Takahashi, hiternodes on Nerve Fibers. 187 



Frog 5 becomes 16. i per cent or nearly that for the lengthening 

 of the nerve, and the grand average becomes 16.4 per cent, or a 

 little greater than 15.6 per cent, which represents the lengthening 

 of the nerve. 



It seems allowable therefore to conclude that the internodes 

 in the 5.3/< and 6.3/i diameter classes, grow, on the average, at 

 approximately the same rate as does the nerve in which they are 

 found. Nevertheless on passing distally along the nerve, the 

 length of the internodes in a given diameter class, tends to 

 increase in such a way as to suggest that it is influenced by the 

 growth of the segment of the limb to which the internodes belong, 

 although this influence becomes less marked as the frog becomes 

 larger. 



3 THE LENGTH OF THE INTERNODES ON FIBERS IN THE ROOTS 

 OF THE SPINAL NERVES. 



Touching this point we have observations on the roots of the 

 IX nerve in five frogs of diff^erent sizes. In his plate VI, Har- 

 DESTY ('99) has given some excellent drawings of the nerve roots 

 in this frog. The species used by Hardesty was designated 

 Rana virescens but is the same as that here designated, Rana 

 pipiens (see Donaldson '07). 



The present data are brought together in Table 12. Each speci- 

 men is given the number which it bears in Table 2 but the series 

 is arranged in the order of the increasing length of the nerve roots. 



Table 12 shows that as the nerve roots increase in length, the 

 internodes on the fibers in these roots also increase in length. The 

 average length of the internodes is somewhat less in the dorsal 

 roots than in the ventral, and this, in each instance, goes along 

 with a smaller average diameter of the fibers measured. Fig. 7 

 shows these relations also. 



Using the data in Table 12, we may form the supplementary 

 Table 13 in which are compared the values for the length of the 

 ventral or dorsal root, with the corresponding values for the inter- 

 nodes on fibers in this root. The series of ratios given in Table 13 

 indicate that the internodes on fibers of both roots lengthen in 

 about the same proportions as the roots in which they appear. 

 It is interesting to observe that this lengthening of the roots is 

 quite independent of the increase either in the total length, or in 



