90 MICRO-ORGANISMS AND DISEASE. [CHAP. 



bacteria. Growing in solid Agar-Agar and peptone mixture, 

 they produce an imperfect liquefaction, numerous gas bubbles 

 appearing in the material. 



(b} Bacterium lineola ( Vibrio lineola, Ehrenberg, Dujardin), 

 differs from bacterium termo in being longer and thicker. 

 The cells are about 0*003 to 0-005 mm. long, about 0-0015 

 mm. thick. They occur in well-water and stagnant water, 

 where no distinct putrefaction is going on, and form zoo- 

 glcea, and pellicles, on the surface of potatoes and various 

 infusions. 



* ~s 



FIG. 36. BACTERIUM LINEOLA. FIG. 37. BACTERIUM LACTIS. 



2. Zymogenic Bacteria. Two kinds are known : Bacterium 

 lactis and Bacterium aceti. 



(a) Bacterium lactis. According to Pasteur, these bacteria 

 are about 0*0015 to o'o3 mm. long, constricted in the centre; 

 they form short chains, or even zooglcea, and they are motile. 

 They produce the lactic acid fermentation, in the course of 

 which lactic sugar is transformed into lactic acid ; they are 

 anaerobic. Lister, 1 by means of pure cultures, established 

 experimentally their causal relation to the lactic fermentation 

 or souring of milk. 



(c) Bacterium aceti (Mycoderma aceti} is a little smaller 

 than bacterium lactis, being about 0*0015 mm ' m length, 

 and often forms chains, and also pellicles, on the surface of 

 the fluid; it is motile. Pasteur maintains that it is the 

 ferment of the acetic acid fermentation. Cohn 2 found it in 



1 Pathological Soc. Transactions, 1878. 



2 Biol. d. Pflanztn, ii. p. 173. 



