The Bessemer indicator., 1893-04-22
MAPPING THE BRAIN.
rb. xso~l.ats0 074s8 ., sh. Are.
cartsln Aotiona and SApsskiona,

The EpowlAdcS VA4516 u the Ares u
cartsin Notioas and Ssnsstions.
Az the mshAus and sensataous oi
the various yay6 ei the bsdy ere rep,
resented In the surface OF the train
as on q map, says the Popular Science
Monthly. Thus, there is a separate
brain urea necessary for sight. an
other for hearing, another for tho mo-
tions Of the fingers, and SO on. Each
OF these areas is called a center.
Four OF these are especially con
eerned in the use OF language, and
may therefore be called language.
oonters-tho auditory center, by
which excitss the vocal organ in
speaking; the visual center, by which
written words are seen and tho writ
ing center, which guides the motion
OF the hand in writing. These CEN
ters are capable Of individual davsl-
opment by practice, and in order that
each may receive its due share OF
cultivation it is necessary to know its
relative importance in the different
ways OF using language.
Disease instructs us on this point
by making some interesting though
ruthless experiments. Inflammation
or the growth of q tunor or the
rupture or plugging of a blood vessel
may destroy any of these centers, in
volving, of course, loss Of the cor
responding function. Consequently
the various defects in tho use OF
language are tho subjects of large
and very important chapter of the
treaties on brain disease. So far as
am aware no practical use has been
mado OF this knowledge outside the
domain of medicine.
Yot it would be very strange II,
from the ways in which the use Of
language is lost or suffers varying
degrees and kinds of impairment, we
could learn nothing as to how it may
best be acquired. The loss occasion
ed by the destruction of any language
center is an indication of the defect
that must result from neglecting to
cultivate the same center by practice
and, as disease selects now one and
now another for attack, we learn the
extent to which each is necessary in
hearing, speaking, reading, or writ
ing. The auditory center receives
the nervous impulses started by
sound.
When 1t is aroused by impulses
| coming from the ears the sensation OF
sound occurs, but when it is aroused
by nerve currents not from the ear,
but from other parts OF the brain, we
have only the memory of sound. For
q word to be understood tho auditory
| MI 10, fat1 la
| sound must awaken the memories OF
other sensations.
The word "orange," for instance,
has meaning, because the auditory
center, when the word is heard,
arouses in the visular center the
memory of the color and form of an
orange; in tho centers for touch, tenn
perature, posture and muscular sense
the memory of the sensations which
occur when the fruit is grasped by
the hand; in the centers for smell
and taste the memory of its peculiar
odor, flavor and tartness. These
sensations are said to be associated
with the sound OF the word, and to.
gether with it they form the concept
"orange."
The nerve currents passing from
one center to another are called asso.
citation impulses. If we have often
eaten oranges and at the same time
heard the name the auditory center,
whenever it perceives or remembers
the sound, will send vigorous i'm
pulses to the other centers, and the
idea will be vivid. But if our expert
ence of oranges has been very limited,
or If instead of tho correct name
merely some similar sound has been
heard, the association impulses will
be sent slowly, feebly, and uncer-
tainlY. SO that the idea will be yarun