320 



Journal of Comparative Neurology. 



2. Average areas for the nerve fibers above and below the 

 branches to the thigh and shank. 



The average area for each nerve fiber at the selected levels 

 is shown in Table XV, 



TABLE XV. 



Showing the average area for •^ach nerve fiber of the sciatic and 

 crural nerves and their subdivisions at the levels above and below the 

 thigh branches and above and below the shank branches. 



Frog II B. 



Si& C. 

 Si 



S2. 



T. &P. 



Pi.Ti. 

 P2.T2. 



Sciatic and crural nerves above branches 



to thigh. 



Sciatic nerve above branches to thigh. 



Sciatic nerve below branches to thigh. 



Tibial and peroneal nerves above branches 



to the shank. 



Tibial and peroneal nerves below branches 



to shank. 



Looking at the left side alone, the average area for each 

 fiber above the branches to the thigh is 97.2 square micra, 

 when the average of both the sciatic and crural nerves is taken, 

 100.9 square micra, when the attention is confined to the sciatic 

 nerve alone. The computation for the crural nerve should be 

 disregarded in the discussion of changing caliber, since the 

 crural nerve sends all its fibers to the thigh and hence furnishes 

 but the one level for measutement. 



The comparison of the average area mentioned with the 

 area of y6.6 square micra for each fiber at a level below the 

 branches to the thigh, S^ , shows a considerable lessening in 

 the average area for each nerve fiber. By comparing the 

 average area above the shank branches, T & P, 62.2 square 

 micra, with that below the shank branches Ti, T2, Pi, P2, 

 51.5 square micra, we find a similar if not proportionate lessen- 

 ing in the average area /"cr each nerve fiber. We find then in 

 both the thigh and the shank a greatly decreased average area 

 at the level below the branches. This decrease is in part due 

 to the absence at the second level, below the branches, of the 

 largest fibers which appeared at the level above the branches, 



