I$o LABORATORY GUIDE IN BACTERIOLOGY 



consists in transferring the cultures for three consecu- 

 tive days in broth and incubating at 20 C. From the 

 third transfer they are plated in gelatin and a colony 

 from this transferred to slant agar, from which sub- 

 cultures are made. 



SECTION 6 

 ISOLATION OF B. TYPHOSUS FROM WATER 



1. Prepare 10 tubes each of Endo's medium, Dri- 

 galski and Conradi's medium, aesc. bile-salt agar (p. 33). 



2. Prepare plates from water containing B. typhosus 

 from both of these media. 



3. Incubate at 37 C. for 24 hours and isolate the 

 colonies. 



4. Carry the colonies through all media and apply 

 the agglutination test with typhoid immune serum. 



SECTION 7 



STUDY OF REACTION OF BACTERIA ON NEUTRAL- 

 RED BROTH 



Prepare a number of fermentation tubes with dex- 

 trose or lactose broth and add enough of a i per cent 

 neutral -red solution until a decided red color has been 

 imparted. Inoculate these tubes with a variety of 

 colonies from water or sewage plates and note the differ- 

 ence in color reaction after 24 and 48 hours' incubation. 



