332 Prof. Tyndall on a peculiar case of Colour Blindness. 



It was my intention to make a guess at the cause of colour 

 blindness in the case above described; but guesses, without the 

 means of verifying them, are so unsatisfactoi-y, and so apt to pro- 

 duce fruitless discussion, that for the present at least I will con- 

 fine myself to the statement of the facts. 



Two other cases of a different nature were also brought under 

 my notice by Mr. Cooper, and may, on account of their rarity, 

 be worthy of a brief reference. 



The first is that of a little girl, about seven years old, the 

 development of whose eyes had been arrested before birth. The 

 child's sight, however, though imperfect, was sufficient to enable 

 her to distinguish colours with accuracy. When the spectrum 

 was displayed before her, she ran her fingers prom])tly over the 

 colours and named them correctly. She could also I'cad large 

 print. The phsenomena of irradiation presented themselves to 

 her as they did to me ; an incandescent platinum wire became 

 thicker as she receded from it. As far as I could judge, the 

 retina was perfectly healthy. I placed her within a foot of the 

 coal-points of the electric lamp, and establishing the current, 

 allowed the full splendour of the light to fall upon her eyes : she 

 never even winked, but looked steadily into the light, and stated 

 that she did not feel the slightest inconvenience. This perhaps 

 was due to the partial opacity of the humours of the eye. The 

 position of the iris in her case was mariied by a few gray spots, 

 and the pupil had no definite boundary. The eyes were, as 

 might be expected, out of all proportion with the growth of the 

 child : the arrestation of development extended to the teeth also, 

 which caused the child to appear much older than she really was. 

 She was veiy intelligent ; and her mother, who accompanied her, 

 was a healthy intelligent woman, with fine brown eyes. She 

 stated to me, that neither in her own nor her husband's family 

 did a case of the kind ever occur ; and yet she had four children, 

 and the whole of them, without exception, were afflicted in a 

 similar manner. 



The second case is that of a distinguished artist, also sent to 

 me by Mr. Cooper. Several months ago he noticed, on looking 

 at any distant point of light, a whitish luminosity spreading 

 round the point, and first observed this appearance on the 

 occasion of rubbing his right eye somewhat severely. As time 

 advanced, the luminosity merged into a series of coloured rings 

 which encircled the luminous point ; and as these were becoming 

 brighter and larger, his fears of the ultimate blindness of the eye 

 became excited. He had consulted several eminent oculists, and 

 had, I believe, been subjected to severe treatment, on the sup- 

 position that the retina was the seat of the malady. The co- 

 loux'ed curves were not perfect cirqles. I placed Mr. S. upon his 



