CIV BOWMAN LECTURE. 



vision and occasional nystagmus, and the occurrence in 

 some cases of various slight ophthalrnoscopic changes, 

 suggest that in this group the night-blindness, although 

 congenital, is truly pathological, the result of a limited 

 intra-uterine elongation of the eyeball interfering with 

 the development of the choroid and outer layers of the 

 retina. But why the condition should usually be limited 

 to males is as great a mystery as in other sex-limited 

 conditions. It is to be noted that ordinary myopes some- 

 times complain of seeing worse in twilight, but the 

 significance of the symptom in such patients is open to 

 more than one interpretation, and its proper analysis is 

 full of difficulties, as I believe some of my friends who 

 are investigating the subject have found. About a dozen 

 fairly good pedigrees of this sex-limited myopic night- 

 blindness are known, and may be found in my paper 

 already mentioned. Consanguinity of the parents was 

 present in at least three of them. 



Since the publication of the paper in which all the 

 above cases are given I have obtained the new and 

 quite characteristic, although small, pedigree of this 

 sex-limited myopic night-blindness, fully described with 

 its Fig. 44 in Appendix Y. There was no consanguinity. 



Another case (44a), seen at the same time as the 

 above, was less thoroughly examined, and is given in the 

 same Appendix for what it is worth. In this case two of 

 the three affected siblings were girls ; the parents were 

 first cousins. 



I owe these two new examples to the kindness of Mr. 

 W. J. Cant and Mr. Clements, of Lincoln, who courteously 

 allowed me and Mr. C. H. Usher to examine the affected 

 members for ourselves last autumn. To the Rev. C. N. 

 Usher, of Wellingore, I am indebted for the kindness 

 and trouble he took in arranging for our meetings with 

 the patients at his house. 



Some few small pedigrees of night-blindness are found 

 in which, though descent is discontinuous, the disease 

 affects both sexes ; myopia appears to be common in the 



