Dark or Douhle-lordered Nerve Fibre. 215 



The difference between the view of Max Sehultze and my own con- 

 sists therefore only in the nature of the fibrils and the inter-fibril- 

 lous substance, and also in the absence and presence of a sheath. 

 We will now pass over to the details of the examinations, and try, 

 by means of sufiicient proofs and reasons, to demonstrate the 

 granular nature of these fibrils as a fact. 



With the assistance of a first-class objective and a well-adapted 

 illumination of the object, especially with oblique hght, the granular- 

 fibrillous composition of the axis cylinders, projecting from the torn 

 ends of many fresh nerve fibres, may even without difficulty be 

 recognized. But better specimens may be obtained from nerves or 

 spinal marrow, that have been laying in a very weak solution of 

 chromic acid from about twelve to twenty-four hours. This reagent 

 seems to promote the decomposition of the medullary layer, while it 

 produces an opposite effect upon the axis cylinder. In carefully 

 dissecting, now, a bundle of such nerve fibres with very finely- 

 pointed needles, it always happens, that during the manipulation a 

 number of axis cylinders are drawn out to some extent from their 

 respective fibres; but frequently also that one of them becomes 

 torn or pressed by the point of the needle, offering an opportunity 

 of examining somewhat more accurately the details of its con- 

 struction. In this way I came to recognize, some years ago, on 

 some axis cylinders, partially torn and drawn out from their re- 

 spective peripheral nerve fibres of the alligator, their granular- 

 fibrillous structure. In referring, therefore, to Fig. 13, some of 

 these axis cylinders and also a nerve fibre will be found repre- 

 sented, which I copied from nature at that time ; a represents the 

 entire nerve fibre, showing all its parts ; but as it was considerably 

 magnified when drawn, it was necessary, by shghtly altering the 

 adjustment, to bring the axis cyhnder into focus; the drawing 

 represents, therefore, all parts of the fibre almost in the same 

 focus. At h, a piece of axis cylinder is seen which, near its middle, 

 has been pressed flat and slightly torn by the point of a needle, in 

 consequence of which a number of granules were displaced and 

 escaped through the orifice thus produced. The small fragment c 

 shows even the rent and the granules displaced from their natural 

 fibrinous arrangement. The membranous sheath manifests itself 

 on each of the specimens by a fine double contour. As the speci- 

 men was removed from the body immediately after the death of the 

 animal and put into a solution of chromic acid, the fine fibrils of the 

 fibrinous layer remained to a certain extent in their natural position. 

 They can be seen, of course, only on the sides of the fibre, but by a 

 slight change of the adjustment they could be traced, though not as 

 distinctly, over the whole nerve fibre. 



Among the smaller as well as the larger nerve fibres of the spinal 

 marrow, a number of axis cylinders, drawn out from their coverings 



