74 



GENERAL BACTERIOLOGY 



d. Remove the paper and incubate. 

 References. F. 71 ; M. & R. 20 ; L. 77 ; McF. 41 ; P. 135. 

 Special Directions. Use B. prodigiosus (Ehrenb.) Fluegge. 

 Sketch. 



EXERCISE 47. DETECTION OF GAS (Shake Culture). 



General Directions. 



a. Melt a tube of dextrose agar or dextrose gelatin and inoculate 

 with a gas-producing organism. 



b. Thoroughly mix and solidify by placing in ice water. 



c. Incubate over night. 



References. H. 70 ; L. & N. 89 ; M. & R. 78 ; McF. 49 ; P. 82. 

 Special Directions. Use B. coli; incubate. Make sketch. 



EXERCISE 48. QUANTITATIVE ANALYSIS OF GAS (Fermentation 



Tube). 



General Directions. 



a. Inoculate the open arm of 

 a fermentation tube with a gas- 

 producing organism. 



b. Incubate at 38° C. 



c. By frequent observations 

 determine : 



1. Whether growth takes 

 place in the open or closed arm, 

 i. e., whether it is aerobic or an- 

 aerobic. 



2. The rapidity and total 

 amount of gas formation. Use Frost's gasometer. (Plate I.) 



3. Kinds of gas. When the culture has ceased producing gas, 



completely fill the open arm with a 2% solution of sodium hydrate ; 



place the thumb over the mouth of the tube and thoroughly mix the 



NaOH with the gas in the closed arm, then without removing the 



thumb return the gas to the closed arm, remove the thumb, when the 



r:edium will rise in the closed arm to take the place of the absorbed 



GO^. Measure. The remaining gas is considered as hydrogen; 



bring this into the open arm, remove the thumb and introduce a 



lighted match. Air mixed with the hydrogen present causes a 



slight explosion. Express the amount of CO and H. in the form 



f ,. CO, 

 01 a proportion. = . 



H 



Fig. 19. Fennentation tube, showing' 

 method of using: gasometer. 



