M. Traube expresses himself thus:  “Pasteur’s conclusion, that yeast in the absence of air is able to derive the oxygen necessary for its development from sugar, is erroneous; its increase is arrested even when the greater part of the sugar still remains undecomposed.  It is in A mixture of albuminous substances that yeast, when deprived of air, finds the materials for its development.”  This last assertion of M. Traube’s is entirely disproved by those fermentation experiments in which, after suppressing the presence of albuminous substances, the action, nevertheless, went on in a purely inorganic medium, out of contact with air, a fact, of which we shall give irrefutable proofs. [Footnote:  Traube’s conceptions are governed by a theory of fermentation entirely his own, a hypothetical one, as he admits, of which the following is a brief summary:  “We have no reason to doubt,” Traube says, “that the protoplasm of vegetable cells is itself, or contains within it, a chemical ferment which causes the alcoholic fermentation of sugar; its efficacy seems closely connected with the presence of the cell, inasmuch as, up to the present time, we have discovered no means of isolating it from the cells with success.  In the presence of air this ferment oxidizes sugar by bringing oxygen to bear upon it; in the absence of air it decomposes the sugar by taking away oxygen from one group of atoms of the molecule of sugar and bringing it to act upon other atoms; on the one hand yielding a product of alcohol by reduction, on the other hand a product of carbonic acid gas by oxidation.”

Traube supposes that this chemical ferment exists in yeast and in all sweet fruits, but only when the cells are intact, for he has proved for himself that thoroughly crushed fruits give rise to no fermentation whatever in carbonic acid gas.  In this respect this imaginary chemical ferment would differ entirely from those which we call soluble ferments, since diastase, emulsine, &c., may be easily isolated.

For a full account of the views of Brefeld and Traube, and the discussion which they carried on on the subject of the results of our experiments, our readers may consult the Journal of the Chemical Society of Berlin, vii., p. 872.  The numbers for September and December, 1874, in the same volume, contain the replies of the two authors.]

IV.  FERMENTATION OF DEXTRO-TARTRATE OF LIME.

[Footnote:  See Pasteur, Comptes rendus de l’Academie des Sciences, t. lvi., p. 416.]

Tartrate of lime, in spite of its insolubility in waters is capable of complete fermentation in a mineral medium.