BUTYRIC ACID BACTERIA. 131 



Clostridium Pasteurianum, discovered by Winogradsky, is 

 of particular interest. He isolated it from garden soil by 

 heating for ten minutes at 75 C., and then cultivating in a 

 stream of nitrogen in a substratum free from nitrogen. The 

 species can, therefore, absorb free nitrogen from the air and 

 assimilate it. It can, however, utilise nitrogen in combina- 

 tion. It forms butyric acid, acetic acid, minute quantities of 

 alcohol, carbon dioxide, and hydrogen, and occurs as short, 

 thick motile rods, which at a later stage expand into spindle 

 shapes, and during the production of spores gives a violet- 

 brown colour with iodine. The free spores are surrounded 

 by an irregular mass of jelly. 



Beijerinck has drawn special attention to the possibilities 

 of butyric acid bacteria which display bodies resembling 

 granulose in the swollen cells and may be coloured with 

 iodine, and has formulated a group which he calls Granulo- 

 bacter. It consists of a series of species, some of which are 

 identical with those previously described. The true origin- 

 ator of the butyric acid fermentation, the preparation of which 

 has been described, he calls Granulobacter saccharobutyricum ; it 

 forms varying quantities of butyl alcohol, carbon dioxide, and 

 hydrogen from saccharose, better from glucose, and also from 

 maltose, and it secretes diastase. 



Schattenfroh and Grassberger examined a long series of 

 species, both pathogenic and non-pathogenic, and found that 

 the latter consisted chiefly of two species, one of which is 

 motionless, and is very widely distributed. It forms both 

 short and long rods, particularly on alkaline substrata con- 

 taining starch. It exhibits the granulose reaction in the 

 Clostridium form (this usually disappears with the formation 

 of spores), and it liquefies gelatine. The other species is 

 motile, and forms thin rods with from six to twenty cilia on 

 ach. In the spore stage they are motile, and they do not 

 liquefy gelatine. These two species include many of those 

 previously described, which may be regarded as varieties. 

 Neither of them attacks cellulose. We must here recall 

 Paraplectrum foetidum (Weigmann), which is widely distributed 

 in milk. It coagulates the milk, and then dissolves the coagu- 

 lated mass, and develops a very objectionable smell of cheese. 



