Takahashi, Internodes on Nerve Fibers. l8l 



First, that on fibers of a given diameter, the internodes are not 

 of the same lengths at the several levels; 



Second, that in general, the internodes become longer as we pass 

 toward the periphery; 



Third, that they are markedly elongated at T^, the level of the 

 foot. 



In attempting to explain these relations, we naturally call to 

 mind the fact that in Rana pipiens, the average proportional 

 lengths of the leg bones are 



Femur 26 . i 



Tibia 29.6 



Tarsus and pes 44-3 



These figures are the averages from Table XI in Donaldson 

 and ScHOEMAKER '00. 



As these relative values remain practically unchanged during 

 the growth of the leg in length, it follows that the increments in 

 length must be in the same proportion, and therefore a lengthen- 

 ing of 100 units in the femur, is accompanied by a lengthening of 

 1 13.4 units in the tibia, and 169.7 units in the tarsus and pes. If, 

 for the moment, we assume that the portion of the nerve in each 

 segment of the limb is so Hnked with that segment that it lengthens 

 at the same rate, then we should expect a corresponding relation 

 in the length of the internodes; provided, of course, they were of 

 equal length when first laid down. It appears worth while to 

 put this conclusion to the test, so far as the data in hand will per- 

 mit. 



Before this can be done however several adjustments and cor- 

 rections must be made in the raw values. In the first place, as 

 the intermediate level T is within the hmits of the thigh, and 

 hence associated with the femur, the measurements at T are 

 excluded from the following comparisons, and we contrast only 

 the length of the internodes at ^i with that found at T^, to deter- 

 mine whether these lengths stand in the same relation as the incre- 

 ments of growth in these segments of the limb, namely, as 100 : 

 169.7. In order to do this, it is necessary to compare the inter- 

 nodal lengths belonging to classes of fibers having exactly the same 

 diameters. We choose as the standards for the diameter classes, 

 4^, 5.3//, 6.3// and y.'^iJ., since the observed values can be reduced 

 to these standards by alterations which never amount to more than 



