CXXVI BOWMAN LECTURE. 



There are all sorts and degrees of albinism between 

 these cases which I have ventured to include and the 

 well-marked general albino whom we all know. It may 

 be hoped that in describing future cases of hereditary 

 nystagmus attention will be bestowed upon the present 

 and past colour of hair, eyebrows, eyelashes and iris, 

 aspect of fundns, colour-vision and refraction.* 



In their heredity these partial cases appear to be 

 almost perfectly sex-limited ; of forty- three affected per- 

 sons, forty were males, and the descent was through the 

 mother in every case ; no affected male ever had an 

 affected child. t In these characters, the group I am 

 calling incomplete ocular albinism differs from general 

 albinism. It is true that in general albinism the descent 

 is usually discontinuous, but the normal parent who 

 acts as carrier is by no means always the mother ; again, 

 although there is a decided excess of males with general 

 albinism over females it is much less than in the small 



Usher within the last year have shown that apart from the tapetum in 

 those animals every possible combination of pigment deficiency in the 

 retinal epithelium and choroid or iris may be present, a result supporting-, 

 so far as it goes, the above contention. I believe we do not know any- 

 thing positive about increase of pigment in the hexagonal epithelium 

 after birth ; but even if such increase were proved to occur in cases of 

 incomplete albinism, it does not follow that visual acuity would be im- 

 proved ; the pigment might come too late for the otherwise developed 

 retina to benefit by it ; we know as a fact that improvement of visual 

 acuteness in albinos, although by no means unknown, is decidedly rare. 

 A great puzzle is the frequency and high grade of the ametropia and 

 especially of astigmatism in nearly all recognised albinos, and the same 

 problem meets us for these cases of blue-eyed nystagmus, and appears to 

 furnish another link between the two groups. 



* I do not suggest that everyone with blue eyes, nystagmus, and 

 amblyopia is albinotic in any degree : but some certainly are so, and 

 many others probably ; whilst if the essential feature of an albinotic eye 

 is lack of pigment in the hexagonal retinal epithelium, we are not yet in 

 a position to deny the possibly albinotic nature of any clinical case where 

 no more reasonable explanation of the nystagmus and defective acuity 

 can be found. 



t These small numbers are given for what they are worth. But even 

 if a few other pedigrees of nystagiims are included where the evidence 

 for albinism is even less than in the above, the excess of males affected 

 over females affected remains very large 3 or 4 to 1 . 



