Hardesty, spinal Nerves of the Frog. 343 



in length, and also, as in the case in hand, the roots of the 

 same spinal nerve taken from specimens of different weights 

 may vary much, both in length and in the number of fibers 

 contained in them. Because of these differences in number and 

 length, the absolute differences in the number of fibers found 

 in the two sections of a root or trunk would mean very little 

 as to the actual rate at which new fibers are growing in. There- 

 fore, in order to compare the differences in number found to 

 occur between two sections of a small root or trunk taken nec- 

 essarily close together, with the differences found between two 

 sections of a larger root or trunk taken further apart, it is ob- 

 vious that just comparisons can only be made by computing 

 the percentage values of the differences in number for a unit of 

 length through which these dififerences occur. 



The first three columns of Table III give the result of such 

 computations for the various specimens employed. Other col- 

 umns, taken from Table I, contain the figures from which these 

 computations were made. It will be seen that the columns of 

 the table are arranged in sets of three, one column of each set 

 representing the dorsal root, one the ventral root, and one the 

 conditions found for the nerve trunk. Set 3 gives the number 

 of fibers by which the sections taken near the cells giving origin 

 to the fibers contained in them were found to exceed those taken 

 farther away. Set 4 gives the actual numbers of fibers found in 

 the sections taken nearest the cells of origin (in the spinal cord 

 or spinal ganglion as the case may be). In other words, set 4 

 represents the sections of the roots and trunk found to contain 

 the greater number of fibers and therefore contains the excesses 

 given in set 3. The three columns forming set 2 show the 

 amounts per cent, of the excesses given in set 3, based upon 

 the numbers given in set 4; i. e., set 2 is obtained by dividing 

 the numbers of fibers by which the one section exceeds the 

 other, by the number of fibers in the section containing the 

 excess or the section containing the greater* number of 

 fibers. Set 5 gives the lengths between the sections of 

 the dorsal root, ventral root and nerve trunk respectively, 

 or the distances through which the excesses occur. There- 



