have been proposed for colour-blindness are very numerous, but some
are so defective that it is rare to detect a single colour-blind
person with them. I have, for instance, tested men whom I knew to be
colour-blind with certain lanterns with the result that not a single
one was detected. In these so-called tests all the requirements of
a test and facts of colour-blindness have been neglected. I must,
however, refer to three tests constructed by exceptionally able men,
each with considerable knowledge of the subject. I refer to the tests
of Professor Holmgren, Professor Stilling, and Professor Nagel.
All these tests can be passed at the first attempt without coaching by
certain dangerously colour-blind persons, chiefly varieties not known
to the inventors, but the chief defect of each is that it is very easy
to coach a colour-blind person to pass it. The surgeon to one of our
largest railway companies told me that when they used Holmgren’s test
they rejected one man in three hundred, but with my lantern twelve in
the same number. All these three tests are much better tests when the
persons to be examined have not seen them before. A colour-blind man
may make only one mistake, say for instance, as in a case I examined
the other day, with Nagel’s test (last edition), he passes the test
perfectly with the exception of one mistake, that of calling a grey on
one card, green. All he has to do is to look for some distinguishing
mark on this card in order to go through the test with the ease and
certainty of a normal-sighted person. It is the same with Stilling’s
letters, he has only to note the letter which he was not able to read
and the appearance of the card. A normal-sighted man or woman would
readily help him. The confusion of green and grey does not appeal
to the average man as a serious defect, especially when he sees his
friend go through the rest of the test perfectly. He says to himself,
“I suppose he sees a tinge of green in that grey.” The same man would
rightly regard it as a most iniquitous proceeding to endeavour to coach
his friend through a test when he had seen him mistake a red for a
green light.
Holmgren’s test rejects a large number of normal-sighted persons, as
may be seen by the reports of the Board of Trade; about 50 per cent
of those who appeal are found to be normal-sighted and to have been
rejected wrongly.
WILLIAM BRENDON AND SON, LTD.
PRINTERS, PLYMOUTH
Reiner and Keeler, L^{td.}
OPTICIANS
----AND----
INSTRUMENT MAKERS
_MANUFACTURERS OF_
The Edridge-Green Colour Perception Lantern
The Edridge-Green Classification Test
The Edridge-Green Pocket Test
and other
Optical and Scientific Instruments
THE ABOVE COLOUR TESTS ARE CERTIFIED BY PROF. F. W. EDRIDGE-GREEN
9 Vere Street,
Cavendish Square, =London, W.=
Telephone: 447 Mayfair.