230 



Journal of Comparative Neurology. 



leg is 5385, for the right leg 5273. (See Table III). For frog 

 C (Table III), the number for the left leg is 5987, and for the 

 right leg 601 1. By reference to Table IV, similar variations 

 are found in the thigh branches for the corresponding sides. 

 For frog B, the thigh branches of the sciatic nerve supply 1609 

 fibers to the left side and 1643 fibers to the right side. For the 

 same frog the crural fibers for the left side number 991, for the 

 right side 980. For the left side in frog C, the sciatic thigh 

 fibers are 1600, for the right side 1576, while in the same frog 

 1 177 crural fibers innervate the left thigh, 1238 crural fibers, 

 the right thigh. 



In the individual branches the same symmetry for the two 

 sides prevails. In two instances, see Table IV, frog B, S 8 x, 

 and frog C, S 8, in both of which only muscular fibers pass, the 

 count on the two sides tallies exactly. In the larger sections 

 the greatest difference is not more than 5 % (frog C, crural 

 nerve). While, for the sections containing less than 100 fibers, 

 in which the percentage variation would be very great, the 

 greatest difference was found in frog B, S 7, left side 47 fibers, 

 right side 54 fibers. 



No significance can be attached to any seeming excess in 

 the number of fibers supplying either the right or the left side, 

 as in successive observations the excess is not constant for either 

 side. The simplest explanation for these differences between 

 the two sides is that of individual variation. 



TABLE in. 



Showing the number of fibers in the Crural Nerve, and in the Sciatic Nerve 

 above and below its branches to the thigh, and the calculated number of fibers 

 to the thigh. 



