ICHIJI TASAKI AND CONSTANTINE S. SPYROPOULOS 



203 



of the preamplifier. The potential drop across this resistor gave a measure 

 of the action current. 



In the interface method for recording the action current (fig. IB), the 

 single fiber preparation was suspended in a vessel containing Ringer's 

 solution below a layer of mineral oil. The portion of the nerve on one side 

 of the operated region was attached to a non-polarizable grid electrode 

 located in the layer of mineral oil. The portion of the nerve on the other 



A/\ 



c J\ 



rn I PREAMPLIFIER 



IK 



I 



300 K 



Fig. 1. Four different methods used for stimulating a single myelinated nerve fiber 

 and for recording its action currents. 



side of the operated region was immersed in the Ringer. The Ringer fluid 

 was grounded by another non-polarizable electrode. The preparation was 

 mounted in such a way that the oil-Ringer interface crossed one of the 

 isolated internodal segments. 



In the third method, the three-comyartment method, of recording ac- 

 tion currents of a single fiber the preparation was mounted in a chamber 

 composed of three relatively large compartments (fig. IC). One lateral 

 compartment was filled with mineral oil, the middle compartment with 

 normal Ringer and the other lateral compartment with either normal 



