Radix Serpentariæ Virginianæ; Virginian Snake-root, Serpentary Root; F. Serpentaire de Virginie; G. Schlangenwurzel.
Botanical Origin—Aristolochia Serpentaria L., a perennial herb, commonly under a foot high, with simple or slightly branched, flexuose stems, producing small, solitary, dull purple flowers, close to the ground. It grows in shady woods in the United States, from Missouri and Indiana to Florida and Virginia,—abundantly in the Alleghanies and in the Cumberland Mountains, less frequently in New York, Michigan and the other Northern States. The plant varies exceedingly in the shape of its leaves.
History—The botanists of the 16th century, being fond of appellations alluding to the animal kingdom, gave the names of Serpentaria or Colubrina, i.e. snake-root, to the rhizome of Polygonum Bistorta L. In America it was not the appearance, but the application of the drug under notice to which it owes the name snake-root.
The earliest account of Virginian snake-root is that of Thomas Johnson, an apothecary of London who published an edition of Gerarde’s Herbal in 1636. It is evident however that Johnson confounded a species of Aristolochia from Crete with what he calls “that snake-weed that was brought from Virginia and grew with Mr. John Tradescant at South Lambeth, anno 1632.” It was very briefly noticed by Cornuti in his Canadensium Plantarum Historia (1635), and in a much more intelligent manner by Parkinson in 1640. These authors, as well as Dale (1693) and Geoffroy (1741), extol the virtues of the root as a remedy for the bite of the rattlesnake, or of a rabid dog. Serpentary was introduced into the London Pharmacopœia in 1650.
Description—The snake-root of commerce includes the rhizome, which is knotty, contorted, scarcely 1 inch in length by ⅛ of an inch in thickness, bearing on its upper side the short bases of the stems of previous years, and throwing off from the under, numerous, slender, matted, branching roots, 2 to 4 inches long. The rhizome is often still attached to portions of the weak, herbaceous stem, which sometimes bears the fruit,—more rarely flowers and leaves. The drug has a dull brown hue, an aromatic odour resembling valerian but less unpleasant, and a bitterish aromatic taste, calling to mind camphor, valerian and turpentine.
Microscopic Structure—In the rhizome, the outer layer of the bark consists of a single row of cuboid cells; the middle cortical portion (mesophlœum) of about six layers of larger cells. In the liber, which is built up of numerous layers of smaller cells, those belonging to the medullary rays are nearly cuboid with distinctly porous walls, those of the liber bundles being smaller and arranged in a somewhat crescent-shaped manner. Groups of short, reticulated or punctuated vessels alternate in the woody rays with long, porous, ligneous cells; those close to the pith having thick walls. The largest cells of all are those composing the pith; the latter, seen in transverse section, occupies not the very centre of the rootstock, but is found nearer to its upper side. The rootlets exhibit a central fibro-vascular bundle, surrounded by a nucleus-sheath. In the mesophlœum both of the rootstock and the rootlets, there occur a few cells containing a yellow essential oil. The other cells are loaded with starch.
Chemical Composition—Essential oil exists in the drug to the extent of about ½ per cent.; and resin in nearly the same proportion. The outer cortical layer, as well as the zone of the nucleus-sheath, contains a little tannin, and a watery infusion of the drug is coloured greenish by perchloride of iron. Neutral acetate of lead precipitates some mucilage as well as the bitter principle, which latter may also be obtained by means of tannic acid. It is an amorphous, bitter substance, which deserves further investigation. By an alkaline solution of tartrate of copper the presence in serpentary of sugar is made evident.
Commerce—Virginian snake-root is imported from New York and Boston, in bales, casks or bags.
Uses—The drug is employed in the form of an infusion or tincture as a stimulating tonic and diaphoretic; it is more often prescribed in combination with cinchona bark than by itself. Its ancient reputation for the cure of snake-bites is now disregarded.
Adulteration and Substitution—Virginian snake-root is said to be sometimes adulterated with the root of Spigelia marilandica L., which has neither its smell nor taste ([see p. 433]); or with that of Cypripedium pubescens L., which it scarcely at all resembles. It is not uncommon to find here and there in the serpentary of commerce, a root of Panax quinquefolium L. accidentally collected, but never added for the purpose of adulteration.