F. G. GUSTAFSON 625 



in a neutral solution. These experiments confirm the data obtained 

 by measuring the production of CO2, and show that in an acid med- 

 ium the increase in oxygen consumption is greater than the increase 

 in the production of CO2, while in alkaline solution the two are about 

 the same. 



In all cases control experiments were made with solutions contain- 

 ing no fungus but having the same pH values as the solutions con- 

 taining the fungus. 



The results indicate that the increased production of CO2 in acid 

 solution is due to respiration and not to the action of the reagent in 

 setting free CO2 previously stored in the tissue (in the form of car- 

 bonates) . 



The work of certain investigators might lead to the expectation 

 that, in general, moderate concentrations of acid would decrease 

 respiration, while moderate concentrations of alkali would increase it. 

 It is evident that the organism here studied behaves in the opposite 

 manner. This raises some interesting questions regarding the reac- 

 tions in the organism which result in the production of CO2; further 

 investigation will be necessary to clear up these questions. It is 

 possible that the results obtained from the study of PenicilUum are 

 connected with the fact that it grows best on an acid medium. In 

 the experiments of the writer spores grew best on media with a pH 

 value of from 4 to 6. 



SUMMARY. 



1. Variations in pH value between 4 and 8 produce practically no 

 effect on the normal rate of respiration (the rate at neutrality is 

 called normal). 



2. Increasing the pH value to 8.80 causes respiration to fall to 

 60 per cent of the normal, after which it remains stationary for the 

 duration of the experiment. 



3. Decreasing the pH value to 2.65 causes a gradual rise and a 

 gradual return to normal; at pH 1.10 to 1.95 the preUminary rise 

 amounts to 20 per cent and is followed by a fall to below the normal. 



4. The decrease in respiration brought about by solutions of a 

 pH value of 1.95 or less are irreversible, while a similar decrease 



