47 



Medicinal Plants. 



The cultivation of these barks under such skillful management has thrown 

 light on many questions as to the formation of alkaloids in these barks. Samples 

 of wood and leaves of the trees were carefully examined for the alkaloid, but none 

 was found in either ; it seems, therefore, that the elaboration of the alkaloids takes 

 place solely in the downward course of the sap. Further, that the percentage of 

 alkaloid constantly increases in the bark from the twigs to the ground, and certainly 

 in the less flourishing tree the root bark is richer still. Another curious point is 

 shown by such analyses, namely, that the root alkaloid invariably contains more 

 of the dextogyrate alkaloids, quinidin and cinchonine, than the bark of the same 

 tree above the ground. 



Another point of great interest that has been made very clear is, that the 

 more flourshing a tree is the more alkaloid it will produce, and the result of culti- 

 vation has been to produce bark yielding 10 per cent, or even more of alkaloid ; 

 this is three or four times as much as was found in the average wild barks of 

 commerce. I remember that the first 5 per cent, bark I tested, astonished me so 

 much that I at once repeated the analysis, thinking that my weighings must have 

 been wrong. To obtain such results as these, however, it is necessary to have the 

 best varieties as well as healthy trees. The yield from trees growing side by side, 

 all from the same cultivation, of the same seed, in the same soil differs very widely, 

 and a great number of analyses of individual trees showed by the irregular 

 incidence of good and bad tests that the variation must be in the trees and not in 

 the conditions of growth. 



* * * By the application of various manures to these trees, it was shown 

 that such manures as increased the apparent vigour of the trees increased their 

 alkaloid yield, and that for this purpose nitrogenous manures were the best. 



I may mention that for the purpose of these analyses, the trees were not cut 

 down, but strips taken from them at the same height above the ground. 



As the wood of the trees is of little or no use, a system of bark collection 

 was adopted in India and Ceylon, similar to that by which cork is obtained. In this 

 country, if a portion of the bark is taken from a tree, nature makes an attempt to 

 heal over the wound, but the process is capricious and often fails, but in hot climates 

 it takes place much more freely, provided always that the cambium is not 

 damaged. Of course, the partial removal of the bark must be longitudinal, ringing 

 a tree will kill it even in the tropics. 



The plan successfully introduced by Maclvor was as follows :— Incisions 

 were made down the trees about an inch apart and of any convenient length, 

 the enclosed strip being carefully cut across at the top and bottom, the strip 

 was pulled off and dried, a strip of bark was then left untouched, and then 

 another strip taken and so on all around the tree, which was then wrapped 

 round with moss to keep off the sun and air, and in an amazingly short space 

 of time the cambium poured out sap which formed bark all over the wound, 

 not only at the side as we so often see in this country. The next year the 

 strips left on the tree, or a portion of them, could be similarly treated, and 

 the second or third year the renewed bark could be taken off and the same 

 process of healing would take place. A similar process has also been treated 

 by cutting shavings off the trees with a spokeshave, but though involving much 

 less labor, it is less effectual, as it is most difficult to cut deeply enough into 

 the bark to ensure the process of renewal without damaging the cambium. 



The renewed bark gives very interesting results, it is in the first place richer 

 in alkaloid ; this is not surprising, as it has always been found that the alkaloids 

 were chiefly contained in the cellular tissue of the bark, not in the fibrous 



