Encyclopædia Britannica, Ninth Edition/Cinchona

From volume V of the work.
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CINCHONA, the generic name of a number of trees belonging to the Natural Order Rubiaceæ, but which, with a few allied genera, have been by some authorities established as a distinct order under the name Cinchonaceæ. Botanically the genus includes trees of varying size, some reaching an altitude of 80 feet and upwards, with evergreen leaves and deciduous stipules. The flowers are arranged in panicles, white or pinkish in colour, with a pleasant odour, the calyx being 5-toothed superior, and the corolla tubular, 5-lobed, and fringed at the margin. The stamens are 5, almost concealed by the tubular corolla, and the ovary terminates in a fleshy disk. The fruit is an ovoid or sub-cylindrical capsule, splitting from the base, and held together at the apex. The numerous seeds are flat and winged all round. According to the enumeration of Bentham and Hooker, 36 species have been distinguished, but of these not more than about a dozen have been economically utilized. The plants are natives of the western mountainous regions of South America, their geographical range extending from 10° N. to 22° S. lat.; and they flourish generally at an elevation of from 5000 to 8000 feet above sea level, although some have been noted growing as high up as 11,000 feet, and others have been found down to 2600 feet.

The trees are valued solely on account of their bark, which as cinchona bark, Jesuits' bark, or Peruvian bark is, and long has been, the source of the most valuable tonic and febrifuge medicines that have ever been discovered. The earliest well-authenticated instance of the medicinal use of cinchona bark is found in the year 1638, when the countess of Chinchon, the wife of the governor of Peru, was cured of an attack of fever by its administration. The medicine was recommended in her case by the corregidor of Loxa, who was himself said to have practically experienced its supreme virtues eight years earlier. The name Cinchona is due to the connection of the countess of Chinchon with the introduction of the remedy; and it is argued by Mr Markham and others that therefore the term should be written Chinchona. A knowledge of the virtues of the bark was disseminated throughout Europe by members of the Jesuit brotherhood, whence it also became generally known as Jesuits' bark. According to another account, this name arose from its value having been first discovered to a Jesuit missionary who, when prostrate with fever, was cured by the administration of the bark by a South American Indian.

The procuring of the bark in the dense forests of New Granada, Ecuador, Peru, and Bolivia is a work of great toil and hardship to the Indian Cascarilleros or Cascadores engaged in the pursuit. The trees grow isolated or in small clumps which have to be searched out by the experienced Cascarillero, who laboriously cuts his way through the dense forest to the spot where he discovers a tree. Having freed the stem from adhering parasites and twining plants, he proceeds, by beating and cutting oblong pieces, to detach the stem bark as far as is within his reach. The tree is then felled, and the entire bark of stem and branches secured. The bark of the smaller branches, as it dries, curls up, forming “quills,” the thicker masses from the stems constituting the “flat” bark of commerce. The drying, packing, and transport of the bark are all operations of a laborious description conducted under most disadvantageous conditions.

The enormous medicinal consumption of these barks, and the wasteful and reckless manner of procuring them in America long ago, caused serious and well-grounded apprehension that the native forests would quickly become exhausted. The attention of European communities was early directed to the necessity of securing steady and permanent supplies by introducing the more valuable species into localities likely to be favourable to their cultivation. The first actual attempt to rear plants was made in Algeria in 1849; but the effort was not successful. In 1854 the Dutch Government seriously undertook the task of introducing the trees into the island of Java, and an expedition for that purpose was fitted out on an adequate scale. Several hundreds of young trees were obtained, of which a small proportion was successfully landed and planted in Java; and as the result of great attention the cultivation of cinchona plantations in that island is now highly prosperous and promising. The desirability of introducing cinchonas into the East Indies was urged in a memorial addressed to the East India Company between 1838 and 1842 by Sir Robert Christison and backed by Dr Forbes Royle; but no active step was taken till 1852, when, again on the motion of Dr Royle, some efforts to obtain plants were made through consular agents. In the end the question was seriously taken up, and Mr Clements R. Markham was appointed to head an expedition to obtain young trees from South America and convey them to India. In 1860 under Mr Markham's superintendence a first consignment of plants was shipped from Islay in Peru, and planted in a favourable situation in the Neilgherry Hills. For several years subsequently additional supplies of plants of various species were obtained from different regions of South America, and some were also procured from the Dutch plantations in Java. Now the culture has spread over a wide area in Southern India, in Ceylon, on the slopes of the Himalayas, and in British Burmah; and recently plantations which already present a promising appearance have been established in Mauritius. Exclusive of private enterprise, the trees in the Government plantations in India now amount to several millions, and in the Neilgherry plantations they have attained a height of from 20 to 30 feet. The species introduced in the East are principally Cinchona officinalis, C. Calisaya, C. succirubra, C. pitayensis, and C. Pahudiana, some agreeing with certain soils and climates better than others, while the yield of alkaloids and the relative proportions of the different alkaloids differ in each species.

