Hardesty, spinal Ganglion Cells. 49 



for the purpose in Birge's records give for all of the spinal 

 nerves also a higher gain in the dorsal root. And Hatai's 

 counts ('03) for the rat, when tabulated in a similar way (Table 

 V), show a considerably greater absolute gain of fibers in the 

 dorsal root per gram of weight gained. The dorsal roots of all 

 the spinal nerves here used of the frog and all of those used by 

 Hatai of the rat contain many more fibers than the ventral roots 

 (col. L, Table I and col's. G and E, Tables IV and V). One 

 would therefore expect the absolute gain to be greater in the dor- 

 sal root. But the gains in proportion to the number of fibers con- 

 tained in each may show differently. It is seen in column C that the 

 three ventral roots of the average frog of 14.2 grams gain about 

 45% in fibers with the increase to the average weight of 51.6 

 grams while the dorsal roots (col. B) gained but 23 ^. By 

 comparing percentages of gain in this way it will be found that 

 the figures for the Vlth nerve alone in the paper above referred 

 to also give a somewhat greater gain in the ventral root. By 

 grouping Hatai's figures in the same way (Table V) the dorsal 

 roots appear to gain 30.5 fibers per gram of weight gained, 

 while the ventral roots gain only 11.7 fibers and, in proportion 

 to the fibers contained in them, the dorsal roots gain 80% and 

 the ventral roots 71 % — a group result still in favor of the dor- 

 sal root. However, Hatai makes it one of his conclusions 

 that the increase of meduUated fibers in the ventral root is more 

 rapid than in the dorsal root. He reaches this not by group- 

 ing as above, but by simply comparing the relations of the 

 nerve roots of the youngest rat with those of the adult individ- 

 ual. In column E of Table V it is seen that in the 10.3 gram 

 rat, for each fiber in the ventral root there are 2. 8 fibers in the 

 dorsal root, while in the 167 gram rat the ratio is 1:2.4, thus 

 showing that, as far as these two individuals are concerned, the 

 increase of ventral root fibers must gain on that of the dorsal 

 root fibers during the growth of the animal. When, on the 

 other hand, the ratios of the groups are considered it is evident 

 that in the younger the average ratio of ventral root to dorsal root 

 fibers is 1:2.3 while in the older it is 1:2.4, thus indicating a 

 slightly more rapid increase in the dorsal roots. The same ratios 



