54 GENERAL BACTERIOLOGY LESSON 



Bacterium coli much more slowly ; in other 

 respects the two organisms in cultures resemble 

 each other closely. 



(2) Prepare " shake cultures " of these two organisms. 



(a) Melt two ordinary gelatine tubes, and inoculate one 

 with the Bacterium coli and the other with the Bacillus 

 typhosus. 



(b) Shake the tubes and allow them to set. 



(c) Keep them at 22 C. 



Examine them next day : very active gas formation 

 takes place in the gelatine in the case of the 

 Bacterium coli commune, none in the case of the 

 typhoid bacillus. 



(3) Prepare films of these two organisms in the usual 

 manner. 



Stain with aniline gentian-violet for one to two 

 minutes, wash in water, dry and mount. 



Examine with ^ in. oil immersion, and compare the 

 two organisms. 



There are several varieties of the Bacterium coli commune. 



(4) Prepare agar-agar shake cultures of Varieties L, II., 

 and III. 



(a) Melt the agar-agar either by placing it in boiling 

 water or by carefully heating the tubes over a small 

 Bunsen flame, and allow the tubes to cool to 40 C. 



(b) Now inoculate them with Varieties L, II., and III. 

 respectively. 



