MICROSCOPICAL OBSERVATIONS. 
vii 
Appendix. The comparison with “ the second crop of renewed bark ” will there he found, and it will be 
seen that whilst there is a certain amount of increase in the total amount of the alkaloids obtained, yet in 
the production of crystallized sulphate of quinine there is a falling off in the third crop, and that it proved 
more difficult to work than the second. 
The different season of the year at which the two crops of bark were gathered may have had something 
to do with this. The second crop was stripped from the trees in September and October, I860, and, as it 
appears,* “ at a season of full and luxuriant growth, when the sap is in full flow.” It seems to me that the 
sections show the cellular structure to be gorged with recent supplies of nourishing sap, bringing with it 
abundance of the mother substance from the wood. This is probably just changing into Cinchona red and 
other products; among which the alkaloids are the most important, but the colouring matter the most 
manifest to the sight. At an early stage of oxidation this colouring matter is probably in a state comparable 
to that which I have described in another place.f A solution of pale liquor from red bark, after the fully 
oxidized Cinchona red had separated out by cooling, was mixed with isinglass, and when formed into a jelly, 
suffered to oxidize slowly; this it did very prettily, turning red from the outside ; ammonia greatly expedited 
the process. The colour in these sections partakes both of the Cinchona red tint and that of another 
colouring substance of the bark, which is probably simultaneously formed. 
The bark from which the specimens in this present Plate III. was taken, was (on the other hand) 
gathered in March, which must be a period of complete rest to the plant ; for even in Eebruary, being the 
dry season, this is said to be the case,); and “ the sap begins to rise in the early part of April.” Everything 
in the appearance of the specimens seems to agree well with the period of rest. The abundance of liber 
fibres well filled up even to the region of the cambium — the segregation of the different products of vegeta- 
tion into different regions of the bark, all coincide well with this view. 
Pesin is deposited in abundance near the outside, and some other indications in the same zone direct 
attention to the deteriorating change which goes forward in the outer bark, even to some extent when this 
is mossed. 
In the liber are seen feathery crystals as of a kinovate, and, in the lax cellular tissue, globular concre- 
tions of imperfect crystalline structure (some also transparent and homogeneous) of more soluble salts of 
quinine ; such I judge these to be from finding this state of things common in rich Calisaya bark. The lax 
fibre of the cellular envelope in the Calisaya is often filled with such masses, sometimes reminding of the 
appearance of candied honey. 
I cannot help connecting with the above state of things the large proportion of uncrystallizable 
quinine in this third crop. My own view of the matter (differing from some able chemists, and which there- 
fore, though sustained by experiments of my own, I express with reserve) is that this amorphous condition of 
quinine is not one connected with its formation , but with its degradation , and this latter in some way through 
the influence of resin which is associated with it at the same time. The same circumstances, viz. heat and 
light, which favour the production of cinchonidine, are noticed by both Mr. Broughton and myself to favour 
that of resin ; and as these must tell most on the outside of the bark, we have a reason for that deposition 
of resin near the cork, which is evident in many of the sections. It is particularly difficult to purify 
cinchonidine from resin. 
More extended researches will indicate the proper season for gathering the bark ; but the conclusions 
to be drawn from the examination of the second and third crop of renewed bark seem, as far as they go, 
to indicate the period of the full flow of the sap as more favourable than that of the repose of the plant 
for obtaining the maximum of quinine in a crystallizable state. 
* W. G. MGvor to Sec. Gov., 3rd Oct. 1863, No. 91 also. f Illustr. Nueva Quinologia, Mic. Illustr. p. 8. 
J W. G. MGvor to Sec. Gov., 17 March, 1864; also 3rd May, 1865. 
