222 THE BIOPHYSICAL PROBLEM OF NERVE CONDUCTION 



fibers; (2) the absolute refractory period is not independent of fiber size 

 in group A, but increases as the fiber size decreases. Note that the 

 positive after-potentials of the three groups persist more definitely as 

 the fibers decrease in size. It is particularly noteworthy that no nega- 

 tive after-potential follows the action potential response of the group B 

 fibers. 



TABLE VI-1 

 Properties of Three Groups of Mammalian Nerve Fibers 



By Courtesy of H. Grundfest [1940], 



*Gasser and Grundfest [1939]. Delta (cat) are small A fibers. 



tHursh [1939]. 



J Grundfest [1939]. 



§ Grundfest and Gasser [1938]. 



|| Gasser and Grundfest [1936]. 



1 Lehmann [1937]. 



After-Potentials 



In recording the monophasic action potential from a single nerve fiber 

 (group A) as shown in the insert in Fig. VI-9, it has been found that the 



