Chapter 14 of 45 · 1424 words · ~7 min read

chapter I

propose to give a brief account of each of these regions, of their chinchona-trees, and of the investigations of botanists down to the time when measures were taken to introduce these inestimable plants into Java and India. Such an account will naturally divide itself into five sections:--

I.--The Loxa region, and its _crown barks_. II.--The _red-bark_ region, on the western slopes of Chimborazo. III.--The New Granada region. IV.--The Huanuco region in Northern Peru, and its _grey barks_. V.--The _Calisaya_ region, in Bolivia and Southern Peru.

Before entering on this subject, however, it will be well to cast a hasty glance at the progress of those investigations which ended in the discovery of the febrifugal principle in Peruvian bark.

The roots, flowers, and capsules of the chinchona-trees have a bitter taste with tonic properties, but the upper bark is the only part which has any commercial value.[26] The bark of trees is composed of four layers--the epiderm, the periderm, the cellular layer, and the liber or fibrous layer, composed of hexagonal cells filled with resinous matter and woody tissue. In growing, the tree pushes out the bark, and, as the exterior part ceases to grow, it separates into layers, and forms the dead part or periderm; which in chinchonas is partially destroyed, and blended with the thallus of lichens. The bark is thus formed of the dead part, or periderm, and the living part, or derm. On young branches there is no dead part, the exterior layers remaining entire, while the inner layers have not had time to develop. In thick old branches, on the contrary, the periderm or dead part is considerable, while the fibrous layer of the derm is fully developed. In preparing the bark the periderm is removed by striking the trunk with a mallet, and the derm is then taken off by uniform incisions. The thin pieces from small branches are simply exposed to the sun's rays, and assume the form of hollow cylinders, or quills, called by the natives _canuto_ bark. The solid trunk bark is called _tabla_ or _plancha_, and is sewn up in coarse canvas and an outer envelope of fresh hide, forming the packages called _serons_.

The character of the transverse fracture affords an important criterion of the quality of the bark. Cellular tissue breaks with a short and smooth fracture, woody tissue with a fibrous fracture, as is the case with the _calisaya_ bark. The best characteristics by which barks containing much quinine may be distinguished are the shortness of the fibres which cover the transverse fracture, and the facility with which they may be detached, instead of being flexible and adhering as in bad barks. Thus, when dry _calisaya_ bark is handled, a quantity of little prickles run into the skin, and this forms one of its distinguishing marks.[27]

Until the present century Peruvian bark was used in its crude state, and numerous attempts were made at different times to discover the actual healing principle in the bark, before success was finally attained. The first trial which is worthy of attention was made in 1779 by the chemists Buguet and Cornette, who recognised the existence of an essential salt, a resinous and an earthy matter in quinquina bark. In 1790 Fourcroy discovered the existence of a colouring matter, afterwards called _chinchona red_, and a Swedish doctor named Westring, in 1800, believed that he had discovered the active principle in quinquina bark. In 1802 the French chemist Armand Seguin undertook the bark trade on a large scale, and found it necessary to study the means of discovering good barks, and distinguishing them from bad ones. He found that the best quinquina bark was precipitated by tannin, while the bad was not precipitated by that substance. In 1803 another chemist found a crystalline substance in the bark which he called "_sel essentiel fébrifuge_" but it was nothing more than the combination of lime with an acid which was named _quinic acid_. Reuss, a Russian chemist, in 1815, was the first to give a tolerable analysis of quinquina bark; and about the same time Dr. Duncan of Edinburgh suggested that a real substance existed as a febrifugal principle. Dr. Gomez, a surgeon in the Portuguese navy, in 1816, was the first to isolate this febrifugal principle hinted at by Dr. Duncan, and he called it _chinchonine_.[28]

But the final discovery of quinine is due to the French chemists Pelletier and Caventou, in 1820. They considered that a vegetable alkaloid, analogous to morphine and strychnine, existed in quinquina bark; and they afterwards discovered that the febrifugal principle was seated in two alkaloids, separate or together, in the different kinds of bark, called _quinine_ and _chinchonine_, with the same virtues, which, however, were much more powerful in quinine. It was believed that in most barks chinchonine exists in the cellular layer, and quinine in the liber, or fibrous layer; but Mr. Howard has since shown that this view is quite incorrect.[29] In 1829 Pelletier discovered a third alkaloid, which he called _aricine_, of no use in medicine, and derived from a worthless species of chinchona, growing in most of the forests of Peru, called _C. pubescens_.[30]

The organic constituents of chinchona barks are--

These materials are in different proportions according to the barks. Grey bark chiefly contains chinchonine and tannin; Calisaya, or yellow bark, much quinine, and a little chinchonine; red bark holds quinine and chinchonine in nearly equal proportions; while the barks of New Granada chiefly contain chinchonidine and quinidine. The two latter alkaloids were definitively discovered in 1852 by M. Pasteur; although the Dutch chemist Heijningen had, in 1848, found what he called β quinine or quinidine. Chinchonidine is only second to quinine itself in importance as a febrifugal principle.

_Quinine_ is a white substance, without smell, bitter, fusible, crystallized, with the property of left-handed rotatory polarization. The salts of quinine are soluble in water, alcohol, and ether. Of all the salts the bisulphate of quinine is preferred, because it constitutes a stable salt, easy to prepare, and containing a strong proportion of the alkaloid. It is very bitter and soluble, and crystallizes in long silky needles. It is prepared by adding sulphuric acid to the sulphate.[31]

_Chinchonine_ differs from quinine in being less soluble in water, and being altogether insoluble in ether. It has the property of right-handed rotatory polarization.

_Quinidine_ also has the property of right-handed rotatory polarization, and forms salts like those of quinine. It becomes green by successive additions of chlorine and ammonia.

_Chinchonidine_ has not the property of turning green, and forms a sulphate almost exactly like sulphate of quinine.[32]

The discovery of these alkaloids in the quinquina[33] bark, by enabling chemists to extract the healing principle, has greatly increased the usefulness of the drug. In small doses they promote the appetite and assist digestion; and chinchonine is equal to quinine in mild cases of intermittent fever; but in severe cases the use of quinine is absolutely necessary. Thus these alkaloids not only possess tonic properties to which recourse may be had under a multitude of circumstances, but also have a febrifugal virtue which is unequalled, and which has rendered them almost a necessary of life in tropical countries, and in low marshy situations where agues prevail. Many a poor fellow's life was saved in the Walcheren expedition by the timely arrival of a Yankee trader with some chests of bark, after the supply had entirely failed in the camp.[34] Dr. Baikie, in his voyage up the Niger, attributed the return of his men alive to the habitual use of quinine; and the number of men whose lives it has saved in our naval service and in India will give a notion of the vast importance of a sufficient and cheap supply of the precious bark which yields it. India and other countries have been vainly searched for a substitute for quinine, and we may say with as much truth now as Laubert did in 1820--"This medicine, the most precious of all those known in the art of healing, is one of the greatest conquests made by man over the vegetable kingdom. The treasures which Peru yields, and which the Spaniards sought and dug out of the bowels of the earth, are not to be compared for utility with the bark of the quinquina-tree, which they for a long time ignored.[35]