Roi/al Microsco])ical Society. 157 



This method is as follows : — The cornea of a rabbit or a guinea- 

 pig is cut out (it is of no consequence if this is done a quarter or 

 half an hour after death) and placed in a half per cent, solution of 

 chloride of gold. The cornea of the rabbit remains in the solution 

 for from one hour and a half to two hours ; that of the guinea-pig 

 for from one hour to one hour and a quarter. After that the cornea 

 is washed in distilled water, and exposed to the light in distilled 

 water for from twenty-four to thirty-six hours (the water being 

 changed twice, or oftener) ; after this time has elapsed the cornea 

 is transferred into a mixture of one part pure glycerine and two 

 parts distilled water, where it remains for two or thi'ee days. Up 

 to this time the cornea has not assumed a darker colour than ash 

 grey, perhaps having in a small degree a violet tint ; at all events, 

 the whole of the cornea is transparent. The cornea is then brushed 

 over on its anterior surface under water with a fine camel's hair 

 brush very gently, so as to remove the precipitates of the gold salt. 



It is quite sufficient to brush it only once very gently and deH- 

 cately, so as to clear the surface, even if not over its whole extent, 

 still over the greater portion of it. No great practice is required to 

 obtain from such a cornea, with a sharp razor, thin horizontal and 

 oblique sections, by placing it simply with its concave surface on 

 the volar side of the last phalanx of the first finger and fixing its 

 scleral border with the thumb of the same hand. The sections are 

 examined in glycerine. 



The sections which are made in an oblique direction through 

 the anterior epithelium and the superficial portions of the proper 

 substance of the cornea are as valuable as the horizontal sections. 

 The latter are necessary for the examination of the sub-epithelial 

 nerve fibres as well as for the intra- epithelial nerve fibres, both 

 separately, although in a binocular microscope there is no difficulty 

 whatever in seeing how the latter spring ofi" from the former. 



The examination of the oblique sections proves this thoroughly. 



I have prepared, by the above-mentioned method, sixteen corneas 

 in a relatively short time, and not one of these has failed. Of 

 course, not all of them were in all parts equally perfect. 



I do not wish to give any long description of the relation of the 

 sub-epithelial plexus of the coarse non-medullated nerve fibres, or, 

 more properly speaking, of the sub-epithelial plexus of the nerve 

 trunks, nor of the sub-epithelial network of fine fibres, nor of the 

 immense number of very fine fibrillse which spring ofi", in bundles 

 like a brush, from several branches of the sub-epithelial trunks, 

 which branches run close to the under sm'face of the anterior epithe- 

 lium. I wish only to mention shortly the fine nerve fibrillae which 

 enter the epithelium, and there form a deep and a superficial intra- 

 epithehal network. I refer simply to the description I have 

 already given, and to the adjoining figures. 



