DEGENERATION AND REGENERATION OF NERVES 65 



with no leg weakness showed, by the same methods, myeUn 

 degeneration in their fibers. It was a constant observation that 

 different fibers of a given nerve present the greatest variation in 

 the degree of their degeneration. In two fowls killed after 

 feeding 7 days on white rice, small areas of blackening after 

 treatment by the Marchi method were observed in approximately 

 one-third of the fibers of the sciatic. These areas very seldom 

 involved the entii'e diameter of the individual fiber at any one 

 point and the great majority ranged from 1 to 8 microns in 

 diameter (fig. 32). 



In the sciatic nerve of those fowls fed for a longer time and 

 which developed a typical paralysis in the legs, every fiber showed 

 larger areas of blackening. Advanced degeneration was found in 

 from 10 per cent to 20 per cent of the fibers. The change shown 

 by these latter fibers presents an identical picture of degenera- 

 tion with that in medullated fibers of a mammalian nerve 10 to 

 14 daj^'s after section, but for the nuclei of the neurilemma sheath. 

 The nuclei of the neurilemma sheath have undergone Uttle or 

 no multiplication. This will be again referred to and more fully 

 discussed in the consideration of the ^'embryonic nerve fiber." 

 By both the ]\Iarchi method and the Weigert method for the 

 medullar}^ sheath, the change of the medullar}^ sheath substance 

 into fatty globules and droplets appears complete in some fibers. 

 As I have pointed out in a previous paper ('12), 



Fibers showing advanced degeneration are marked by accumulation 

 of degenerated myelin in large globules and droplets, a swelling and 

 bulging of the nerve sheath at these points and a disintegration of the 

 axis cylinder. The largest globules usually appear vesicular and in 

 their center, segments or fragments of the axis cylinder are frequently 

 to be seen. In these larger, and in some of the smaller globules alSo, 

 the stainable material is found at the periphery and appears lami- 

 nated. This laminated appearance is very characteristic in Weigert 

 preparations and is the rule in the larger globules. Usually 3 distinct 

 layers are clearly visible, of which the outer is the thickest. Other 

 incomplete la3^ers and fragments are seen centrally. 



But for an increase in the number of nuclei of the neurilemma 

 sheath, this description applies with equal exactness to fibers 

 of similar preparations of the peripheral segment of the sciatic 

 nerve of a fowl 7 days after section. Figures 2, 3, 4 and 5 



THE JOURNAL OF COMPARATIVE NEUROLOGY, VOL. 24, NO. 1 



