352 Journal op Comparative Neurologv. 



By applying these values to the numbers in Table V 

 doubled, we get for each gram the frog increases in weight, an 

 increase for both sides of 49 ventral root fibers, 80 dorsal root 

 fibers and 145 fibers in the trunk and dorsal branches combined. 

 If the 2nd and loth nerves could be included, the numbers 

 would of course be some larger. 



While the results are not comparable, it may be of interest 

 to see what relations exist in the figures of Birge when the 2nd 

 and loth nerves are excluded. Birge counted both the ven- 

 tral and dorsal roots of only two frogs. The larger of these 

 was 40 grams heavier than the smaller. If, exclusive of the 

 2nd and loth nerves, the sums if the dorsal and ventral root 

 fibers, computed for both sides of the smaller frog, be sub- 

 tracted respectively from the like sums of the larger, and the 

 differences be divided by 40, it will be seen that for each addi- 

 tional gram of weight, the larger specimen gains 39 ventral root 

 fibers and 58 dorsal root fibers. It is seen that these figures 

 for Rana esade^ita are lower than the 49 and 80 obtained for 

 Rana virescens. The figures give perhaps some notion of the 

 relations existing between the two species. 



IX. The Influence of Season. 



Concerning this important point, very little information 

 has been obtained from the figures. In hibernating animals, it 

 seems- probable that growth tends to be periodic. The warm 

 seasons of the year should be conducive to the more rapid 

 growth. During exactly what months this more rapid growth 

 occurs, or whether it occurs at all, has not been determined for 

 the frog. All that can be concluded from the figures here ob- 

 tained as to the season during which the nerves acquire fibers 

 more rapidly, is shown in Table VI. This table groups the 

 specimens, the 6th nerves of which were investigated, under 

 two seasons. The first includes June, September and October, 

 and the second, January and April. Also in each group, the 

 figures are recorded in sets, each set constituting those obtained 

 for a given month. In each set the specimens are entered in 

 the order of their weights. The table is made up from material 



