EXPERIMENTS ON LIVING CINCHONAS. 
No. 1 refers to a kind (whether species or variety is not accurately determined) which 
was found on the plantation among some plants raised from seed brought by Mr. Cross 
from the Loja district; it gives the largest yield of quinine of any kind known. The 
first five are quinine-yielding kinds, but in which cinchonidine may occur in greater or 
less degree. Nos. 6 and 7 are nearly destitute of quinine. 
The thin bark on the larger roots is still richer in alkaloids, and in C. succirubra the 
yield is generally about 9-70, and may reach 12 per cent. It consists principally of 
cinchonidine and cinchonine. The root-bark of C. officinalis is also rich in alkaloids ; 
analysis gave 5 -4 per cent. The root-bar k has been little investigated, as the difficulty 
of obtaining; it would render it an unsuitable source of alkaloids. I ascribe its richness 
in alkaloids, for reasons given below, to the circumstance of it being shielded from the 
rays of the sun. 
The leaves of cinchona are bitter from the presence of quinovin, and acid from free 
quinic acid. In many early trials I failed to get full and satisfactory evidence of the 
presence of alkaloids. By working with great care upon 20 lbs. of the leaves, I obtained 
a small amount of rough uncrystallizable alkaloid, which, by solution in weak acetic acid, 
exposure to a stream of air to facilitate oxidation, decolorization with animal charcoal, 
reprecipitation, drying, several times repeated, I procured tolerably pure and colourless. 
From this I obtained well-defined crystals of the quinine sulphate and oxalate, and un- 
mistakable crystals of cinchonidine and cinchonine from their weak alcoholic solutions : 
the amounts are, however, very small. Other trials, conducted quantitatively, gave the 
following results, which are given in percentages of the dry and fresh leaves : — 
C. succirubra. 
C. officinalis. 
In fresh. 
In dry. 
| In fresh. 
In dry. 
Total alkaloids 
0-0041 
0-019 
0-0035 
0-0111 
Quinine 
0-0016 
0-008 
0-0015 
0-005 
Cinchonidine and cinchonine 
0-0025 
0-011 
0-0020 
0-006 
Quinine sulphate obtained in crystals ... 
0-000/8 
0-0037 
0-0008 
0-002 
It is evident from the above that the leaves are useless as a source of alkaloids. The 
state of their occurrence is wholly different to that in which they occur in the hark. 
The wood of cinchona also contains the alkaloids in small amount ; they are there 
associated with a red resin and the cinchona tannin. In C. succirubra the alkaloids may 
amount to 0T per cent., of which 0 - 03 is quinine and the remainder cinchonine and cin- 
’WittsteijSt’s cinchonidine. In my examination of the hark of G. peruviana, I also found a form of cinchonidine 
the pearly centre of whose crystalline sulphate and other properties agreed exactly with Wittsteix’s description. 
By repeated crystallization of its sulphate from water, and then of the free base from alcohol, it was obtained 
apparently pure ; it was then carefully compared with a standard specimen of ordinary cinchonidine in the 
polarimeter, and found to possess precisely the same rotatory power. I cannot therefore consider it a distinct 
substance ; I therefore only recognize one form of cinchonidine in the text. 
B 2 
