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XIII. On the Nervous System. By Sir Charles Bell, F.R.S. fyc. 
Received February 24, — Read April 2, 1840. 
Twenty years have passed since the Society honoured me by printing my first 
paper on the functions of the nervous system. It is thirty years since I circulated a 
short essay, in which the idea of the new principle which has guided me in my inqui- 
ries into this subject was pointed out. The Society will acknowledge that since 
that time, investigations into the nervous system have been prosecuted with a success 
strongly in contrast with that attending the inquiries during the long period of some 
hundred years, in which a false hypothesis had satisfied the minds of the medical 
profession, and chained down physiologists in inactivity. 
In 1821 I had made so much progress in these investigations, that I was encouraged 
to present my first paper to the Society, as no longer the expression of mere opinions 
founded on experiments too delicate to be generally appreciated, but demonstrations 
of substantial facts, easily proved to be correct, and such as the Society has always 
sought to encourage. After the principle had been once established by anatomy 
and experiment, that the nerves possess distinct functions in correspondence with 
their origins from the brain and spinal marrow, time and opportunity were alone 
wanting for collecting the pathological facts which were to give importance to the 
observations in these early papers. Those facts I am now desirous of placing before 
the Society, to complete the subject as far as regards my own labours. 
First in regard to 
The Spinal Nerves. 
In the earliest part of my investigations I performed experiments on the roots of 
these nerves. I exposed the spinal marrow, separated the distinct roots, and found 
that the anterior root on being irritated excited motion, while the posterior root 
did not excite the muscles. By inference, and by comparing the spinal nerves with 
those of the encephalon, I was at length led to conclude that the anterior root is 
provided for motion, and the posterior for sensation; and that the spinal nerves, 
instead of being common nerves, are in truth combined of roots, one of which gives 
motion and the other sensation. 
Many instances have presented themselves in the prosecution of this subject, to 
6how that, until directed by a knowledge of function, we are inattentive to facts of 
daily occurrence. To take an example, since I had reason to conclude that the 
columns of the spinal marrow, and the roots arising from them, were distinct in func- 
