84 ELBERT CLARK 



These findings having indicated that, under favorable condi- 

 tions, regeneration of the axis cyhnder may take place in the 

 degenerated nerves of the rice-fed fowls, more definite evidence 

 of regeneration was sought. This was a difficult and tedious 

 task because it was necessary to show beyond doubt that an axis 

 cylinder in a particular nerve was a new and not an old axis 

 cylinder. Therefore a most careful search was made of sectioned 

 and teased preparations of nerves taken at varying lengths of 

 time after recovery from paralysis. 



The sciatic of fowl No. 38 — 108 days after regeneration diet 

 was begun and 49 days after paralysis had disappeared — was 

 particularly studied because, in addition to being a typical case 

 of peripheral neuritis, the axis cylinders stained exceptionally 

 well and many globules and droplets of myelin were shown by 

 the Marchi stain (fig. 13). In a large fiber containing several 

 large globules of degenerated myeUn along its course, a well stain- 

 ing axis cyhnder was seen running a tortuous course to one 

 side of the large globules which often occupied almost the entire 

 diameter of the fiber. Two such vesicular globules of degen- 

 erated myelin in close proxunity to the axis cylinder were seen, 

 which contained in their center segments of a structure which 

 was identified as the old axis cylinder. In figure 17, m shows 

 one of the globules in question with its axis cylinder contents. 

 In this figure, m clearly represents a single globule of degenerated 

 myelin which has been cut on the tangent by the microtome 

 knife. Part of the old axis cylinder was also probably taken 

 away. The different portions of a and a' , the new and the old 

 axis cylinders, were not in focus at the same time and the draw- 

 ing has been constructed, with the aid of a camera lucida outline, 

 to show as nearly as possible in one plane, the relations of these 

 structures. In this figure, a' is the exact counterpart of a in figure 

 6 which is readily recognized as broken up axis cylinders within 

 large globules of degenerated myelin. That a, figure 17, repre- 

 sents an axis cylinder there can be no doubt. 



This observation has been confirmed in other fibers of this 

 same nerve, as well as in the fibers of the sciatic of fowl No. 

 51, No. 54, and No. 61. In each of these there could be no 