In the original memorial above alluded to, presented to the East India Board by Sir R. Christison, he, according to a communication to the Edinburgh Botanical Society (Trans., vol. xi. p. 111), pointed out that “the transplantation, if successful, would become remunerative. For although it would be a very arduous undertaking were the bark to be collected only by cutting down large trees, which do not attain sufficient growth in less than twenty or twenty-five years, being the only American method, the case would be very different were it shown that bark could be profitably taken from trees very much younger, and without either destroying or even injuring them. Now, I had ascertained,” continues Sir Robert, “by chemical analysis that—contrary to the analysis of some French chemistssulphate of quinia was to be obtained from fine quills of yellow bark taken from twigs two or three years old in as large proportion as from the large flat bark from the trunks and great branches. Consequently, as it appeared, from the facility with which the trees grew in their native forests by suckers from the old roots, when the trunks are properly cut down, that young twigs might safely be cut from them at an early period, it followed that the collection of cinchona bark might be conducted in the same way as that of cinnamon bark at Colombo, where only twigs of one or two years' growth are cut for the purpose, and without injuring the trees . . . . This doctrine has proved true, so true that it has been found suitable in India even to treat the cinchona plants like osier beds in England, by cutting them down altogether when young, thus using only twigs for the bark, and trusting to suckers for renewing the growth of the plants; and that the result has been the introduction of fine bark from India in such bulk as to have been sold by auction in the London market only nine years after the first cinchona plants were transplanted to India.” Mr. W. G. M‘Ivor, to whom the success of Indian plantations is largely due, introduced a system of mossing the plants, which consists in wrapping the growing stems in a layer of damp moss, whereby the yield of alkaloid is increased, and the growth of renewed bark promoted. It has been pointed out by Dr De Vrij, and the observation is confirmed by Mr D. Howard, that renewed bark contains the alkaloids not only in different proportions from the original bark, but that it even develops principles altogether absent in the natural bark.

The officinal barks of the British Pharmacopœia are three in number:—(1) the pale or Loxa bark (cortex cinchonæ pallidæ) yielded by Cinchona officinalis; (2) the yellow, royal, or Calisaya bark (cortex cinchona flavæ), the produce of C. Calisaya; and (3) red bark (cortex cinchonæ rubra) derived from C. succirubra. These are the sources of the tinctures, extracts, and other preparations of pharmacy, while, in common with several others, they also yield the alkaloids which now constitute the chief form in which the active principles of the barks are administered in medicine. Among the other barks used as sources of quinine, &c., the principal are—the ashy crown bark, C. macrocalyx; Carthagena bark, C. lanceolata; Columbian bark, C. lancifolia; Pitayo bark, C. pitayensis; grey or Lima bark, C. micrantha, C. nitida, and C. peruviana.

Leaving out of view certain alkaloids unimportant as yet in a commercial view, and found very sparingly in particular barks, the four primary alkaloids yielded by cinchona barks are quinine, quinidine, cinchonine, and cinchonidine. Certain secondary alkaloids are developed by chemical treatment of these primary principles, and an amorphous substance precipitated from the mother liquors of the quinine manufactured under the name of quinoidine is in considerable medicinal use. Much confusion has arisen in the terminology of the alkaloids by the application of the same name to chemically distinct principles, and by the converse description of the same alkaloids or products under different names. It is found that different barks derived from the same species vary greatly in richness in alkaloids, and that equally great fluctuations occur in the relative proportions of the various principles they yield. When a comparison is instituted among the barks of different species the variations are of course even more marked,—some barks having been found to yield as high as 13 per cent. of alkaloids, while in others not a trace has been obtained. Certain barks, however, are known as a rule to contain quinine in largest proportion, and in others cinchonine is the most abundant principle. Generally quinine is the most constant and abundant constituent, after which cinchonine, then cinchonidine, while quinidine is the rarest both in proportion and in frequency of occurrence of the principal alkaloids.

The preparation of cinchona bark most extensively employed in medicine is the alkaloid quinine in the form of a sulphate. As the barks from which it is extracted contain besides proportions of one or other of the principal alkaloids above enumerated, a demand for any of them might be supplied without interfering with the production of quinine, and as they also have been proved to be potent febrifuges their non-utilization is a regrettable waste. From the record of an extensive series of experiments instituted by the Indian Government it is demonstrated that quinidine is even more active than quinine, and it forms the principal constituent of a variety of calisaya bark in extensive cultivation in Java. Cinchonidine is only a little less powerful in its febrifugal effect than quinine, and it is abundantly formed by the red bark cultivated in British India. Cinchonine, although the least potent, is an abundant principle, and still a highly valuable and efficient remedial agent.

(j. pa.)