Takahashi, Internodes on Nerve Fibers. 191 



An examination of Table 15 shows that for fibers of the same 

 diameter, the internodal lengths are nearly alike in the two nerves. 

 If we make a general average, we find the relations given in Table 



16. 



TABLE 16. 



Giving the average diameters and average length of internodes on the fibers from 

 10// to 15// in diameter, found in the ventral roots of the III and IX nerves of 

 Frog 2. 



In view of the small number of observations, we may look upon 

 these values as similar, but the fact that they are similar, is the 

 surprising result, since in this particular case (see Table 12) the 

 length of the ventral root of the III nerve is 2.6 mm., while that 

 of the IX nerve is 7.0 mm., giving a ratio of i : 2.7. If we assume 

 that these roots had the same length when meduUation began, 

 it would appear that since the IX nerve had become 2.7 times as 

 long as the III, the internodes should stand in a like relation. 



The measurements show that such is not the case. Unfortu- 

 nately, at the moment, it is not possible to explain this result. 

 The discrepancy possibly arises through taking as the distal limit 

 of the ventral roots the point of junction of the ventral with the 

 dorsal root, and yet the assumption of this limit fitted perfectly 

 with what has already been found in the case of the IX nerve. 

 There are of course many suggestions which might be made, but 

 it seems best to leave the question in abeyance, until a larger 

 number of observations, especially on the dorsal root of the III 

 nerve, has been made. 



4 THE NUMBER OF MEDULLATED FIBERS AT DIFFERENT LEVELS 

 IN THE LEGS OF TADPOLES OF INCREASING SIZE. 



To fill out our information as to the way the medullary sheaths 

 of the nerve fibers are acquired in the frog, the number of the med- 

 ullated fibers at the level of the knee was counted, and compared 

 with the number at the entrance to the foot, in the legs of tadpoles 

 of increasing size. To prepare this material, the legs, or so much 



