188 COLOR-BLINDNESS IN ITS RELATION TO 



and boldly; the latter with over anxiety aud a certain dread. The lowest 

 class are those who have the opposite desire, that is, to pass for color- 

 blind, although in possession of normal sight. We will speak of these 

 later, to enable us now to devote ourselves to those who undergo the trial 

 in good faith, or, at least, with the desire to appear normal, even al- 

 though color-blind. 



In the trial it is especially desirable to confine the range of selection 

 to the lighter shades of tbe test color (say green), for tbe trial would 

 cause great loss of time and be less reliable if it included every shade 

 of green. In fact, no little judgment has been exercised in the selection 

 of the very lightest shade of the green proposed as a sample color. For 

 it is exactly what the color-blind most readily confounds with the paler 

 shades of gray, drab, straw, and salmon-color. If the subject were 

 allowed to depart from the narrow limits established by the trial, it would 

 include every shade of green, the result of which would be that he would 

 prefer to select all the vivid shades, and thus avoid tbe dangerous ground 

 where his defect would certainly be discovered. This is why it is neces- 

 sary to oblige him to keep within certain limits, confiuing him to pure 

 green specimens, and, for greater security, to recommend him to select 

 especially the lightest shades. What we have just said of green applies 

 also of course to jiurple. 



Tbe principle of our method is to force the one examined to reveal, 

 himself, by an act of his own, the nature of bis chromatic sense. Now, 

 as this act must be kept within certain limits, it is evident that the ex- 

 aminer must direct him to a certain degree. This may present, in certain 

 cases, some difficulty, as he will not always be guided, and does 

 either too much or too little. In both cases, the examiner should use 

 his influence in order to save time and gain certainty, and this is usually 

 very easily done. Tbis intervention is, of course, intended to put tbe 

 examiner in the true path, and is accomplished in many ways according 

 to tbe case in point. 



We will here mention some of the expedients we have found useful ; 



A. Interference during an extended selection. — It is not always easy to 

 confine tbe one examined within thelimitsof tbe method. He easily slips 

 in the first test, for example, a yellow-green or blue-green skein among the 

 others, and as soon as there is o«e, others follow usually, and it thus 

 happens that, in a few moments, he has a whole handful of yellow-green, 

 a second of blue-green, a third of both these shades at tbe same time. 

 Our process has assisted us in more than one case of this kind. 



(a) When tbe person examined has begun to select shades of one or sev- 

 eral other colors than those of the sample, his ardor is arrested by taking 

 from him the handful of skeins he has collected, and asking him whether 

 his eye does not tell him there are one or several which do not match 

 tbe others, in which case he is solicited to restore them to tbe pile. He 

 then generally remarks that there is some obscuration, and pro3eeds in 

 one of the following manners : 



