The Charleston daily news. [volume] (Charleston, S.C.) 1865-1873, 1870-08-18
RIeHr AyD LEFT HANDEDNEss.
An Interesting Explanation.

l In the July number OF DR.. Hammonds Jour
4 nal of Psychological Medicine there is an able
article on fright and Left Handedness," by
DR.. Thomas Dwight, Jr., OF Brooklyn, from
which We quote.
The right half of the body is usually more
developed and more used than the left, and
this has been the case at all times and in all
races, as is shown by words in ancient and
modern languages.
Hyrthaccounts for this by the anatomical ar
rangemeAt OF the arteries from the arch Of the
aorta.
| "The greater development Of the right tsu-
per;or) extremity and its consequent greater
usefulness depend upon purely anatomical
relations, to wit, the order In which the great
| arteries arise from the arch ca the aorta. The
| right subclavian arises nearer the heart than
| the left, and is, therefore. more exposed to
all its branches must have a greater capacity
than the left, because the blood circulates in
them under a greater pressure. More blood
in them is the same as more material for nu-
triton, and hence more interchange OF matter
and stronger development. But there occurs
the arch in which the right suoclavian Is
given off after the LETT. This IS not
very rare. I should say it occurs twice in
one hundred cases. This is shown oy
the average obtained from the oDserva-
tions Of several years In the dissectng,roon,'
tions on the frequency OF left-handedness. II
the right subclavian arises after the left. we
| have. In regard to pressure, the reverse OF
what occurs in the normal arrangement. Inc
| left extremity will be stronger, anu conSe-
quently used in preference to tne rlgnI;. my
| friend, DR.. 0ehl, Of Pavia, has communlca!etu
| to me TWO cases of left-handedness IN wnlcn
| the anatomical examination showed that the
| right subcarian arose later than the lett. Two
| other cases which have observed IN the past
| wear, place beyond all doubt the original anu
| necessary relation OF anomaly OF vessels 10
lefthandedness. we received su9ec1 ~ 1sans ,,ie
| anatomical department with complete trans,
position Of all the viscera. All that should
| have been right was left, and rice rsrsa. The
| left arm did not appear stronger man tne
right land, indeed, the right does NOT always
snrpass the left but it could. be infer
red, from the thickened and horny eAdermis
on the palm Of the LETT hand ana ,ta Ir9 ams 1eH
that the individual had been left-handed. AT
| almost the same time learned that man,
| locksmith by trade, then under treatment at
Prof. Oppolzers clinic. had a complete trans,
position of the viscera. On being. asked
whether he worked better and by preference
1 Win ln6 lSlL uhuu, uO QuSNSASuf ~ .A'"
nected. that up to his fifteenth year he had
| done everything with the left hand. till his
| master. by scolding and punishment, had
compelled him TO use the right; but that when
ever he wished his work to 60 oriSkly tne leit
| hand was the more useful. Thus the anatoml-
ccl cause OF left-handedness Is no longer
| riddle"
The most obvious defect Of this theory is,
that it accounts only for the arm. The author
| appears to forget that it is not only the right
arm that is used more than its fellow, but also
the right leg, the right eye, and perhaps the
right ear. 4 boy will hop longer on the right
| foot than on the left, and will look through an
optical instrument with the right eye. The
abdominal aorta divides into the lilaes very
little to the LETT OF the med:an line. so that any
| difference in the supply OF blood for the legs
| would be in favor of the left. Again, as the
right half of the brain is to the lett, In regard
to arterial distribution, precisely as the right
arm is to its fellow, it should be the more de-
| veloped, which Is not the case.
Another and more philosophical theory
| first enunciated, l believe, by Trousseau,
makes the greater proficiency OF the right side
depend on the greater development Of the lett
! half of the brain. This is due to the fact that,
when fluid passes suddenly from a tube Of
large to one OF small calibre, its velocity is in
creased. The right carotid Is separated from
| the aorta by the innominata, so that the blood
| flows through q channel Of gradually decreas-
| ing size, but the left carotid rises directly
from the arch, and has therefore swiiter cur
rent.
The next theory is that Of those who hold
| that it is entirely matter OF education; that
| we use our right hands because as children we
were taught to do 30, and that the right hand
| is as awkward as the left when one tries to do
| the work of the other. Undoubtedly dexterity
in the use of either hand is the result OF prac-
tice; but in the infant that is to become right
handed man there is an Impulse to use the
right hand by preference. 1t does not depend
on education, for it is not very uncommon to
see child belonging to right-handed family
become most perversely left-handed, although
| Its earliest motions had been watched with the
same care that had been bestowed on t..ose OF
| the other children. Besides, it is incredible
| that all the races of men, differing as they do
| in habits and customs, should unite in preferr-
ing the right hand, were there not some in
born impulse TO do so.
Mr. MoXon holds that as we have but one
attention for two sides, 1t is devoted chiefly to
| one, namely, the right, that in associated
movements the left side follows the other, and
| that, tLcngh either side can acf independently.
it can do so Ill perfection only when the other Is
at rest This, though probably true, does not
touch the whole subject, for We are right and
left-handed in sensation as we'll as in motion,
and, very curiously, while the sense OF touch
is most developed on the right side, that Of
temperature and that Of weight (Which last is
nearly allied to the muscular sense) are more
acute on the LETT In O left-handed person
whom lately examined, this was reversed,
the tac;ile sensation being greatest on the ie!t,
and that of temperature on the right; Tne
perception OF weight was not tested. IL Ger
tainly Is not proved that the difference IN the
perception Of the various kinds Of sensation
| is not due to the receptive and conductive al-
paratus of the two sides of the body, but it
| appears more in accordance with analogy to
place 1t in the brain. This being admitted, the
following propositions may be advanced:
l. There is an inborn impulse to use, to eX-
cite motion, one half of the brain (the left in
preference to the other.
2. One-half of the brain (the le1t) has a more
acute perception of tactile perfectiOns, while
the other 1.-THE right distinguishes more readi,
ly different degrees OF temperature and
weight.
3. This arrangement is occasionally inverted
There is no doubt that this inclination u use
one side more than the other is far greater in
man than in the lower animals; in fact, have
never been able to observe any trace of it in
them, but would not deny, however, the pos