No. 3] PERIPHERAL NERVES. 71 1 



fibres are to be seen within the old sheaths, while others are 

 found between them. Now and then the axis cylinder will be 

 seen to end abruptly in the protoplasm of one of the degenerated 

 old fibres. In PI. XXXV, Fig. 15^ (in which portions of 

 three fibres from the muscular branch to the flex. carp. ul. are 

 represented), the axis cylinders end in a bulbous enlargement 

 at c, beyond which the old sheath {s) could be traced through 

 several fields of the microscope. Above the bulbous enlarge- 

 ment the axis cylinder is enclosed within a narrow layer of 

 myelin {71m), and surrounding this is seen a new sheath of 

 Schwann. B of the same diagram presents essentially the 

 same condition, except that the end of the axis cylinder is 

 not enlarged, but has for a short distance a wavy course. (I 

 would crave indulgence for the awkward way in which the 

 fibres in PI. XXXV, Fig. 15, are placed. It will be noticed 

 that the peripheral end of one [y^] points toward the right, 

 while that of the other [R] points toward the left. The sketch 

 was made from teased preparations, and the error was not 

 noticed until the diagram was completed.) This same appear- 

 ance was met with in other parts of the peripheral ulnar, as 

 is shown in PI. XXXV, Fig. \6 E (from a teased preparation 

 of the peripheral ulnar at the wrist 1 1 7 days after operation. 

 Exp. 17). In this fibre the new axis cylinder is not sur- 

 rounded by a medullary sheath. In the nerves from this 

 experiment nearly all the fibres of the peripheral ulnar at the 

 wrist present the appearance of a completely degenerated nerve 

 (see PI. XXXV, Fig. \6 A). In a few of the degenerated 

 fibres unabsorbed fragments of myelin are still present 

 (PI. XXXV, Fig. \6B). One such fibre containing a new 

 axis cylinder is shown in D of the same figure. 



The appearance presented in specimens made from nerves 

 removed 149 to 182 days after implantation (Exps. 21 to 25) 

 differ from the ones above described only in the extent of 

 regeneration. I may briefly state that the longer the interval 

 between the implantation of the nerve and the time of its 

 removal, the more complete is the return of function, and the 

 more regenerated fibres are to be seen in the peripheral end of 

 the injured nerve. In all of the last-named experiments elec- 



