e origin of
perceptions--as the essential organ of sensations; in a word, as the
common sensorium. This supposition has appeared so simple and natural
that its physical impossibility has been overlooked, an impossibility,
however, which should be sufficiently apparent. For how can a part
which cannot feel--a soft inactive substance like the brain--be the very
organ of perception and movement? How can this soft and perceptionless
part not only receive impressions, but preserve them for a length of
time, and transmit their undulatory movements (_en propage les
ebranlements_) throughout all the solid and feeling parts of the body?
It may perhaps be maintained with Descartes and M. de Peyronie that the
principle of sensation does not reside in the brain, but in the pineal
gland or in the _corpus callosum_; but a glance at the conformation of
the brain itself will suffice to show that these parts do not join on to
the nerves, but that they are entirely surrounded by those parts of the
brain which do not feel, and are so separated from the nerves that they
cannot receive any movement from them; whence it follows that this
second supposition is as groundless as the first."[96]

What, then, asks Buffon, _is_ the use of the brain? Man, the quadrupeds,
and birds all have larger brains, and at the same time more extended
perceptions, than fishes, insects, and those other living beings whose
brains are smaller in proportion. "When the brain is compressed, there
is suspension of all power of movement. If this part is not the source
of our powers of motion, why is it so necessary and so essential? Why,
again, does it seem so proportionate in each animal to the amount of
perceiving power which that animal possesses?

"I think I can answer this question in a satisfactory manner, difficult
though it seems; but in order that I may do so, I would ask the reader
to lend me his attention for a few moments while we regard the brain
simply _as brain_, and have no other idea concerning it than we can
derive from inspection and reflection. The brain, as well as the
_medulla oblongata_ and the spinal marrow, which are but prolongations
of the brain itself, is only a kind of hardly organized mucilage; we
find in it nothing but the extremities of small arteries, which run into
it in very great numbers, but which convey a white and nourishing lymph
instead of blood. When the parts of the brain are disunited by
maceration, these same small arteries