322 



Journal of Comparative Neurology. 



Table xvi. 

 :Showing the average areas of the largest nerve fibers at the various 

 levels of the sciatic nerve and its subdivisions at which the areas 

 for the nerve fibers had been computed. The number of fibers 

 measured at each level is proportionate to the entire number at 

 that level. 



TABLE XVIJ. 



Showing the average area (?/the largest fibers in the thigh and shank 

 branches. The first computation in each instance is for the num- 

 ber of fibers corresponding to that measured at a level just above 

 the separation of the branches. The smaller number of fibers is 

 proportional to the total number in the branches. 



No. of 

 fibers. 



16 

 6 



Level selected 



Branches to left thigh, 

 Branches to left thigh 

 Branches to left shank 

 Branches to left shank 



Averages areas 



2i2.8n/^. 



232-9 

 127.9 

 144.9 



We have, then, in Table XVI, the average areas for the 

 same relative number of fibers at various distances from the 

 spinal cord. These largest fibers at each level are highly- 

 uniform in size and hence the average represents also the 

 individual fiber. 



If the largest fibers in the lumbosacral plexus run the 

 longest distance, the largest fibers at the highest level should 

 appear again and again with at least only slightly decreasing 

 diameter at the successive levels. By reference to Table XVI, 

 the largest fibers at S^ , and S^ , points separated by not more 

 than one centimeter, do not show this equality, but reveal at 

 the second level a marked diminution in the average area, one 

 of 46.7 square micra or 20%, Conical diminution cannot 



