MEDICINAL PLANTS. 
215 
specimens of sugar and tannin extracted from plants, not 
of the same family, present numerous differences : while the 
comparative analysis of sugar, gum, and starch; the dis- 
covery of the radical of the prussic acid (the effects of which 
are so powerful on the organization), and many other 
phenomena of vegetable chemistry, clearly prove that sub- 
stances composed of identical elements, few in number and 
proportional in quantity, exhibit the most heterogeneous 
properties, on account of that particular mode of combi- 
nation which corpuscular chemistry calls the arrangement of 
the particles. 
Leaving the ravine which descends from the Imposible, 
we entered a thick forest traversed by many small rivers, 
which are easily forded. We observed that the cecropia, 
which in the disposition of its branches and its slender trunk, 
resembles the palm-tree, is covered with leaves more or less 
silvery, in proportion as the soil is dry or moist. We saw 
some small plants of the cecropia, the" leaves of which were 
on both sides entirely green.* The roots of these trees are hid 
under tufts of dorstenia, which flourishes only in humid and 
shady places. In the midst of the forest, on the banks of 
the Bio Cedeno, as well as on the southern declivity of the 
Cocollar, we find, in their wild state, papaw and orange- 
trees, bearing large and sweet fruit. These are probably the 
remains of some conucos, or Indian plantations ; for in those 
countries the orange-tree cannot be counted among the in- 
digenous plants, any more than the banana-tree, the papaw- 
tree, maize, cassava, and many other useful plants, with the 
true country of which we are unacquainted, though they 
have accompanied man in his migrations from the remotest 
times. 
When a traveller newly arrived from Europe penetrates 
for the first time into the forests of South America, he be- 
scarcely any febrifuge quality, yields a green precipitate like the real 
cinchonas. Notwithstanding the extreme imperfection of vegetable che- 
mistry, the experiments already made on cinchonas sufficiently show, that 
to judge of the febrifuge virtues of a bark, we must not attach too much 
importance either to the principle which turns to green the oxides of iron, 
or to the tannin, or to the matter which precipitates infusions of tan. 
* Is not the Cecropia concolor of Willdenouw a variety of the Cecropia 
peltata ? 
