Garlic. N. F. IV. Allium. English Garlic.—The genus Allium includes a large number of species, of which nearly seventy are indigenous in this country. Many, and perhaps all, of these species contain volatile oil upon which their activity depends. The cultivated garlic, of which the bulbs are official in the N. F., is Allium sativum L., for which, according to Griffith, A. canadense L., has been substituted and found efficient.
Allium sativum, L., is a perennial plant with numerous bulbs which have a common membranous covering, from the base of which the fibers that constitute the proper root descend. The stem is simple, and rises about two feet. The leaves are long, flat, and grass-like, and sheathe the lower half of the stem. At the termination of the stem is a cluster of flowers and bulbs mingled together, and enclosed in a pointed spathe, which opens on one side and withers. The flowers are small and white, and make their appearance in July. This species of garlic grows wild in Sicily, Italy, and the south of France. The bulbs, or so-called cloves, are usually six or eight in number, oblong or wedge-shaped, and covered with dry membranous scales, with a pungent odor and a disagreeable and acrid taste.
The N. F. description is as follows: "The fresh bulb of Allium sativum Linne (Fam. Liliaceae). Bulb subglobular, from 4 to 6 cm. in diameter, compound, consisting of from eight to fifteen bulbels and surrounded by one or two dry, whitish, membranaceous scales and attached to a flattened circular base from the lower portion of which arise numerous yellowish-white roots; bulbels more or less ovoid, in transverse section on three to four sided, the outer surface being convex, summit acute and narrowed into a thread-like fibrous portion, base truncate, each bulbel covered by one or two layers of whitish, membranaceous, scale-. like leaves, beneath which is the light brown or pinkish, thin and coriaceous layer of epidermis, cohering but easily separable from the solid portion of the bulbel. Odor of broken or bruised bulbels powerfully alliaceous, taste intensely pungent and persistent. Under the microscope, transverse sections of the bulbel show, three distinct portions: (a) the large fleshy scale consisting chiefly of parenchyma enclosing scattered vascular bundles, epidermis in both ventral and dorsal surfaces consisting of small tabular cells; (b) the middle layer nearly circular in outline, about 0.75 mm. in diameter, the tissues resembling those of the outer fleshy scale, but the cells containing numerous yellowish-brown plastids; (c) an innermost bright green layer consisting of a single leaf folded lengthwise along the midrib so that the ventral surfaces lie close together."
The oil of garlic is of a dark brownish-yellow color, heavier than water, and decomposed at its boiling temperature. It may be purified by repeated distillation in a salt water bath, and is then lighter than water, of a pale yellow color, and not decomposed by boiling. Semmler obtained from garlic bulbs 0.09 per cent. of the volatile oil, sp. gr. at 14.5° C. (58° F.) 1.0525; it was yellow, having an intense odor and optically inactive. By fractional distillation he obtained four products, C6H12S2, C6H10S2, C6H10S3, and C6H10S4, which decomposed during distillation, and hence could only be obtained by distillation in vacuo. The oil, according to Semmler, is free from allyl sulphide, the latter having the sp. gr. 0.8991. (A. Pharm., 1892, p. 434.) The impure oil has an exceedingly pungent odor and a strong acrid taste, and, when applied to the skin, produces much irritation and sometimes even blisters. The pure oil combines with silver nitrate, forming a precipitate soluble in heated alcohol and afterwards separating in crystals. Besides this oil, fresh garlic, according to Cadet de Gassicourt, contains, in 1406 parts, 520 of mucilage, 37 of albumen, 48 of fibrous matter, and 801 of water. Bouillon-Legrange mentions among its constituents sulphur, a saccharine matter, and a small quantity of starch. The fresh bulbs yield upon pressure nearly a fourth part of juice, which is highly viscid, and so tenacious as to require dilution with water before it can be easily filtered. When dried, it serves as a lute for porcelain. It has the medicinal properties of the bulbs. Water, alcohol, and vinegar extract the virtues of garlic. Protracted boiling renders it inert. According to Semmler (A. Pharm., 1887, p. 927), Allium ursinum contains a volatile oil which consists mainly of vinyl-sulphide, C4H6S or (C2H3)2S.
Medicinal Properties and Uses.—The use of garlic as a medicine and as a condiment can be traced to earliest antiquity. When taken internally, and even when applied externally, the oil is absorbed and imparts its odor to the breath, urine, perspiration, etc. The oil of garlic has some influence upon the human system as a general mild stimulant. Its chief value in medicine is for its local action upon the stomach and as a stimulant expectorant. The garlic itself is sometimes employed as a rubefacient which, by yielding its volatile oil to absorption, stimulates the nervous system, especially in the case of young children. The oil may often be given with advantage in chronic bronchitis and in the advanced stages of obstinate acute bronchitis. It is especially valuable in the treatment of children when there is a distinct nervous element. In catarrhal pneumonia of young children the bruised garlic cloves are often applied as a poultice to the lungs, and similar applications were formerly used upon the feet for the nervous restlessness or even the convulsions of young children. Garlic clove may be swallowed either whole or cut into pieces of a convenient size, but the syrup has replaced most other methods of administration. The dose in substance is from half a drachm to two drachms (2-7.7 Gm.) of the fresh bulb. That of the juice is half a fluidrachm (1.8 mils). A syrup is official in the N. F. (see Part III).
The Dispensatory of the United States of America, 1918, was edited by Joseph P. Remington, Horatio C. Wood and others.