The sun. [volume] (New York [N.Y.]) 1833-1916, 1898-03-06
BLIND AND DEAD SPOTS.
CURIOUS THINGS REFEALED IN Il
PsTCHOLOGICaL LABORATORY.

III may greatly 6uTDr1Sc many DBTSOnS 10 learn
that everybody has q blind spot in each oyc.
Not only this, but every person has n great mum.
Der Of blank or nerveless spots on tho skin In
which there is little or no sensation. These
facts have been developed by certain export
mcnts carried on in Cornell University. Tho
experimenting professors say that when you
look at n great painting or n play, or n news
paper, or anything that comes within the limits
Of ordinary vision, you do not see It all ut once.
There is n point directly opposite your indi.
vidual blind spot which Is invisible TO Won. II.
is SO in the best Of eyes. The lower animals arc
In the sam condition.
As to the blank spots on the skin. the profess
sors say that YOU could be touched with n hot
iron on ono of these places and not feel any pain.
Stranger still, these spots are scattered all over
tho body. They are small in size, but they arc
to be found on the hands. arms. face. chest.
legs and feet, and, in fact. everywhere on tho
human ,rono Tn orlor 20 erd tho,, 40 ona
human frame. IN oroor 70 ma mem out ana
IL possible mako n man of n mans blank skin
spots, tho professors in Cornell applied scaldipr
water to the subjects skin. In places the warm
water was TOO painful TO 30 borno; In others 1t
could not DO felt at all.
popularity. Through the habit of dlsregardins
in.,pnos of seeing, ing ,d foEF o, g ,1 1T Is the, there. ,v1 For Or
inStunCc, Wuch VIC iooh AT u Dlbilh WAL, We 10
not see a hole, as we would IL we were not used
, - a;.u.u.,a,,n 49,. ,,,.s -. WI. -,
10 o,sreRardihg our pinu SPOT. "hat would
otherwise remain blank is, so to speak, filled up.
Tie brain very kindly fills that space for Won by
tho oid ~ rour msn,orr Won 40 IN
nv I" y sou, n''y. u ale Il d .n'asure'
in the position of the amateur artist who
sketches in the opposite side of an object which
No Acc not = sin,n,r hooauaa ~ -" =. ~
no does not see' simply because he knows lis
there. In LOOKING at an OBJECT you know. by a
sort Of inherent experience. that it is all there;
viz y, pi'e VI :" WIN spo'' Sou Iuink you
sec 1t all.
Blind spots are caused by the optic nerve itself.
TL,o. ,,,;ot, it,, - ,,a..u a.. -. -,
inav Mni ~ I've w .ne esupa.i /, most VIA
principle mt this particular point detracts from
1t. Tho eve is merely a camera in which what
,ve ,o,k n, 10 nbotoyronhod nm tho -o,;na o,.ane
- "" .o'in" VI 'en'
sltlNe plate, at inc Dack. Now, the optic
nerve enters through the retina, and its very
ontranco carscs n hre,k IN tho snoath ~.
fccting surface of the retina. 1t is of a stringy
n maths S Thot rsS so-f e. Cnts string 1Eo is so BY no h means
Of what would be an irrcgularly shaped hole.
This is the blind spot. The nerve interferes
with perfect sight to the extent Of an irregularly
shaped spot IN the retina. This spot when en-
iarged through the very natural process of look
ing at a white wall a few feet away. appears,
OF ink about as large, as a quarter of II dollar.
The shape OF ne blind e spot IN different persons
In the laboratory of psychology in Cornell
College there Is a map OF the blind spot Of the
eyes or Prof: Tichener. II was procured in a
very, curious yet very simple manner. On a
blank sheet Of paper several feet square there
were drawn eighty merldians or lines, extending
sheet of paper represented an enlarged diagram
OF the retlna of The eye. The subject whose
straight ut the paper on the wall. A round piece
OF black, paper one inch in diameter was now
produced, and was moved very slowly up and
down the meridlans or curved lines on the wall.
and thus going from line to line. the
n nf hlnPE NTnG gu 81 / n hn II 4 ho tn naaGAI
over, every part of the design on the wall.
While it was being moved along one of the lines
noh. cannot see il, now"
Then rs II proceeded n little further on, he
His blind spot had been in focus. and he could
see nothing at the point where the black piece of
paper had apparently disappeared. Having locat.
moving the black piece OF paper in and out OF TO-
Gus and tracing the result as the work proceeded.
with irreEularly shape, tentatles dartine out
from II IN several directions. Any person could
f follow ing the the pam JAM os St'Grs d. MS OF her eyes by
hard to find. They exist all over the body.
substance comes in contact with the skin, you
instantly feel IT., because its bulk. in ninety.
many dead spots on the skin. but equally as
many sensitive spots. You are in the habit of
SSTieP Po pain Ii inds seeiy by aIh, heat al t or s sSlh Is sn s4s ,ba pr.
fore you imagine That every part of that touched
Is IN pam; Bnt II heal or cold can be con.
vcyed TO the skin through some delicate point
of contact. 1t will be found tn At in tho aggre-
gate some very extended patches OF skin are
vertically dead.
In Cornell University there is a diagram of an
ordinary mans thigh, on which are shown spaces
which are insensiblc to heat. cold, or pain. In
some places there are almost no sensations of
temperature. Against these places you might
almost lay.a hot iron, and.it would have but lit
tic effect. You might prick other spots with u
sharp needle, and unless you penetrated too
deeply, 1t would not be folt. Some. of the in;
strunnents are sharply pointed affairs, heated
with boiling water. They travel forward and
backward over the skin, touching every mi
mute part OF 1t in succession,, and reproducing,
by means OF a pqntagrapli'iikS instrument, as
tue sensations Of the subject indicate, a complete
diagram OF the dead spaces on his skin.
In line with these experiments on dead spaces
one of the biggest things Cornell has done has
been TO prove that We have not. after all. a
varied sense OF touch. That Is, II any part of
the body Is touched we do not become aware OF
II by any.sense or acute feeling in that part. but
by he mental. picture of the proceeding which
we instantly form. In other words. the sense
of touch in normal persons is entirely ..domi.
mated 10y, sight; suppose you are touched
while in the dark. how do you know where you
are tOuchedi Cornell professors assert, and