150 RELATION OF RESPIRATION TO RHYTHM 



rate of change in hydrogen ion concentration which resulted from the 

 formation of CO2 by the excised cardiac ganglion. The ganghonic 

 cord was immersed in 3 cc. of a standard non-buffer balanced saline 

 solu'tion in small Pyrex glass tubes. The initial pH was 7.8 and the 

 time required to reduce the alkalinity to pH 7.4 was used as an index 

 of the rate of CO2 formation. To facilitate manipulation the gangHon 

 was draped over glass hooks on a non-soluble glass rod which was 

 cemented into the paraffined cork used to stopper the indicator tube. 

 The standard immersion solution was made by adding 2.2 cc. of 

 m/2 GaCl2 to 100 cc. of m/2 NaCl and the desired initial pH, 7.8, was 

 secured by adding the requisite amount of sodium hydroxide. 



EXPERIMENTAL RESULTS. 



Electrical Stimulation. — Faradic stimulation of the posterior end 

 of the cardiac ganglion always produces acceleration of the beat of the 

 intact heart. The excised immersed ganglion was similarly stimu- 

 lated by means of platinum electrodes passed through the cork of 

 the indicator tube. The rate of change in the CO2 production was 

 compared under this treatment with that of the unstimulated ganglion 

 and the results indicate that during stimulation the rate of CO2 pro- 

 duction is enormously increased, being at least doubled or trebled 

 as shown in Table I. This result is unquestionably due to increase 

 in the chemical processes in the nerve cells, for the faradic shocks 

 do not produce the color changes in the solution, even when the elec- 

 trodes dip directly into the solution or when applied to a narcotized 

 ganglion. The decrease in CO2 production, when the inhibitory 

 nerve to the ganglion is stimulated, also forms a control experiment 

 which supports the conclusion that we are concerned with a true 

 stimulation of the processes of respiration in the nerve cells in question. 



Mechanical Stimulation. Stretching. — A further check upon the 

 results of faradization is obtained by stretching the nerve cord. 

 Carlson* had found that distension of the Limulus heart cavity in- 

 creased the rate of the heart beats by its mechanical effect upon the 

 cardiac ganglion. That stretching the nerve cord might produce 



* Carlson, A. J., Am. J. Physiol., 1907, xviii, 149; Ergebn. Physiol., 1909,viii, 

 423. 



