INOCULATING SPECIAL MEDIA 47 
however, to determine the acid and gas production in the test 
tubes than to use the fermentation tubes, and it is cheaper. 
It is convenient, therefore, to use these tubes with the sugar 
media as follows : 
1. If to determine the power of the organism to produce 
gas, use only the agar tubes. 
2. If to determine the power of the organism to ferment 
sugars, producing acids, use only test tubes of bouillon. 
3. If to determine the quantity of gas produced and approxi- 
mately its composition, use the fermentation tube. In this 
exercise all three are called for. 
