No. 3] PERIPHERAL NERVES. 723 



tion in the implantation of a nerve segment, or the perform- 

 ance of a bone-drain suture. The down-growing axis cylinders 

 of the central end would seem to make much slower progress 

 in cases where the suture a distance is made, than in those 

 where the resected ends are bridged with a segment of a 

 nerve trunk. In Exp. 16, where a nerve segment 7 ctm. long 

 was implanted, newly formed nerve fibres were found in the 

 central end of the peripheral portion of the resected ulnar, and 

 through the whole length of the implanted segment thirty- 

 nine days after the implantation. In Exp. 38, of like dura- 

 tion, a segment 5 ctm. in length was removed from an ulnar 

 and the resected ends united by a suture a distance ; in this 

 case regeneration of the peripheral part of the ulnar was not 

 accomplished. Small bundles of axis cylinders were found in 

 the connective tissue about 4 ctm. below the central wound, 

 but in cicatricial tissue surrounding the central end of the 

 peripheral stump none were found. In longitudinal sections 

 through the peripheral end of the central stump and the con- 

 nective tissue just below, bundles of small nerve fibres, the 

 majority of which consist only of an axis cylinder surrounded 

 by the pale blue sheath seen in anilin blue and safranin stained 

 preparations, are seen to extend from the undegenerated part 

 of the central stump into the connective tissue. Here they at 

 first have quite a regular course which, however, must soon 

 be lost, as in sections made of the tissue i to 2 ctm. nearer the 

 periphery, only short, twisted, and bent segments of the small 

 nerve bundles, surrounded by fibrous tissue, are met with. 

 Below this point the bundles become less numerous, and, if 

 anything, more twisted, until, as already stated, they cannot be 

 found. The nerve fibres found in the cicatricial tissue uniting 

 the central and peripheral stumps in this experiment, have a 

 much more irregular course than do the newly formed fibres 

 seen in longitudinal sections of the implanted segment in 

 Exp. 16, which would, I think, seem to indicate that in 

 the former experiment the budding axis cylinders met with 

 much greater resistance in their down-growth toward the pe- 

 ripheral portion of the resected nerve, than do developing axes 

 which grow through a degenerated implanted nerve segment. 



