560 RESPIRATION AND FERMENTATION 



accti and B. Pastcuriamtm 1 especially well known, obtain their energy by 

 this process of oxidation, and so long as alcohol is present no carbon dioxide 

 appears to be formed (Sect. 96), although it is produced in abundance 

 when in the absence of alcohol the acetic acid is still further oxidized. 

 Here alcohol protects acetic acid, but this is not the case with Mycoderma 

 aceti*. Similarly, acetic acid is consumed by Penicillium even when the 

 most suitable organic food is supplied (Sect. 67). The process is a vital one 

 and ceases at death 3 , although it is not certain whether it is solely intra- 

 cellular or in part extracellular (Sect. 10). An apparently similar oxidation 

 may be induced by finely divided platinum, but this affords no conclusive 

 evidence as to what occurs in the living cell. According to A. J. Brown 4 

 acetic bacteria are able to oxidize propyl-alcohol to propionic acid, but 

 they do not attack butyl-, amyl-, or methyl-alcohol. It is not yet known 

 whether these bacteria will grow upon glycerine, sugar, &c., and what 

 products are then formed. Acetic fermentation is most active between 

 20 C. and 30 C., and ceases to be provoked by B. Pastenrianum at 4C., 

 but continues to be set up slowly by B. aceti at this temperature 5 . Under 

 favourable conditions acetic acid may accumulate to the extent of even 

 14 per cent, before further activity ceases . (On oxalic and citric fermenta- 

 tions, cf. Sects. 85 and 86 ; on other oxidations, Sect. 96.) 



Conjoint actions of different organisms may induce productive activities 

 of which the individual organisms are incapable (Sects. 51, 64, 92). This 

 is seen when a bacterium prepares a particular substance for assimilation 

 by other plants to which it was previously inaccessible, or when cellulose 

 is converted into fermentable sugar 7 . Putrefaction is due to the action 

 of several bacteria, and differs according to the putrefying substances 

 and other conditions. Proteid putrefaction yields an especially large 

 number of products, including many malodorous gases. When well aerated 

 these and many other products do not appear, owing to the fact that the 

 activity of the obligate anaerobes is suppressed and that of facultative 

 anaerobes modified (Sect. 102), while obligate or facultative aerobes attain 

 the upper hand. The latter may oxidize any sulphuretted hydrogen 



1 Hansen, Med. f. Carlsberg Lab., 1894, Bd. Ill, p. 182. 

 1 Cf. Beyerinck, Centralbl. f. Bact, 1892, Bd. XI, p. 71. 



3 Kinerim u. Ad. Mayer, Versuchsst., 1873, Bd. XVI, p. 305. 



4 A. J. Brown, Jonrn. Chem. Soc., 1896, Vol. XLix, pp. 172, 432; 1887, p. 638; Seifert, 

 Centralbl. f. Bact., 1897, II, Bd. in, p. 336. Nageli supposed that they could decompose methyl- 

 alcohol. 



* Lafar, Centralbl. f. Bact., 1895, Abth. ii, Bd. I, p. 145. 



* Lafar, I.e., p. 139; Steinmetz, Jahresb. d. Gahrungsorg., 1892, p. 243. 



7 Certain organisms can not only dissolve cellulose, but also ferment the sugar produced. On 

 cellulose fermenlation, cf. Fliigge, I.e., p. 241 ; Herfeldt, Centralbl. f. Bact., 1895, Abth. ii, Bd. I, 

 p. 1 16 ; Omelianski, Compt. rend., 1895, Nov. On mixed cultures, cf. Sects. 64, 92. On the ginger- 

 beer plant, cf. Marshall Ward, Phil. Tians., 1892, p. 125. On Kefir, cf. Fliigge, I.e., p. 262; 

 Freudenreich, Centralbl. f. Bact., 1897, Abth. ii, Bd. in, p. 87. 



