1891.] 



Colour of Cases of Tobacco Scotoma, 



499 



the place of the greatest difference in degree of luminosity, com- 

 pared with the normal, is near F, where it is more than eight times 

 more luminous than the normal eye. The area of their luminosity 

 curve is 1800 ; that of the normal eye being 1650. If we take their 

 appreciation of light as being 1'5 that of the standard, their lumino- 

 sity curve should be 1650 by 1'5 or 2475. Theirs is 1800 as measured, 

 the ordinates of their curve should therefore be multiplically 1'37 for 

 a strict comparison with that of the normal eye. We may therefore 

 take it that near F their sensation of light is 11*88 times that of the 

 normal eye. 



In the three patients we have cases of abnormal vision, one in 

 which practically the only sensations in the central part of the eye 

 are white and blue, and in the other two there is only one sensation. 

 In these last two cases we have apparently a curve of the funda- 

 mental sensation, since it must be the same as the luminosity curve, 

 and it appears to agree with that found by Koenig. In regard to 

 Alfred C., it should be remarked that he begins to feel the blue 

 sensation in the spectrum near the point where Koenig places its 

 origin. 



Addendum. Received June 18, 1891. 



On Four Cases of Colour Blindness Examined for the Colour Vision 



Committee. 



Case III. The next case, "W. S., is one of progressive atrophy of 

 both eyes. When tested with spectrum colours a patch of white 

 light being placed in juxtaposition with the colour it was found that 

 he was absolutely blind to colour from 26'75 (A, 4733) on the scale of 

 the spectrum to the termination of the red of his spectrum, which was 

 close to 63 on the scale (A 7082). Above scale No. 26' 75 W. S. saw 

 blue, and his spectrum was continued normally in the violet. Mr. 

 Nettleship has promised to furnish a chart of his retina. His lumi- 

 nosity curve (fig. 4) was made without any difficulty, and, compared 

 with my own, is slightly deficient, from the red to the yellow, but his 

 perception of luminosity increases as the blue is approached. 



The following is the table applying to his curve of luminosity : 



