to err in using it; nor is it proper in the latter to depreciate 
such knowledge without previeusly ascertaining the truth or 
discovering the fallacy, by means of experiments and obser- 
vations, undertaken with a clear and distinct knowledge of 
the medicine itself, of the state in which it is found, and of its 
constituent principles ; because, without these premises, rea- 
son may convince us how uncertain all the experiments must be 
which we may try for ascertaining the virtues and uses of any 
substance whatever. : 
In order to remedy the mixtures made.of other roots with those 
of the genuine Calaguala, it appears to me that the only ob- 
vious and practicable method for the present, is, that the traders and 
merchants of Cadiz, as well as other individuals or companies, 
should charge their correspondents in Peru, to take care that 
in’ those regions the very roots of the Calaguala should be col- 
lected which are sold fresh in the Square of Lima, and that there be 
left to each root, or to most of them, a leaf, which may serve as a 
criterion for the identity of the species, until such time as our 
merchants, druggists, and professional men, have acquired such 
skill in distinguishing it, as not to require an indication which 
is at present so important and necessary. 
