varluus Species of Cinchona. 141 



properties. This principle is not identically the same in all 

 cinchonas ; it differs in those which precipitate the infusioa 

 of tan and emetic, and in those which precipitate glue only. 



It is probable that it is a very analogous principle whicli 

 most commonly gives vegetables their bitter taste. 

 The Properties of Cinchova resumed. 



1. Wc may dividcvthe different species of cinchonas into 

 three sections, relative to their cheinica! properties. 



In the first we comprise all those which precipitate tan- 

 nin, and do not precipitate animal gelatine. 



Ill tlie second we include the cinchonas which precipitate 

 arimal gelatine and do not precipitate tannin. 



hi the third we tlass those which precipitate at the same 

 time tannin, animal gelatine, and emetic. 



2. We may conjecture, with every appearance of proba- 

 bilitv, that every vegetable substance which does not possess 

 at least one of the properties above indicated will not be a 

 febrifuge; and it is probable, also, that the more of these 

 properties is possessed by cinchona and other vegetable sub- 

 stances, the more remarkable will their febrifuge properties be. 



3. The property of precipitating tannin not being common 

 to all the cinchonas, it is not from that exclusively they de- 

 rive their febrifuge virtue, since there are several of them 

 which do not precipitate it, and which yet cure fevers. 



4. It would seem, however, that the principle which pre- 

 cipitates the infusion of oak bark and gall-nuts ie a febri- 

 fuge ; because in general it is acknowledged in medicine that 

 the kinds which produce this effect are best. 



5. On the other hand, the cinchonas which do not preci- 

 pitate the infusion of tan nor gall-nuts being febrifuge, it 

 may be concluded that the principle in virtue of which these 

 precipitations were formed is not the only one in cinchonas 

 •which cures fever. 



6. The principle which precipitates the infusion of tan 

 and gall-nuts, is of a brown colour and of a bitter taste : it 

 is less soluble in water than in alcohol : it also precipitates 

 emetic, but not glue. It has some analogies with the re- 

 sinous bodies, although it furnishes ammonia on distillation. 



7. It 



