ICHIJI TASAKI AND CONSTANTINE S. SPYROPOULOS 



205 



Ringer divided by two narrow air gaps. The width of the middle pool was 

 1 mm and that of the air gaps approximately 0.1 mm. When the property 

 of the nodal membrane was to be examined, an exposed node of the prep- 

 aration was introduced into the middle pool. The section of fiber on this 

 pool was immersed in choline (sodium-free) Ringer. For measurements 



ISOTONIC KCI 



r^^^^^^ yyyyy^Ayy yyyyyyy^^^^^ ^^^^^^^^^ 



HOOt 



NODE 



UYEUN SHEATH 



Off 



RINGER 

 AIR 

 GAP 

 \ 

 NODE OF RANVIER 



Fig. 2. A : diagram illustrating the method of recording the action potential of a 

 single myelinated nerve fiber. B: diagram showing the method of measuring the le- 

 sistance and the capacity of the myelin sheath and of tlie nodal membrane. 



of the physical constants of the myelin sheath, only the myelinated portion 

 of the preparation was immersed in the middle pool. The two lateral pools 

 were filled with normal Ringer and were directly grounded with large 

 electrodes. The small middle pool was grounded through resistance r in 

 the figure. 



When two impulses arrived simultaneously at the nodes located in the 

 lateral pools (see figure) , the myelin sheath in the middle pool was trav- 



