Bepoi-t of the Committee on Colour- Vision. 



381 



perhaps already tested, and practised themselves in preparation 

 for the trial ; others have never been familiar with colours. 

 Among' those already tested some may be colour-blind. Some 

 of these latter are uncertain about their mistakes, and act with 

 great care ; whilst others again, having been practised in dis- 

 tinguishing signals, conclude that their colour-sense is perfect. 

 They make the trial quickly and without thought ; of course 

 regularly making the mistakes characteristic of their special 

 form of colour-blindness. 



" The majorit}^, however, desire to perform their task as well 

 as possible; that is, to do what the normal-eyed does. This 

 of course assists in testing them, provided it does not lead to too 

 great care, as then the testing the colour-blind is more difficult ; 

 the trouble being that much time is thus wasted. Only a very 

 small part have a contrary desire ; namely, to pass for colour- 

 blind, though normal-eyed. We will speak of these later, and 

 now only concern ourselves with those who stand the test in 

 good faith with the desire to appear normal, though perhaps 

 they are colour-blind. 



u The trial generally goes on rapidly and regularly. We will 

 only mention those hindrances and peculiarities which most 

 frequently occur. The examiner must watch that no mistake is 

 made from not understanding. The names of the colour need 

 never be used, except to ascertain if the name learned hides the 

 subjective colour-sensation, or to find the relation between the 

 name the colour-blind employs and Ins colour-perception. 



k 'The person examined who thinks more of names than the 

 test itself (this being generally a sign of school-learning) selects 

 not only the wools of the same shades— that is, those of the 

 same colour to his eye — but all which generally have the name 

 of this colour: for instance, in the first test I, not only the 

 g-reen like the sample, but all that are green; and with the 

 second test, not only the purple (and what are generally called 

 red), but all which Look reddish, scarlet, cinnabar, or sealing-wax 

 red. This is of no importance ; for those who only do this have 

 scarcely such defective chromatic sense as that with which we 

 are concerned. He is either normal-eyed or violet-blind. Simply 

 as a test of violet-blindness in the interest of science, we can go 

 on with the examination, and ascertain how far the grouping of 

 the two colours was due to a confusion of names or to defective 

 colour-perception. Otherwise this examination does not concern 

 the practical point we aim at. 



'* Under any circumstance it is better to correct the mistakes 

 just mentioned, when arising from misunderstanding, and it is even 

 necessary, in reference to the mistakes we explained might occur 

 with the first test. It might be said that it was sufficient if the 

 examined confounded the test-colour with green only; that it 

 was indifferent whether he distinguishes carefully between the 

 various kinds of green. But, in fact, this is not so unimportant. 

 We must give full weight as to whether the infraction of the 



