Chemical Composition—The most interesting constituents of hemp, from a medical point of view, are the resin and volatile oil.
The former was first obtained in a state of comparative purity by T. and H. Smith in 1846.[2036] It is a brown amorphous solid, burning with a bright white flame and leaving no ash. It has a very potent action when taken internally, two-thirds of a grain acting as a powerful narcotic, and one grain producing complete intoxication. From the experiments of Messrs. Smith, it seems to us impossible to doubt that to this resin the energetic effects of cannabis are mainly due.
When water is repeatedly distilled from considerable quantities of hemp, fresh lots of the latter being used for each operation, a volatile oil lighter than water is obtained, together with ammonia. This oil, according to the observations of Personne (1857), is amber-coloured, and has an oppressive hemp-like smell. It sometimes deposits an abundance of small crystals. With due precautions it may be separated into two bodies, the one of which, named by Personne Cannabene,[2037] is liquid and colourless, with the formula C₁₈H₂₀; the other, which is called Hydride of Cannabene, is a solid, separating from alcohol in platy crystals to which Personne assigns the formula C₁₈H₂₂. He asserts that cannabene has indubitably a physiological action, and even claims it as the sole active principle of hemp. Its vapour he states to produce when breathed a singular sensation of shuddering, a desire of locomotion, followed by prostration and sometimes by syncope.[2038] Bohlig in 1840 observed similar effects from the oil, which he obtained from the fresh herb, just after flowering, to the extent of 0·3 per cent.
It remains to be proved whether an alkaloid is present in hemp, as suggested by Preobraschensky.[2039]
The other constituents of hemp are those commonly occurring in other plants. The leaves yield nearly 20 per cent. of ash.
As to the resin of Indian hemp, Bolas and Francis in treating it with nitric acid, converted it into Oxycannabin, C₂₀H₂₀N₂O₇. This interesting substance may, they say, be obtained in large prisms from a solution in methylic alcohol. It melts at 176° C. and then evaporates without decomposition; it is neutral.[2040] One of us (F.) has endeavoured to obtain it from the purified resin of charas, but without success.
Uses—Hemp is employed as a soporific, anodyne, antispasmodic, and as a nervous stimulant. It is used in the form of alcoholic extract, administered either in a solid or liquid form. In the East it is consumed to an enormous extent by Hindus and Mahomedans, who either smoke it with tobacco, or swallow it in combination with other substances.[2041]
Charas.
No account of hemp as a drug would be complete without some notice of this substance, which is regarded as of great importance by Asiatic nations.
Charas or Churrus is the resin which exudes in minute drops from the yellow glands, with which the plant is provided in increasing number according to the elevated temperature (and altitude?) of the country where it grows. The varieties of hemp richest in resin, at least in the Laos country in the Malayan Peninsula, scarcely attain the height of 3 feet, and show densely curled leaves.[2042] Charas is collected in several ways:—one is by rubbing the tops of the plants in the hands when the seeds are ripe, and scraping from the fingers the adhering resin. Another is thus performed:—men clothed in leather garments walk about among growing hemp, in doing which the resin of the plant attaches itself to the leather, whence it is from time to time scraped off. A third method consists in collecting, with many precautions to avoid its poisonous effects, the dust which is caused when heaps of dry bhang are stirred about.[2043]