OBSERVATIONS ON COPAIBA. 295 
leaves absorb the chemical rays of the sun so completely as 
to give no image in the daguerreotype." [Graham.) This 
deoxidizing and carbon-depositing action appears to go on 
to a much greater extent in oleiferous and resiniferous plants 
than in others. 
Now it appears from observations made by different ob- 
servers,that as the copaiba trees get older, their juices become 
more oleo-resinous, that is to say, the process of oxidation to 
which the volatile oil is subjected, causes it to become more 
resinous, year after year; and it is only after a certain age, 
that, in the opinion of the copaiba collectors, the trees are 
fit to be tapped. The analysis of Ros& proves that copaivic 
acid is the oxide of the oil of copaiba ; thus the formula of 
the acid is C 40 H 3 i O 4 whilst that of the oil is C 10 H 8 , which 
quadrupled— C 40 H 32 , and this plus 4 =the formula of the 
acid. 
Again ; as the juices of the older trees are more resinous* 
the juices of the younger trees are more oily and less resinous? 
and beyond doubt there is a period in their growth when the 
volatile oil is associated with comparatively little resin. Now 
the writer is willing to hazard the opinion that the specimen 
of copaiba distinguished by (a) in the table was extracted at 
this period of the growth of the tree, when not only the oil was 
in great excess, but the resin not completely elaborated, in other 
words, not converted into copaivic acid. This view is indirectly 
corroborated by the fact that there are one or two oleo-resins, 
containing but a trifle of resin, which are obtained by tapping, 
from trees, growing in Venezuela. One of these, called " na- 
tive oil of laurel or sassafras," obtained from trees growing on 
the banks of the Orinoko, about 400 miles from its mouth, is 
now under examination, and will be noticed in the next num- 
ber. 
The judgments of the medicinal value of copaiba, have gen- 
erally been based on its consistence and solidifying property. 
The observations of writers on therapeutics, have shown that 
early all its peculiar efficacy is due to the volatile oil. If 
