CHEMICAL AND MICROSCOPICAL INVESTIGATIONS, 
11 
the tissues and component portions of the hark.* This is not more wonderful than many similar facts, 
both in the animal and vegetable world ; but the truly remarkable circumstance is the very large amount 
of alkaloid found in the bark of the third time of renewal, in a state also easily purified and better fitted 
for the extraction of Quinine than the bark in its normal condition. 
Is this state of things to last and become permanent, so that by continually stripping the trees of 
portions of their external covering, it should become in the same proportion more rich in the very product 
that we need ? This seems very improbable ; and yet it is the conclusion to be arrived at from the above 
experiments ; and even theoretically considered, it may not be so unlikely as at first it appears. If the 
Quinine, like the chlorophyll, had to be elaborated almost entirely in the leaves, I confess that such a result 
would seem very unlikely, as it would render a more vigorous condition of the leaves necessary, or else a 
more abundant production of these respiratory organs of the plant ; and it is quite certain that nothing of 
the sort could happen from the removal of the bark. Moreover, chemical analysis comes in aid of our 
conjectures, and shows conclusively that the leaves are so far from being a chief seat of the alkaloids that 
they possess only a trace of these. 
Neither can the bark which remains round the decorticated portion be looked upon as the chief source 
of supply of alkaloids, more particularly since the following experiment of Mr. Broughton seems con- 
clusively to show the contrary, and that, instead of finding an increase in the alkaloids in such a case, the 
reverse is the fact. In Mr. Broughton’s Beport for April, 1867, he says -. — 
“ It appeared to me that an examination of the hark that had been renewed by natural processes, without the 
aid of moss, would possess considerable interest. It was suggested by a statement in Howard’s £ Nueva Quinologia 
of Pavon,’ and also given on the authority of Ruiz. I was able to obtain a small quantity of such renewed bark 
from two succirubra trees, Avhich had been injured and partially stripped of their bark by the falling of a log in 
October, 1864. The renewed bark was thicker than that of the natural bark, measuring 0-19 to Q-22 inch, instead of 
0-16, and had replaced itself mainly from the edges of the ivound , not from the surface , as is the case with mossed hark ; 
but its analysis gave but 5 per cent, of alkaloids, of which about 3 - 25 appeared to consist of Chinehonidine 
and Chinchonine.” 
This experiment seems to me important, as tending to the conclusion that the sap which is conveyed 
from the adjoining bark does not contain all the materials needful for the abundant production of Quinine 
and the other alkaloids. Nehemiah Grew was perhaps right in saying “ that the concurrence by two 
specifically distinct fluids is as necessary to nutrition in plants as in animals.”f Whence then can the 
cambium derive these supplies if not from the heart-wood? — a source which, as we have seen by the 
appearance of the sappy matter at the end of the medullary rays, is already rendered probable. 
Mr. Broughton remarks, in a letter dated March 16, 1868, “ I have long remarked that the bark, 
when carefully removed without injury to the cambium , quickly renews itself from beloAV, not from the edge. 
The analysis made of bark so renewed, of six months’ growth, has at present corroborated your statement 
respecting the old practice of the cascarilleros, as being richer in alkaloid than the original.” 
Mr. MTvor writes, f “the new bark rises direct from the sap-wood if the old bark is carefully removed ; 
in three days the new baric is formed entirely over the tvhole surface, i. e. rising directly from the sap [wood], 
and not formed by a current of cambium from under the remaining bark ; as, in the general opinion, is the 
manner in which all wounds are repaired.” 
The Heart-wood . 
The heart-wood comes next in review as a possible source of alkaloid. My attention was directed to 
the examination of it for Quinine by a letter from Mr. Broughton, in which he mentions, in the following 
* “ Les jeunes tissus A^egetaux, ceux de la couche generatrice en particular, ont la propriete de se modifier, de se metamor- 
phoser pour produire tel ou tel organe dans telle ou telle situation, suivant les besoins de la planted — Trecul, Ann. des Sciences 
Naturelles, tome xvii. 1852, p. 276. + f The Anatomy of Plants/ book iii. p. 131. J In Letter, 3rd June, 1868. 
