370 



BACILLI WHICH CAUSE FERMENTATION. 



Iodine reac- 

 tion. 



Other fer- 

 mentative 

 action. 



Distribution. 



A property which occurs under certain circumstances, 

 and which is peculiar to the butyric acid bacillus, is the 

 power of forming a material (granulose) in the plasma, 

 which assumes a blue or blackish-violet colour with 

 iodine. This property can be most readily observed 

 when the bacillus is cultivated in media containing 

 starch; but the coloration also occurs in the absence 

 of starch when, instead of it, cellulose, or lactate of lime, 

 or glycerine is present; it seems to occur seldom in 

 nutrient solutions containing dextrine and sugar. Young 

 rods stain of a pure blue colour, older rods of a dark 

 violet; in some only a few transverse zones are blue, 

 in others the rods are continuously stained (compare also 

 Leptothrix, page 392 ; bacillus polymyxa, page 374 ; 

 bacillus Pasteurianus, page 390). 



It is possible also that the bacillus butyricus has 

 another fermentative action, in that it is able to cause 

 fermentation of cellulose; according to Tappeiner, 

 methane, carbonic acid, and sulphuretted hydrogen, or 

 only hydrogen and carbonic acid are formed according 

 to variations in the composition of the nutrient substrata. 

 (See the chapter on " Fermentation.") This decomposi- 

 tion of cellulose has probably a certain technical im- 

 portance, for example in the preparation of flax, and 

 is perhaps also of physiological significance in the 

 digestion of cellulose by herbivora. (Van Tieghem 

 ascribes the property of destroying cellulose to a special 

 bacterium called bacterium amylobacter, an organism, 

 however, which this author stated at a later period 

 to be identical with the butyric acid bacillus described 

 by Pasteur). 



Bacillus butyricus seems to be extremely widely 

 distributed in nature; it can be obtained from hay-dust, 

 from a great variety of putrefying vegetable infusions, 

 from sauerkraut, from old cheese, from milk which has 

 been kept for a long time; according to Deherain and 

 Maquenne* it occurs also in the earth of fields. It has 

 also been observed in the cells of plants which have a 

 milky juice. Van Tieghem was able to recognise it 



* Bull. soc. chim. (2), 39. Compt. Rend., 97. 



