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NATURAL HISTORY MISCELLANY. 47 
become that the reference to it may seem childish; but from mechanics 
o 
analysis of organic substances, and set themselves to study their proxi- 
mate constituents, a great number of definite chemical compounds were 
obtained which could not be formed artificially. I do not know what may 
of formation. Probably it may have been imagined that chemical affini- 
ties were indeed concerned in their formation, but controlled and modi- 
fied by an peri vital force. But as the science progressed many of 
these organic substances were formed gehe n some cases from 
other and perfectly distinct organic substances, in other cases actually 
fro PARERA amy ts. This statement must indeed be accepted with one: 
pies key 
It was por several years ago by M. Pasteur, e I believe the state- 
ment ies remains true, that no substance, the solution of which possesses 
n e plane 
polarizatjon, and therefore in these cases the inactive artificial substances 
cannot be absolutely identical with the natural ones. But the inactivity 
bears to ta c; that it is, so to speak, a mixture of the natural sub- 
stance with its image in a add And when we SOA by what a 
peculiar and troublesome process M. Pas succeeded in separating 
racemic acid into the cues ue ected eis acids, it will 
be at once understood how easily the fact, if it be a fact, of the existence 
in the natural substance of the mixture of two substances, one right- 
handed and the other left-handed, but otherwise identical, may have 
escaped detection. This is a curious point, to the clearing up of which 
it is desirable that chemists should direct 2 attention. Waiving then 
the difference of activity or inactivity, which, as we have seen, admits o 
a simple physical explanation, though the correctness of that explanation 
remains to be investigated, we may say that at the present time a consid- 
some kind, under the agency in many cases of light, an agency sometimes 
employed by the chemist in his laboratory. And since the boundary line 
between the natural substances which have, and those which have not, 
