238 Journal of'Comparative Neurology, 



The cutaneous thigh branches of the sciatic nerve run for 

 some distance with certain of the muscular branches. On this 

 account the muscular and cutaneous classification of branches 

 cannot be adhered to, and the sciatic branches cm best 

 be tabulated in the order of their separation. Fixing- the 

 attention as before upon the left leg we find, Table X, that 

 the total number of sciatic fibers to the left thigh in frog B is 

 1609. The total area for the various branches is .291 of a 

 square millimeter. The resulting area for each fiber is 181 

 square micra. 



For the right thigh of the same frog the sciatic branches 

 number 1643 fibers, cover an area of .287 of a square milli- 

 meter, and furnish an average area of 174 square micra for 

 each fiber. 



Of the thigh branches of the sciatic nerve, S 2 and 3, and 

 S 6 contain both cutaneous and muscular fibers. The remain 

 ing branches contain no cutaneous fibers. 



Table XI, combining the computations for the sciatic and 

 the crural branches, indicates that for frog B the left thigh 

 branches contain 2600 muscular and cutaneous fibers. As these 

 branches have a total area of ,442 of a square millimeter, we 

 determine the average area for each fiber to be 170 square 

 micra. The measurements for the right thigh are very similar 

 and yield an average area of 166 square micra for each nerve 

 fiber. 



In addition to these measurements of the thigh fibers, sec- 

 tions of the crural nerve, and of the sciatic nerve both above 

 and below its branches were studied. The proximal section of 

 the sciatic nerve shows, Table XII, 4394 sciatic fibers contribut- 

 ing to the innervation of the left leg. This section has an area of 

 .6^6 of a square milHmeter. From these figures we derive an 

 average area of 154 square micra for each sciatic nerve fiber of 

 the left leg. The proximal section for the right leg differs but 

 slightly, giving an average area of 150 square micra for each 

 sciatic nerve fiber. 



As no fibers from the crural nerve supply the shank and 



the computations for the crural leg fibers will be 



