Takahashi, Internodes on Nerve Fibers. 169 



In view of the results obtained by Boycott, it was thought best 

 in the present study to examine especially some points which he 

 has left untouched. 



These will be presented under the following heads: 



1. The average length of the internodes at different levels along 

 the nerves to the leg. 



2. The length of the internodes at different levels on fibers of 

 like diameter. 



3. The length of the internodes on fibers in the roots of the 

 spinal nerves. 



4. The number of medullated fibers at different levels in the 

 legs of tadpoles of increasing size. 



5. A comparison of the length of the internodes in the Amer- 

 ican frog, Rana pipiens,with their length in the English frog, Rana 

 temporaria (fusca). 



Before proceeding to the discussion of the special topics, I 

 desire to state that this study was made under the direction of Prof. 

 H. H. Donaldson, to whom I am indebted also for the revision of 

 my manuscript. Moreover, I wish to thank both Dr. E. H. Dunn 

 and Dr. S. Hatai for their aid and suggestions given to me dur- 

 ing the conduct of this investigation. 



MATERIAL AND TECHNIQUE. 



For this study, the common leopard frog, Rana pipiens (Schre- 

 ber) was used, the specimens having been obtained from a local 

 dealer and probably collected in the country about Chicago. The 

 frogs were killed with chloroform; the body weight, corrected for 

 ova in the case of the females, was taken in a closed box, and the 

 total length, i. e., the length from the tip of the nose to the tip of 

 the longest toe, as well as the body length, i. e., from the tip of the 

 nose to the tip of the urostyle, were both recorded. In some 

 cases also, the length of both the dorsal and ventral roots of the 

 III and IX nerves (Gaupp's numbering) was determined. The 

 data thus collected are given in Table 2. 



In preparing the material, the following methods were employed : 

 A short piece of the fresh nerve was cut out and laid on a wedge- 

 shaped strip of cardboard, the piece of nerve being extended to its 

 normal length. This was fixed, and at the same time macerated, 

 by being placed for twenty-four hours in the following solution (A) : 



