48 DYNAMICS OF NERVE CELLS. I 



subject to variations of temperature as when the whole heart is sim- 

 ilarly treated. Furthermore chemical alteration in the gangHon 

 determines the rate of heart beat.^ 



CONCLUSIONS. 



In the case of the heart of Limulus polyphemus the same magnitude 

 and variation of the temperature coefhcient (Qio) is obtained from 

 the whole heart as from the ganglion alone. From the magnitude of 

 the temperature coefficients and their variation with changes of tem- 

 perature we may conclude that the rate of the heart beat is determined 

 by alteration of chemical processes in the ganglion cells. 



^ The denervated heart muscle of Limulus was shown by Carlson to be without 

 rhythmicity in its own blood or in sea water so that it is impossible to speak in 

 connection with the tissue of a temperature coefficient which can have any bear- 

 ing on the results communicated in this paper. The author has made this muscle 

 rhythmic in M /2 NaCl and has been able to show that a rise of temperature of 

 10° may double the rate, but owing to the rapid incidence of toxic effects and to 

 concomitant changes in rate, it is impossible to present reUable quantitative data 

 at this time. 



