DEGENERATION AND REGENERATION OF NERVES 87 



Other than the rami as just noted (fig. 27), an outgrowing 

 axis cylinder with its end bulb, as described by Cajal ('07), has 

 been observed only once by me. Figure 30 — from a teased prep- 

 aration of the sciatic nerve of No. 38 — shows in a, a structure 

 with an end bulb which stained intensely with phosphomolybdic 

 acid hematoxyhn and which is lodged in a band of poorly stain- 

 ing tissue rich in nuclei. Whether the band of tissue is a group 

 of embryonic nerve fibers or non-medullated fibers in regener- 

 ation, I cannot say. 



In the light of this group of evidence which bespeaks an out- 

 growth of the axis cylinder into the old nerve fiber sheath, cer- 

 tain observations of Cajal ('07), Marienesco ('06), Ranson ('12) 

 and others gain an additional interest. These investigators found 

 that, almost immediately after section, the axis cylinders of the 

 central stump showed evidence of growth activity, "Marien- 

 esco, in one of his recently published papers has demonstrated 

 that the lengthening of the regenerating fibers (i.e., axis cylinders) 

 is demonstrable twenty-four hours after a nerve has been cut" 

 (Halliburton). Ranson ('12) says: 



On the first day after the lesion some of the axons grow out into the 

 exudate and break up into many branches (fig. 16). Others on the 

 first day, give off fine branches from their surface within the sheath 

 in the immediate neighborhood of the lesion (fig. 17), some of which 

 find their way into the exudate. Thus from the end of the first day 

 on, fine nerve fibers, which are demonstrably branches of the medulhited 

 axons of the proximal stump, are present in the developing scar, and 

 running for the most part within the sheath of the old 

 axon from which they arose, they arrange themselves into fascicles, etc. 



Cajal' s beautiful figures illustrate most clearly the axis cylin- 

 der growing down into the old sheath of that portion of the 

 central stump which showed degeneration after section. Howell 

 and Huber ('92) also observed a similar growth of the axis cylin- 

 der in the central stump. Branches of these axis cylind'ers are 

 also to be seen growing up the medullated fiber in a central 

 direction; others burst through the sheath into the interfibrillar 

 tissue, and still others after invading the blood clot and inflam- 

 matory tissue between the sutured central and peripheral stumps 



