182 STUDIES ON RESPIRATION. II 



any desired pH value by means of borates and boric acid has been 

 published by Palitzsch^ and later republished by Osterhout and 

 Haas.' 



In the experiments 10 cc. of tap water were used in each tube to 

 which five drops of a 0.01 per cent solution of phenolsulfonephthalein 

 were added as indicator. That this indicator was not toxic to the 

 fungus was proved by sowing spores in a nutrient solution contain- 

 ing the same concentration of indicator as used in the experiments. 

 A control with the same amount of spores was inoculated at the same 

 time and grown under similar conditions. The two cultures matured 

 at the same time and behaved similarly when treated with anesthetic. 



Respiration was measured in the nutrient solution and in sugar solu- 

 tions in preliminary experiments, but as the results were the same as 

 when tap water was used, the nutrient solution was replaced by tap 

 water, which was easier to handle. The tap water was very near the 

 neutral point and was brought to the desired alkalinity by boiling off 

 some of the dissolved CO2 or by washing out some of the CO2 by 

 means of a current of air free from CO2. 



When an experiment was started, some of the fungus was thor- 

 oughly rinsed in tap water to wash off the nutrient solution. Any 

 adhering bubbles of gas enclosed in the interwoven hyphse had to 

 be got rid of before the readings were begun, either by gently 

 squeezing the material between the fingers or by a continued shaking 

 in several changes of water. The mass of hyphae was then separated 

 into pieces small enough to be shaken about easily in the tube. They 

 were then put into a Pyrex glass tube which was closed at one end, 

 while at the other was attached a paraffined rubber tube about 3 

 inches long.^ Before putting the fungus in the tube, 10 cc. of tap 

 water (plus five drops of indicator) had been poured in. When the 

 fungus had been put in, the rubber tube was closed with a spring 

 clamp, in such a way as to enclose a small bubble of air, to act as a 

 stirrer. In all experiments this bubble was made as nearly the same 

 size as possible. The tube was now shaken until any gas that may 

 have adhered to the material was detached. The color of the experi- 



^ Palitzsch, S., Biochem. Z., 1915, Ixx, 333. 



^ Osterhout, W. ]. V., and Haas, A. R. C, Science, 1918, xlvii, 420. 



