Hardesty, spinal Nerves of the Frog. 71 



different nerves. In order therefore to determine the variations 

 more exactly it was necessary to compute for each nerve, the 

 average amount of variation occurring in a unit of length and 

 convert the variations thus obtained into percentage values. To 

 do this the total amount of variation in a given case was di- 

 vided by the number of millimeters through which it occurs. In a 

 ventral root, for example, the number of fibers found in the sec- 

 tion nearest the ganglion was subtracted from the number found 

 in the most proximal, or section nearest the cord. The difference 

 thus obtained was divided by the number of millimeters be- 

 tween these points (sections i and 3, Plate VI). This average 

 variation per millimeter having been found, its percentage 

 value of the entire number of fibers contained in the most prox- 

 imal section was determined. For the dorsal root, of course, 

 since the variation occurs in the opposite direction, the number 

 found nearest the ganglion (section 3) was used as that on 

 which to compute the percentage of variation ; and for the 

 trunk, the number in section 4, the section containing the larg- 

 est number of fibers. 



The percentages of the average amounts of variation per 

 millimeter of length obtained for the several spinal nerves in- 

 cluded in Tables I and II are as follows : 



TABLE III. 



Frog, female, weight 48.2 grams. 



VI 



VII 



VIII 



IX 



Frog, female, weight 59.5 grams. 



Average percentage decrease per mm. 



0.57/0 

 0.50/0 

 0.19/0 

 o.40^f 



0.70/0 

 0.38/0 

 0.60% 

 o.26^„ 



0.88/0 

 0.79% 

 0.22/0 

 0.06/, 



