescriptions are regularly written in Latin, the advantages of this being that they are without ambiguity, are readable in any part of the civilized world, and are not intelligible to the average patient, who frequently has erroneous preconceived notions of the efficacy of certain drugs.

English names are often ambiguous, for example, the name "snake-root" is applied in different parts of the country to the plants Cimicifiga racemosa, Aristolochia serpentaria, Asarum Cana-dense, Eupatorium aromaticum, Polygala Senega, etc.

The parts of the ordinary prescription are:

1. The name of the patient, and date.

2. The symbol R representing the Latin word recipe, take thou. This is known also as the superscription.

3. The names and quantities of the ingredients, known also as the inscription.

4. Directions to the pharmacist: What he is to do with the ingredients, whether to make them into pills or capsules or a plaster, etc. Known also as the subscription.

5. Directions for the patient. To be placed by the pharmacist on the label. Known also as the signature.

6. The signature of the physician. Example:

For Mrs. B------.1 July 3, 1899.

* Olei morrhuae, Vini albi,

Glyceriti vitelli, q. s. ad

Fiat emulsio.4 Sig. Tablespoonful after meals.5

Dr. P------.6

* In ancient times it was customary to preface a prescription with a pious invocation to Jupiter or some guardian deity. These prayers were finally abbreviated, until they came to be expressed by the simple astronomical sign U., symbol of the planet Jupiter. The upright stroke across the letter R heading modern prescriptions is a curious relic of the above heathen usage condensed in the planetary sign.

Here the small numerals or exponents are (1,2) the superscription; (3) the inscription; (4) the subscription; (5,6) the signature.

Formerly a typical prescription was said to consist of four divisions:

1. The basis, or principle active agent.

2. The adjuvant, or auxiliary, to aid the action of the basis;

3. The corrective, to correct or modify its action;

4. The vehicle, to give proper form or taste to the whole.

But it is not necessary that all prescriptions shall include the above four divisions.

Each ingredient should have a separate line.