344 PROTOPLASMIC ACTION AND NERVOUS ACTION 



view has long been entertained (by Hering and others) 

 that the rising phase of the bioelectric variation is 

 coincident with a period of breakdown of living material, 

 and the return phase with its reconstruction.^ In 

 Tait's experiments just described, the delay in the 

 return phase of the variation was found to be associated 

 with a delay in the recovery of normal irritability and 

 conductivity; hence his proposal to identify the relative 

 refractory period with the period of recovery or recon- 

 struction of which the return bioelectric variation is the 

 index. There are, however, various facts indicating 

 that the return variation and the recovery of irritability 

 may vary independently. Trendelenburg has shown 

 that in cardiac muscle excitability does not return 

 until some time after the bioelectric variation is com- 

 pleted; poisoning with muscarin lengthens the refractory 

 period without greatly affecting the bioelectric variation.^ 

 From general considerations a complete coincidence is 

 hardly to be expected. Although the existence of a 

 certain normal bioelectric potential between protoplasm 

 and medium, the so-called '^ physiological polarization," 

 is apparently necessary for stimulation, it is known that 

 a tissue may be rendered inexcitable by conditions 

 that have little effect on this potential, e.g., the presence 

 of anaesthetics, Mg salts, etc. It is probable that the 

 normal physiological polarization is regained rapidly 

 during the early part of the refractory period, as shown 

 by the completion of the return variation of potential; 

 this change apparently indicates the return of the altered 



^ Cf. Hering, "Theory of the Functions in Living Matter," Brain, 

 XXII (1897), 232 (translation of article in Lotos, IX, Prague [1888]). 



2 Cf. Trendelenburg, loc. cit.; also the discussion in Adrian's paper, 

 loc. cit. (192 1). 



