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XXVI. Researches into the Structure of the Spinal Chord*. 
By J. Lockhart Clarke, Esq. Communicated by Samuel Solly, Esq., F.R.S. 
Received October 15, — Read December 5, 1850. 
By reflecting on certain facts connected with the respiratory movements, and which 
seem to derive no explanation from our actual knowledge of the structure of the 
spinal chord, I was induced to undertake a series of observations with the view of 
determining, if possible, the relations which appear to subsist between the spinal 
nerves and the respiratory nervous centres. These observations, however, led me 
into a more extended inquiry than I at first contemplated, the results of which I now 
venture to lay before the Royal Society. 
It is needless to point out the difficulties which attend, not only the minute investi- 
gation, but a clear and connected description, of a structure so intricate and delicate 
as that of the spinal chord. It may be proper however to state, with regard to the 
contents of this paper, that those facts only which were verified by cautious and re- 
peated examination have been brought forward with confidence ; while in cases where 
the results of my observations were less satisfactory, I have expressed myself with 
corresponding reserve. Yet, no labour has been spared in order to arrive at correct 
conclusions. My observations were made, by means of one of Mr. Ross’s finest 
microscopes, on many thousand preparations of the spinal chord of Man, of the Calf, 
Sheep, Pig, Dog, Cat, Rabbit, Guinea Pig and Frog, and occupied a period of more 
than two years. 
In making these preparations, the two following methods were adopted : — a per- 
fectly fresh chord was hardened in spirits of wine, so that extremely thin sections, in 
various directions, could be made by means of a very sharp knife. A section so 
made was placed on a glass slide and treated with a mixture composed of one part 
of acetic acid and three of spirits of wine, which not only makes the nerves and 
fibrous portion more distinct and conspicuous, but renders also the grey substance 
much more transparent. The section was then covered with thin glass, and viewed, 
* At the time these inquiries were begun, and nearly up to the period of their completion, I had not seen any 
of the works of Dr. Stilling, and knew no more of his investigations into the structure of the spinal chord 
than what I had gathered from the anatomical and physiological works published in this country. However 
nearly, therefore, a few of the facts brought forward in this paper may correspond to the results of his in- 
quiries, I may state that they were made out without any knowledge of Dr. Stilling’s views, excepting only 
those which regard the origin of the spinal nerves. On showing some of my preparations to Mr. Solly and 
Mr. Grainger, I was advised by those gentlemen to look over the works of Dr. Stilling ; and having done 
so, I shall refer to them whenever they appear to oppose, or coincide with, my own observations. 
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