IMPORTANT PATHOGENIC BACTERIA 121 



5. Special study. — Make cover-slip preparations of 

 B. dysenteriae from glucose agar cultures 10-12 days 

 old. Involution forms are then plentiful and can be 

 studied. 



SECTION 4 



THE PROTEUS GROUP 



Inoculate agar slants from laboratory cultures of 

 Bacillus proteus, Proteus zenkeri, and Bacillus cloacae. 



1. Routine study. — Observe the action on milk and 

 gelatin. 



2. Special study. — Make plates in gelatin and agar, 

 and observe the colonies after 24, 48, and 72 hours. 

 Note the appearance of the colonies of B. proteus 

 and of Prot. zenkeri on both media. 



3. Special study. — ^Inoculate fermentation tubes and 

 determine the percentage of gas formed and the gas 

 formula. Compare the results with those of the in- 

 testinal bacteria. 



Note. — In order to obtain a clear picture of the differential 

 characteristics of the three groups of colon-typhoid bacilli and the 

 proteus group, it is recommended to tabulate the results in 

 columns, as outlined below. Express positive results by the 

 sign -|-; negative, by — . Complete agglutination is expressed 

 by-t- +; slight, by +. 



