THE MEMBRANE THEORY 



By Rudolf Hober 

 University oj Pennsylvania, Philadelphia, Pennsylvania 



The classical objects of the study of bioelectric phenomena are mus- 

 cle and nerve. Resting, injury, and action potentials and currents are 

 studied with both of them. On the basis of Wilhelm Ostwald's investi- 

 gations upon the electric properties of artificial inorganic precipitation 

 membranes (1890), the physiological membrane potentials have been 

 looked upon as being special forms of Nernst concentration potentials; 

 in other words, potentials arising when solutions of different electrolytes 

 are separated by a membrane characterized by a more or less selective 

 ion permeability. As it was from the beginning of the electrophysio- 

 logical era, both nerve and muscle have been used for solving the basic 

 problems, and information gained from one type is valuable for both. 

 Therefore, although our object is primarily a discussion of physico- 

 chemical mechanisms of nerve activity, muscle potentials will also be 

 treated. 



The Membrane Theory was established, in 1902, by Bernstein, when 

 he ascribed the EMF of the locally injured muscle fiber to selective 

 permeability to potassium ions present inside the fiber in a considerably 

 greater concentration than outside. He conceived of the action poten- 

 tial wave as a self-propagating depolarization by breakdown of this 

 selective permeability. It was early assumed that this alteration is 

 accompanied by chemical reactions. 



THE ION PERMEABILITY OF THE RESTING MUSCLE 



AND NERVE 



In immediate connection with Bernstein's theory, in order to become 

 acquainted with the general properties of the selective ion permeable 

 membranes, it seemed to me that one of the main tasks was to study 

 the effect of local application of the neutral inorganic salts upon the 

 resting potential of muscle (Hober^). 



A. The Inorganic Cations 



At first, the alkali cations only were varied, and potassium was 

 found to produce the strongest negative pole, similar to the effect of 



(381) 



