GENERAL VIEW OF FERMENTATIVE ACTIVITIES 555 



those cases of marked physiological decomposition which arc not the result 

 of complete physiological combustion. Minute lower plants are especially 

 capable of excreting non-volatile products, and a very large number of 

 hetcrotrophic fungi and bacteria possess the power of exciting fermentation 

 (cf. Sect. 94). A marked evolution of gas, to which Beyerinck 1 attaches 

 primary importance, is not a necessary accompaniment of fermentation, 

 and indeed appears never to be set up by certain anaerobes (Sect. 98). 

 When it occurs, it may serve to ensure continual agitation and admixture, 

 as well as to carry aerobic ferment-organisms to the surface where a supply 

 of oxygen may be secured. The term ferment-organisms is, therefore, 

 merely a conventional one of somewhat vague application, and even 

 although an alcoholic enzyme has been isolated the plant which produces 

 it still remains a ferment-organism (Sect. 102). 



For a fuller discussion of the better known fermentations than is 

 possible here, reference may be made to the works by Lafar, Flugge, 

 Ad. Mayer, Schiitzenberger, &c., which have been already mentioned. 



Alcoholic fermentation 2 . The pow r er of fermenting sugar into ethyl- 

 alcohol and carbon dioxide (C 6 H 12 O 6 = 2 C 2 H G O + 2 CCX) is not possessed 

 by all plants, although in certain species of Mucor it may become almost 

 as pronounced as in the case of the more active yeasts, which are able to 

 carry on a prolonged anaerobic existence by means of their fermentative 

 activity (Sect. 98). 



The different forms of yeast are able to ferment only certain hexoses, 

 as well as a few artificially produced trioses and nonnoses, but not tetroses, 

 pentoses 3 , heptoses, and octoses. Moreover, polysaccharides can be 

 fermented only when they are first converted into monosaccharides, and 

 this takes place by the agency of an enzyme, which has ultimately 

 been detected in all cases, and which appears usually but not always 

 to be excreted (cf. Sect. 91). The latter is the case in Monilia Candida, 

 which was formerly regarded as being directly able to ferment cane-sugar. 

 Saccharomyces octosporits can neither invert nor ferment a polysaccharide, 

 though it is capable of splitting and fermenting maltose. Saccharomyces 

 Marxianns has properties which are precisely the opposite of those pos- 

 sessed by vS. octosporns. An enzyme which decomposes milk-sugar has 

 been isolated from those yeasts which ferment lactose 4 , and various negative 



1 Beyerinck, Centralbl. f. Bact., 1892, Bd. xi, p. 73; Butylalkoholgahrung, 1893, pp. 44, 51. 

 Cf. also Flugge, Mikroorganismen, 1896, Bd. i, p. 219; Ad. Mayer, I.e., p. 19; Lafar, I.e., p. 23; 

 Wehmer, Centralbl. f. Bact., 1894, Bd. xv, p. 544. 



2 In addition to the works of Flugge, Lafar, and Ad. Mayer, cf. Jorgensen, Mikroorganismen d. 

 Gahrungsindustrie, 1892; Hansen, Unters. a. d. Praxis d. Gahrungsindustrie, 1890, and Meddelelser 

 f. Carlsberg Laboratoriet, 1888, Bd. n, p. 143; Lintner, Handb. d. landw. Gewerbe, 1893, &c. 



3 Arabinose is, according to Frankland and M c Gregor (Jahrb. d. Gahrungsorg., 1892, p. 232), 

 fermented by certain bacteria into ethyl-alcohol and acetic acid. 



4 Details by Tollens, Handb. d. Kohlenhydrate, 1895, Bd. n, p. 48. Of the newer works, cf. 



