W. J. V. OSTERHOUT 



175 



change in acidity; hence it represents the average rate for that period. 

 If the rate changes during the period, the average rate is probably 

 the actual one somewhere near the middle of the period. Hence in 

 Fig. 1, each ordinate representing the average rate is placed in the 

 middle of the period. In these papers all curves in which rate is 



T?at6 of T^espirati on 

 200J 



% 



100.- 



FlG. 1. Curve showing the rate of respiration under normal conditions (dotted 

 line), and under the influence of a reagent (unbroken line). The periods during 

 which measurements are made are indicated by horizontal shading; the intervals 

 during which no measurements are made are left blank. Each measurement 

 gives an average rate for the period ; as this average rate is probably the actual 

 rate near the middle of the period, the ordinate expressing the average rate is 

 placed in the middle of the period. For convenience in comparison, time is 

 reckoned from the beginning of exposure to the reagent. 



plotted against time are made in this -manner. For purposes of com- 

 parison the time expressed on the abscissae is usually reckoned from 

 the beginning of exposure to the anesthetic. The preceding part of 

 the experiment, during which respiration was going on under nor- 

 mal conditions, is also represented on the curve but in this part the 



