•44 



DYNAMICS OF NERVE CELLS. I 



as illustrated in this experiment, but the coefficients at very low tem- 

 peratures are usually larger than those recorded above. 



Extremes of temperature may alter the value of temperature 

 coefficients subsequently determined. It seems best in view of this 

 fact to show separately the effects of depression and of elevation of 

 the temperature starting with the normal temperature of the sea 

 water. Each series thus is based on observations only on one side 

 of the normal temperature, i.e. between it and a single limiting tem- 

 perature, and thus the secondary effects of excessive heat or cold are 

 avoided. In Table II the results of ten experiments are given in 

 each of which the posterior seven segments of the whole heart with 

 its ganglion were subjected to temperature variations. 



TABLE II. 



Observations on the Ganglion. 



We may now compare the above results with those obtained by 

 varying the temperature of the ganghon alone after dissecting it free 

 from all adherent muscle tissue except the anterior segment. It 

 would seem best for purposes of comparison with the results obtained 

 above on the whole heart to observe the same precautions and to 

 avoid the eft'ects due to exposure of the ganglion to excessive heat or 

 cold. The results tabulated in Tables III and IV are thus strictly 

 comparable to those given in Table II since they show the simple 

 effect of a progressive change in the temperature of the ganglion above 

 or below the initial normal temperature of 20°C. In order to illus- 



