The Savannah morning news., 1904-05-15
WHY WE ARE RIGHT HANDED.
From the New York Sun.

From the New York Sun.
About "a per cent. of otherwise nor
NAL persons use the right hand in pref
erence to the left; per cent. are eth
er left handed or ambidextrous one
third of the per cent. are ambidex-
trous. Left-handedness is practical
ly an abnormality and is often assoc
ciated with defective moral sense. OF
hundred criminals, nineteen were left
handed, these including assassins, in
cendiaries and burglars. Highway
men, however, presented the normal
proportion. The largest proportion of
left-handedness was in incendiaries-
2S.5 per cent. According to these fig
ures, 6S.4 per cent of the left handed
are not to be classed as criminals.
The normal man not only is right
handed, but he uses the right leg and
the right eye in preference to the left.
The reverse is true of the left handed.
AS the action of nerves going to and
coming from the cerebrum is crossed,
right-handedness points to predomi-
nance of the left half of the brain;
but it has been shown that the left
brain exceeds the right in weight only
by about one-eighth of an ounce. Why
the le1l DTdlIl mas HOI
been satisfactorily explained by anato-
mists; but it has been noted that the
brain is more complex on the left side
in the right handed and on the right
side in the left handed. The only pos
sible explanation of the greater weight
of the left side of the brain is in the
fact that the arteries going to the left
side usually are larger than those on
the right. There are no observations
in regard to the comparative size of
the arteries on the two sides in left
handed persons.
Generally it is true that the MEM
bers of the right side are stronger than
the left, particularly the arm; but this
is not always the case, even in the.
right handed, although the right hand
is more conveniently and easily used
than the left. In many feats of
strength, the left arm appears less
powerful than the right because there
is less command over the muscles.
While it is not yet possible to ex-
plain why the left side of the brain
sessed by the right side, it is never
theless true that intellectual processes
take their origin mainly-and in some
instances entirely-from the left half
of the cerlebrum. In man, sight, hear
ing and speech are closely connected
with mental operations, at least in so
far as they give rise to or express ideas.
The two eyes are necessary to perfect
vision; but the psychic visual center,
which receives ideas or meaning con-
veyed by objects seen, is on the left
side, except in the left handed The
same may be said of the sense of hear
ing, the psychic auditory center be-
ing on the left side, except in the
left handed. The location of the
speech center was made in 1885, by
Marc OAK; and "a case of aphasia Qoss
of the power to express ideas in lam
guage) was infinitely described by
Pourfour du Petit in 1866. Agraphia,
or inability to express ideas in writ
ten language. like apffasia, is due to
injury of the left side of the brain.
All these conditions are reversed, how
ever, in the left handed. When one
eye Is used as a means of forming
judgment or opinion, is usually the
right eye for the right handed and the
left eye for the left handed.
Curiously enough, it has lately been
observed that deaf mutes may have an
aphasia that prevents the use of the
right hand in the sign language. 1t
seems, indeed, that movements, more
or less automatic, may be executed by
the muscles of either side-remember-
ing always that muscles of the left as
"NAA 90 VI thS Ai5hI oluc may ne eQu-
Gated; but in movements that involve
mental operations and attention at the
time they are made the right side
usually predominates.
Apart from the question of education
of muscles, it appears that the more
automatic acts are performed indif-
ferently by either the right or the left
side; but movements more closely con-
nected with direct mental operations
are made preferably by right muscles
in the right handed and by left mus
Giles in the left handed. Still, while
this may satisfactorily explain dex
trail pre-eminence, it does not explain.
the pre-eminence of the left side of the
brain, Austin ErIint