466 Bacteria in Relation to Country Life 



liquid, although they may become accustomed slowly 

 to gradually increasing concentrations until an alcohol 

 content of 10 per cent is reached. Even then, however, 

 the growth is markedly retarded. Thus, it was found by 

 Henneberg, that in the case of Bacterium xylinoides, 

 growth occurred in five days with 0.2 per cent of alcohol; 

 in thirty-two days, with 3 to 5 per cent of alcohol; and in 

 forty-five days with 6 to 8 per cent of alcohol. The differ- 

 ent species are unequally affected, likewise, by the con- 

 centration of acetic acid. According to Henneberg, the 

 greatest amount of acid that would still allow bacterial 

 development under certain laboratory conditions was 

 9.3 per cent for Bacterium xylinoides; 9 per cent for Bac- 

 terium orleanense; 8 per cent for Bacterium vini acetati, 

 and 10.9 per cent for Bacterium Schiizenbachi. 



The (i mother of vinegar." An examination of the 

 "mother of vinegar," or "mycoderma," as it was called 

 by Persoon as early as 1822, will show it to consist of 

 small, usually cylindrical cells imbedded in a mucilagi- 

 nous substance. The latter causes the entire mass to 

 form a continuous skin or membrane of variable thick- 

 ness. The organisms imbedded in the membrane may 

 occur singly, in twos, or in chains, and may also undergo 

 more or less striking modifications in shape and size, as 

 the temperature falls below or rises above certain limits. 

 At temperatures below 60 Fahr., the cells become 

 long and exhibit pear-shaped swellings, while at 104 

 Fahr. they not only undergo variations in shape, but 

 may attain an extraordinary length, occasionally one 

 hundred times that of normal cells. 



As the temperature is again lowered to approximate 



