704 HUBER. [Vol. XI. 



This conception of the regeneration of the new axes was first 

 defended by Ranvier, and has since been held by Vanlair, 

 Assaky, Howell and Huber, Stroebe, Notthaft, and Willard. 

 After this brief summary, of the views held concerning the 

 formation of the axis cylinder during the process of regenera- 

 tion, I will now turn to the results obtained in my experiments. 

 In longitudinal sections and teased preparations through the 

 junction of the central end of the ulnar and the implanted seg- 

 ment, made from two nerves removed twenty-one days after 

 the implantation (Exps. 14 and 15), the following observations 

 are to be made : — 



At this time it is quite easy to determine the extent to which 

 the central end has degenerated, as, in the area marking the 

 upper limit of the degenerated part of the fibres, the myelin is 

 found in larger or smaller fragments, and does not present the 

 normal appearance seen in the same fibre a short distance 

 nearer the center. In these fragments of myelin one now and 

 then finds remnants of the old axis cylinder taking the charac- 

 teristic stain. In many of these fibres nothing is seen of the 

 new axis cylinder in that part containing the fragments of 

 myelin, or just below, while it is clearly made out in the 

 normal portion of the fibres just above. In others, the new 

 axis cylinder can be traced for a short distance into the portion 

 of the fibre containing the fragments of myelin ; here it often 

 has a somewhat tortuous course, and ends free in the prolif- 

 erated protoplasm. The fragments of myelin are not disposed 

 around the axis cylinder in the form of a sheath, but are 

 usually to the side of it. In still other fibres, the axis cylinder 

 can be traced through the segment of the nerve, showing the 

 broken up myelin, into the more distal portion of the degen- 

 erated central fibre, which presents structurally the appearance 

 of a completely degenerated nerve, that is, a collapsed sheath 

 of Schwann containing a homogeneous nucleated protoplasm. 

 One such fibre is represented in PI. XXXIV, Fig. 6. The 

 central end of the fibre points toward the top of the page. In 

 this part the axis cylinder is surrounded by the medullary 

 sheath ; just below are seen a number of fragments of myelin ; 

 between them the somewhat wavy axis cylinder is winding its 



