Active Ingredients. - The root has a very pungent odor, and an acrid taste, depending on a volatile oil, C4H5NS, produced by the action of myrosin or myronic acid in the presence of water; it is identical with oil of mustard, and is readily dissipated by heat or exposure to the air. It is very volatile; one drop is sufficient to odorize a whole room. It imparts its properties to water, vinegar, and alcohol; is very easily soluble in alcohol, less so in water. It is of a pale-yellow color, and heavier than water.

Physiological Action. - Horse-radish has a very pungent odor, very irritating to the nostrils, and causing the eyes to flow profusely with tears. Its taste is sweetish, hot, and acrid. Taken with food, it produces a sense of warmth in the stomach, and is said to assist the digestion, especially of animal food. Freely administered in the form of infusion, it produces a sensation of soreness and relaxation in the throat, with a burning heat in the stomach, soon followed by nausea and vomiting; the urine is increased in quantity, and often acquires the peculiar odor of the plant.

Tiedemann injected an ounce of the juice into the crural vein of a dog, and immediately after detected its odor in the animal's breath. On the skin it produces perspiration when administered internally; and when the scraped root is applied externally, it causes redness of the surface, which often leads to vesication.

Therapeutic Action. - Sydenham highly valued horse-radish in cases of dropsy supervening upon intermittent fever. In modern practice it is not much employed. Its effects are similar to, though more energetic than mustard seed. It has been employed with good results in atonic dyspepsia, chronic rheumatism, and paralytic affections, especially of the tongue, and in this last it often helps mastication by its powerful sialagogue property. A syrup prepared from a concentrated infusion of the root, and swallowed leisurely, a teaspoonful at a time, removes hoarseness arising from relaxation of the throat. Hoarseness may also be relieved by employing horse-radish as a masticatory, or as a gargle.

The infusion, taken with draughts of warm water, readily produces vomiting, and may be employed by itself, or to assist the operation of other emetics. As an antiscorbutic it is much praised by Cullen and others.

Preparation and Dose. - Spiritus Armoraciae compositus, (B. Ph.), 3i.-ij- (4.- 8.).