74 ELBERT CLARK 



the swelling of the fiber and out-bulging of the sheath at the 

 large globules obtained and the larger globules were still vesicu- 

 lar. Figure 13 is a photomicrograph of a Marchi preparation 

 of the sciatic nerve from this fowl. Droplets of degenerated mye- 

 lin are clearly visible in every fiber and the larger globules occur 

 at frequent intervals. Figure 14 is a similar picture of the sciatic 

 of No. 54, 171 days in regeneration. The droplets and globules 

 of degenerated myelin are equally definite here. 



Degenerated myelin was found to persist in the sciatic nerves 

 of a fowl 10 months after all signs of paralysis had disappeared 

 and 1 year and 14 days after regeneration diet was started. 

 Figure 15 is taken from a Marchi preparation of the sciatic nerve 

 of No. 57, whose recovery history was as is just indicated. The 

 largest globules have completely disappeared or more probably 

 have considerably decreased in size. The smaller droplets are 

 also decidedly less numerous and the total amount of degenerated 

 myelin is comparatively small. 



In view of the finding that the sensory nerves usually show an 

 apparent recovery before the motor, it was thought worth while 

 to compare the sensory and motor portions of the sciatic nerve 

 of No. 57 (1 year and 14 days in regeneration). Accoroiingly the 

 motor and sensory portions of one of the larger roots were sepa- 

 rated for some distance peripheral to the dorsal root ganglion, 

 each stained by the Marchi method and teased. No difference 

 whatever could be distinguished between the two. It was quite 

 impossible to tell one from the other (compare fig. 15 and fig. 16). 



It would thus seem that, in the present case at least, phago- 

 cytes are in no way concerned in the removal of degenerated 

 myeUn. Phagocytosis is clearly excluded inasmuch as the dis- 

 appearance of myelin is so extremely slow and since wandering 

 cells are as a rule not found in degenerating nerve fibers of the 

 fowls under consideration. 



Just why degenerated myelin should persist so long in nerve 

 fibers of these fowls and disappear so quickly from those nerves 

 which have beeVi sectioned or ligated or even from No. 78 of 

 my series, whose leg had been bandaged for 24 hours, is not 

 clear. The above observations would seem to exclude removal 



