St. Paul daily globe. [volume] (Saint Paul, Minn.) 1884-1896, 1885-07-12
COLOR BLINDNESS.
Red and Green Most Bother Those
Whose Vision is Imperfect.

The most frequent defect in color blind
ness is the inability to distinguish red. a
distinguished professor in an English uni
versity once wore 4 scarlet gown through
the streets. much to the amusement of
many who saw him. On being asked by
friend what appeared to him to be the color
of his robe. be answered. pointing to some
evergreens near by: at seems TO NE TO re-
Semb.e those rs closely as possible" The
next color most frequently mistaken for
some other is green. The importance of
this defect Is estimated by the frequency
Of its occurrence. If it occurs only once in
ten thousand persons, it is of course of less
importance than if happening once in
one hundred. Men are more frequently
affected with this defect in vision than wO-
men. The defect when il Is cOngenital.
rs it is i'm most of the cases under the OBJ
servatiOn of physicians, is durable. 1t is
sometimes induced by immOdeTate use of
tobacco 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 case of accident by travel on land
and sea cannot readily be detected be-
cause of the difficulty Of tracing the cause
of the accident. One thus affected cannot
tell red from a green light. but one of
these lights appears darker or less bright
TO him than the other.
The test of the eolOr-blindneSs is not how
well one can name colorS. but how much
he sees them. If two letters be drawn,
one red and another green. on n back
ground. a person who is red blind will dis
tinguish only the green letter, and 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 purple or a green alongside of i
rose color. supposing them all to be the
same shade. The green blind will con-
found the blue and the gray with the rose
color. The test for an engineer is not to
name colOrS and shades of color, but to
know red as red. and green as green and TO
match red with red and green with green
of their various shades. -Four per cent of
the so, 200 employees of the Pennsylvania
have been found totally color blind
and 10 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 lives a well-known animal
painter who is entirely color blind. He
selects his color not by knowing the color
itself, but by reading their names on the
tubes. He employs only black, brown and
white in his work.
DR.. Jeffries of Philadelphia instituted q
very efficient test of color blindness by sus-
| pending numbered skeins of worSted of
different colors from rod. The standard
cOlOrs of rose, red. and green. with all the
various shades of these colors. were num-
bered with the odd numbers. All other
colors were numbered with even numbers
The persons examined for color blindness
We're invited to match shades of the three
named before as the standard, and if any
so named were among those numbered with
the even numbers it was seen at once that
they were unable to distinguish colors.