Observations and Experiments on Peruvian Bark. 37 
From a number of experiments which I have made upon 
Peruvian bark in different states, I have observed as an une- 
—— result, that the same species of bark which when 
fresh is very producti ve of quinine, when old will produce 
little or none of this active principle, upon which its virtue 
as a medicine entirely depends 
It will appear therefore an important duty, critically to ex- 
amine the state of hark as to age, and it may perhaps be 
useful in this place, describe the physical characters of 
ark in this state, a y which it may be readily known. 
The prominent Genii which characterize old bark, and 
distinguish it from recent, are the following. Old ba rk has 
lost nearly all that bitter and astringent taste and peculiar 
aromatic odor, which are such prominent nthe of 
the color very frequently passes from a bright orange toa 
dull brown, as the bark advances in age, particularly if much 
ex y attention to these few conspicuous characters, 
taste, smell, specific gravity, fracture and color, no m istake 
can arise in the selection of good bark, unless tists is a 
gross deficiency of judgment. Yet notwithstanding the dis- 
tinguishing characters of Peruvian bark in these two states 
are so prominent and striking, we regret to say, that gross 
mistakes have been made Pek in this particular, by men 
whom we might suppose most capable of appreciating the 
quality, under the. influence a an incidental circumstance. 
aris in the six tion of his Pharmacologia, makes 
the fo lowing remarks under the caficle cinchona. The 
frauds committed under this head are most extensive ; it is 
not only mixed with inferior bark, but frequently with genu- 
ine bark, the active constituents of which have been extract+ 
ed by decoction with water. In selecting cinchona 
the following precautions may be useful; it should be dense, 
heavy and dry, not musty, nor spoiled by moisture ; a decoc- 
tion made of it should have a reddish color when warm, but 
when cold it should become paler, and deposit a brownish 
red sediment. When the bark is of a dark color, between 
red and yellow, it is either of a bad species or it has not been 
well preserved. Its taste should be bitter, with a slight acid- 
ity, but not nauseous nor very astringent; when chewed, it 
should not appear in threads nor of much length, the odour 
