158 PUBLIC HEALTH BACTERIOLOGY 



B. subtilis, flesh-coloured mycoderma ; Streptococcus, 

 invisible growth ; B. megatherium, a yellow, raised, moist 

 growth. 



Blood Serum. Inoculate, and incubate at 37 C. for 

 two to three days, and examine. 



B. coli communis, serum solid ; B. pyocyaneus, serum 

 liquefied. 



Milk. Inoculate, incubate at 37 C. for forty-eight 

 hours, and examine. 



B. coli communis, milk clotted and acid ; B. denitri- 

 ficans, no clot, alkaline ; B. pyocyaneus, casein pre- 

 cipitated and partly dissolved ; Streptococcus, no clot, 

 slightly acid. 



MacConkey's Broth with Durham's tubes. Inoculate, 

 incubate at 37 C., and examine daily. 



B. coli, acid and gas ; B. typhosus, acid, no gas. 



Peptone Water. Inoculate, incubate at 37 C., and 

 examine in four or five days. 



B. coli communis, indol formed ; B. typhosus, none ; 

 Sp. cholerae, nitroso-indol. 



Aerobic and Anaerobic. Make gelatin stabs and 

 incubate at 20 C. for two days. 



B. zopfii, growth only on surface (strict aerobe). Torula 

 alba, on surface and in depth (aerobe and facultative 

 .anaerobe). B. butyricus, growth only in depth (strict 

 anaerobe) . 



Colour Formation. 



1. Inoculate two agar tubes with B. prodigiosus, and 

 incubate ; (i) at 37 C., (2) at 20 C. Examine in forty- 

 eight hours, (i) is white or grey, (2) is pink. 



2. Presence of oxygen is necessary in most cases for 

 pigment to be developed. Make two gelatin stab cultures 

 of Bacillus fluorescens liquefaciens. Incubate one 



. aerobically and the other anaerobically. Examine in forty- 

 eight hours. The aerobic culture is pigmented, the other 

 is not. 



3. A few require absence of oxygen. Make gelatin 

 stab of Spirillum rubrum and incubate at 20 C. for 3 to 4 

 days, when growth is found in depth to be red and on 



surface to be white. 



