42 Experiments upon the 



agents as its infusion ; but the latter differs from the decoc- 

 tion of yellow cinchona in not becoming turbid during cool- 

 ing : thus the Santa-F^ bark not only does riot contain the 

 matter which precipitates emetic, but is also deficient in the 

 quantity of the principle which precipitates the other me- 

 tallic solutions ; for I am assured that the deposit formed in 

 the decoction of cinchona, upon cooling, is the substance 

 which in this species precipitates iron green, lead yellow, 

 copper brown, &c.; and that it has no action upon emetic. 

 Thence we may presume, at least, that it would be neces- 

 sary to employ in intermittent fevers a greater quantity of 

 this than of the yellow bark. 



Third Species. — Graij Cinchona, called Superior Cinchona. 



Tlie infusion of this kind of bark is almost colourless; its 

 taste is bitter and astringent. 



It precipitates very abundantly the solution of glue white; 

 the infusion of tan red ; the solution of emetic white, and 

 very abundant ; sulphate of iron a very fine emerald green ; it 

 produces no change in tlie infusion of yellow cinchona. 



Fourth Species. — Gray Cimiamon Cinchona. 



The infusion of this bark has a deep red colour, a bitter 

 and astringent ta^te. 



In solution of glue it yields a fawn-coloured precipitate, 

 and communicates a green colour to solution of sulphate of 

 iron, but does not precipitate the emetic solution like the 

 gray and yellow cinchona. It occasions no change in the 

 infusion of superior grav" cinchona. 



This species differs, therefore, from the yellow and supe- 

 rior gray cinchona, in so far as it does not seem to contain 

 that principle which precipitates the emetic ;^ and in this re- 

 spect it resembles that of Santa- F(>. 



The infusion of tills bark yields a very abundant fawn- 

 coloured brown precipitate in an infusion of yellow cincho- 

 na, and does not precipitate the infusion of tan. 



These vegetable infusions, precipitated the one bv the other 

 a"? completely as it is possible, have no effect upon emetic ; 

 ;\hcnc(. it follows, that the principle which in the yel- 

 low 



