20 STUDIES ON RESPIRATION. IX 



noticed, and control experiments made in this way kept up to normal 

 for several hours, or as long as the experiment lasted. 



Various concentrations of NaCl were used. Lower concentrations 

 such as 0.125m, 0.25m, and 0.5m caused a rise in respiration. At 1m 

 the results were rather variable, some experiments showing a rise and 

 others a fall. Solutions of 2m always gave a decided decrease which 

 was followed by a small increase. The respiration then remained con- 

 stant for more than an hour or to the end of the experiment. Figs. 

 1 and 2 give a graphic representation of the results obtained with 

 various concentrations of NaCl. 



Fig. 1. Respiration of Aspergillus niger. The broken straight line to the left 

 of the point marked on the abscissa represents the normal rate of respiration 

 before the addition of the salt. Curve A represents the respiration in 0.125m 

 NaCl, Curve B respiration in 0.25m NaCI, Curve C respiration in 0.5m NaCl, 

 Curve D respiration in 2m NaCl, and the broken Hne the control in 0.05 per cent 

 dextrose. A, B, and C were in 0.05 per cent dextrose while D was in 1.5 per cent 

 dextrose. Curves A, C, and D are each an average of 3, B of 4 experiments. 

 Probable error less than 3 per cent of the mean. 



The results with the lower concentrations are somewhat variable as 

 to the amount of increase, as well as in respect to the time of maximum 

 respiration. Thus in some experiments with 0.25m NaCl the max- 

 imum was reached at about 30 minutes after the introduction of the 

 salt, while in most the maximum was not reached until at the end of 

 50 minutes. 



