92 ELBERT CLARK 



as noted, if regeneration in the peripheral nerves was accom- 

 plished without the embryonic nerve fibers, then clearly in these 

 fowls the absence from the cord of the neurilemma sheath and 

 its derivative, the embryonic nerve fiber, would afford no expla- 

 nation of a failure or regeneration in the fibers of the cord, and 

 an outgrowth of the axis cylinder in the fibers of the cord might 

 well be expected. Such, however, as the evidence shows, is 

 probably never the case. 



Although at the time of paralj^sis the marked changes described 

 above were seen in the nerve cells of the lumbo-sacral cord, it 

 is doubtful that this should be termed degeneration. The mito- 

 chondria seem to have undergone no alteration whatsoever. They 

 were just as numerous as in the nerve cells of the cord of the 

 normal fowl. In the cells of the cord of fowl 79, killed as soon 

 as all signs of paralysis had disappeared (after 30 days on a 

 special regenerative diet), the tigroid bodies again presented an 

 appearance similar to the normal. This was also true for fowl 

 No. 57 (10 months after complete recovery). No ^shadows' or 

 other evidences of degenerated nerve cells were found in either 

 case. 



GENERAL SUMMARY 



In the experiments described above degeneration of medul- 

 lated nerve fibers was brought about in fowls by a prolonged 

 feeding of polished rice, and regeneration was accomplished by 

 a return to an adequate nutritive diet. 



In such fowls the fibers are intact during degeneration and all 

 traumatic and inflammatory effect produced by cutting the tis- 

 sues and the nerve or of tying the latter are obviated; the process 

 of degeneration can be stopped at almost any stage or greatly 

 prolonged, and several stages of degeneration are to be observed 

 in different fibers of the same nerve. In regeneration the possi- 

 bility of an ingrowth of fibers from other nerves into the regen- 

 erating nerve under observation is eliminated and repair of the 

 medullated nerves can be induced after any stage of degeneration. 



Ten to 20 per cent of the medullated fibers of the nervus 

 ischiadicus showed a complete fatty change of their medullary 



