The Hazlehurst signal., 1883-12-27

III on looking NJ thcsc ua>hes Win one
eye the reader discovers that the per-
pcndicular dashcs are blackcr than the
horizontal. or vice versa. he needs u
cylindrical glass for that eye. set mt IN
angle to be- determined by seeing which
dash in the wheel j. the blacklist. This
d feet is called astigma,ism, and is be-
in. discovered To be- quite common.
The most valuable instrument to the
oculiSt was discovered by man who
was not an oculist. There was con-
s'dcr;. BILE discussion among the scien-
lists of Germany rs 10 the cause of the
red light emanating from the eyes of
animals and men in dark room. One
man discovered that the ligh, was only
visible when directly on level with
and in front of the eye.
ielmholz took small concayc mir
ror and scratched the silyering of the
back so rs To make little pccp-hole In
Il. 4 beam Of light was allowed on the
mirror and reflected back into the sub
icct's eve. and Helinhok could look
through the little pccp-ho'c and see the
interior of the eye. lie thus found out
that the light was reflected from the
rel surface of the retina of tho eye.
but he also discovered an instrument
without which oculists would be very
much handicapped. n young man,
named Ned Loring. has invented very
valuable adjunct To the opthalmascopc.
by which little lenses of various powers
and kinds are moved over the little hole
in the back of the mirror so that the
operator can see what glasses are need
cl by the owner Of the eye. When the
eve is incorrect the retina appears of
dull red, which becomes distinct when
the right glass is used. An ivory indi-
dicator shows the number of the glass
used by the operator. Various diseases
can bc detected by the appearance of
the rctina OF the eve. Affections OF tho
Kidneys. tumors and hcmorrhagos of
the brain can be- told from the color OF
the rctina.
In nearly the center of the retina is
round spot of lighter color than the
rest. This is where the nerve enters
the eve. and is supposed To be what is
called "the blind spot" This peculiar
spot can be detected by the following
figures:
Close the left eve. hold the newspaper
OIL ut arms length and look steadily ut
the round dot. Bring the paper nearer,
and when few inches from the eye tho
dagger will disappear. The rays of
light coming from il fall upon the blind
spot. and are not perceived.
r.l.,. l., q. I.Enet that 4.
quite common, although those afflicted
with il may 90 years without discover
ing il. Strange aS il may seem. red
and green. the colors most easily de.
tcctcd by the normal eve, are very fire.
qurntly conioundcd. Many people in
this city are unable to tell the ripe cher
ricS on "a tree from the leaves except by
the shape and size. Colors are told by
these people more by the intensity ot
the light than from the hue. Yellow IL
/ color that no one seems unable 10
perceive. although red is sometimes
called yellow by the color-blind. Saw
/ ages perceive only the more vivid col
ors. and the percentage of color-blind'
ness among the colored children is far
/ greater than among the white. There
I is no known remedy for color-blindncss,
nor is there known cause. Dalton,
who first discovered the defect and was
himself thus afflicted, supposed it to be
due to colorcd liquid in the eye. but
dissection after death failed 10 support
! his hypothesis. rs his ewes were appar-
emily perfect. There was deficiency
in the brain directly over and between
the eyes, which all the color-bind have.
Artists. whose perception OF color Is cx-
traordinary, have unusually prominent
foreheads at that point.-CercIand Her.
/ aid.