This section is from the book "A Text Book Of Materia Medica, Being An Account Of The More Important Crude Drugs Of Vegetable And Animal Origin", by Henry G. Greenish. Also available from Amazon: A Text Book of Materia Medica : Being an Account of the More Important Crude Drugs of Vegetable and Animal Origin.
The drug known as Indian hemp, or Cannabis indica, is derived from Cannabis sativa, Linne (N.O. Urticaceoe), cultivated in tropical districts of India.
The plant is an annual dioecious herb, indigenous to Central and Western Asia, but largely cultivated in temperate countries for its strong fibres (hemp) and its oily seed (hempseed), and in tropical countries also for the resinous secretion which it there produces. This secretion possesses powerful medicinal properties, but it is not produced by the plant when grown in temperate climates; on the other hand, the fibre of the plant under the latter condition is stronger than that of the tropical plant.
The cultivation of hemp for its seed and fibre dates from very remote periods. It was used as an intoxicant by the Persians and Arabians in the eleventh and twelfth centuries, and probably much earlier, but was not introduced into European medicine till comparatively recently (1838). It is largely grown in the districts to the north of Calcutta, and westward thence through Central India to Gujerat. Very good qualities of the drug are produced in Madras.
As the staminate plants produce but little resin they are eradicated and the pistillate plants pruned in order to produce flowering branches.
The tops of these are collected, allowed to wilt, and then pressed, by-treading them under the feet, into more or less compact flattened masses. This forms the drug known on the London market as ' guaza'; it is exported from Bombay, formerly in rounded canvas bales called ' robbins,' but now more frequently in wooden cases.
In the Calcutta districts a somewhat different procedure is adopted. The tops that are collected are short, and, after being allowed to wilt, they are rolled under the feet of men, who support their weight by grasping a horizontal bamboo pole. In this way rounded, instead of flattened masses are produced. This variety is known as 'round' or Bengal ganjah (or guaza); it is more active than the flat Bombay drug, but is not seen in commerce in England, such quantities as are imported being immediately re-exported to the West Indies for the use of the coolies.
The larger leaves and young twigs collected and dried form the drug known as 'bhang'; it is chiefly consumed in India, made up into an electuary.
In addition to these drugs the resin secreted by the plant is also roughly collected by beating the plants on cloths to which the resin adheres; in this way a greenish brown soft mass is obtained, which may be freed from vegetable debris by warming and pressing through cloths. This resin is known as 'charas' or 'churrus,' and, like ganjah, is usually smoked. The Pharmacopoeia guards against the use of the plants thus exhausted by limiting the drug to that ' from which the resin has not been removed.'
All these varieties of the drug are largely used in India for producing an agreeable form of intoxication.
In English commerce the drug usually occurs in flattened, compressed, rough masses of dull dusky green colour, harsh and resinous to the touch. Sometimes the tops are only 5 to 10 cm. in length, but more frequently they are 15 to 30 cm., the former being preferred. They consist of a straight stem with ascending branches, longitudinally furrowed, and bearing numerous, small, curved, appressed hairs and occasional glands. The hairs are characterised not only by their shape, but by being enlarged at the base and containing cystoliths.
The leaves on the drug (that is, the upper leaves of the plant) are alternate; the lower are digitate, and consist of three or five linear-lanceolate leaflets with distinctly serrated margins; the upper are simple. The upper part of the stem and branches bear numerous flowers or fruits.
The pistillate flowers are small and consist of a single ovary, surrounded by a perianth and supported by an ovate bract, beyond which two long brown stigmas, easily visible under a lens, protrude. The fruit is ovoid, slightly reticulated, and contains a single oily seed.
All parts of the plant, but particularly the bracts, stipules, and upper leaves, bear numerous hairs and large stalked glands, the latter secreting a quantity of viscid adhesive resin.
The drug has a powerful odour, but is almost devoid of taste.
The student should observe
(a) The rough, dusky green masses,
(b) The curved appressed hairs,
(c) The linear-lanceolate leaflets.
Fig. 109. - Indian Hemp. a, young leaf. b, pistillate flower enclosed by a bract and supported by a stipule. c, bract, showing glands. d, ovary, cut longitudinally. e, fruit (hemp-seed). / and g, fruit in transverse and longitudinal section (figures after Holmes).
It is advisable to free the drug from resin by macerating it in spirit, and then to soak it in water, when the leaves can easily be separated and the flowers dissected.
The resin secreted by the glands is undoubtedly the part of the plant that produces the narcotic effect of Indian hemp. This has been separated as a soft brown substance, cannabinone, from which, by distillation in vacuo, a viscous resin, cannabinol, which melts to an oily liquid when warmed, has been separated (Wood, Spivey, and Easterfield, 1896). Cannabinol produces a powerful narcotic action and is believed to be the active constituent of the drug.
On exposure to the air it resinifies rapidly and becomes less active. A similar change, due possibly to the presence of oxydase enzymes, takes place in the cannabinol in the drug. This rapid deterioration is well recognised in India, and persons addicted to the use of the drug refuse that which is more than a year old.
In addition to cannabinol and resin, the drug contains the alkaloid choline and traces of volatile oil; it yields from 10 to 18 (not less than 12.5, B.P. 1914) per cent. of alcoholic extract and about 15 per cent. of ash. The activity is not, however, accurately indicated by the amount of alcoholic extract it yields, and the drug cannot be assayed by chemical means. Its activity is usually estimated by the action upon animals.
To avoid deterioration by oxidation of the cannabinol the drug should be completely dried and kept in hermetically sealed containers.
Indian hemp may be identified chemically by saponifying a petroleum spirit extract of the drug with alcoholic potash when a persistent purplish violet colour is produced.
Indian hemp acts upon the nervous system, producing first excitement accompanied by hallucinations and afterwards lethargy and sleep. It is used as a sedative in mania and hysteria, as well as for spasmodic cough, asthma, neuralgia, etc.
In addition to the guaza above described, the plant, cultivated in Eastern Africa (Zanzibar) and also in France has been imported. Both varieties may be distinguished by their less resinous and matted appearance and by their brighter colour; they are much less active than the Indian drug. Indian hemp of fair quality (about half as active as the Indian drug) has been grown in the United States under Government supervision and considerable quantities have been imported into this country. It is also cultivated in Greece.