light on the physiology of the cell. We shall not follow
the discourse in all its developments, which are some-
times digressions, but shall ask only what it had to reply
to the new doctrine on the fermentations.

On this point his position became more and more
embarrassing. Already, at the time when he had first
developed his theory, he had been obliged to admit that
the yeast was a living organism which renewed and
destroyed itself continually, and it was only the products
of the destruction which made the sugar ferment. That
point had become difficult to maintain and support
after Pasteur had shown fermentation to be a cellular
phenomenon. It is curious to see how Liebig extricates
himself from this difficulty. He considers that life is
accompanied at every instant, in every cell, by a move-
ment of decomposition and reconstruction, and, naturally,
it is to the first that he has recourse. He admits then
the physiological phenomenon but he takes into con-
sideration only a part of it and, once more, the chemical
side, endeavoring "to reduce the chemical decomposition
of the sugar to a simple formula common to all analogous
phenomena."

The attempt is bold, and we recognize in it the general-
izing mind of Liebig. We shall see how he succeeded.
Let us note in the beginning that, from a chemical point
of view, the vital phenomenon of Pasteur does not differ
essentially from the phenomenon of movement of Liebig,
and that it is possible to reconcile them. "I admit,"
says Liebig, "that the yeast consists of vegetable cells
which come into existence and multiply in a liquid con-
taining sugar and an albuminoid substance (it is I who
underscore). The yeast is necessary in order that there
may be formed in its tissues, by means of the albuminoid
substance and the sugar, a certain unstable combination,"
which alone is capable of undergoing dismemberment.

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