F. G. GUSTAFSON 191 



The action of caffeine seems to be very much slower and less pro- 

 nounced than that of the other substances tried. 



The absence of any noticeable buffer action in any of the solu- 

 tions was determined by means of an apparatus which has been 

 described by Osterhout.* A measured amount of CO2 is introduced 

 into a certain amount of solution with indicator and the change in 

 pH is noted. This is compared with the change caused by an equal 

 amount of CO2 in the same amount of tap water. 



The above results agree in the main with those obtained by Haas^ 

 on Laminaria. Usually stronger solutions were needed to cause any 

 effect on the respiration of Aspergillus niger, and the changes were 

 not so great. With all reagents tried there was an increase, though 

 with some concentrations only a decrease was noted. 



SUMMARY. 



1. In concentrations which are high enough to produce any effect, 

 formaldehyde, ether, and acetone cause an increase, followed by a 

 decrease, in the rate of respiration. 



2. 3.65 per cent ether, which causes an increase with certain 

 cultures, produces only a decrease with others. 



3. The reaction producing an increase in the respiration with 7.3 

 per cent ether is a reversible process, while the reaction producing 

 the decrease is not reversible. 



4. 0.5 per cent caffeine produces only a decrease in respiration while 

 a saturated solution causes an increase, which is followed by a 

 decrease. 



^Osterhout, /. Biol. Cheni., 1918, xxxv, 237. 



