a 



302 ACETIC FERMENTATION 



met with. Globular cells, measuring up to 10 /* in diameter, are also by no 



means rare. 



Finally, the threads become entirely dismembered into short rods (Fig. 87), even 



the bulged cells undergoing this conversion, and leaving only the thickest portion 



(Fig. 88) unchanged. This portion eventually, after the filamentous ends on 



either side have broken up into short 

 rods, collapses in the surrounding liquid 

 and dissolves. An examination made 

 after the lapse of twenty-four hours then 

 reveals only chains of short rods. We 

 have thus induced a reversion to the 

 original forms of cell, and have there- 

 by learned the morphological influence of 

 temperature. Of course, neither the com- 

 position of the nutrient medium nor the 

 condition of the seed is a matter of in- 

 difference. Thus, for instance, if, instead 

 of sowing the young cells presupposed 

 in the foregoing demonstration, those 

 already forty-eight hours old are em- 

 ployed, then the conversion into threads 

 becomes very difficult. In the case of 

 lager- beer the development proceeds some- 

 what differently to that occurring in the 

 FIG. 88. Bacterium rastcuriuuuiii. , u MI-AI. 



" doppel-bier hitherto mentioned. 



Residue of swollen loiig threads after a sojourn of / < j /> /-* 



one to two days m doppei-bicr " at 34 c. Bacterium aceti and J>. Ktilzingianum 

 in the pear-shaped swelling has tapered behave very similarly under the circuin- 

 out into two thin threads, in 6 the lower stances now in question. A few small 

 ^^S differences are, however, unmistakably 

 the pinsmai cell contents escaping, in rfthe evident. Thus, for instance, in harmony 

 evacuation is complete only the thick cell w j th the pl um p er form of the short rods 

 wall being left. c. spindle-shaped swollen - n n . r .-, i jtu r-i. i 



form, with two long threads undergoing in- of & PasteunanMn, the breadth of its long 

 Hpieut subdivision. Magn. 1000. Differ threads is also greater, as will be evident 

 //0 " s '"- ) on reference to Figs. 85 and 89; the 



long threads of B. aceti are thinner, but 



attain a greater length, viz., up to 500 p. On the other hand, the long threads of 

 B. Kutzingidumn are considerably smaller than those of the other species. 

 Finally, it should be stated that branching of the long threads occasionally occurs. 

 A few of these comparatively rare forms are shown in Fig. 90. Pleomorphism 

 seems to be a general property of the acetic acid bacteria, since it was also found 

 by Hansen to prevail in four other species, including those discovered by Zeidler. 

 Like most of the other ScMzomycetes, the acetic bacteria exhibit a preference 

 for darkness. Their development as M. GIUNTI (I.) discovered is restricted 

 (though not entirely prevented) by diffused 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.) likewise 

 found that the discharge of strong electric sparks at a short distance above the 

 surface of the liquid also restricts development. 



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, 



