, 1885-05-31
y %RLINDNEss.
Red and Green most Bother those VIII
Vision is Imperfect.

From n Paper by Dr, George s. Munson.
The most frequent defect in color bind
ness is the inability to distinguish red. A
distinguished professor in an English uni
versity wore n scarlet gown in the streets,
much to the amusement ofmany who saw
him. On being asked by a friend what
appeared to him TO be the color of the
robe, he answered, pointing 10 some ever
greens near by, st seems to me to resem-
bic those as closely as possible. The
next color most frequently mistaken for
some other is green. The importance of
this defect is estimated by the frequency
Gifts occurrence. If 1t occurs only once in
10000 it is of course of less importance
than if happening once in a hundred.
Men ARE more frequently affected with
this defect in vision than women. The
defect, when it is congenital. as it is in
most Of the cases under the observation of
physicians. is incurable. 1t is sometimes
produced by the immoderate use of tobac-
co or liquor. AS many as one in twenty five
of the men employed on lines of travel
are affected by this inability to distinguish
red from green. The color blind in cases
Of accident on land and sea cannot be
readily detected because of the difficulty
of tracing the causes of the accident.
One thus affected cannot tell a red from a
green light, but one of these lights appears
darker or less bright to him than the
other.
The test of color blindness is not how
well one can name colors, but how much
he sees them. If two letters be drawn,
n red and the other green, on a back
ground, a person who ia red blind will
distinguish only the green letter, and a
person who is green blind, would fail to
distinguish or see the green letter. In
other words, to the first the red color is
suppressed, and to the second the green.
The red blind will place a purple or a
green alongside a rose color, supposing
them all to be the same shade. The
green blind will confound the blue and
the gray with the rose color. The test
for an engineer Is not to name colors or
shades of color, but to know red as red,
and green as green, and to match red with
rcd and green with green of their various
shades. four per cent Of the $4,000 m
ployes Of the Pennsylvania, have been
found to be totally color blind, and ten per
cent more or less affected with this defect
of vision. five per cent of the same were
found with imperfect hearing. In this
city there lives a well-known animal pain
ter who is entirely color blind. He selects
his color not by knowing the color itself,
but by reading their names on the tubes.
He employees usually. only black, brown
and white in his work.
DR.. Jeffries, of Philadelphia, instituted
a very efficient test Of color blindness by
suspending numbered skeins of worsted Of
different colors from a rod. The STAN
dard colors Of rose, red. and green, with
all the various shades of these colors we're
numbered with the odd numbers. All
other colors were numbered with even
numbers. The persons examined for col
or blindness were invited to match shades
of the three named before as the standard
and II any so named we're among those
numbered with the even numbers, it was
seen at once that they were unable to dis
tinguish COLOR.