INOCULATING SPECIAL MEDIA 37 



EXERCISE XI 

 INOCULATING SPECIAL MEDIA AND EXAMINING CULTURES 



60. Work for this Exercise. — Inoculate a tube of potato, 

 one of milk, one of litmus milk, one of glucose agar, a fermen- 

 tation and test tube of glucose, one each of lactose and of sac- 

 charose bouillon. Label each, and place all of them in the 

 incubator. 



Examine microscopically the agar and bouillon cultures made 

 from the colony on the agar (41). Examine and carefully 

 describe the bacteria from each culture in (i) a hanging-drop 

 preparation, and (2) stained cover- glass preparations. Stain a 

 preparation with alkaline methylene-blue, one with carbol fuch- 

 sin, and one with an aqueous solution of methyl-violet. Make 

 a careful comparison of the 3 preparations and note any dif- 

 ference in the appearance of the bacteria or in the degree of 

 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 methyl-violet (36). 



61. 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 

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

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



62. The Use of Media containing the Sugars. — The sugars 

 are employed as tests to determine whether 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. 



