THE NERVOUS SYSTEM. 401 



sometimes as a transparent streak of uniform breadth throughout; 

 sometimes, when the grumous particles .are more numerous, it 

 may be concealed by them, so that the entire contents of the 

 nerve appear to be coagulated. They arc so, however, only in 

 appearance, the clear fibre always lying in the interior ; and I 

 have never yet seen it coagulated or grumous. Non-mcdul!ated 

 nerve-fibres occur in many situations. I enumerate among 

 them: 1. the pale fibres in the Pacinian bodies; 2. the 

 nucleated pale fibres in the terminations of the olfactory nerves j 

 3. the perfectly transparent, non-nucleated nerve -fibres in the 

 cornea ; 4. the pale, branched, and partially anastomosing 

 terminations of the nerves in the electrical organ of the Torpedo 

 and Ray (11. Wagner, Ecker) ; 5. the similarly constituted 

 terminations of the nerves in the skin of the Mouse {rid. 

 1 Mikroskop. Anatomic/ §11); 6. the pale processes of the 

 nervc-ceJls in the central organs and ganglia, even though they 

 may not all pass into dark-bordered fibres. Of these fibres, 

 those which occur at the extremities of nerves were, even bv the 

 earliest observers of them, unconditionally regarded as nerve- 

 fibres; and as respects the processes of the nerve-cells, I described 

 this to be their nature as early as the year 1846; but these views 

 could not be considered as fully established, until the relation 

 of the fibres with the elements presenting the dark borders was 

 completely elucidated. But since it has been ascertained by 

 Schwann, Ecker, and myself, that the nerve-fibres of the embryo 

 are in precisely the same condition as the pale fibres now in 

 question, and since I, Wagner, Robin, and Bidder and Reichert, 

 have shown that the pale processes of the nerve-cells pass into 

 dark -bordered fibres, it has become more possible to arrive at 

 positive conclusions on the subject. R. Wagner was the first 

 to broach the supposition, that the pale fibres in the Pacinian 

 bodies, and in the electric organs, were nerve-sheaths, with axis- 

 cylinders, and that the processes which pass into nerve-fibres, 

 were themselves bare axis-cylinders, and, moreover, that the 

 entire granular contents of a nerve-cell are nothing but an 

 axis-cylinder enlarged into a globular form ; and after I had 

 demonstrated the constant existence of the axis-cylinder in the 

 living nerve, and that it was a structure distinct from the 

 medullary sheath, I considered myself fully justified in asserting 

 that the dark-bordered nerve-fibres were in direct connection on 

 i. 2G 



