, 1870-08-07
RIGNT AND LEFT-HAl1DEDEEss.

An Interesting Explanation.
III the Jnlr number Of DR.. Ilanarnond's
journal of Psychological Medicine there IL at
able article on ''lsight and Lcft-1fandeduess,"
w Dr.. Thomas Dwight, Jz.. OF brooklyn, tEozn
THE right half Of tho body ii usually mcrs
! developed and more used than tho left, Aul
tlils has been the case at al times and in all
races, as is sllown Ly words IN ancient aud
modern languages.
"uyrtl aeconuta for this br the anatomical
| arrangement Of the a.ter.cs from the arch Of
| the aartA:
1.-THE greater development of tho righ.
| tsurcror) extremity and it's consequent gtcat-
relations, to Wit. the order in which the great
| attcries arise from the arch OF the aorts. Tie
| right eubciarian arises nearer the heart t1sa
the left. and il, therefore. more cxpo=cl to
the sSstclic force. The right snbclAyian aud
| all us branches must hate q greater capacitr
them under greater pressure. Mora blood in
| them Is the came As more material for nutri-
ton. and hence more interchange Of matter
and stronger Development But there occusa
All anomaly in the onEiu OF the vessels from
! tie arch in which the eubclaviau is given otr
| after the left. This is not very rare. 1ahould
say it occnra twice In one hundred cases. This
is elown By tho average obtained from the OBJ
| ser,Atiors Of several Years IN the dseactnE-
room, and sgree- tole1ably with Malyaignos
observations on tho frequency Of lef4-h4,ldel-
ners. II the right snbc!ayiatl arises after tic
Left. we have in regard 10 rressure. the 1e-
vrrsc of!whas occnrs in the normal arrlnSe-
| nvnt. The left extremity will be stronger, and
consequently used in preference 10 the night.
| Aix friend 1r. Oehl. Of ravia. has cornmrni-
Gated to me two cases Of left-h1ndedncss in
which the anatomical examination showed that
the right sutclavian arose later than thu laft.
Two other cares, which hive observed In tho
past yc.r. place beyond hll doubt tho otISinA
aid necessary relation Of anomaly Of vessels
to lcft-haudeaness Nc received sutject st
tranarositiou of al the yissc1a-. Al that
should bavc been right was left, and cice ccrs..
The left arm did not appear stronger than tho
n6tt (aud, indeed, tho right docs not alwsyB
turpass the Left, but il could DO inferred,
from the tliekcncd and horny epideEais on the
palua OF the left hand aud tzo!3 Thick callns
ou tho EypothcEar Of the little finger, TINT the
individual 1lad heco !cft-hanacd. Al almost
the eatne tiule I learned that a 1uan. lock-
| smith by trade. then under trcatncnt ut pTof.
OF the visceza. On being asked whethaz he
wctkcd better md ts preference with tbs left
hand, he answered, as hal expected, 18th at
up TO his fifteenth year be had donc every.
thing with the left hand, til his master. bs
| scclding and punishment. had compelled hia
to uac the right but, inst whenever he uisled
| bis work to Go bsiskls the left hand Was the
] nero useful. Thus the anatomical cause oi
I 1eft-hsndednessi Is no longer ridlle-
''Ihc mott Obvious defst Of this theory ie
| that it accounts only for tho arm Tbs autho'
aEpear= to forget th.es II il not ouly the EiSh
arm that is used mare than its fellow, bat also
the right leg. the night eye. and perhaps tht
1 night esr- 4 boy viii hop longer OIL the riGh
foot than on tho left. and VIII look though II
optical inssrument with the right eye. Tht
! | little to tho left OF tho nedisn limo. so thai
! any difference in the supply OF b.ood for ths
legs would be in fasor Of the left ASsn, =.
tic right half Of tho braiu is to the left, in re
! 1 ga1d to a1tcrial distribution, precisely as TIL
j right arm Is to its fellow, it should be th,
] \ more developed, which Is not the case.
E "4Anotber ard = more philosophical theory
frt enuncistcd. believe, by Troussc,u
makce the greater proficiency Of the right I'D
. depend on the G1eatcr Development Of the Jet
that. when fluid passes suddenly from tub
: Of large to one OF small csllhze, it's velocity
:. | increased. The right carotid is scps17te'
!. fscm the acztA By the snonaiuata, 20 thst h
!. tlocd flows through a channel Of gr7duall
Il decreasing zc, but the LETT c:fatid nses ii
o | 1tetiv from the arch, And haa therefore
= t.Ibe next theory is that OF those who hol
= TINT it is entirely matter OF education; thu
4 I We uee our ticht har1ds becauee ~ children y
e. snd tn. @ 1aaa =, sa y
!, work OF the ether. Cudoubtedlv dc1teElte !
i The use Of either hand is the result Of pm.
!. lice, but in the infant that is 10 become
risbt-handed man, there is m impulse to y
!. tie right hand by preferences, It does not d.
y rcna On EDUCATION, for It Is not very uncon
- mon 10 eee chlld belonging to = neht.handt
Z family become most pe7erse'y lett-hAnde
- although i,s earliest motions hai bet
y. watrhed With tho saue care that hai bet
70 .e bestowed On thoee OF the other ehitdre
:, Besides. il is Incredible that ~ The races
81 81 mep. dGering .s they do in habits and g
~ toms. should unite in FrefcsTnG the r1g
a. ~ hand, were there not some inbosn napa'se
"a ! co 10. ...
RI ..Mr. Mo1ou holds thai, IL ve have eus o
, i attention for two sideB, il is devoted chlens
~ one, namely. tho right; that IN aaso1a. s
nv movements tho left side follows sae o.ne
I and that, though either side c1n act 'ne
Al, | rendcntly, il can do 60 III perteenon M o.
ny when the other IL At rest This thou
I'D probably true, does not touch the Hho!e 81 st
In 5sct, for We a1s right and 1ett.handed N q
ration - well - in motion, and, Tef{ eu1so'
Fas ", while the sense ot tonnh Ia most deselop
J IL On Tho right sids, th,t Of tempe
no ,uze and that Of weight (Which
but Ii nearly Llied TO tbs muscnlAr sen
ATS arc more Acute on the loft. Ia Il
Fss hsn5ed peEsou whom 1ase!J -ezanined