70 ELBERT CLARK 



Teased preparations from the sciatic of this fowl stained to 

 bring out the nuclei revealed a few fibers of the embryonic nerve 

 fiber type. These were very slender fibers with nuclei at fre- 

 quent intervals. Protoplasm was scant even around the nuclei, 

 though the structures stained well (fig. 9). Many resembled 

 very closely non-medullated nerves in degeneration described by 

 Ranson ('12). Others were found, however, which contained a 

 larger amount of protoplasm and in which small droplets of 

 degenerated myelin could occasionally be found (fig. 10). This 

 observation clearly shows these to have been derived from medul- 

 lated nerve fibers. No axis cylinder could be demonstrated by 

 special stains. Another fowl. No. 9, G, on a similar diet and 

 with a somewhat similar history developed paralysis of the legs 

 after 51 days. Teased preparations from the sciatic of this fowl, 

 when stained to bring out the nuclei, also showed embryonic 

 nerve fibers. These were a little more numerous than in No. 

 17, G, were larger and contained more protoplasm. Protoplasmic 

 granules were seen in the immediate neighborhood of the nucleus 

 and droplets of degenerated myelin were of rather frequent oc- 

 currence. Many of the fibers bore an exact resemblance to the 

 protoplasmic bands to be seen in medullated nerves after section. 

 Figure 11, which is from a teased preparation of the sciatic nerve 

 of No. 9, G, illustrates this resemblance and shows beyond ques- 

 tion their identity with the embryonic nerve fibers of a sec- 

 tioned nerve. 



Fowl No. 57, which came down with severe paralysis and 

 prostration after 23 days on a diet of polished rice and which 

 made a most difficult recovery, was killed 1 year and 14 days 

 after being placed on a regeneration diet and approximately 10 

 months after all symptoms of paralysis had disappeared. Teased 

 preparations, stained as above, showed among several thousand 

 fibers one very frail fiber with nuclei at frequent intervals. The 

 fiber appeared scarcely more than a strand of connective tissue 

 with well staining spindle-shaped nuclei along its course. This 

 was probably an embryonic nerve fiber. Previous observations 

 had convinced me that regeneration of the axis cylinder fails 

 to take place in a very small percentage of those fibers which 



