Sacramento daily record-union. [volume] (Sacramento [Calif.]) 1875-1891, 1882-04-15
DICHRoMAToPIA,

Color blindness has been defined as
partial or total inability to appreciate,
as the normal eye does, one or more of the
three base colors-red, green and violet. :"
That there was such disease as color
blindness was first definitely made known
by Joseph Huddart, about one hundred
years ago. In 1894 Dalton, the English
chemist, who was red. blind, published an
analysis of his own case, and the disease
was then called Daltonism. The term is
now discarded. In 1887 Professor A. See
beck discovered that there were degrees of
color blindness 1t was not until after
1850 that any representatives of the medi.
cal profession began to make systematic
investigation into the causes and frequency
of this disease, and only within the last
few years has it begun to attract general
attention. Even now the dangers to trav-
elers by land and sea from this cause are
not well enough appreciated for legislative
bodies to pass laws protecting the public
from the incapacities of color blind en-
gineers and pilots. Statistics show that
one person in every twenty is sufficiently
color blind to make it extremely dangerous
for him to hold either of those positions, or
any other in which power OF discrimination
between colors is necessary. In France
the percentage of color. blind is nearly
twice as great as in this country, England
or Germany. Statistics are, however, not
yet accurate or general enough to be very
positive on this point, especially as differ
ent tests are employed. The colored-letter
test, which was the usual one some years
ago, has been generally discarded as made
quate, and the method of Professor Holm.
gren, of Upsala, Sweden, substituted. By
this method skein Of worsted of any color
is given to person to be examined and he
is asked to pick out from bunch of many.
colored skeins different shades of the same
color as the one he has. There are three
kinds of color. blindness. There are
the red blind, green-b blind and violet
blind. A very large proportion of
those afflicted are red blind, some are
green blind, and very few are violet.
blind. Some are blind as to two of the base
colors, generally red and green. There are
only few authentic cases of total color
blindness. To such everything in nature
appears black or white, or light or dark
gray in various degrees. To a red blind
red will appear yellow, green, brown or
black, according to the shade of red used
and the degree of his blindness. A bright
red will appear dark green, and an equally
bright green can be distinguished from it
only by being of a lighter shade. To the
color blind every change in intensity of
light, from twilight, fog, or from changed
physical condition, as by fatigue or excite
ment, represents a change in color, or
shades Of color Santonine, medicine
not very frequently used, temporarily
makes everything appear yellow, while
alcohol and tobacco used to excess perma.
nently impair the chromatic sense. To the
green. blind, whose only two concepts of
base colors are red and violet, green, being
composed of almost equal parts of those
colors, appears gray; reds appear brighter
than normal, orange and yellow as more or
less luminous red, blue as an intense
violet