Notes on Cinchona Bark.


A curious evidence of the singular scientific acumen shown by the late Mr. McIvor in working out his process for renewing cinchona bark is given by some of the samples of "renewed" C. succirubra bark which reach us from Ceylon.

As is well known, in Mr. McIvor's process, alternate strips of the bark were removed down to the cambium, and the tree wrapped round with moss. The bark then renews over the whole surface, the new bark consisting almost entirely of cellular tissue, the total alkaloid being increased, and the cinchonidine giving place to quinine.

The "renewed" bark to which I call attention, on the other hand, shows a totally different structure; there is a mere skin of cellular tissue, the remainder being remarkably fibrous.

The explanation is not far to seek, the shaving process recommended by M. Moens as a substitute for Mr. McIvor's process gives good results just in proportion as it imitates the latter process. If the cut is sufficiently deep to cause the effusion of new bark, if I may so call it, the result both in quantity and quality of the renewed bark closely resembles that yielded by the stripping process.

But if, as is often now the case, the shaving is merely superficial and carried all around the tree the result is entirely different; in this case there is little or no formation of cellular tissues to replace that removed, a fresh epidermis forms, but apparently the circulation is carried on in the remaining fibrous tissue, which in fact seems to be developed further. The alteration in the composition of the alkaloid which is so characteristic of the true renewal does not take place in this case; if there is any change it is rather in the direction of an increase of the cinchonidine instead of quinine.

The subject is not merely interesting from the light it throws upon McIvor's process, but it is one of great commercial importance. Unless the shaving process is so carried on as to produce, at least in part, the beneficial results of the older process of renewal it will lead to grievous disappointment, for the trees seem to suffer more from the wrong treatment than from the right.

It is to be feared that in many cases the temptation to get a quick return from the plantation by over-frequent and unskilful shaving is risking not only the quality of the crop but the health of the trees. Some planters are even advocating a return to the barbarous system of coppicing; but it is difficult to believe that this will generally be the case, with the strong evidence before their eyes of the benefits to be obtained by the more scientific system of treatment.

I do not venture into the vexed questions of hybrids and species in red bark; but when I find that "red bark" can be obtained yielding up to 4 and 5 per cent. of quinine from natural bark, I am very sure that there is a great field for skill in the selection or cultivation of cinchonas. There is much to be learned in these matters. In the last drug sales, some samples of bark marked "hybrid" gave 4 per cent. of quinine, while others, also "hybrid," gave only 1 per cent. of quinine.

It is evidently no easy matter to distinguish by the eye the different varieties of trees which produce red bark of widely different quality. Some time ago I analyzed a number of samples of bark from individual trees, sent me by J. A. Campbell, Esq., from Ceylon. They were renewed bark from trees giving red bark of very fine quality; the plants were all from the same nurseries, and were supposed to be of identical quality.

I found, however, that they varied very widely in the richness of the bark, as will be seen from the following table:

No. Quinine. Cinchonidine. Cinchonine. Quinidine.
1 6.2 0.3 0.3 0.1
2 2.6 0.6 trace. 0.4
3 2.0 1.6 1.2 0.2
4 4.0 0.2 0.2 0.1
5 4.0 0.2 0.7 0.7
6 2.3 0.5 1.2 0.8
7 2.3 0.9 1.7 0.0
8 2.8 0.3 1.3 0.1
9 4.1 0.1 0.2 0.1
10 3.9 0.1 0.2 0.2

Mr. Campbell tells me that "notwithstanding the extraordinary difference in the analysis there is little difference to be seen between the most of the trees. Some are pubescent, however, and some are glabrous; some have rounder leaves than others and in some the flower is white, except in the centre of the corolla tube which is pink. Others, again, have pink flowers. Nos. 1, 2, 4, 9 and 10 are what we used to call hybrids; of these 4, 9 and 10 are much like officinalis in leaf and bark. No. 2 is subpubescent in leaf and only a moderate grower, the leaf being rounder than 4, 9 and 10, and lighter in color. No. 1 is exactly what we would imagine, from Mr. Cross and Colonel Beddome's description, to be a true Pâta de Gallinazo. Leaf glabrous shiny on upper surface, soft, flat, and pointed at end; a fine grower considering the soil it is in." It is evident, therefore, that no general description will suffice to guide a planter in selecting the best sorts, but that the subject requires a minute study of individual trees of which the bark has been analyzed.

Calisaya bark shows equal variations between different trees. I have found individual trees growing together in Ceylon to vary from 3.1 per cent. to 9.2 per cent. of quinine, and individual trees similarly growing together in the Wynaad to vary from 7.6 per cent. to 0.7 per cent. of quinine.

These variations can hardly be attributed to soil; the red barks were all growing in similar soil and under similar circumstances, and the Ceylon calisayas were also apparently growing under similar conditions.

No doubt soil does influence the richness of the bark to a very great extent; samples of bark from trees grown on poor soils, as far as my experience goes, always test below similar barks on rich soils. The richest bark, both succirubra, and calisaya, that I have tested from Ceylon has been from land richly manured for coffee.

I think I have given instances enough to show how great are the possibilities of advantage in selection of the richest varieties of bark, while the study of soils, and the best mode of manuring and of preserving the bark, offer a wide field for profit to the intelligent planter. It is evident that if an 8 per cent. bark can be obtained from a tree giving an equal crop to those yielding 1 per cent. bark the increased value of the crop must be out of all proportion to the extra care in selection. Whether planters will have to adopt grafting or propagation by layers or cuttings, or whether it will prove practicable to obtain certain results from selection of seed or plants, is a matter of experience. Everything points to a great over-production of inferior bark, but there is little fear of the better qualities bringing remunerative prices if wisely cultivated.— Phar. Jour. and Trans.

The American Journal of Pharmacy, Vol. 55, 1883, was edited by John M. Maisch.