252 STUDIES IN ELECTRO-PHYSIOLOGY: 



or a fall of nearly fifty per cent, of resistance, or (roughly) 

 five per cent, per degree. 



Inasmuch as the human nerve-current escapes through 

 the dielectrics of the body, despite the fact that the tension 

 is not more than from 4 to 5 millivolts, it is evident that 

 their resistance is infinitely lower than that of gutta- 

 percha. 



We have no means of determining with accuracy the 

 resistance of any of these dielectric structures or substances 

 in their natural and normal environment, nor, while we 

 know that a rise of temperature affects them adversely, 

 must we at once assume that the relative fall in resistance 

 of a nerve-sheath is the same as that of gutta-percha. 

 Maxwell's recent experiments, however, went to show that 

 a rise of 10 C. approximately doubled the velocity of 

 nerve-conduction by lowering the resistance of the nerve- 

 substance. 



Heat decreases the resistance of liquid and increases the 

 resistance of metallic conductors in a known ratio. Com- 

 paring a nerve with a copper wire, the increase in resistance 

 of copper per 10 F. would be one-fifth or twenty per cent. 

 =to two per cent, per degree, but the fall in resistance of 

 gutta-percha due to the same increase is nearly fifty per 

 cent. By this process of reasoning we find some ground 

 for the belief that the effect of temperature upon the 

 dielectrics of the body is approximately the same as upon 

 gutta-percha ; involving roughly a fall of five per cent, 

 per degree Fahrenheit within certain limits, although I 

 believe the loss to be much greater. 



Now, it is quite obvious that if the organs of the body 

 connected with the transmission of impulses, the mainte- 

 nance of neuro- electrical equilibrium, the conservation of 

 energy, and the contraction of muscular tissue are to 

 function properly, the temperature of every part of the 

 whole organism must not exceed the normal, which we may 



