553 



in supposing that growth was a necessary accompaniment of fermentative activity. 

 Liebig 1 recognized the distinction between the two processes but regarded fermen- 

 tation almost solely from a chemical point of view, and failed to recognize its 

 physiological importance. 



In every case it depends upon the specific properties and capabilities of the 

 organism itself whether a given substance can be assimilated and used as a source 

 of energy, and hence the fermentative activity of a living organism is a problem of 

 metabolism. Even Nageli's theory of fermentation fails to recognize with sufficient 

 clearness the intimate connexion existing between the two. Fermentation was first 

 clearly indicated as a physiological process owing to the works of Schwann, 

 Schroder, Dusch, and Pasteur 2 . 



SECTION 103. General View of Certain Fermentative Activities. 



The power of exciting fermentation and the relation of the latter to 

 growth varies in different ferment-organisms 3 , which are in some cases 

 able to ferment many different substances, but in others only a few or 

 a single one. The latter is more commonly the case in disintegratory 

 fermentation, such as is induced by beer-yeast, than in typical oxidatory 

 fermentation, such as the oxalic fermentation which certain omnivorous 

 fungi can bring about in a variety of nutrient media. In many fermenta- 

 tions only one or two products are formed, but in other cases these are 

 numerous ; indeed every one of the substances which may result from 

 respiratory metabolism (Sect. 98) will probably be found as a product of 

 some fermentative activity or other. 



Fermentative activity is only exercised when the whole or a portion of 

 the energy must be obtained by its means. The growth of Penicillium 

 or Aspergillus remains about the same whether an abundant supply of 

 sugar is fermented to oxalic acid, or whether it undergoes complete physio- 

 logical combustion 4 . According to Liborius 5 Bacillus prodigiosus grows as 

 a fermentative anaerobe in the presence of sugar, but under other condi- 

 tions does not exhibit any fermentative activity. Fermentation is not 

 a necessary accompaniment of anaerobic life, and hence it may be possible, 

 as in the case of pigment-production, to suppress permanently or temporarily 

 the fermentative activity, and thus to obtain races which may or may not 

 recover this power. Fitz 6 states, indeed, that the latter occurs in Bacillus 



1 tiebig, Ann. d. Chem. u. Pha/m., 1870, Bd. CLIII, p. i. 



2 Cf. Fliigge, Mikroorganismen, 1896, 3. Aufl., Bd. i, pp. 6, 266; Lafar, Techn. Mykologie, 

 1897, Bd. i, p. 6; Ad. Mayer, Die Gahrungschemie, 1895, 4. Aufl., pp. 20, &c. 



3 Cf. the text-books mentioned above, as well as P. Frankland, Centralbl. f. Bact., 1894, Bd. xv, 



p. 103. 



* Wehmer, Bot. Zeitung, 1891, p. 553. Cf. Sect. 85. 



5 Liborius, Zeitschr. f. Hygiene, 1886, Bd. I, p. 172. 



6 Fitz Ber. d. Chem. Ges., 1882, p. 867. According to Wehmer (Centralbl. f. Bact., 1897, 



