PRESCRIPTION, in Law, denotes a particular mode of establishing a Right or Title.

Prescription, in Medicine, signifies much the same with what in common language is called a receipt, being a form of direction for the preparation and administration of some compound medicine. These medical receipts are commonly called formulae by physicians; and the term prescription is applied to what is written by a physician on seeing his patient, instructing the apothecary what medicines are to be prepared, how they are to be composed, and how administered to the patient. In this sense, a prescription may contain two or more formulae.

These prescriptions are almost always writen in Latin, and are expressed in a peculiar style, which, though well known to physicians and apothecaries, may require the illustration of an example. The following is a specimen of a modern prescription, as it rvould be written by a physician, according to the nomenclature of the pharmacopoeia:

For Mr. Muddleton.

R. Pulv. Rad. Rhei palmati gr. xxv. Tartratis Potassae Jij.

Tincturae Sennae compositae, Syrupi Rosae centifoliae āā gij. Aquae Menthae piperitae giss, M.f. Potio summo mane sumenda.

Jan. 31, 1839∙

From the above example, it will be seen that a prescription, properly so called, contains several circumstances beside the formulae or receipts, as the name of the patient, for whom the prescription is written; the signature of the physician, as J. B. for John Balfour, and the date of prescribing; none of which should be omitted, as the prescriptions are carefully preserved by the apothecary, for future reference.

It may be proper to explain some circumstances respecting the formula given in the above prescription. The R with which it commences signifies recipe or take ; and is prefixed to all medical receipts. Then follow the several ingredients of which the medicine is to be composed, with the quantities of each. These quantities are usually marked by peculiar characters or symbols, and the numbers employed are usually the Roman numerals. After the ingredients have been enumerated, and their quantities specified, there follows the title of the medicine, as Potio in the present instance, signifying potion or purging draught, with Μ. f. prefixed to it, which stand for misce fiat, or miscc ut fiat, mix to make; and lastly, the direction how the medicine is to be taken or administered, summo mane sumenda, to be taken early in the morning.

The ingredients of which a formula is composed have been, by u riters on medical prescriptions, arranged under four heads: 1. The basis of the formula, which in the present instance is the rhubarb, constituting the principal ingredient, on whose action, modified where necessary, the chief success of the medicine, in fulfilling the required indication, is to depend. 2. The adjuvant or auxiliary, added to the basis, for the purpose of increasing its power, expediting its action, or rendering it more easily soluble in the juices of the stomach; in the above formula the tartrate of potash is the principal adjuvant. 3. The corrector, added to the basis, when we wish to moderate or delay its action, to correct some unpleasant or injurious property of it, such as its odour, taste, acrimony, &c., or to prevent it from acting on the body in a different manner from that which the indication requires: thus, in the present formula, the warm tincture of senna is added, rather to correct the griping quality of the rhubarb, than to increase its action, and the syrup of roses to correct the unpleasant taste of the medicine; and the essential oil in the peppermint-water contributes to both these purposes: these, therefore, are to be considered as the correctors. 4. The constituent, or that ingredient which serves to reduce the rest into the form which is considered as most convenient for the exhibition of the medicine; in the present case the peppermint-water is the constituent, serving to reduce the medicine to the form of a potion or draught.

Medical formulae are either officinal, or extemporaneous ; the former being such as are directed by authority of some public medical college to be kept in the shops of apothecaries, and the preparation of which is described in their pharmacopoeias or dispensatories; the latter such as are prescribed by the physician or surgeon, as occasion may require.