332 AGRICULTURAL AND INDUSTRIAL BACTERIOLOGY 



species of Bacterium (such as the Bacterium lactis viscosum 

 producing ropy milk) will not be discussed in this section 

 as they do not produce disease and are not of particular 

 pathologic significance. 



The true intestinal bacteria belonging to the genus Bac- 

 terium are divided usually into three principal sub-groups, 

 the separation being made upon the basis of the ability to 

 produce acid and gas in the sugars lactose and glucose. The 

 bacteria which can produce acid and gas from both lactose 

 and glucose belong to the first or colon subgroup. Those 

 which can produce acid and gas from glucose, but not ?rom 

 lactose, belong to the intermediate or enteritidis subgroup. 

 Those which produce no gas or acid from lactose, no gas 

 from glucose, and may be either positive or negative as to 

 acid production from glucose, belong to the third or 

 typhoid-dysentery subgroup. 



Each of these subgroups has been differentiated into a 

 large number of species about thirty altogether being well- 

 characterized and recognized in the literature. It will be 

 noted that in the differentiation of the subgroups the 

 first shows high fermentative power and for the most part 

 the organisms belonging to it are nonpathogenic. The 

 second group is intermediate both in power of fermentation 

 and in power of disease production. The third subgroup 

 has the lowest fermentative power and has belonging to it a 

 considerable number of highly pathogenic bacteria. 



THE COLON OR COLON AEROGENES SUBGROUP OF BACTERIA 



The most important species belonging to this subgroup 

 are Bacterium coli, Bacterium acidi-lactici f Bacterium com- 

 munior f Bacterium neapolitanum f Bacterium coscoroba f 

 Bacterium cloacce and Bacterium aerogenes. 



The Bacterium coli and the Bacterium aerogenes are 

 more important than the other species and are the only 

 ones which will be discussed in detail. The differentiation 



