The bark and the prepared resinous exudate of the Abies canadensis, Michaux. (Pinus canadensis, Linné; Picea canadensis, Link; Tsuga canadensis, Carrière).
COMMON NAMES:—Hemlock, Hemlock spruce.
Botanical Source.—This common forest tree seldom rises above 75 feet, with the trunk large in proportion, straight, and covered with a rough bark. The branches are brittle and nearly horizontal, with pubescent twigs. The leaves are about half an inch in length, linear, obscurely fine-toothed, glaucous beneath, in two opposite rows. The cones or strobiles are very small, ovoid, terminal, and drooping, with a few rounded, entire scales. The foliage of this tree is delicate, bright-green above and silvery-white underneath; its timber is very coarse-grained-(G.—W.).
History and Chemical Composition.—The Hemlock spruce is a well-known indigenous tree, abounding in the forests of the Northern States and Canada. The tree is found in the same latitudes and elevations as the A. balsamea. It flowers in May. The juice or oleoresin, known as Canada pitch, or incorrectly as Gum hemlock (for a description of which see Pix Canadensis), oozes from the tree, without any incisions being made, and concretes upon its external surface; the bark is removed from the tree, cut into large fragments, and boiled in water. As the resin ascends to float upon the water, it is removed by skimming and thrown into cold water. It is then placed in a coarse linen bag, and boiled a second time, to remove its impurities—(Jour. Phil. Col. Pharm., Vol. II, p. 20).
It is also collected by cutting into the live tree small cotyloid depressions, into which the oleoresin exudes and from which it may be easily collected. The bark contains a large amount of tannic acid, and on this account is extensively employed by tanners, who also use an aqueous extract of the bark known as "extract of hemlock bark." It contains also a volatile oil, known commercially as oil of hemlock or oil of spruce, which may be obtained by boiling the boughs in water. This oil from the leaves, known also as pine-needle oil, has, according to Schimmel & Co. (Semi-Annual Report, Oct., 1893), a specific gravity of 0.907 at 15° C. (59° F.), and an optical rotation of -20°54'; and its known constituents are pinene, bornyl acetate, and cadinene. Two preparations now largely used are Kennedy's White Pinus Canadensis and Kennedy's Concentrated Extract of Pinus Canadensis. The latter is red, and is used both externally and internally; the former is white, does not stain, contains alum and zinc sulphate, and is designed for external use only.
Action, Medical Uses, and Dosage.—A strong decoction of the bark of this tree is beneficial in leucorrhoea, prolapsus uteri, prolapsus ani, diarrhoea, etc., administered internally, and used in enema; it is likewise of service as a local application in gangrene, and in aphthous, and other oral ulcerations.
The essential oil of this tree, the oil of hemlock, has occasionally been used by pregnant females to cause miscarriage, but serious effects are apt to follow therefrom. As a liniment this oil has been used in croup, rheumatism, and other affections requiring a stimulating local application. The essence (oil) of hemlock is diuretic and highly stimulant. Dr. W. K. Everson states it to be a superior remedy in gastric irritation to allay vomiting in cholera morbus, etc. The dose is 5 or 10 drops in water, every 10 or 20 minutes, until relief is afforded.
The alcoholic preparations of this drug usually pass under the name of Pinus canadensis. Such preparations are of much value where a mild stimulant and astringent is required, and especially in catarrhal disorders of the mucous tissues, with marked pallidity and relaxation. It is likewise of value in passive hemorrhages, and is useful topically in scalds and burns. Tincture, 5 to 30 drops; specific Pinus canadensis, 2 to 10 drops, preferably in equal parts of water and glycerin; the oil, 2 to 5 drops.
Specific Indications and Uses.—General asthenic state, with feeble digestion, vascular weakness, and pale mucous membranes; broncho-pulmonary irritation, with profuse secretions; coughs and colds; renal torpor; pyrosis and gastric irritation, with vomiting and diarrhoea; some cutaneous affections. Never to be used in inflammatory or sthenic conditions.
King's American Dispensatory, 1898, was written by Harvey Wickes Felter, M.D., and John Uri Lloyd, Phr. M., Ph. D.