714 HUBER. [Vol. XI. 



preparations fixed in osmic acid, or for the imbedding of por- 

 tions of nerves in celloidin, so that Weigert's method might 

 be used. 



In each experiment alternate longitudinal and cross-sections 

 of the portion of the nerve involved were made, so that I might, 

 if possible, come to some definite conclusions concerning the 

 mode of development of the axis cylinders. On some of the 

 sections of nerves hardened in Miiller's fluid and imbedded in 

 paraffin, the Weigert method was tried, but with no results. 

 I was, therefore, compelled to forego a closer study of the 

 development of the medullary sheath, and confine my attention 

 to regeneration of the axis cylinder, a structure of far greater 

 importance. 



In closing this part of the discussion, I may, however, be 

 permitted to quote the following from Howell and Ruber's 

 article : — 



** It is quite easy to find in the peripheral trunk newly 

 regenerated fibres, showing a delicate continuous layer of 

 myelin ; but to demonstrate how this myelin is deposited is 

 more difficult ; to ascertain this one must obtain his specimens 

 from just that portion of the nerve in which the process is 

 actively going on. Figs. 36, 37, 39, 40, and 41 give an 

 idea of how the myelin first appears. As shown in these 

 figures, it appears first as irregular deposits in the proto- 

 plasm of the embryonic fibres, and usually first in the neigh- 

 borhood of the nuclei. Delicate prolongations of the myelin 

 are often seen running from one small mass of myelin to 

 another, and eventually these latter become connected together 

 forming a varicose tube, shown in various stages in Figs. 

 36-51. There would seem to be no doubt that it is first 

 formed as disconnected drops. These may afterwards become 

 united into slender processes to form a bead-like string, which 

 sooner or later elongates to an even tube, or the drops may 

 first elongate to form cylindrical segments, which eventually 

 unite to form continuous delicate tubes of myelin." I possess 

 at the present time no facts which would prevent my accepting 

 the above statements. 



The following brief conclusions, based on a review of the 



