190 BUTYRIC ACID FERMENTATION. 



of view, it is closely allied to the first-named species, but the spores 

 are somewhat smaller ; also, like the other, it does not liquefy 

 gelatin. Probably identical with, or at least very closely related to 

 G. saccJiarobutyricum is an anaerobic ferment (Bacillus butyricus), 

 isolated by S. Botkin (I.) from Berlin and Breslau milk, and also 

 frequently noticed by FLUGGE (II.) in market milk. 



Granulobacter lactobutyricum is probably identical with the 

 organism causing butyric acid fermentation in calcium lactate, de- 

 scribed by Pasteur. When cultivated in the absence of air, it 

 grows in the form of plump, short clostridia, which stain violet- 

 blue (not pure blue) with iodine and convert calcium lactate into 

 butyrate, hydrogen and carbon dioxide being liberated. The 

 endospores are smaller and shorter than those of the first-named 

 species. When kept in presence of air, this organism converts 

 calcium lactate into large spheroidal crystals of the carbonate, and 

 in this case takes the form of slender short rods, resembling those 

 of Bacillus subtilis and staining yellow with iodine. From the 

 fact, recorded by Beyerinck, that this species in a state of pure 

 culture dies out after several re-inoculations, whether air be ad- 

 mitted or excluded, it may be presumed that the organism needs 

 for its prosperous development the symbiotic association of another, 

 still undetermined, species of fission fungus. 



Granulobacter Polymyxa is frequently found on cereal grains, 

 and is presumably identical with Prazmowski's Clostridium Poly- 

 myxa. This species develops most satisfactorily in an unrestricted 

 supply of air, and then assumes the form of motile rods. When 

 the aeration is deficient, spore-bearing clostridia appear, and a weak 

 fermentative action is noticeable, a small quantity (traces) of butyl 

 alcohol, together with carbon dioxide, being formed, but neither 

 hydrogen nor butyric acid. The Leptothrix buccalis, very fre- 

 quently found in dental mucus, and whose thread chains are 

 generally stained blue by iodine, is also classified by Beyerinck 

 along with the Granulobacteria. 



117. The Equation of Butyric Fermentation 



is set out in a very simple form in most text-books on chemistry, 

 that for the decomposition of the hexoses (glucose, &c.) being 

 given as follows 



= 2H 2 + 2CO 2 + C 4 H 8 2 , 



or, with lactic acid (or its lime salt) as the raw material 

 2C 3 H 6 3 = 2H 2 + 2C0 2 + C 4 H 8 Oa. 



In the preceding paragraphs we have, however, made the 

 acquaintance of a very large number of bacterial species with 

 divergent methods of action, so that we must at once admit that a 

 general equation for butyric acid fermentation is not to be thought 



