i88 BUTYRIC ACID FERMENTATION. 



and forms one of the many connecting links between the butyric 

 acid bacteria (in the restricted sense of the term) and the so-called 

 potato bacilli. No sharply denned limit can be drawn between 

 these two groups. In the same category must also be included 

 one of the two species of bacteria which were isolated in 1894 by 

 W. KEDROWSKI (I.) from a butyric fermentation produced by a 

 method approximating to that of Pelouze. In still closer relation 

 to the potato bacilli are a few anaerobic species isolated by C. 

 FLUGGE (II.) from boiled milk, as also the Bacillus liodermos, 

 frequently observed by LOEFFLER (III.) in imperfectly sterilised 

 milk. 



116. The Genus Granulobaeter. 



As the reader will be aware, organic chemistry distinguishes 

 between two kinds of butyric acid, only one of which, viz., the 

 propyl carboxylic acid, having tlie subjoined formula 



CH 3 -CHo CH 2 COOH, 



is, in the present state of science, known to result from butyric 

 acid fermentation, on which account it is also called fermentation 

 butyric acid. On the other hand, the isomeric acid, which, in 

 accordance with its constitution 



CH 3 H CH 3 



XT = CH.COOH 



CH 3 COOH CH 3 



is also styled dimethylacetic acid or isopropyl formic acid, has not 

 hitherto been obtained by the aid of fermentation. However, not 

 only the first- named acid, but also the corresponding alcohol, viz., 

 normal butyl alcohol, CH 3 CH 2 CH 2 CH 2 OH, can be pro- 

 duced by the activity of fission fungi ; so that we may also speak 

 of a group of the bacteria of butylic fermentation. In this con- 

 nection we are indebted to M. W, BKYERINCK (XII.) for some 

 thoroughgoing researches, which have not only brought new facts 

 to light, but also led to a more definite characterisation and limita- 

 tion of a number of species of butyric acid bacteria. This observer 

 has given to the bacteria of butylic fermentation the common 

 generic name of Granulobacter, since they all possess the faculty 

 of storing up granulose in the interior of their cells, owing to 

 which they are stained blue by iodine. The characteristics of this 

 genus are given by Beyerinck as follows : " Strictly or temporarily 

 anaerobic fermentative bacteria, which in a condition of complete 

 anaerobiosis become partly or entirely filled with granulose and 

 then assume the clostridium form. In presence of traces of 

 oxygen, short motile rods are quickly produced, which are stained 

 yellow by iodine. Endospores make their appearance in the 

 clostridia. They are able to remain uninjured for a few seconds 



