TIIE HUNTERIAN ORATION. 
159 
theory of the nervous system. Having called attention to the 
prevailing doctrines of the anatomical schools — that the mind, by 
the same nerves which receive sensation, sends out the mandates 
of the will to the moving powers — he proceeds to announce his 
own opinion, that the parts of the cerebrum have different func- 
tions, and that the nerves which we trace in the body are not 
single nerves possessing various powers, but bundles of different 
nerves, whose filaments are united for the convenience of distribu- 
tion, but which are as distinct in office as they are in origin from 
the brain. Pointing to the fact of the medulla spinalis having a 
central division, and a distinction into anterior and posterior fas- 
ciculi, he relates how he was thereby led to make experiments, of 
which he describes the results, upon the anterior and posterior 
columns of the spinal marrow, and upon the anterior and posterior 
roots of the spinal nerves, and how he thereupon came to the 
conclusion that every nerve possessing a double function obtains 
this by having a double root. 
“ Adhering to the important principle thus laid down, Bell 
next directed his inquiries to the facial nerves, and, aided by his 
indefatigable pupil and coadjutor, Mr. John Shaw, instituted ex- 
periments to assist him in determining their functions, more espe- 
cially that of the portio dura of the seventh pair, and those of the 
fifth. Happily he did so ; for, without the fortunate circumstance 
that in certain parts of the body, especially on the face, the nerves 
of sensation and motion are distinct throughout their whole course, 
his great discovery could never have been clearly established. 
“ It was about this time, when he was making the most im- 
portant advances in obtaining positive and undeniable proofs of 
the truth of his doctrines, that we find him, under an impulse 
like that exhibited in 1807, addressing his brother in Edinburgh 
in a letter, bearing the date of the 17th of August, 1819, to the 
following effect: — 
“ ‘ When you left us, I told you that I was to sit down to 
my notes of the nervous system. Believe me, this is quite an 
extraordinary business. I think the observations I have been able 
to make, furnish the materials of a grand system which is to re- 
volutionize all we know of this part of anatomy, more than the 
discovery of the circulation of the^blood. I have a good deal still 
to do. How I am to bring it forward I do not know. I think 
by lectures in the first place, then by a little essay explaining the 
outline of a new system, and, finally, by magnificent drawings 
and engravings of the whole nervous system. In the meantime, 
I am making gigantic drawings of the nervous system for my 
class/ 
“The gigantic drawings for his class to which he alludes, were 
