■446 REPOET— 1893. 



decompositions which are induced by bacteria, for the discovery of so 

 many of which we are indebted to Pasteur and Fitz. The substances 

 which have already been shown to be capable of undergoing fermentative 

 change through the agency of bacterial life, although numerous, are 

 practically confined to the carbohydrates, polyhydric alcohols, and oxy- 

 acids. 



Moreover, the products obtained in these numerous fermentations are, 

 if we except comparatively minute traces, still more limited in number. 

 The most common are — 



Alcohols : Ethyl, butyl, amyl. 



Polyhydric Alcohols : Mannitol. 



Monobasic Acids : Formic, acetic, propionic, butyric, valerianic. 



Oxyacids : Lactic. 



Dibasic Acids : Succinic. 



Gases : Carbonic anhydride, hydrogen, marsh gas. 



In almost all cases the products formed in these fermentations are of 

 simpler molecular structure than those from which they have been 

 derived, the most conspicuous exception to this general rule being the 

 fermentative synthesis of butyric from lactic acid. 



In almost all cases, moreover, the fermentative decomposition includes 

 a process of oxidation and reduction, one part of the original molecule 

 being oxidised at the expense of the other. Thus, one of the commonest 

 forms of fermentation is that in which a fatty acid and an alcohol, 

 generally the one corresponding to the acid in question, are simultaneously 

 produced. 



Two questions naturally suggest themselves in connection with these 

 bacterial decompositions: — (1) Does the same substance yield different 

 products when fermented by different micro-organisms ? (2) Does the 

 same micro-organism produce the same products in the fermentation of 

 •different substances ? 



The first of these questions has been answered by the researches of 

 Fitz, who found that one and the same substance was capable of yielding 

 different fermentation products, according to the fermenting material 

 employed. Nor is this result in any way modified by the fact that we 

 have no guarantee that the ferments used by Fitz were pure cultivations ; 

 in fact, in many cases, they were admittedly mixtures. 



On the other hand, the answer to the second question can obviously 

 only be furnished by experiments made with pure cultures of fermenting 

 organisms. 



I have for some time past been conducting experiments on this 

 subject, and, as far as these have yet proceeded — ^for they are necessarily 

 of the most laborious character — they clearly show the most striking 

 tendency for the products elaborated by one and the same organism from 

 different fermentable substances to be the same. Thus I have shown 

 that one and the same bacillus, operating on such different substances as 

 dextrose, galactose, maltose, milk-sugar, mannitol, arabinose, glycerin, 

 and glyceric acid, yields qualitatively the same products— viz., ethyl 

 alcohol, acetic and formic acids (traces of succinic acid), carbonic 

 anhydride, and hydrogen. 



Similar results have more recently been obtained by Grimbert, who 

 has studied the fermentation induced in starch, inulin, dextrose, maltose, 

 <5ane-sugar, invert-sugar, milk-sugar, arabinose, mannitol, and glycerin. 



I 



