STUDIES ON FERMENTATION. 283 



culled attention to certain fermentations that cannot be com- 

 pleted under such conditions without going into the causes 

 of these peculiarities. 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, u-lien 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 albu- 

 minous 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* 



* Traube's conceptions were 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 mole- 

 cule 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 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 fei-nientation 

 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 easilj' 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 

 F^ociety of Berlin, vii. p. 872. The numbers for September and 

 December, 1874, in the same volume, contain the replies of the two 

 authors. 



