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Some Observations on the Structure of Nerve- Fibres. 

 By Joseph Lister, Esq., F.R.C.S. Eng. and Edinb., 

 Assistant- Surgeon to the Royal Infirmary of Edinburgh ; 

 and William Turner, Esq., M.B. Lond., Senior De- 

 monstrator of Anatomy in the University of Edinburgh. 



Having recently had the opportunity, through the kindness 

 of Mr. Lockhart Clarke, of inspecting some of his beautiful 

 preparations of the spinal cord, we were struck with an 

 appearance which had not yet received a satisfactory inter- 

 pretation ; and, having been induced to investigate the point, 

 we have met with some facts which seem of sufficient interest 

 for publication. 



For the sake of clearness it may be well to state briefly 

 the method employed by Mr. Clarke in preparing his speci- 

 mens. 



A portion of perfectly fresh spinal cord having been 

 hardened by steeping in dilute chromic-acid solution, thin 

 sections are made with a razor, and these, after immer- 

 sion for a while in an ammoniacal solution of carmine, are 

 soaked in spirits of wine to remove the water, and then 

 treated with oil of turpentine. The last-named agent has 

 the effect of rendering the sections transparent, so that the 

 nerve-cells of the gray matter, finely coloured by the carmine, 

 are seen with the utmost distinctness, giving off in various 

 directions long branching processes ; while the nerve-fibres, 

 which are similarly tinted, may be traced with equal facility 

 in their course through the cord. 



In the preparations which we saw, the cord had been sliced 

 crosswise, and in the columnar regions, where the nerve-fibres 

 have for the most part a longitudinal direction, the transverse 

 section of each fibre showed itself as a carmine- coloured 

 point, surrounded by a perfectly pellucid and colourless ring. 

 This was the appearance which seemed to demand explana- 

 tion ; the question being whether the transparent ring was a 

 mere space, resulting from shrinking of the object during 

 the preparation, or the white substance of Schwann (medul- 

 lary sheath) rendered transparent by the turpentine, the 

 axial cylinder alone, in that case, having received the carmine 

 colour. 



It occurred to us that the point might probably be deter- 

 mined by applying a similar mode of preparation to some 

 nerve the dimensions of whose fibres could be readily ascer- 



