52 LABORATORY BACTERIOLOGY 



EXERCISE XIII 



THE EXAMINATION OF CULTURES (continued) 



79. Work for this exercise. Reexamine the cultures made 

 on special media and make notes on all changes which have 

 occurred in their appearance. 



Examine microscopically in hanging-drop preparations the 

 bacteria from the glucose bouillon culture. 



Make a stained cover-glass preparation from the milk 

 culture. Stain with carbol fuchsin. 



Reexamine all of the cultures previously made and make 

 careful notes of any changes that have occurred in their 

 appearance. 



Measure the gas in the fermentation tubes and determine 

 the ratio of CO2 to H. 



80. Making cover-glass preparations from milk cultures. 

 Spread as thin a film of the milk culture as possible on the 

 cover glass and allow it to dry in the air. Immerse the prep- 

 aration in a watch glass or other receptacle containing a few 

 cubic centimeters of ether and absolute alcohol in equal parts, 

 which dissolves out the fat and fixes the film to the cover glass 

 at the same time. Then remove and, after the ether and alco- 

 hol have evaporated, stain as usual. The amount of albumen 

 in the milk will usually cause a heavy background, which will 

 require decolorizing with alcohol or weak acetic acid. 



