128 TRANSMISSIVITY IN PASSIVE IRON WIRES 



tervals group themselves with fair regularity into a curve of the usual 

 type but of more gradual slope (Fig. 4). 



The characteristic temperature coefi&cient shown (Qio = 2-3) is 

 evidently an expression of the dependence of repassivation and recov- 

 ery of transmissivity upon chemical reactions occurring at the metallic 

 surface. These reactions rebuild the surface film and restore it to 

 its original condition. The temperature coefficients of the duration 

 of the refractory period in cardiac and skeletal muscle and in nerve 

 are closely similar.!^ This resemblance may be regarded as a further 

 confirmation of the view that in the latter case also the recovery of 

 irritability and transmissivity is dependent primarily upon the chemi- 

 cal processes concerned in the restoration of the protoplasmic surface 

 fUms. 



