SOME CONDITIONS WHICH DETERMINE THE 

 LENGTH OF THE INTERNODES FOUND ON THE 

 NERVE FIBERS OF THE LEOPARD FROG, RANA 

 PIPIENS. 



BY 



KATASHI TAKAHASHI, Rigakmhi. 



(From the Neurological Laboratory of the University of Chicago.) 

 With Seven Figures. 



INTRODUCTION. 



In the winter of 1903-04, the following study of the growth of 

 the internodes on the nerve fibers of the leopard frog, was begun, 

 in order to determine whether on a lengthening nerve fiber the 

 number of internodes increased or remained constant. While 

 this study was in progress, the interesting paper by Boycott '04, 

 "On the number of nodes of Ranvier in different stages of the 

 growth of nerve fibers in the frog," was pubhshed. The species 

 of frog used by Boycott was the common Rana temporaria (fusca) 

 of England. 



After briefly referring to the scanty Hterature on the subject 

 of the internodes (see Kolliker '96), which shows that they have 

 different lengths in different species of animals, are longer in old 

 than in young animals, and longer in fibers of great than in fibers 

 of small diameter. Boycott presents evidence which demonstrates 

 beyond reasonable doubt, that in the growing sciatic nerve, at the 

 point where it divides into the nervus tibialis and nervus peroneus, 

 the average length of the internodes increases very nearly as does 

 the length of the nerve itself. It would seem from this to follow 

 that the number of internodes should remain constant. The cal- 

 culations show however a very sHght but regular increase in the 

 estimated number of the internodes as the frogs become larger. 

 This result, noted but not explained by Boycott, and touched on 

 later in this paper is, I believe, susceptible of an explanation, which 

 at the same time leaves Boycott's main conclusion intact. 



