146 BUTYRIC ACID FERMENTATION 



as will produce a thick gruel, and then cooling down to about 35 C. so quickly 

 that the final portion of barley-meal will have been exposed to 100 C. for a few 

 seconds only. The mixture is kept at a temperature of 35-37 C. At the 

 expiration of twelve hours bubbles of gas will be perceptible, and the presence of 

 butyl alcohol will be manifest, by its odour, after a further twenty-four hours. 

 If the aforesaid temperature be strictly maintained, almost pure Gramdobacter 

 butylicum will develop in the liquid, and a pure culture can be obtained there- 

 from, unhopped malt-wort gelatin forming a suitable medium, and one of the 

 methods described in 114 being employed. In this medium the fission fungus 

 in question will develop into milk-white, visco-rnucinous non-liquefactive colonies. 

 The fermentations induced therewith (e.g. in unhopped malt-wort of not more 

 than 10 Sacch.), and which must be carried out in the absence of air, progress 

 in two stages : so long as any free oxygen remains dissolved in the liquid, deve- 

 lopment will proceed but slowly, only carbon dioxide and hydrogen (no butyl 

 alcohol) being produced. When the liquid is finally purified, then not only can 

 the appearance of the alcohol be observed, but also an unusually vigorous increase 

 of the cells, which will be found to be so full of granulose that a drop of the 

 liquid will become stained quite blue-black by iodine. The endospores, which 

 soon make their appearance, attain, with a breadth of i /*, a length which may 

 be as much as 2 /x. This species is very sensitive to butyric acid. 



A second species is Granulobacter saccharobutyricum, the true butyric acid 

 bacterium, generally so called, and presumably identical with the Bacillus buty- 

 licus examined by Fitz. It is more widely distributed and of more frequent 

 occurrence than the last-named species, with which it is associated on cereal 

 grains and in the green malt, groats, and flour prepared therefrom. It is this 

 species, also, which occurs, and gives rise to damage, in badly prepared distillery 

 yeast-mash. Glucose and (but with greater difficulty) maltose are decomposed 

 by this species, butyl alcohol, carbon dioxide, and hydrogen in variable propor- 

 tions being produced, in addition to butyric acid. From a morphological point 

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

 what smaller ; also, like the other, it does not liquefy gelatin. Probably identical 

 with, or at least very closely related to G. saccharobutyricum is an anaerobic 

 ferment (Bacillus butyrlcus), 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, described by Pasteur. When culti- 

 vated 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 admitted 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. 



Granulobacler Polymyxa is frequently found on cereal grains, and is pre- 

 sumably identical with Prazmowski's Clostridium Polymyxa. 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 frequently found in dental mucus, 



