, 1879-06-01
COLOR-BLINDNESS.

Why Passengers upon Railroads Are I'm
periled.
Cnester (n1.) CprTesDond~nce Philadelphia Times.
At to-day's session Of the Pennsylvania State
Medical Society paper was read oY Dr.. D. T.
KeYser, Surgeon Of the Willis Eye HosDital.
His subject was color blindness. In order to
ascertain just to what extent cofor-blfndress
exists in Philadelphia and among train-men on
various railroads, Dr.. Keyscr addressed letter,
in July last, to railroad Presidents, asking an
opportunity to examine their train employees:
The permission was given, and Dr. keyser set
about the work, continuing it for eight months.
He said that he had examined the train-hands
of the Philadelphia, Wilmington Il Baltimore,
the Delaware, the North Pennsylvania, and the
Bound Brook Railroads, and had found 81 per
cent of the whole number who mistook colors
one for the other, and 859 per cent who, al
though able to distinguish the colors, were un-
able to tell the shades. Those who mistook
colors had defects OF such character as to
make them really incapable and unsafe to fill
the positions they occupied. In the examina-
ton several methods were used. The method
Of P1ot: H4ansren, Of Sweden, in testing xith
that OF DR.. Stilling, In which colored letters on
a black card are displayed, after which plates Of
colored glass are held in front Of gas-dame In
a darkencd room. Finally, the different signal
lamps used on the roads we're brought before the
men in various ways. The examinations were
at first made in the evening BY gaslight and
those found defective in the least were ;re-e1-
amined very carefully in daylight The refrae-
ton Of the eyes was carefully examined with
ined 70 per cent were found Of perfect vision
and q per cent defective. OF the color blind
II per cent we're Of perfect vision and 56 per
cent defective. Of those who only shaded bad
II u were Of perfect vision and % per cent de-
ective.
1T will thus be seem" the Doctor continued
!" that color blindness is not governed bY any
defect of refraction. Neither has age anything
to do with this anomaly. for those found de-
fectire in the least range from 20 to IS
per cent were green blind, II red, aud
6 blue. Of the 81 per cent defective
in shading 95 Der cent were so In greens and
per cent in red I have no doubt that the
cause Of these being so defective in shading
colors is due to the want Of education. None
had ever been placed in position Or condition
to have examined colors.
The Doctors attention was attracted to two
pccu1iaritics among those found color-blind.
One was the fact that two men, who could not
Gated themselves to know that red was an in-
tense color, and thus distinguished bright red
signals, but at the same time bright greens and
other bright colors we're red to them, and tor
such they said they would stop the
But green they called a. deep or dull
color, and dark reds, dark greens, and
browns were all green TO them, and they would
pass them by as signifyfng that all WIS right
The other peculiarty was the power Of dstin-
gushing bright red when held within three feet
OF the eyes, while at ten, twenty, and thirty feet
it was invariably called green. In sorting the
woods bright reds and light greens we're picked
out together for red.
Last winter, DR.. Keyser, with the assistance
Of Drs. Thomas H. Fenton and Frank Fisher,
examined the boys Of the Keystone Grammar
School, 176 in number, Of whom eighteen were
defective; none, however, were really color
said that all the dark shades OF yellow we're
brown; with eight others purples were blue;
two said that dark green was brown; one took
light browns for red, and the rest shaded badly