It is true that this is not always the case, and Pasteur
would have been able to find contrary examples in the
history of the malates if he had not made the error which
we have pointed out above. But, on the whole, one
can accept this way of looking at it as sufficiently ex-
act, and Pasteur was right to introduce it into science.
The marked differences which one observes between the
various sugars encountered in nature, for example be-
tween rock candy and its constituent sugars, are evidently
of the same order and have the same origin. I will ven-
ture to add that it is reasons of the same kind which render
so baffling the study of albuminoid substances, in which
differences of molecular structure are expressed exter-
nally otherwise than by differences in crystallization.

If we now recall that the protoplasm of all living
cells is endowed with the rotary power, that it con-
tains, therefore, dissymmetrical molecules, and that
this dissymmetry in relation to the stability or insta-
bility of the compound, cannot fail to play a rôle in all
the chemical combinations of which the protoplasm is
the seat, we shall conclude that there are in these con-
siderations indications of a profound mechanism of life.
We encounter here one of those flights of imagination
which Pasteur permitted himself sometimes and which
were for him the recompense and the repose derived
from works of research. But when he had thus boldly
explored the horizon he made haste to regain the solid
ground of experiment. Let us follow his example and
enter the laboratory.

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