164 Elements of Water Bacteriology. 



B. alcaligenes stands at the lower end of the whole series 

 in fermentative power. B. typhi forms a slight initial 

 acidity in milk and a slight acidity in dextrose broth, 

 while the reaction of B. alcaligenes in sugar media is 

 always alkaline. B. dysenteriae, on the other hand, 

 differs from B. typhi in the direction of the B. enteritidis 

 group, producing a well-marked acid reaction, but no gas 

 in dextrose media. B. typhi and B. dysenteriae are, of 

 course, also distinguished by their specific serum reactions. 

 Neither B. alcaligenes nor any other member of this 

 group (except the disease-producers themselves, when 

 clearly identified by agglutination tests) has any well- 

 established sanitary significance. Non-acid-forming bac- 

 teria of this general type are frequently found in feces, 

 but they are also found in other habitats, and comparative 

 data are entirely lacking to show that they are more 

 abundant, proportionately, in polluted than in normal 

 waters. 



The second great division of the colon-typhoid bacteria 

 is the hog cholera group, or the Gartner group, as 

 Durham (1898) called it. As defined by him, it differed 

 from the typhoid group by gas formation in dextrose, 

 and from the colon group by the production of a final 

 alkaline reaction in milk. It includes the Gartner bacillus 

 (B. enteritidis), the hog cholera bacillus (B. cholerae 

 suis), and the paratyphoid bacilli. Some of these forms, 

 the paratyphoid bacilli, for example, and B. enteritidis 

 (isolated in cases of meat poisoning), produce intestinal 



