BACTERIA AND FERMENTATION 1 33 



ferments give rise to oxidation of certain products of decom- 

 position ; the anaerobic organisms, on the other hand, only 

 commence to grow when the aerobic have used up all the 

 available oxygen. Thus in such fermentations certain bodies 

 (carbohydrates, fatty acids, etc.) undergo decomposition, and 

 by oxidation become carbonic acid gas, and the remainder is 

 left as a '* reduced '' product of the whole process. Hence 

 sometimes this is termed fermentation by reduction. The 

 chemical formula of this butyric reaction may be expressed 

 thus: — 



CgHigOg (by simple decomposition) = 2 CgHgOg- 

 Glucose, Lactic acid. 



which is followed by the fermentation of the lactic acid : — 



2 CgHgOs = QHgOg + 2 CO 3 + 2 IJ 3 . 



Lactic acid. Butyric acid. Carbonic Free hydrogen, 

 acid gas. 



Bacillus Butyricus, Long and short rods, generally 

 straight, with rounded ends, single or in chains, reproduc- 

 ing themselves both by fission and spores, and sometimes 

 growing out into long threads, actively motile, anaerobic, 





B. BUTYRICUS 



and liquefying. The spores are widely distributed in 

 nature, and grow readily on fleshy roots, old cheese, etc. 

 The favourable temperature is blood-heat, and on liquid 

 media they produce a pellicle. The resistant spores are 



