SOME OBSERVATIONS ON THE STRUCTURE 
OF NERVE-FIBRES 
WRITTEN IN COLLABORATION WITH WILLIAM TuRNER}?, Esq., M.B., Lond., 
Senior Demonstrator of Anatomy in the University of Edinburgh. 
[Quarterly Journal of Microscopical Science, October 1859.] 
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 specimens. 
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 immersion 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 grey 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 longi- 
tudinal 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 explanation, 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 (medullary 
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 determined by applying 
a similar mode of preparation to some nerve the dimensions of whose fibres could 
be readily ascertained. With this view we steeped in chromic acid portions 
of the sciatic nerve of a cat just killed, and also parts of the spinal cord of the 
* Now(1908) Sir William, K.C.B., F.R.S., Principal and Vice-Chancellor of the University of Edinburgh. 
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