46 LABORATORY BACTERIOLOGY 



EXERCISE XI 



INOCULATING SPECIAL MEDIA AND EXAMINING 

 CULTURES 



71. Work for this exercise. Inoculate, from a culture fur- 

 nished of B. pro tens vulgaris? a tube of potato, one of milk, 

 one of litmus milk, one of glucose agar, a fermentation and 

 test tube of glucose, one each of lactose and of saccharose 

 bouillon. Label each and place in the incubator. 



Stain a preparation with alkaline methylene blue, one with 

 carbol fuchsin, and one with an aqueous solution of gentian 

 violet from the bouillon and agar cultures ( 47). Make a 

 careful comparison of the preparations and note any difference 

 in the appearance of the bacteria or in the intensity of the 

 stain. Preserve as a permanent specimen, to accompany the 

 notes, a preparation stained with each of the dyes. 



Prepare the aqueous solution of gentian violet ( 38). 



(For methods of making anaerobic cultures, see Exercise 

 XXXIX.) 



72. The inoculation of glucose agar to determine the power 

 of the organism to produce gas. Boil the tube of glucose agar 

 in an open water bath until it is liquefied, then cool it down to a 

 temperature of 40 C. and inoculate it with a loopful of the cul- 

 ture, carefully stir the agar with the loop, after which solidify 

 it as quickly as possible. Label and stand in the incubator. 



73. The use of media containing the sugars. The sugars are 

 employed as tests to determine whether or not the bacteria in 

 question will ferment them, producing acids. Some bacteria 

 will produce gas as well as acids. The latter is determined in 

 the sugar-agar tubes. 



In the fermentation tubes we can determine both of these 

 properties and also the quantity of gas set free. It is easier, 



1 Or any other gas-producing bacillus. 



