Smyrna times., 1890-02-19
COLOR BLINDNESS.
HOW EYEsleHT is TESTED BY RAIL
ROAD PHYSICIANS.

Worsted and blackboard ExercIses-Four
Per Cent. Are Found to Be Unfit for the
Responsible Places.
"What color is that2"
The speaker was DR.. B. F. Clark, phv-
sician of the O., II. and D. railroad.
A tall, gangle legged man stood before
table on which were piled in 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
pNrple, gray, cherry and brown.
The doctor continued: "fhe 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 a little pile by them
selves
The man watched him closely. and the
greens were all thrown back into the
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 man began fumb-
ling over the pile.
The man put gray and light yellow
and brown together.
'That'l do" said the doctor.
"That man is not fit for an enoineer
fireman, brakeman, switchman. con.
ductor, or, in fact, any one who has use
for signals. Heis color-blind. That test
alone is sufficient for any railroad, armv
or navy.
HIS PECULIAR WEAKNESS.
NOW to determine what this mans
chromatic defect is we select a pink
skein.
eff he is red 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 red
skein, and the party selects browns or
greens in their different shades"
what percentage do you find, of all
those examined, to be color blindY'
About per cent. are color blind
That is one out Of every twenty-five in
dividuals. There are more red blind than
any other color"
1t is often asked why we don't ex-
anime the men by the lamps. It is one
of the most difficult things to stain the
glass regularly. When the glass is
blown it cannot be made all the same
color. Then, if the glass is thicker the
color will be darker. Again, sometimes
the wick is turned higher, and then the
light has greater luminosity, while the
other is very dull light There NAV he
dust or steam over the glass. and the
light will be darker. A dirty white flag |
to one color blind would be taken for a
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 congenitaI
defect?" 1'''''''
"Yes; but it may also arise from dis.
ease, 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 a nephew"
DO you examine for anything elseP"
"Oh, yes. 1t is just as important to
examine for vision and hearing as it is
for color blindness. In order to make the
test for vision this is the programme; A
test plate containing letters that can 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 twentieths-that is. the
letters representing twenty feet-he has
normal vision. Both eyes are put to this
test-first the right, then the left. If he
has a vision in both eyes of twenty
hftieths minus-that is to say, if he can't
see at twenty feet what he ought to see
at tifty-he is rejected, provided glasses
don't improve the vision. If a man can't
see that big B, the large letter, which he
ought to see at 200, at twenty feet with
only one eye, then he has practically onlv
one eye and there have been several ex.
amined who never knew that thev could
noe see out of only one eye."
TESTING FOR HEARING.
''How do you test for hearing?"
Il