The Dickinson press., 1889-12-21
COLOR BLINDNESS.
HOW EYEsIGHT is TESTED BY RAIL-
ROAD PHYSICIANS.

Applicants for Positions Put Through the
Worsted and Blackboard Exercises-Four
Per Cent. Arc Found to BE Unfit for the
Responsible Places.
"What color is that%
The speaker was DR.. B. T. Clark, ply
sician of the c., II. and D. railroad.
A tall, gangle legged man stood before
a table on which, were piled il great
confusion several hundred skeins of diff
ferent colored worsteds. They were of
every shade and hue, from pea green to
Mazarin blue, from solferino red to
purple, gray, cherry and brown.
The doctor continued: "The object of
this test is to select the light and dark
shades. Now, I'll go on and select them
first" and the doctor put all the light
and dark shades running from pea green
to dark green in n little pile by them
selves.
The man watched him closely, and the
greens were all thrown back into tho
heap, and the man began.
Don't let your hand run over the
worsted, but let your eye do the work."
said the doctor, as the mar began fumb-
ling over the pile.
The man put gray and light yellow
and brown together.
''Thatn do" said the doctor.
"That man is not fit for an engineer,
fireman, brakeman, switchman, con-
ductor, or, in fact, any on who has use
for signals. He :, culor-blind. test
alone 10 eu1Irclcnt for any railroad, army
or navy.
HIS PECULIAR WEAKNESS.
Nov to determine what this mans
chromatic defect is we select n pink
skein.
"If lie is rcd blind he will pick out blues
or %violets, or both. If he should be green
blind he will select grays and greens or
blue greens. Sometimes, to verify the
two previous tests, we lay out the rcd
skein, and the party selects browns or
greens i'll their different shades"
What percentage do you find, of all
these examined, TO be color hlind?'
"About i per cent. are color blind.
That is one ont of every twenty-five in
dividuaIs. There are more red blind than
any other color"
at is often asked why we don't OK
anime the men by the lamps. 1t is one
of the most difficult things to stain the
glass regularly. When the glass is
blown it annot be made all the same
colon. Then, if the glass is thicker the
color will be darker. Again, sometimes
the wick is turned higher, and then the
light has a greater luminosity, while the
other is Il very dull light. There may be
dust or steam over the glass, and the
light will he darker. y dirty white flag
to one color blind would be taken for n
green flag, which means safety. They
would take a dirty dark green for red,
which means danger. This would lead
to endless confusion"
"Do you believe this to be a congenital
defect"
YES; but it may also arise from dis.
ease, il INJURIES and the excessive use of
tobacco and alcohol. In one family |
know of four who are color blind, two
brothers and two sisters; in another
family an uncle and Il nephew"
do you examine for anything clsc?"
"Oh, yes. 1t is just as important to
examine for vision and hearing as it is
for color blindness. In order to makethe
test for vision this is the programme: A
test plate containing letters that car be
seen at 200 feet and twenty feet, twenty
feet being the normal eye, is placed at
one end of the room.
The room is darkened. The patient
placed twenty feet distant, and then is
requested to cover one eye while the
other is being examined. If he sees what
we call twenty twenticths-tbat is, the
letters representing twenty fcct-hc has
normal vision. Both eyes are put to this
test-first the right, then the left. If lie
has 4 vision in both eyes of twenty
fiftieths minus-that is to say, if he can't
see at twenty feet what he ought to see
at ffty-hc is rejected, provided glasses
don't improve the vision. If a man can't
sec that big b., the large letter, which he
ought to see at 200, at twenty feet with
only one eye, then he has practically oniv
IL eye, and there have been several eX-
amincd who never knew That they could
not see out of only one eye"
TESTING o HEARING.
"How do you test for hearing:%
"With my watch. The man is reuuir-
ed to cover up his eyes and 1 place my
watch to his ear, gradually removing it
away until the exact distance that he
can hear the ticking is known. He saws
No when he ceases to hear it. Now,
two-tilirds of all the engineers arc hard
of hearing, or, better, defective in the
right ear, which is due to their leaning
out of the cab window, coming in con-
slant contact with the wind; that is to
say, the force of the wind cominginc con-
slant contact with the drum Of the car it
becomes affected. The constant pressure
ola the drum Of the ear has the effect of
retracting it. 1t becomes concavc. The
range OF vision is also tested. This is
done by placing Il man twelve or eight
cen inches from q blackboard. lie is re.
quested to keep his eye directly on a
chalk spot, which is on a level with the
eye, the other eye being closed. lie is
directed TO say Yes the moment he secs
anything moving toward that spot from
above, below, to the right and to the left.
This constitutes his range of vision. If
he has any disease or injury to the eve
we can always map out his range of Wis
ion, as the range is usually contracted i'll
II of the four different directions. To
illustrate, one man had a range of vision
in the right eye, three inches to the left,
six inches above, eight inches to the
right and ten inches below. OF course
he was rejected, because he could not
see an approaching train.-Cincinnati
Enquirer.