THE DEVELOPMENT OE MEDULLATED 

 NERVE-FIBRES. 



With Plate II. 



By C. L. Herrick. 



It is remarkable that a question apparently so simple as 

 that respecting the development of the nerve fibre should re- 

 main without an answer. The necessity for a clear comprehen- 

 sion of the course of normal development of nerves is more 

 important than it might otherwise appear because of its bearing 

 on the vexed question ot the degeneration and regeneration of 

 the same structures. The literature upon the latter subject has 

 been steadily increasing without affording unambiguous evidence 

 as to the exact method of regeneration. While several writers, 

 like Notthaft/ claim that the regeneration proceeds from the 

 central stump peripherad, others, like Howell and Huber, find 

 that the new axis-cylinder originates cotemporaneously through- 

 out the newly-formed sheath. Much obscurity still prevails as 

 to the part played by the nuclei of Schwann's sheath during the 

 regeneration of the axis-cylinder though it is not doubted that 

 the remarkable proliferation which they undergo sustains some 

 important relations to the absorbtion of the exudates from the 

 decomposing nerve and the regenerative processes which follow. 



The influence of high authority has supported the view 

 that a nerve fibre is derived from a central neuron (cell of vent- 

 ral cornu or spinal ganglion) and extends unbrokenly to its 

 peripheral end-organ whether the distance thus covered be mil- 

 limeters or meters. So long as the dogma of nervous conduc- 

 tion by continuity prevailed this seemed to physiologists a 

 natural if not a necessary postulate. When, however, we dis- 

 covered that within the neuraxis the tracts of nervous conduc- 

 tion are frequently composed of series of contiguous neurons, 



I. Neue Untersuchungen iiber den Verlauf der Degenerations- und Re- 

 generations-processe. Zcitsch. f. wiss. Zool. iv. i. 



