394 



ACETIC FERMENTATION. 



should be stated that branchings of the long threads occasionally 



occur. A few of 

 these comparatively 

 rare forms are shown 

 in Fig. 90. Pleomor- 

 phism seems to be 

 a general property of 

 the acetic acid bac- 

 teria, since it was 

 also found by Hansen 

 to prevail in four 

 other species, includ- 

 ing those discovered 

 by Zeidler. 



Like most of the 

 other Schizomycetes, 

 the acetic acid bac- 

 teria exhibit a pre- 

 ference for darkness. 

 Their development 

 as M. GIUNTI (I.) dis- 

 covered is restricted 

 (though not entirely 

 prevented) by dif- 

 fused daylight, as 

 well as by direct 

 exposure to the sun ; 

 but according to the 

 discoveries made by 

 G. TOLOMEI (III.), 

 this result is due to 

 the chemically active 

 light rays alone. 

 TOLOMEI (IV.) like- 

 wise found that the 



discharge of strong electric sparks at a short distance above the 



surface of the liquid also restricts development. 



FIG. 90. Bacterium aceti. 



Filamentous cells of unusual form from cultures (several 

 days old) on wort and on " doppel-bier " at 39-4iC. 

 Magn. 1000. (After Hansen.) 



212. The Equation of Acetic Fermentation. 



For a long time no clear perception was obtained of the mode 

 of action of the "mother of vinegar." True, it was known that 

 the acetic acid is formed from the alcohol present, and also that 

 acidification does not occur when air is excluded, but the reasons 

 for these phenomena could not be given. The ABBE ROZIER (I.) 

 concluded from his experiments that air is absorbed by the wine 

 in process of turning sour, but LAVOISIER (I.) afterwards showed 

 that this is only true of one of the constituents of the atmosphere, 



