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Two Cases of Congenital Night- Blindness. 

 By Sir W. de W. Abney, K.C.B., F.RS. 



(Eeceived July 21, 1917.) 



In the recent communication of my paper on a " Fourth Sensation in 

 Colour Vision," in April last, attention was called to the case of night-blind 

 eyes as throwing light on the question of the functions of the rods and cones 

 in the retina in regard to colour and colourless vision. I cited two cases 

 of congenital stationary night-blindness, which, through the kindness of 

 Mr. jSTettleship, were brought to my laboratory for examination in view of 

 certain researches in which Prof, (now Colonel) Watson and myself were 

 together interested. As Colonel Watson has been long at the Front in 

 France, and as he conducted a principal part of the only partially completed 

 examination, I hesitated to give the details without his collaboration. I 

 have now obtained his acquiescence in my request that I should communicate 

 the results obtained to the Eoyal Society. I now do so. As a matter of 

 fact, I had worked out the observations before my colleague left me for the 

 Front some 2|- years ago, and these results I have put in the following com- 

 munication : 



I may say that any other form of night-blindness than those to which 

 the late Mr. E. Nettleship introduced us would have been useless for the 

 investigation on which we were engaged, as, if it were not so, night- 

 blindness due to disease might call in question some of the deductions to 

 be made. Mr. ISIettleship's investigations of the family to which they 

 belonged, and its history, left no doubt that we were dealing in our two cases 

 with genuine cases of congenital stationary types. 



The subject of congenital night-blindness (sometimes called moon-blind- 

 ness) has been left with several obscure points unexplained, and the present 

 communication, it is hoped, may throw light on some of them. 



The late Mr. E. Nettleship collected a large number of pedigrees in which 

 the characteristics of night-blindness are shown. His papers on the subject 

 contain, it is believed, nearly everything that is worth knowing. The papers 

 were published in the ' Eoyal London Ophthalmic Hospital Eeports.'* He has 

 amply proved that congenital night-blindness is hereditary. He commenced 

 with the work that the late Florent Cunierf published in 1838 on a family in 



* See vol. 17, Part III, and vol. 27 of the 'Ophthalmic Society's Transactions,' besides 

 others. 



t Fl. Cunier, ' Medecin Militaire,' " Histoire d'une Hemeracopie Hereditaire depuis 

 Deux Sifecles dans une Famille de Vendemair prfes Montpellier." 



