128 BACTERIOLOGY. 



but a whole series of bacteria are able to form 

 lactic acid out of sugar ; and the same thing 

 was later ascertained in regard to other kinds 

 of decompositions. In the lactic fermentation 

 the kind of sugar determines the nature and 

 course of the process, and from the bacterio- 

 logical point of view it might almost be said 

 that every germ that produces lactic acid seems 

 to prefer a special kind of sugar. Hansen has 

 lately found a new germ which is capable of 

 causing the oxidation of alcohol to acetic acid, 

 and which is the third germ known to possess 

 this power as two others had been previously 

 discovered, one by Kiitzing and one subse- 

 quently by Pasteur. 



The same thing has been shown to be true 

 of the power to produce disease, and the once 

 prevalent conception of " specific " germs of 

 fermentations, pigments, and diseases, has been 

 completely shattered. 



There are certain well-known fermentations 

 evoked by bacteria, the chemical side of which 

 formerly attracted most attention. These are 

 especially the lactic acid fermentation of sugar, 

 in which alcohol and acetic acid often appear 

 as by-products ; the alcoholic fermentation of 

 sugar, in which lactic acid is always produced 

 as a by-product ; the butyric acid fermenta- 

 tion of sugar and lactic acid salts ; the forma- 



