638 HUBER. [Vol. XI. 



which, with Stroebe, I must condemn as unsuitable for axis 

 cylinder differentiation. I am, furthermore, in accord with 

 this writer in believing that neither Biinger's illustrations nor 

 the description of his section sustain him in his statements. 

 The unequivocal results obtained by the anilin blue-safranin 

 method, as first employed by Stroebe, a stain which gives an 

 axis cylinder differentiation far clearer than when safranin alone 

 is used, leads me to say that the proliferated nuclei of the 

 sheath of Schwann of a degenerating peripheral nerve, or of a 

 degenerating implanted segment, play no part in the develop- 

 ment of the axis cylinder. It is an outgrowth of the axis 

 cylinder of the nerve in the central end, as was first clearly 

 shown by Ranvier, later held by Vanlair, Howell and Huber, 

 Stroebe, and Notthaft. 



It may further be stated that a number of embryological 

 observations show that the sheath of Schwann and its nuclei, 

 as also the medullary layer, are of mesoblastic origin, while 

 nerve cells and axis cylinders are developed from the epiblast. 

 The axis cylinders are outgrowths from nerve cells ; the naked 

 axis cylinders constitute, at one stage in the development, the 

 entire peripheral nerve. Mesenchymal cells apply themselves 

 to the outside of bundles of naked axes, and grow in between 

 them, and from these the medullary and sheath of Schwann 

 are developed. Minot states " that each cell is the anlage of 

 a medullary segment, the junction of two adjacent cells is the 

 anlage of a node of Ranvier, and the nucleus becomes the inter- 

 nodal nucleus of the sheath of Schwann." (See, also. His, 

 Vignal, and Kolliker.) 



In the three experiments of transplantation mentioned -by 

 Notthaft only y^ ctm. was removed from the sciatic of a rab- 

 bit. In one instance the exsected segment was again inserted ; 

 in the other two a portion was removed from the opposite 

 sciatic, implanted, and fixed with sutures between the resected 

 ends. After fifty days there was regeneration through the 

 implanted piece. Notthaft's experiments can be of little prac- 

 tical importance, as the distance between the resected ends 

 could easily have been overcome by stretching the nerves and 

 applying a suture in the ordinary way. 



