56 DYNAMICS OF NERVE CELLS. II 



ported by Garrey for the rate of neurogenic rhythm of Limulus 

 hearts. The data strongly support the view that the chemical proc- 

 ess within the nerve cells which is responsible for the rate of the 

 heart beat is one which is associated with the development and rate 

 of diffusion of carbon dioxide. 



SUMMARY. 



1. It is possible to determine by the colorimetric method the rate 

 of production of carbon dioxide by the cardiac ganglion of Limulus. 



2. Carbon dioxide formation in the cardiac ganglion was found to 

 run parallel to the rate of heart beat for different temperatures. 



3. The conclusion seems justified that the rate of cardiac rhythm of 

 Limulus depends upon a chemical reaction in the nerve cells of the 

 cardiac ganglion and that this reaction is associated with the produc- 

 tion of carbon dioxide since the rate of beat and the rate of CO2 

 production are similarly affected by changes in temperature. 



