the metaphysical cobwebs of its long
incarceration.

FUNCTIONS OF THE NERVES

While studies of the brain were thus being inaugurated, the nervous
system, which is the channel of communication between the brain and the
outside world, was being interrogated with even more tangible results.
The inaugural discovery was made in 1811 by Dr. (afterwards Sir Charles)
Bell,(1) the famous English surgeon and experimental physiologist.
It consisted of the observation that the anterior roots of the spinal
nerves are given over to the function of conveying motor impulses from
the brain outward, whereas the posterior roots convey solely sensory
impulses to the brain from without. Hitherto it had been supposed that
all nerves have a similar function, and the peculiar distribution of the
spinal nerves had been an unsolved puzzle.

Bell's discovery was epochal; but its full significance was not
appreciated for a decade, nor, indeed, was its validity at first
admitted. In Paris, in particular, then the court of final appeal in
all matters scientific, the alleged discovery was looked at askance, or
quite ignored. But in 1823 the subject was taken up by the recognized
leader of French physiology--Francois Magendie--in the course of his
comprehensive experimental studies of the nervous system, and Bell's
conclusions were subjected to the most rigid experimental tests
and found altogether valid. Bell himself, meanwhile, had turned his
attention to the cranial nerves, and had proved that these also are
divisible into two sets--sensory and motor. Sometimes, indeed, the two
sets of filaments are combined into one nerve cord, but if traced to
their origin these are found to arise from different brain centres. Thus
it was clear that a hitherto unrecognized duality of function pertains
to the entire extra-cranial nervous system. Any impulse sent from the
periphery to the brain must be conveyed along a perfectly definite
channel; the response from the brain, sent out to the peripheral
muscles, must traverse an equally definite and altogether different
course. If either channel is interrupted--as by the section of its
particular nerve tract--the corresponding message is denied transmission
as effectually as an electric current is stopped by the section of the
transmitting wire.

Experimenters everywhere soon confirmed the observations of Bell and
Magendie, and, as always happens after a great discovery, a fresh
impulse was given to investigat