DEGENERATION AND REGENERATION OF NERVES 69 



could have taken place as gangrene early manifested itself — bj^ 

 the twelfth day of the loss of control. Fibers from that portion 

 of the leg affected by gangrene presented an appearance from 

 which they were readily recognized as embryonic nerve fibers 

 (fig. 8). For the most part these were very slender with long 

 nuclei, an appearance which is readily accounted for by the par- 

 tial desiccation. Many still contained droplets of degenerated 

 myelin. It is difficult to see how the least regenerative reaction 

 could have taken place in this nerve. 



As stated above, I have not observed a single instance in which 

 there was a marked increase in the number of nuclei of the sheath 

 of Schwann in those degenerated fibers of fowls which showed 

 paralysis of the legs after 20 to 30 days on polished rice. In 

 fibers showing the most advanced degeneration, that is, marked 

 globulation of myeUn and breaking up of axis cylinder, measure- 

 ments were made between neighboring nuclei of the sheath of 

 Schwann. Among these measurements, there were observed such 

 distances as these between successive nuclei: 368, 386, 477 and 

 379 microns respectively. The distance between 2 nodes of 

 Ranvier is variously estimated as from 80 m to 900 /x according 

 to the diameter of the fiber, and ''in the higher vertebrates a 

 single nucleus is found midway between each two nodes" — Huber. 

 Mitosis has not been observed. 



Some few fibers, however, were seen in which the nuclei of 

 the sheath of Schwann occurred at intervals frequent enough to 

 be suggestive of a slight increase in their number. This was 

 suggestive enough to make it desirable to examine, for an in- 

 crease of the number of nuclei of the sheath of Schwann, nerves 

 of fowls with which the onset of paralysis had been deferred b}^ 

 the addition of very small amounts of other foodstuffs to the 

 rice. At this period I was fortunate in securing from Dr. R. 

 B. Gibson of the Department of Physiology, a fowl, No. 17, G, 

 which suddenly developed paralysis of the legs after 60 days on 

 a diet of white rice and calcium lactate. This fowl developed 

 a typical case of leg paralysis two days before death. Marchi 

 preparations of the sciatic showed very extensive and advanced 

 myelin degeneration. 



