

ACETIC ACID BACTERIA. 



261 



which is added 0.5% of alcohol). We have not our- 

 selves studied these varieties, which have so far been 

 studied upon solid media with little thoroughness. Macro- 

 scopically the cultures resemble those of the Bact. pneu- 

 moniae, lactici and coli. Thus far, three " species" have 

 been distinguished, Bacterium aceti Hansen, Bacte- 

 rium Pasteurianum Hansen, and Bacterium Kiitzin- 

 gianum Hansen, and they are characterized as follows: 



Bacterium aceti 

 Hansen. 



Bact. Pasteurian- 

 um Hansen. 



Bact. Kutzingian- 

 um Hansen. 



Pellicle on sterile ale, 

 at 34° after 24 hours: 



Slimy, smooth, 

 moist, shining, 

 showing a ten- 

 dency to veining 

 like marble. 



Dry surface, early 

 beginning to 

 wrinkle, some- 

 what elevated 

 above the surface. 



Similar to Pasteuri- 

 anum, but the 

 membrane climbs 

 up even on the 

 wall of the tuhe. 



When flasks in which 

 growth has taken 

 place at 34° are 

 brought into room 

 temperature: 



Fluid remains 

 clear. 



Fluid remains 

 clear. 



Fluid becomes 

 cloudy and gradu- 

 ally, under sedi- 

 mentation, it be- 

 comes again clear. 



Microscopic character 

 of the cells of the 

 young membrane : 



Short rods with 

 hour-glass-like 

 constrictions in 

 chains. Long rods 

 and thread forms 

 uncommon. 



Like Bact. aceti. 



Short rods, usually 

 single; at most in 

 pairs ; no chains. 



Staining with iodin 

 of the mucilaginous 

 material holding the 

 bacilli together in 

 young membranes : 



Not at all. 



Blue. In older 

 membranes the 

 blue staining of 

 the mucus is only 

 presented in 

 places ; and in 

 still older, dead 

 cultures, it is en- 

 tirely absent. 



Blue. 



Staining of the bacte- 

 rial cells with iodin : 



Yellow. 



Yellow. 



Yellow. 



We gave above a general presentation of the statements 

 of Hansen, the most successful investigator of this group, 

 in tabulated form. Literature: Lafar (C. B. L. i, p. 129); 

 most important is Hansen, Recherches sur les bacteries 

 acetifiantes (Travaux de Carlsberg, in, 182, and C. B. L. 

 1,31). 



All three forms of acetic acid bacteria possess a wide 

 range of forms, depending especially upon the temper- 



