AGRICULTURAL BACTERIOLOGY. 



in contact with oxygen. But, in spite of the long list which 

 is known, it appears that the ordinary butyric fermentation is 

 probably caused by a single species. This organism was first 

 described under the name of B. aerogcncs capsulatus, but was 

 subsequently given the extraordinary name of Granulobacillus 

 saccJiarobntyricus immobilis liqncfacicns (Fig. 25). It appears 

 to be very widely distributed. It is found in air, dust, dirt, 

 milk, in the intestine of a large number of animals and almost 

 universally in feces. It is perhaps the 

 most widely distributed of all known 

 bacteria. It is a strict anaerobe and 

 produces very resisting spores. In 

 ordinary milk, although commonly 

 present, it never makes itself evident, 

 since it is prevented from growing by 

 the presence of the lactic bacteria or 

 the presence of air. If, however, the 

 milk is sterilized the bacillus is almost 

 sure to be left uninjured and will sub- 

 sequently produce the butyric fermentation if the milk is left 

 without free access of air. It finds its way into butter and is 

 doubtless one of the causes, perhaps the chief cause, of the de- 

 velopment of rancidity. While, then, of universal occurrence, it 

 is of little significance in the dairy except in relation to butter. 

 In addition to these types of normal milk bacteria it must 

 also be stated that other species are very commonly found 

 in milk and are frequently so numerous that they should 

 be regarded as normal dairy bacteria. These species, how- 

 ever, appear to have no noticeable effect on milk. They do 

 not produce acid or any enzyme ; neither do they change 

 the taste, odor or appearance of milk. That they do really 

 produce some changes in the chemical nature of the milk is 

 very probable, but in regard to them nothing is known at 

 present. For ordinary dairy purposes they are therefore of 



