ON GUM AND SUGAR TREES 
plasm itself and they differ from the gum and 
resins that we have just been considering in that 
each molecule contains at least one atom of 
nitrogen. 
The sugars, it will be recalled, occupy an inter- 
mediate place, inasmuch as they, unlike the resins 
and rubber, contain oxygen; but they contain no 
nitrogen. The formulae given by the chemist for 
the different alkaloids are intricate but they differ 
from one another only in the matter of a few more 
or a few less atoms of one or another of the four 
constituents of which they are all made up. 
There is, for example, only the difference of 
one atom of carbon and of four atoms of hydrogen 
between a molecule of quinine and a molecule of 
strychnine. Considering that the molecules com- 
prise in the aggregate not far from fifty atoms, in 
each case, this discrepancy seems trifling. That 
the two drugs should have such utterly different 
effects upon the human system is a mystery that 
will be solved only when a much fuller knowledge 
is gained as to the physiological processes than 
anyone has at present. 
But the plant developer, of course, has no con- 
cern with this aspect of the subject. What inter- 
ests him is the knowledge that different races of 
cinchona trees, for example, are known to vary 
greatly as to the proportion of commercial alka- 
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