222 SECTIONAL ADDRESSES 



It will be noted that with the violet and blue filters, the figures invisible 

 and the figures read are precisely as we find them in typical colour blind- 

 ness, except in Plate III where the figure 5 ought to be, and is usually 

 read, and in the case of the blue filter, Plate XII, where the figure 2 or 6 

 ought to be read. With the blue-green filter, Plates VI, VII, IX, X, XI, 

 give the typical colour-blind results also. Yellow, orange and red filters 

 give the same result as in ordinary daylight. The results with the yellow- 

 green filter are specially noteworthy. Plates IV, VI, VII, VIII, IX, can 

 be read, but only with difficulty, when this filter is used. The results with 

 Plates XII and XIII are also interesting, the plates inserted to distinguish 

 between deuteranopia and protanopia. In Plate XII, the normal read 

 26, the deuteranopes 2, and the protanopes 6. On Plate XIII, the normal 

 read 42, the deuteranopes 4 and the protanopes 2. With the violet filter, 

 6 was read on Plate XII, and 2 on Plate XIII. With the blue and blue- 

 green, green and yellow-green filters, nothing could be read on Plate XII. 

 On Plate XIII, on the other hand, 2 was read with the violet and blue 

 filters, and 4 with the blue-green, green and yellow-green filters. To the 

 normal eye in white light there is no apparent diflterence as respects 

 colour between the pages. 



2. Tableaux-Mosciique pour la Recherche du Daltonisme. 



SchaaflF's Mosaic Plates consist of ten cards, on each of which appear 

 on coloured backgrounds two coloured circles, one smaller than the other. 

 Each circle is incomplete, and the test consists in asking the subject to 

 point out the gap or break in each circle. The cards are square and can 

 be turned round to any angle when placed on the table, so that the circles 

 do not always appear in the same position. 



This test failed the group of colour blinds quite definitely when the 

 results are considered over the whole test (see Table IV). The number of 

 the gaps seen, however, is not constant for each individual, but ranges 

 from 3 to 16. The test does not seem to differentiate between deuter- 

 anopes and protanopes. Plates II, VIII, and X should be seen better 

 by protanopes. Plates VII and IX by deuteranopes. This does not hold 

 consistently. Only two colour blinds saw the gaps in Plate II, and they 

 are protanopes, but the other protanopes failed to do so. Some of them 

 described the card as being composed of nothing but gaps, ' gaps all over,' 

 and they did not know which one to point to. As a matter of fact, the 

 circles on this card offer difficulty to people with quite good normal vision. 



Plate VI is an interesting one. The instructions run that those who 

 fail in Plate VI should not be admitted as engine-drivers unless there is a 

 shortage of applicants. All the colour blinds failed in this card except 

 one who half passed, that is, who saw the gap in one of the circles but not 

 in the other. Table V shows the results of the tests given to the control 

 group as well as to the colour blinds. 



Plate I is seen by all. Plate II is clearly quite difficult, only 60 per cent, 

 of the N group managed to point out the gaps in the circles, and only 

 37 per cent, of the N — group. In the colour-blind group, on the contrary, 

 only 7 per cent, passed, and there is a failure of 78 per cent. Plate VI 

 failed 6 per cent, of the N group, 17 per cent, of the N — group, and 98 



