210 STUDIES ON RESPIRATION. V 



buffer action was identical in the solutions containing anesthetics and 

 in the controls (the ether has practically no buffer action). 



In each case 10 cc. of the solution were placed in a Pyrex glass 

 tube of the same diameter and thickness as the Pyrex glass tubes 

 containing the buffer solutions. The organisms were put in the so- 

 lutions and the time required to change from pH 8.0 to 7.7 was re- 

 corded by means of a stop-watch. After experimentation the solu- 

 tions were tested by driving out the CO2 by means of air free from CO2; 

 invariably the solutions returned to pH 8.0, thus proving that no 

 acids other than the carbonic were responsible for the change in the 

 pH value. 



The temperature was kept approximately constant at 20°C. (with 

 variations of less than 1°C.) by means of a water bath. 



In presenting the results the rate of respiration is taken as the 

 reciprocal of the time required to change the solution from pH 8.0 

 to 7.7. For convenience this rate is expressed as per cent of the 

 normal rate, which is always taken as 100 per cent. The normal 

 rate was in most cases practically constant.' 



Frog Tadpoles. 



The first set of experiments to determine the effects of ether on the 

 carbon dioxide output of frog tadpoles was made with ten concen- 

 trations of ether, ranging from 0.007 to 0.55 per cent by volume. 

 The tadpoles chosen were about 20 mm. in length; at this stage, they 

 respire through the internal gills and the skin. A single tadpole 

 was placed in each tube containing 5 cc. of liquid, and the time re- 

 quired to change the solution from pH 8.0 to 7.7 was noted. Fig. 1 

 (Curve B) shows the effect of ether on respiration, after an expo- 

 sure of 150 seconds; there was no acceleration of respiration at any 

 concentration: on the contrary there was a decrease from 0.15 per cent 

 ether and upward. It might be thought that this was due to the 

 cessation of the breathing movements, by which the water is carried 

 to the gills, or to the stopping of the muscular movements, especially 

 of the tail. As a matter of fact, however, at these concentrations and 



^ For further details see Paper I COsterhout, W. T- V., /. Gen. Physiol., 1918, 

 i. 171). 



