CONDUCTIVITY 149 



processes. Matteucci, later Hermann and finally Boruttau^ have 

 endeavored to apply the results obtained when electricity is intro- 

 duced in a wire covered with a moist envelope (saline solution), 

 to the explanation of conductivity in the nerve. (Figure 25.) 

 The fact has been shown, that in such a model the application of 

 electricity to a point, as a result of polarization between the moist 

 envelope and the metal, produces a weak local current, which in 

 turn disturbs the electrical potential in the next cross section and 

 consequently a new local current is produced and so on through 

 the whole length of the wire. (Figure 26.) This fact, in con- 



Fig. 26. 



Scheme of the conduction by local electric currents 

 in a "Kemleiter." (After Hermann.) 



nection with the apparent similarity in the differentiation of the 

 axial fibers and peripheral envelope in the nerve, has led Borut- 

 tau to apply the principles of conductivity in the "core model" 

 to that of the nerve. Then, however, Nernst and Zeyneck brought 

 forward their theory, according to which the galvanic current is 

 operative as a stimulus in that it brings about an alteration in 

 the concentration of the ions at the junction of two different 

 electrolites which, in turn, produce local currents. Boruttau then 

 dropped the assumption of the existence of a simple physical 

 polarization between the wire and the envelope and replaced it 

 by the assumption of an alteration in the concentration of the 

 ions at this position. Thereby the "core model explanation" was 

 already altered in principle, in that only the differentiation of a 

 central fibrilla and a peripheral enveloping substance was appro- 

 priated. It seems to me that this factor can likewise be consid- 



1 The enormously extensive literature on this subject up to the most recent date is 

 quoted in Cremer: "Die allgemeine Physiologic der Nerven." In Nagels Handbuch der 

 Physiologic des Mcnschcn, Bd. IV, 1909. Braunschweig. 



