DYNAMICS OF NERVE CELLS. 



I. The Temperature Coefficient of the Neurogenic Rhythm 

 OF the Heart of Limulus polyphemus. 



By WALTER E. GARREY. 



{From the Physiological Laboratory of the Tulane University Medical School, 



New Orleans.) 



(Received for publication, June 1, 1920.) 



The temperature coefficient of the rate of heart beat has been 

 determined by many investigators on various anunals both verte- 

 brate and invertebrate.^ In all it was found that the coefficient for 

 10°C. was approximately 2 in the intermediate ranges of temperature, 

 greater at lower temperatures, and somewhat less at high temperatures. 



In none of these determinations has it been possible, owing to the 

 character of the hearts worked with, to determine whether the results 

 were due to an effect of temperature on the coefficient of ganglionic 

 activity, of muscular activity, or of both. 



It has therefore seemed of importance to determine whether varia- 

 tions of temperature, affecting ganglion cells alone, would give tem- 

 perature coefficients of the same order of magnitude as those obtained 

 on the whole heart. 



A suitable preparation for this purpose is the excised heart of Limulus 

 polyphemus, the beats of which have been shown by Carlson to be 

 purely neurogenic.^ Carlson has also described methods by which 

 the ganglion can be separated from the muscle and independently 

 subjected to variations of temperature while the muscle records the 

 beats. 



^ For a general review of the literature of this subject see Kanitz, A., Tempera- 

 tur und Lebensvorgange, Berlin, 1915. Loeb, J., The Organism as a whole, from 

 a physicochemical viewpoint, New York, 1916. Snyder, C. D., Am. J. Physiol., 

 1911,xxviii, 167. 



2 Carlson, A. J., Am. J. Physiol, 1905-06, xv, 220; also Ergehn. Physiol., 1909, 

 viii, 427. 



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