in the grouping of its atoms an arrangement with a super-
posable image. Thus each dissymmetrical substance
offers four variations or, rather, four distinct sub-species:
the right-handed body, the left-handed body, the com-
bination of the right and the left, and the body which is
neither right nor left, nor formed by a combination of the
two." ¹

I shall dwell no longer on the aspartic and malic acids
because, as I have just said, Pasteur had taken the wrong
route. This has been evident since, and it is singular
that its discovery has required no new methods; it has
only been necessary to employ those methods with which
he has made us familiar. By following them M. Bremer
has shown that the inactive malic acid of Pasteur was in
reality a paratartaric acid, that is to say, a combination
of right-and left-handed acids. It has been discovered
also that there are three asparagins, three aspartic acids,
three malic acids, and that the maleic acid and fumaric
acid are more distinct than Pasteur believed them, and
possess a new dissymmetry which is not expressed by
the appearance of a rotary power. In short, our knowl-
edge has been very much extended since Pasteur did his
work, but there has been no change in its source, and in
its immense development it remains faithful to this parent
idea of Pasteur, that all difference in the grouping of the
atoms of a molecule must be expressed externally in some
way. That Pasteur was sometimes self-deceived, and
that there are some defective stones in the foundation
which he has given to the edifice, is of no importance.
The essential thing is that the edifice rises without
crumbling, and that it does rise.

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