332 



LOUIS PASTEUR 



ceding section, we have called attention to certain fermenta- 

 tions that cannot be completed under such conditions with- 

 out going into the causes of these peculiarities. M. Traube 

 expresses himself thus: " Pasteurs conclusion, that yeast 

 in the absence of air is able to derive the oxygen neces- 

 sary 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 albumin- 

 ous 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. 1 



IV. FERMENTATION OF DEXTRO-TARTRATE OF LIME.* 



TARTRATE of lime, in spite of its insolubility in water, 

 is capable of complete fermentation in a mineral medium. 



If we put some pure tartrate of lime, in the form of a 

 granulated, crystalline powder, into pure water, together 

 with some sulphate of ammonia and phosphates of potas- 

 sium and magnesium, in very small proportions, a spon- 



1 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 proto- 

 plasm 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 suc- 

 cess. 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 bring- 

 ing 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 what- 

 ever 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 discus- 

 sion 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. 



1 See PASTEUR, Comptes rendus de I' Academic dcs Sciences, t. Ivi., p. 416. 



