404 PROTOPLASMIC ACTION AND NERVOUS ACTION 



by Du Bois-Reymond and other physiologists.^ Evi- 

 dently the fundamental problem to be solved is the 

 problem of the physico-chemical basis of electrical 

 sensitivity in living matter. The various facts and 

 considerations reviewed in the foregoing chapters indicate 

 that this basis is to be found in the characteristic physical 

 structure of protoplasm; in other words, that the 

 polyphasic and film-partitioned feature of the system 

 is the condition which makes it possible for the electric 

 current to produce such definite chemical effects. The 

 polar action of the current is a clear analogy to electrode 

 action, and "vve have to inquire into the justification of 

 regarding the protoplasmic surfaces as having properties 

 like those of electrode surfaces in general. At the surface 

 of a metallic electrode, chemical action occurs when the 

 current passes between metal and solution; and appar- 

 ently the same occurs when a current passes from one 

 protoplasmic phase to another; e.g., during electrical 

 stimulation from the surface of the plasma membrane 

 to the adjoining medium. As we have seen, the passage 

 of the current (positive stream) in this direction is the 

 condition of stimulation in an irritable cell or nerve 

 fiber. 



The parallels between the surface of a metallic 

 electrode and the surface of a living cell or organic 

 membrane have already been discussed in part, and 

 certain resemblances have been pointed out. It remains 

 to be seen whether the two are similar in the further 

 respect that the passage of an electric current across 



^ Cf. Du Bois-Re>Tnond, Untersuchungen iiher tierische Elektricitdt, 

 II, 387 (" galv^anische Reizung ist uns nichts mehr als die erste Stufe 

 der Elektrolyse eines Nerven"), 



