42 DISSERTATION ON THE 



difference in the proportion of tannin and of 

 extractive matter in the flowers and roots. 

 Most tannin is also shown to reside in the 

 leaves. From the nitrate of silver we have 

 proof that the extractive* principle resides 

 especially in the root. That the leaves pos- 

 sess the greatest quantity of tannin is like- 

 wise shown from the action of gelatin. 



The extract obtained after the manner 

 detailed in experiment the fourth, evidently 

 possessed properties similar to those found 

 in the decoction. The free acid was mani- 

 fested by the infusion of litmus, and modified 

 gallic acid by the sulphate of iron. No 

 change being caused by distilled water, the 

 total absence of any resinous material may 

 be inferred. That the leaves possessed more 

 or less resinous matter, was proved by the 

 fifth experiment. The presence of tannin 



* Though I have here and elsewhere denominated this 

 principle, obtained from the root, the extractive, yet it ap- 

 pears to unite the characters both of extract and gum. 



