a little strong KOH with a bent pipette. Since no free ( ).. wa^ 

 present in the vial what must we conclude the origin of the C< >.. 

 to have been? This phenomenon is a f/cncral characteristic of 

 metabolism. 



292. Review Pasteur's Yeast Experiment (p. 27) which shows 

 very clearly the difference between aerobic and anaerobic 

 respiration. 



293. Organisms can oxidize substances through oxidizing en- 

 zymes. Review the experiments on oxidation under the head of 

 enzyme action (p. 23). Organisms have also a strong reducing 

 power as indicated in the following experiment : 



Cut thin slices of the tissues (muscle, kidney, sex organs, brain 

 or spinal cord, etc. ) of a frog and stain in salt solution plus methy- 

 lene blue. Kill a thin piece of muscle tissue in hot water to serve 

 as a control and stain in the same way. Place all on slides with 

 salt solution under cover-glasses. Does the blue color disappear 

 after a time, thus indicating reduction? Note if the color is local- 

 ized in any region. Lift the cover-glass and determine the effect 

 enzyme action (p. 23). Organisms have also a strong reducing 

 power ? 



294. Simultaneous reducing and o.vidiziny actions. Inoculate the 

 beef-broth-dextrose culture-medium with a collection of bacteria 

 from sewage and place in a fermentation tube. Allow to stand 

 a day or two and note the collection of gas. Gas formation is 

 due to Bacillus coli. 



Fill the tube with io ( /c KOH solution, excluding air, place your 

 ringer over the end and invert. Any absorption? Allow the gas 

 to collect in the upper part of the tube and estimate the per cent 

 absorbed. Again till the tube with water to exclude air. Allow 

 the gas to collect at the open end of the tube, covered by your 

 finger. Remove your finger and quickly apply a match. What 

 gases are indicated by the tests? 



295. Effects of lack of o.vvi/cn on Paramecium. The Engelmann 

 gas chamber is used in this experiment. The Paramecia are ex- 

 amined in a hanging drop of culture fluid on the under surface 

 of a cover-glass placed over the aperture of the gas chamber. 

 Oxygen is removed by passing a current of hydrogen through 

 the chamber. The gas is generated from zinc and dilute H,SO 4 , 

 and is passed through two wash bottles, one containing KMnO t solu- 

 tion, the other 2O c / f NaOH, and then through the chamber; from the 

 exit tube of the chamber a rubber tube opens under the surface 



89 



