158 Transactions of the 



In all the preparations obtained by the method above men- 

 tioned, the nerve fibres, up to theu' finest ramifications, appear as 

 sharp, outlined structures, of a dark colour. No other element is 

 coloured besides the nerve fibres. Of the cellular structures of 

 the proper tissues of the cornea nothing is to be seen. Although 

 the epithelium is also not, at least not for a pretty long time, 

 coloured, still its every cell is very distinctly to be seen. 



In all these preparations the fact which can be deduced with 

 certainty is, that only the trunks of the sub-epithelial plexus, which 

 as well as the trunks which are situated deeper in the substance of 

 the cornea are only bundles of fine nerve fibrillge, are provided 

 with a nucleated sheath. In all other nerve fibres, i. e. the nerve 

 fibres in the proper substance of the cornea (see Fig. 1), the fine 

 nerve fibres of the sub-epitheHal network, as weU as the very deh- 

 cate fibriUse, which close under the epithelium spring ofi" like a 

 brush (see Figs. 2, 3, and 4), and, finally, the nerve fibrillae of the 

 intra-epithelial networks, — in all these, I say, there is nothiug like 

 nucleus to be found. 



As regards the frog's cornea, I also refer to the description and 

 illustrations I have given in my first memoir in the 'Quarterly 

 Journal of Microscopical Science.' Here also only the nerves of the 

 coarser plexus are provided with a nucleated sheath. The nerve 

 fibres, which I have described as nerve fibres of the second order, 

 and which run very often in a winding course, sometimes also 

 rectihnear, exhibit nuclei only in very few places. The nerve 

 fibres of the third order, which run mostly rectilinear, and 

 which are distinguished hke the fine nerve fibres in the rabbit's 

 cornea by more or less regular varicosities, no longer exhibit 

 nuclei. These nerve fibres of the third order, which remain for a 

 long distance undivided, join by rectangular fibres, so as to form a 

 trellis-work, the meshes of which are relatively broad ; in the same 

 manner also the nerve fibrillae of the fourth order, which join to a 

 dense network upon the corneal corpuscles themselves, have no 

 nuclei. 



"We find therefore also in the cornea of the frog, that the finer 

 nerve fibres do not possess any nucleus. The special mode in 

 which the finer nerve fibres of the corneal substance run is not a 

 peculiar one, if we consider that the arrangement of the bundles of 

 the corneal tissue is a regular one, and that the nerve fibres can 

 only run between these bundles. 



Whether the fine fibres described in the rabbit's and the frog's 

 cornea are nerve fibres at all cannot be the subject of any doubt, if 

 we admit, as regards the microscope, that our mental eye is not able 

 to deny what our normal and healthy bodily eye sees as an atomical 

 continuity. 



The second reason why I take the opportunity to speak on the 



