Hardesty, spinal Ganglion Cells. 29 



the specimens of Table I be separated into two groups, letting 

 the first three comprise a group of younger against the last four 

 as a group of older specimens, and the sums of their root 

 fibers compared, it will be found in each of the three nerves 

 that the excess of dorsal root fibers over those of the ventral 

 root is greater in the younger than in the older specimens. 

 The differences in the ratios in favor of the younger, however, 

 are not so marked as Hatai finds in the white rat. This is 

 perhaps due to the fact that the frog has a relatively longer 

 period of general growth than the white rat and, while its ven- 

 tral root fibers do increase more rapidly than those in the dor- 

 sal root, the whole process of growth is slower. This point 

 will be approached from another direction in the discussion of 

 Table IV. 



In every case Table I shows that there is a considerable 

 excess of fibers in the sum of the trunk and dorsal branches 

 above the sum of fibers in the ventral and dorsal roots (col. I). 

 As compared with the sum of fibers on the central side of the 

 spinal ganglion, this excess will be referred to as the "distal 

 excess." It will be considered in more detail under a separate 

 heading and with a differently arranged table, but since Table I 

 better allows a comparison of the three nerves with each other 

 it may be noted here (i) that in each of three nerves the distal 

 excess shows a decided, though irregular, increase with the in- 

 crease in body weight ; (2) that, though it is evidently depend- 

 ent to a certain extent upon the amount of the dorsal branches, 

 in neither of the nerves does it show marked coincident varia- 

 tion with the number of fibers in the dorsal branches (col. H); 

 (3) that while the percentage of the distal excess (col. J) varies 

 to a considerable exent with the proportional relation of the 

 dorsal branches to the nerve trunk, the actual amount of the 

 distal excess does not do so ; (4) the average amount of the 

 distal excess is approximately similar in each of the three nerves 

 and the same is true for the average amount of the dorsal 

 branches in each of the nerves ; (5) the percentage of the dis- 

 tal excess ranges somewhat higher in the Vth than in the Vlth 

 nerve and is much higher in both than it is in the IXth nerve. 



