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.
Shaving. By this modification of renewing, only a portion of the bark is removed by shaving; the remainder is left on as a protection to the tree, which therefore does not require any covering of moss.
Both these methods have been abandoned in favour of the following:
Uprooting. The tree is allowed to grow until it has attained the age at which it yields the maximum proportion of alkaloid. It is then uprooted and the bark stripped from the root as well as from the stem. By this means the valuable root-bark is secured, and the land can then be re-planted.
Coppicing. The tree is cut down to form stools, from which adventitious shoots arise. These shoots yield handsome quills of bark, and the method is specially suited for the production of the quilled bark sold to the pharmacist.
The bark is usually collected in the rainy season, when it separates easily from the stem; the colour of the inner surface of the fresh bark is always pale, but by the action of the air a change in the tannin rapidly takes place, and the bark assumes a brown or red colour. The drying is usually effected in the sun, or frequently by artificial heat in a specially constructed drying machine. For exportation, the bark is usually pressed by hydraulic pressure into firm bales (as in Ceylon) or stamped into sacks (as in Java); fine quills are carefully packed in cases.
The commercial varieties of cinchona bark yielded by the following species of Cinchona may be briefly described.
1. C. Calisaya. - The bark yielded by this species is sometimes called ' yellow ' bark, but as this term is also applied to all cinchona barks exhibiting a distinctly yellowish brown colour it is better to specify this variety of yellow bark as calisaya bark. It was formerly imported in two distinct varieties, viz. (a) flat and (b) quill calisaya, but the former is now seldom seen.
(a) Flat calisaya was formerly imported in thick, flattish, heavy pieces 20 cm. or more in length, from 5 to 10 cm. in width, and varying frequently from 6 to 12 mm. in thickness. The inner surface was tawny yellowish brown in colour and showed a close fibrous structure, the undulating course of the fibres often communicating a wavy appearance to the bark. The outer surface was darker and marked with broad, shallow, longitudinal depressions (digital furrows). These were caused by the formation in the bark of concave lines of cork, by which shallow curved pieces of the bark had been cut off. This outer bark was commonly removed from the drug before exportation.
Fig. 132. - Calisaya bark. A, showing]the longitudinal fissures and transverse cracks, natural size; B, showing in addition exfoliating cork, natural size.
This, which at present is the variety of calisaya bark commonly seen, is principally obtained from plantations of G. Calisaya in Bolivia and Java. It occurs in quills varying usually from 12 to 25 mm. in diameter and 30 cm. or more in length, fine specimens attaining 60 cm. in length and 5 to 8 cm. in diameter. The outer surface is of a dull dark grey or dull brownish colour marked with lighter, whitish patches. The outer layer is rugged, and exhibits shallow, rather broad longitudinal fissures that are frequently of a brownish colour, and hence, even if not deep, are easily seen. Transverse cracks mark the bark at distances of 6 to 12 mm. This layer shows in many pieces a decided disposition to exfoliate, the inner portion, which is of a dull yellowish brown colour, bearing impressions corresponding to the cracks of the cork.
The bark breaks with a shortly fibrous fracture; the section exhibits a narrow dark brown outer layer (cork) and brown inner portion.
The taste is distinctly bitter and astringent, the former quality predominating.
2: G. Ledgeriana. - This species, which is considered by some botanists to be a variety of C. Calisaya, yields a bark that very closely resembles quill calisaya in general appearance and is remarkable for its richness in quinine. On this account the tree is being largely cultivated in Java and also in India in preference to other species; most of the ' yellow ' bark of commerce is Ledger bark imported from Java.
Commercial Ledger bark occurs usually in single, sometimes in double, quills about the same size as quill calisaya. The colour internally is a dull tawny brown, often with a reddish tinge; externally the quills mostly exhibit large light grey or whitish patches of lichen.
They are marked with longitudinal furrows and transverse cracks, which, however, are usually more numerous and less conspicuous than in quill calisaya; hence the bark is rougher than quill calisaya. Some pieces bear distinct longitudinal ridges and scattered reddish warts that recall typical red bark (see below), but from this bark they are easily distinguished by their colour and by their taste, which is bitter but not markedly astringent. Sometimes the cork shows a distinct disposition to exfoliate as it does in quill calisaya, but in this feature the bark varies considerably.
As already observed, Ledger bark bears a close resemblance to quill calisaya; it is best distinguished by its more numerous and less conspicuous longitudinal fissures and transverse cracks.
3. C. officinalis. - The bark of this species, commercially known as pale cinchona or crown bark, is obtained chiefly from India, although some is imported from South America. It occurs in quills only, and these are much narrower than those of quill calisaya, seldom exceeding 12 mm. in diameter, the bark itself being usually less than 1.5 mm. thick. They are frequently inrolled on both margins, so as to form double quills. The outer surface is of a dull brown colour, and often has foliaceous lichens adhering to it. Typical pieces are marked with numerous transverse cracks often less than 6 mm. apart, in addition to which there are numerous less prominent longitudinal cracks, all of which, but especially the transverse, tend to impart to the bark a roughness to the touch that is characteristic.