CLARKE, ON NERVE-FIBRE. 71 



trusion, with part of the transparent interior, has been 

 broken off. It will be understood, then, that all the folds, 

 ridges, or apparent elementary fibres represented in fig. 2, 

 are connected together by an intervening layer of the white 

 substance, which has a convex, concave, or some other kind 

 of plane, surface. Sometimes the surface of a primitive- 

 fibre, hardened in chromic acid, resembles a piece of parch- 

 ment crumpled into a multitude of folds of different shapes 

 and lengths, and loosely arranged around a central axis ; and 

 sometimes it presents very much the same appearance, and 

 is indeed in the same condition, as the fissured bark of an 

 old tree, or the shrivelled bark of a young twig torn while 

 green from the parent stem. At the upper and broken end 

 of fig. 2 the superficial parts of the folds or ridges have 

 been brushed away, but the sharp edges of their bases may 

 be distinctly seen. Fig. 3 represents a primitive-fibre 

 deprived, in the same way, of the superficial parts of the 

 folds, except at a ; but the sharp and fractured edges of the 

 subjacent substance from which they have been swept are 

 very conspicuous, and have, in one place, a kind of spiral or 

 concentric arrangement around the axis-cylinder, which axis 

 is probably the cause that determines such an arrangement, 

 under the corrugating influence of chromic acid. Figs. 4 

 and 5 represent two detached pieces brushed from the 

 surface of a primitive-fibre. In both, the apparent ele- 

 mentary tubules or fibrils are connected by a thin layer of 

 white substance ; and in fig. 5, where this substance is bent 

 in different planes, it is evident that every angular deviation 

 from the plane surface gives rise to the appearance of tubule 

 or fine fibre. 



Although quite satisfied with the above explanation of the 

 appearances in question, I thought that if similar or nearly 

 similar results could be produced in the fresh nerve-fibre by 

 simple mechanical disturbance or manipulation, and without 

 the use of any chemical agency, the facts would be un- 

 deniably established. For the purpose of this inquiry, I 

 examined on several occasions under the microscope some 

 spinal nerves of the ox and of other animals, immediately 

 after death, and moistened only with fresh serum of the 

 blood. The primitive-fibres, when uninjured, had the well- 

 known semblance of translucent tubes with double contours 

 (as shown in fig. 6) ; and no traces of finer elementary 

 tubules or fibrils could be discovered in them, even under 

 high magnifying powers. But when the bundles of nerves 

 were torn asunder, and finely separated by means of needles, 

 the white substance assumed a great variety of appearances, 



