WALTER E. GARREY 155 



were 408, 532, 618, and 803 seconds, but after exposing the ganglia 

 for five minutes to 0°C. then again warming to 10°C. the time was 

 in each case shortened being respectively 320, 416, 482, and 629 

 seconds. The increase in the rate of CO2 production averages 28 

 per cent in these experiments and is in good quantitative corres- 

 pondence to the acceleration rate of rhythm as stated above. 



When on the other hand ganglia are exposed to the upper extremes 

 of temperature compatible with function, e.g., to 35°C. or 40°C., and 

 are subsequently cooled the rate of rhythm is much slower at the 

 lower temperature than before warming process; thus in five ex- 

 periments in which the rates at 25°C. were determined before and 

 after heating the ratios of the actual rates of beat were 20:17, 20:13, 

 18:13, 24:20, and 17:8, This corresponds to an average decrease to 

 70 per cent of the previous rate. Four other experiments in which 

 similar conditions obtained indicated a depression in the rate of CO2 

 to a point only 78 per cent of the value before exposure to the high 

 temperature. These values for both extremes of this temperature 

 range again show a very good quantitative correspondence between 

 the effects upon rate of heart beat and rate of CO2 formation by the 

 ganglia. 



The quantitative relationship between the two processes is made 

 much more striking by the graph given in Fig. 1. This gives the 

 curve for a single typical experiment in which the rates of beat are 

 plotted as ordinates against temperature as abscissae. In this ex- 

 periment the ganglion was progressively cooled from room tempera- 

 ture to 0°, then warmed to 38°, and again cooled. The direction of 

 the temperature change is indicated by the arrows and the rate by 

 outline characters, triangle, circle, and square, respectively. 



A companion graph was constructed for the rate of CO2 formation. 

 For this purpose eleven experiments were taken in which the ganglia 

 had been treated to the same progressive changes in temperature as 

 in the previous experiment on rate of heart beat. The average time 

 required for CO2 formation was determined for different temperatures. 

 It was found that if the rate of CO2 formation was expressed as the 

 reciprocal of the time in seconds and this was multipHed in each case 

 by the constant 1400 a plot of the results gave a curve identical 

 with that shown in Fig. 1. The points obtained by this calculation 



