80 ELBERT CLARK 



able investigators are unable to obtain the same result in a 

 given experiment, just so long will our theories on regeneration 

 of divided medullated nerves remain at variance. One cannot 

 help but suspect, however, that on account of this very differ- 

 ence in results and the very heated controversy on the subject, 

 regeneration of medullated nerves after section has received more 

 attention and investigation that the comparative importance of 

 the subject would warrant. 



It was with no desire to engage in such a discussion that the 

 present work was begun, and the new points brought out by it 

 in regard to degeneration will greatly outweigh the observations 

 on regeneration. On the other hand, however, I considered the 

 controversy of others no excuse for avoiding the subject when 

 a promising experiment was thrown at my door. 



As stated above, in fowls fed for a long time on polished rice, 

 there results an acute degeneration in the medullated nerve fibers 

 resulting in a breaking up of the myelin into large globules and 

 droplets and a segmentation of the axis cylinder. This change 

 takes place in from 12 to 18 days and bears the closest resem- 

 blance to degeneration in medullated nerve fibers after section. 



Clearly then, if it could be shown that the process of degen- 

 eration in the nerve fibers of the rice-fed fowls was identical with 

 degeneration after section and if regeneration takes place in the 

 former, then regeneration of medullated fibers was accomplished 

 without the possibility of an ingrowth of fibers from other nerves 

 and the main ground for a difference of opinion on auto-regen- 

 eration was obviated. If, on the other hand, degeneration in 

 the two is not identical nor comparable, it would still be of 

 interest to know if regeneration in the rice-fed fowls is or is not 

 concerned with -the so-called 'embryonic nerve fiber,' 'Band- 

 faser' or 'protoplasmic band;' if auto-regeneration obtains; or if 

 the new axis cylinder results from an outgrowth of the central 

 connection. Whatever the result arrived at, the facts collected 

 from this new t5^e of experiment would add evidence to one 

 side or the other and argue for or against auto-regeneration. 



While there could be found no other microscopic differences 

 in degeneration in medullated fibers after section and in medul- 



