Volume 5

Treasury of human inheritance / edited by Karl Pearson, R.A. Fisher, L.S. Penrose.

Date:
1909-
Catalogue details

Licence: Attribution-NonCommercial 4.0 International (CC BY-NC 4.0)

Credit: Treasury of human inheritance / edited by Karl Pearson, R.A. Fisher, L.S. Penrose. Source: Wellcome Collection.

    79/190 (page 195)
    When we look for other defects or anomalies characteristically associated with colour-blindness we can find no evidence at all that such exist ; we certainly expected to find a tendency to deafness occurring as an associated defect, from a knowledge of the high percentage of colour-blindness reported amongst deaf-mutes by the Royal Society’s Commission on Colour-Blindness already referred to, but in only two out of our whole series of pedigrees are we told of an associated deafness, and only one colour blind individual was himself a deaf-mute; in two further pedigrees we read of an associated lack of musical ear. Associated eye defects appear to be extremely rare and of no apparent significance. One pedigree with an associated digital deformity is reported and occasional cases of mental defect or epilepsy are noted, which can be regarded as of no significance in the light of the frequency of such diseases in the general population. Of course our information is incomplete and may be misleading, for colour-blindness does not necessarily take its victim to the doctor or to the ophthalmologist, and informa tion about associated defects is not likely to be asked for by the non-medical observer nor volunteered by the individual who is being tested ; nevertheless other eye defects have been too frequently sought for to be overlooked if at all frequent, and we are inclined to the view that colour-blindness is probably not characteristically associated with other hereditary defects and is in this respect markedly contrasted to such conditions as blue sclerotics, aniridia, ectopia lentis, microphthalmos, coloboma iridis, ophthalmoplegia, etc. We might even tentatively suggest that perhaps these sex- limited hereditary diseases, following their typical mode of descent, are as a group found to be characteristically associated with no other defects ; such would appear to be the case for congenital stationary night-blindness (with myopia) and haemophilia so so far as can be judged from the Treasury of Human Inheritance. Evidence, however, is admittedly incomplete and the whole subject needs to be investigated. Congenital Colour-Blindness in Women. This to any marked degree is no doubt relatively rare, but we have succeeded in collecting records of 91 cases. It is repeatedly stated on theoretical grounds that in order for colour-blindness to become manifest in women the father must be colour-blind and the mother must also be a carrier, and further that all the sons of a colour-blind woman must be colour-blind : these views have met with so widespread an acceptance that in some published cases a man is said to be probably colour-blind solely on the theoretical grounds that his daughter has a colour-blind daughter. We hoped to be able to firmly establish or to deny these hypotheses, and indeed we are able to deny them in as far as we have a record of a single sibship containing three colour-blind females, the father of whom has been definitely tested and pronounced to have normal colour vision 1 , and in several unquestionable cases colour-blind women have been demonstrated to have sons with normal colour vision 2 . Nevertheless the hypotheses referred to do undoubtedly hold over so wide a range of cases that we feel there must be some physical basis tending always to produce these associations, and if we qijote figures from our pedigrees which show that 7 4‘6 °/„ of colour-blind women are known to have colour-blind fathers (omitting cases where there is no knowledge of the parents), 91*1 0 / o of colour-blind 1 See Fig. 569. 2 See Figs. 407, 418, 440, 583.