72 CLARKE, ON NERVE-FIBRE. 



which were manifestly clue to nothing but simple mechanical 

 disturbance. The injury was often limited to the sides of 

 the fibre, and consisted only of indentations or fissures, 

 which were sometimes plain and smooth, as in fig. 7, and 

 sometimes, as in fig. 8, more or less twisted into spiral 

 ridges, which had a considerable resemblance to fine ele- 

 mentary fibrils. The white substance between the two 

 contours, represented in fig. 9, had a completely spiral 

 arrangement, and might, if insufficiently examined, have 

 been compared to the fibres of a partially untwisted rope ; 

 but it evidently consisted of a continuous mass, in the same con- 

 dition as a twisted cylinder of glass, so that the appearance 

 of fibrils or tubules was caused by the prominent edges of 

 the spiral. Sometimes (as in figs. 10 to 15) two portions of 

 the white substance between the double contour was drawn 

 asunder to a variable distance, and in such a manner that 

 the intervening and viscid lamina, or expansion, was thrown 

 into a series of folds which might readily have been mis- 

 taken for tubules. But these ridges or folds (represented 

 by the light lines) Avere obviously continuous at their sides 

 with the pearly transparent substance in the spaces between 

 them. In fig. 10, a similar state of the fibre is very satis- 

 factorily seen ; for the lower portion (a) between the separa- 

 tion consists of fibre-like ridges, while the upper expansion 

 (b) is only slightly undulated. 



When the nerve-fibre was stretched and dragged, or other- 

 wise rudely handled, the wrinkles and undulations were not 

 confined to its sides, but extended over its entire surface, as 

 represented in fig. 17. Sometimes they originated from 

 between the double contour, where the white substance was 

 frequently fissured or indented, and after a short but various 

 course, they flattened and subsided into the surrounding 

 surface, or intercommunicated as apparent fibres in a kind of 

 anastomosis. This last-mentioned appearance is remarkably 

 well seen in fig. 18. At the upper part of the fibre, on the 

 left side, the white substance was thrown into a convolution, 

 which gave it the appearance of having two double contours 

 at that spot. Lower down was a thick convex elevation or 

 fold, which stretched transversely across from one double 

 contour to the other; and on cither side of this were mime* 

 rous smaller folds of precisely the same kind, and having a 

 remarkable similitude to anastomosing fibres. In some parti 

 (sec fig. 19) the surface of the fibre consisted entirely of 

 large convolutions like those of the cerebral hemispheres ; 

 While in other parts, as in fig. 20, these convolutions sub- 

 divided into apparent fibres or tubules. Even when the 



