80 



MICRO-ORGANISMS AND FERMENTATION. 



cellulose fermentation, which is employed in various branches 

 of industry. 



A bacterium which, among other substances, produces 

 butyric acid is the Bacillus lupuliperda examined by 

 BEHRENS, which occurs very frequently on hops, and is the 

 cause of the spontaneous ignition of moist hops. The growth 

 consists of movable cocci and short bacilli, which render 

 gelatine liquid. In a medium not containing sugar this 

 fungus produces an abundance of ammonia derivatives, 

 especially trimethylamine (odour of pickled herring) ; in the 

 presence of sugar the solution soon becomes sour, and butyric 

 acid is formed. This species seems to have its abode chiefly 

 in the soil, and bears much resemblance to the Bacillus 

 fluorescens putridus described by FLUEGGE. 



4. ALCOHOL-FORMING BACTERIA. 



Among the fermentation-products of several species of 

 bacteria, alcohol occurs. The first known of these species 



CD CD O O a 

 CXD CO OO* 



FIG. 22. Bacillus Fitzianus (after H. BUCHNER.) a, b, f, g, cocci and short rods; 

 c, e, bacilli ; d, rods with spores. 



is the Bacillus Fitzianus, discovered by FITZ in hay-infusion 



