No. 3.] PERIPHERAL NERVES. 707 



implanted segment, separates the degenerated nerve fibres into 

 smaller and larger bundles, around which it is often arranged 

 in the form of a sheath. In such a cross-section the relation 

 of the newly formed axis cylinder to old sheaths is well seen. 

 The deeply stained dots, representing cut ends of the axes, are 

 now and then found within an old sheath, as shown in PI. 

 XXXIV, Fig. 9 c. Often a very delicate sheath, found 

 within the old one, surrounds them. Others are seen by the 

 sides of the degenerated sheaths, as shown in b of this figure. 

 In longitudinal sections and teased preparations of the periph- 

 eral portion of the implanted segment, relatively few axis 

 cylinders are found ; in PI. XXXV, Fig. 10 b, two are repre- 

 sented, among a larger number of degenerated implanted 

 fibres {a). In the connective tissue uniting the peripheral end 

 of the implanted segment to the peripheral ulnar still fewer 

 axis cylinders are observed. In longitudinal sections of this 

 part of the nerve, several fields are often passed before one is 

 met with. Their course is much more irregular than that 

 presented by the axes seen in the connective tissue of the 

 central wound. Preparations made from the peripheral ulnar 

 about I ctm. below the peripheral wound, show the great 

 majority of the fibres in complete degeneration. Only at very 

 rare intervals is a characteristically stained axis cylinder found. 

 The appearance presented in one of my teased preparations 

 from this locality is given in Fig. 11. The entire peripheral 

 ulnar from a point about i ctm. below the peripheral wound to 

 the wrist, as also the muscular branches to flex. carp, ulnaris 

 and flex. prof, dig., were divided into small pieces, which were 

 used, some for cross, others for longitudinal sections ; but in 

 none of these did I meet with an appearance which might 

 have been interpreted as representing an axis cylinder. It is 

 very interesting to recall that in this experiment (No. 16) 

 stimulation of the peripheral ulnar just below the peripheral 

 wound, with strong induction shocks, excited no contractions 

 of the muscles supplied by this nerve ; however, impulses 

 would seem to have been carried along the few regenerated 

 nerve fibres (some of which, no doubt, were sensory) found in 

 the upper end of the peripheral ulnar and the peripheral 



