F. G. GUSTAFSON 



21 



This variability was of course to be expected with substances that 

 are not more toxic than NaCl, where the least individual variation 

 in the physiological activity of the cultures has a chance to exert its 

 influence fully. This fact has already been noted in respect to some 

 of the weaker anesthetics.^ Though there are differences in the 

 amount of increase and in the time when the maxima occur, yet there 



0.50 



Fig. 2. Respiration of Aspergillus niger. The curves show rate plotted against 

 concentration and represent the same experiments as shown in Fig. 1. Curve A 

 represents the respiration at the end of 10 minutes exposure to NaCl, Curve B 

 at end of 30, Curve C at end of 52, and Curve D at end of 60 minutes. Curve E 

 represents the control in 0.05 per cent dextrose. 



is no doubt about the general result. There is a distinct, though 

 small, amount of increase in the rate of respiration, when Aspergillus 

 niger is treated with NaCl at concentrations between 0.125 and 0.5m. 

 With 1m solutions of NaCl apparently contradictory results were 

 obtained; i.e., some experiments gave a large initial decrease followed 

 by a rise to normal, others gave little or no initial decrease followed 



