KUTZING'S THEORY OF FERMENTATION. 17 



applied merely to one particular group of ferments, viz., those 

 producing alcoholic fermentation. For a considerable period after 

 Cagniard's discovery, however, it was used indiscriminately for all 

 ferments. Thus, for example, Pasteur speaks of the " yeast " of 

 lactic fermentation, meaning thereby Bacteria] and even in 1879 

 Na'geli, the investigator of the fission fungi, refers in his " Theory 

 of Fermentation " to the " yeast " of putrescent urine. This misuse 

 of the term has been abandoned, and the name "yeast" is now 

 only employed when speaking of the budding fungi that excite 

 alcoholic fermentation. 



14. Friedrieh Kutzing's General Theory of 

 Fermentation. 



The views promulgated by this German worker in the field of 

 Vegetable Physiology and the Algae were in harmony with the 

 spirit manifested in the " Elements of Philosophic Botany." 



Published almost simultaneously with the above-mentioned 

 communications of Cagniard-Latour and Th. Schwann though 

 actually compiled at a much earlier date (before 1834) Kutzing's 

 treatise (I.) on this subject surpassed those of his two colleagues in 

 more than one particular. The value of his actual determinations 

 is not, in our opinion, lessened by the fact that he was an advocate 

 for spontaneous generation, since at that time (in 1837) there existed 

 no decisive and unassailable proofs to controvert this theory. 



Kiitzing did not restrict his researches solely to alcoholic fer- 

 mentation, but also instituted comparisons with a number of other 

 similar phenomena, regarding them all from the same point of view. 

 Even though he must share with others the credit of having 

 discovered the organised structure of yeast, that of determining 

 the vegetable nature of the "mother of vinegar" and recognising 

 its mode of action belongs to him alone. With these discoveries 

 are associated a number of others of minor importance, such, for 

 example, as the physiological basis of the method (propounded by 

 Scheele) of preparing gallic acid by allowing a solution of pyro- 

 gallic acid (e.g. gall-nut extract) to become infested with mould. 

 The numerous phenomena he brings under our notice constitute 

 so many proofs of the theory that fermentation cannot be regarded 

 as a purely chemical process. " It is well known that chemistry 

 explains vinous fermentation by the reaction of the so-called gluten 

 on the amylum (starch) and sugar. I must firmly maintain that 

 the explanation does not give me a clear idea of the process, and 

 I am inclined to doubt whether others are more fortunate in this 

 respect. It is, however, certain that the entire process of alcoholic 

 fermentation is dependent on the formation of yeast, and the acid 

 fermentation on the formation of the vinegar plant. . . . Along 

 with the increased growth of these organisms the reproductive 

 impulse also increases and, concurrently, their reaction on the 



VOL. I. B 



