Report of the Committee on Colour- Vision. 385 



"This stratagem generally succeeds when nervousness from 

 over-anxiety causes bis hands to tremble ; but it is not always 

 easy to induce him to keep his hands behind his back until the 

 moment for taking the skein in question. 



" (b) In cases of great caution, the trial is hastened, if the 

 examiner come to the assistance of the other, by holding above 

 the pile one skein after the other, and requesting him to say 

 whether it resembles the colour of the sample or not. It will be 

 advisable first to select the skeins that a colour-blind person 

 would approve. If he is so, he will approve of the selection, and 

 the question is settled ; if not, he rejects them, not without a 

 characteristic smile, or with an expression of wounded dignity. 

 This also enlightens us as to his chromatic sense. But even the 

 colour-blind may, in such a case, refuse what is presented, 

 especially if his caution is premeditated, and he suspects that a 

 snare is intended. It is found quite frequently that he rejects 

 the correct shades likewise presented with the others. This is 

 not the case when one, having a normal chromatic sense, is slow 

 and deliberative when subjected to the test under this form. He 

 has an eye alive to the correct colours. 



u One process, in cases of this last kind, is to select false 

 samples, which are placed close to the correct one, by the 

 side, above, or below, to attract the attention of the examined 

 from the right side. It is necessary so to proceed that the true 

 sample be displaced when the others are drawn out, so that the 

 person examined may see it move. It does not, however, always 

 happen to catch his eye. The best means is then to make him 

 examine the whole, with his hands behind his back, and invite 

 him to freely make his choice. But, whatever the process, it is 

 necessary, in every case where one has been assisted in selecting 

 a certain number of skeins which he has found analogous to the 

 sample-colour, to make a rule not to conclude the trial without 

 examining into the effect of the aid accorded. It is necessary to 

 hold in the hand the approved package, and ask if he is satisfied, 

 or if he would desire any change. If he approve the choice, the 

 diagnosis is established. The same course must be pursued with 

 the defective chromatic sense, that the trial may be made with 

 or without assistance. To be thorough, the name given by the 

 colour-blind to the colours in question may be likewise asked. 



" In cases where any one suspected of colour-blindness has 

 remained some time to see the trial of others, and where, as 

 often happens, he has remarked the samples belonging to a 

 required green shade, he may of course profit by it in his own 

 trial. But this can be prevented by furtively concealing one or 

 two of these samples. If he seem to be disposed to confound 

 green and grey, it will be very easy to entrap him. If we do 

 not succeed, even when assisting him, in entrapping him in this 

 snare, the hidden samples may be put back into their places, to 

 be convinced that the trial is correct. 



*' From the above, it is seen that many artifices may be 



