Isolation of the Colon Bacillus. 103 



appointed to consider the Standardization of Methods 

 for the Bacterioscopic Examination of Water, presented 

 a series of obligatory tests and optional tests; and in 1905 

 the Committee on Standard Methods of Water Analysis 

 of the American Public Health Association drew up a set 

 of diagnostic characters for B. coli. The latter corresponds 

 in general with the plan developed by the Massachusetts 

 State Board of Health (Massachusetts State Board of 

 Health, 1899) and long in use at the Massachusetts 

 Institute of Technology. 



It involves the use of the following seven tests : 



DIAGNOSTIC CHARACTERS FOR B. COLI. 



1. Typical morphology non-sporing bacillus, rela- 

 tively small and often quite thick. 



2. Motility when a young broth or gelatin culture is 

 examined. 



3. Fermentation of dextrose broth, with the formation of 

 about 50 per cent of gas, of which about one-third (CO 2 ) 

 is absorbed by a two per cent solution of sodium hydrate. 



4. Coagulation of milk, with the production of acid, in 

 48 hours or more at 37 C., either spontaneously or upon 

 boiling. 



5. Non-liquefaction of gelatin. 



6. Production of indol in peptone solution. 



7. Reduction of nitrates. 



The English standard procedure corresponds quite 

 closely to this (Committee appointed to consider the 



