No. 3-] PERIPHERAL NERVES. 727 



having a beaded appearance are to be seen. The extent of 

 myehn fragmentation varies, however, in the different fibres. 

 Now and then the medullary sheath is broken up, while the 

 continuity of the axis cylinder would not seem to be interrupted. 

 On this point, however, I can only speak tentatively, as in 

 safranin and licht griin stained sections the axis cylinder is not 

 very clearly differentiated. The larger number of the degen- 

 erated fibres in the central stump is found in the immediate 

 neighborhood of the path traversed by the knife in forming the 

 flap. The degeneration would, therefore, seem to be the result 

 of the traumatism incurred while bisecting the nerve trunk. 



In the experiment of sixty-four days' duration (No. 46) the 

 central stump is slightly enlarged at that point in the central 

 segment where, after bisecting the nerve preparatory to mak- 

 ing the flap, the upper half of the end to be turned down as the 

 flap was severed from the central end. In longitudinal sections 

 through this region of the central segment a large nerve bun- 

 ble, the fibres of which are very irregularly arranged, is observed. 

 This bundle is given off from the peripheral end of the enlarge- 

 ment above referred to. It no doubt represents the half of 

 that part of the bisected central stump which was not cut while 

 making the flap. Many of the nerve fibres making up this 

 bundle do not differ structurally from fibres seen in section of 

 any peripheral nerve, while others have only a very narrow 

 medullary layer, and still others are devoid of this sheath. I 

 assume that the fibres presenting the appearance of fully 

 developed medullary nerves did not undergo degeneration, 

 while such as show only a narrow layer of myelin and the 

 naked axis cylinders, represent regenerated fibres. The bundle 

 above mentioned can be traced for a distance of about 4 ctm. 

 below the enlargement. They then split up, and the nerve 

 fibres are soon lost in the connective tissue surrounding them. 

 Near the peripheral wound, and in the peripheral part of the 

 resected ulnar, no axis cylinders were seen. In sections 

 through the region of the down-turned flap the collapsed 

 sheaths, containing a small amount of nucleated protoplasm, 

 were found. In these no evidence of regeneration was seen. 

 In this experiment the budding axis cylinders of the central 



