298 



Journal of Comparative Neurology. 



c. 



3. Discussion of the increase in the number of fibers at 



successive levels .... 



4. Proportion of the number of muscular to the number 



of cutaneous fibers ..... 



5. Comparison of the number of nerve fibers for the two 



sides . . 



Diameter of the Nerve Fthers .... 



Introduction .... 



Average areas for the nerve fibers above and below the 



branches to the thigh and shank 

 Average areas of the largest fibers at the various levels 

 Possibility of conical diminution in the extent of the 



nerve fiber ..... 



.Area of the axis cylinder substance proportional to the 



area of the section . . . . 



Comparison of the average areas for the fibers with 



those determined by previous measurements 



BllJLlOiJRAPHY. 



315 

 316 



317 



3-8 

 3'8 



320 

 321 



324 



326 



327 

 328 



Summary, 



1. A comparison of the gross nerve supply to the leg 

 shows no marked differences between Rana esculenta and Rana 

 virescens. 



2. In the branches both to the thigh and the shank of 

 Rana virescens the number of fibers observed exceeds the num- 

 ber calculated. This excess seems to be due to dividing fibers. 

 In teased preparations such dividing fibers have been observed 

 occurring near the points where branches are to be given off 



3. A constant increase in the number of fibers at suc- 

 cessive levels of the sciatic where no branches are given off 

 indicates that fibers divide within the nerve trunk. 



4. The proportional number of muscular and cutaneous 

 fibers varies quite widely in different frogs, while for the two 

 legs of the same frog the proportions are similar. 



5. The diameter of the largest fibers going to the differ- 

 ent segments of the leg diminishes in regular order from thigh 

 to foot. Hence, for the leg of Rana virescens at least, it is true 

 that the largest fibers run the shortest course. The conclusion 

 of Schwalbe that the largest fibers run the longest course has 

 been shown to be unsupported by his observations. 



6. A confirmation of the theory of the conical diminu- 



