l68 ^Journal of Comparative Neurology and Psychology. 



The second important point brought out by Boycott, although 

 not especially commented on by him, is illustrated in the accom- 

 panying Table I, which is copied from Boycott's paper, with 

 a shght change made by putting the "sciatic length" in the col- 

 umn where the body lengths are given by him. 



table I. 



Average internodal lengths (,«) corresponding to each diameter. Rana temporaria 

 (fusca). Copied from Boycott, Journal of Physiology (Foster), vol. 30, p. 373, 

 1904. 



It is here seen that on fibers of a given diameter from small 

 (young) frogs, the internodes are shorter than on fibers of the 

 same diameter, taken from large (old) frogs, the size being indi- 

 cated by the sciatic length. If we apply the notion of growth to 

 the interpretation of this table, and remember that a fiber of a 

 given diameter in the small frog, becomes a fiber of greater dia- 

 meter in the large frog, then it is found that the average of the 

 measurements in Group I of fibers from 2;t to ii^ in diameter, 

 which is 546/^, compared with the average of the measurements for 

 fibers from 6 p. to 15/x in diameter, in Group IV, which is 1370/i, 

 gives an increase in the length of the internodes amounting to 

 2.51, and this corresponds very nearly to the increase in the length 

 of the sciatic nerve, from 18.2 to 46.6 mm., which is 2.56. As 

 will be observed, the average diff'erence in diameter in the two 

 series compared is 4//. 



This method of comparison is admittedly crude, but under the 

 conditions, furnishes a satisfactory confirmation of Boycott's 

 general conclusion that the number of internodes is not increased 

 during growth, but that their average length increases as does that 

 of the nerve in which they are found. 



