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- 

 quivocal result, that the same species of bark which when 

 fresh is very productive 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 bark as to age, and it may perhaps be 

 useful in this place, to describe the physical characters of 

 bark in this state, and by which it may be readily known. 

 The prominent features which characterize old bark, and 

 distinguish it from recent, are the following. Old bark has 

 lost nearly all that bitter and astringent taste and peculiar 

 aromatic odor, which are such prominent characteristics of 

 recent bark of good quality. The specific gravity is also 

 sensibly diminished, and the fracture instead of being shin- 

 ing and compact is dull, fibrous and of a loose texture, and 

 the color very frequently passes from a bright orange to a 

 dull brown, as the bark advances in age, particularly if much 

 exposed. By attention to these few conspicuous characters, 

 taste, smell, specific gravity, fracture and color, no mistake 

 can arise in the selection of good bark, unless there 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 public in this particular, by men 

 whom we might suppose most capable of appreciating the 

 quality, under the influence of every incidental circumstance. 



Dr. Paris in the sixth edition of his Pharmacologia, makes 

 the following remarks under the article 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 bark, 

 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 



