ed, withe activity, the medicine could be exhibit 
more advantage. This is in part accomplished by the prepara= 
tions of itthat have been mentioned ; but even these do not convey it 
in all its force: Ifone ounce of the bark be infused or boiled in acer- 
tain quantity of water, the infusion or decoction is not nearly equal. — 
in efficacy to the whole quantity of bark operated on. It is therefore 
evident that during either of these operations, the active matter of 
the bark has not been entirely extracted, or has suffered some shange. 
And here chemistry lends her assistance, and still farther elucidates 
the peculiar nature of this substance, and the changes produced in. 
it by these processes. It has been proved by experiments, that the 
matter on which the power of the bark depends, has a strong uttrae- 
tion for oxygen at a temperature moderately increased ; that during _ 
the infusion, and particularly during the decoction of that drug, this 
active matter absorbs oxygen from the atmosphere, and is converted _ 
into a substance insipid and inert. This leads to the improvement of _ 
the preparations of this medicine; and experiments instituted for 
the purpose, have accordingly proved, that, while by long boilin 
the virtues-of the bark are nearly totally destroyed, they are 
extracted by a few minutes decoction in coyered vessels.” 
investigations have pointed: out the nature of the action ome 
other substances on , formerly not well understood. Thus, it 
hasbeen found by experience, that the alkalies, and more parti 
magnesia, enable water to extract the virtues of bark, more com~ 
* . pletely by infusion,—a circumstance elucidated by the fact since 
discovered, that the extractive matter of the bark, to which its ac- 
tivity is owing, combines with facility with these substances, and 
forms soluble compounds. . 
Similar examples might be given of several other important vege- 
table remedies, which would sufficiently prove the utility to be de- 
rived from the analysis of the vegetable kingdom, and that indeed 
researches of this kind are absolutely necessary for the preparation _ 
of substances belonging to it as medicines. + Seeing 
It remains only to notice the animal analysis. But on this few 
observations need to be made; as there are comparatively but a 
small number of the articles of the materia medica which belong 
- to the animal kingdom. — : 
The animal products have the same general chemical characters 
as vegetables. They differ from them in being more liable to the 
process named Putrefaction ; and in affording a large quantity of 
ammonia, when decomposed by heat. These differences depend 
principally on the presence of azot in a much larger proportion in. 
the animal than in the vegetable products ; which during their de- | 
Composition, combines with the hydrogen they also contain, and fur- i 
Rishes the ammonia which is so abundantly discharged. Animal 
ubstances also contain sulphur and phosphorus ; and in general a _ 
‘oportion of carbon enters into their composition than i 
anding these differences, there are many of the ant 
