Oil. XV.] 



DEGENERATION OF NERVE 



165 



process of disintegration into droplets of myelin, which are ultimately 

 absorbed and removed by the lymphatics. At the same time there is 

 a multiplication of the nuclei of the primitive sheath. This degenera- 

 tive process is evident two or three days after the section has been 

 made. In the case of the non-medullated fibres, there is no medullary 

 sheath to exhibit the disintegrative changes just alluded to ; and the 



FIG. 181. Degeneration and regeneration of nerve-fibres. A, nerve-fibre, fifty hours after operation. 

 my, medullary sheath breaking up into myelin drops, p, granular protoplasm replacing myelin. 

 n, nucleus, g, primitive sheath. B, nerve-fibre after four days, cy, axis cylinder partly broken 

 up and enclosed in portions of myelin. c, a more advanced stage in which the medullary sheath 

 has almost disappeared. Numerous nuclei, n", are seen. D, commencing regeneration ; several 

 fibres (f, t") have sprouted from the somewhat bulbous cut end (6) of the nerve-fibre, a, an axis 

 cylinder which has not yet acquired its medullary sheath, s, s', primitive sheath of the original 

 fibre. (Ranvier.) 



nuclei of the sheath do not multiply ; there is simply death of the 

 axis cylinder. The degeneration occurs simultaneously throughout 

 the whole extent of the nerve ; it does not start from the section and 

 travel to the periphery. Eauvier's original diagram is reproduced in 

 fig. 181. Figs. 182 and 183 are photo -micrographs from actual 

 specimens. 



A great amount of attention has been directed to this process of 

 degeneration, because it has formed a valuable method of research in 



