FOOTNOTES:[1]The investigation of this remarkable family was made originally by Cunier. The facts have been reexamined and the pedigree much extended by Nettleship. The numerical results are somewhat irregular, but it is especially interesting as being the largest pedigree of human disease or defect yet made. It contains 2121 persons, extending over ten generations. Of these persons, 135 are known to have been night-blind. In no single case was the peculiarity transmitted through an unaffected member. It should be mentioned that for night-blindness such a system of descent is peculiar. More usually it follows the scheme described for colour-blindness. It is not known wherein the peculiarity of this family consists.[2]We have knowledge now of seven colour-blind women, having, in all, 17 sons who are all colour-blind. Most of these cases have been collected by Mr Nettleship.[3]An alternative and perhaps more satisfactory interpretation of the same facts has been proposed by Doncaster (Jour. GeneticsI, Pt 4, p. 377). Until more progress has been made with the analysis of sexual differentiation it is not possible to decide which of the two interpretations is correct. The numerical results predicted on both systems are the same; but by introducing a more complicated though quite reasonable formula for the representation of the sex-differences Doncaster's method shows that colour-blindness may be arecessivedue to the absence of a factor which produces normal colour-vision.
[1]The investigation of this remarkable family was made originally by Cunier. The facts have been reexamined and the pedigree much extended by Nettleship. The numerical results are somewhat irregular, but it is especially interesting as being the largest pedigree of human disease or defect yet made. It contains 2121 persons, extending over ten generations. Of these persons, 135 are known to have been night-blind. In no single case was the peculiarity transmitted through an unaffected member. It should be mentioned that for night-blindness such a system of descent is peculiar. More usually it follows the scheme described for colour-blindness. It is not known wherein the peculiarity of this family consists.
[1]The investigation of this remarkable family was made originally by Cunier. The facts have been reexamined and the pedigree much extended by Nettleship. The numerical results are somewhat irregular, but it is especially interesting as being the largest pedigree of human disease or defect yet made. It contains 2121 persons, extending over ten generations. Of these persons, 135 are known to have been night-blind. In no single case was the peculiarity transmitted through an unaffected member. It should be mentioned that for night-blindness such a system of descent is peculiar. More usually it follows the scheme described for colour-blindness. It is not known wherein the peculiarity of this family consists.
[2]We have knowledge now of seven colour-blind women, having, in all, 17 sons who are all colour-blind. Most of these cases have been collected by Mr Nettleship.
[2]We have knowledge now of seven colour-blind women, having, in all, 17 sons who are all colour-blind. Most of these cases have been collected by Mr Nettleship.
[3]An alternative and perhaps more satisfactory interpretation of the same facts has been proposed by Doncaster (Jour. GeneticsI, Pt 4, p. 377). Until more progress has been made with the analysis of sexual differentiation it is not possible to decide which of the two interpretations is correct. The numerical results predicted on both systems are the same; but by introducing a more complicated though quite reasonable formula for the representation of the sex-differences Doncaster's method shows that colour-blindness may be arecessivedue to the absence of a factor which produces normal colour-vision.
[3]An alternative and perhaps more satisfactory interpretation of the same facts has been proposed by Doncaster (Jour. GeneticsI, Pt 4, p. 377). Until more progress has been made with the analysis of sexual differentiation it is not possible to decide which of the two interpretations is correct. The numerical results predicted on both systems are the same; but by introducing a more complicated though quite reasonable formula for the representation of the sex-differences Doncaster's method shows that colour-blindness may be arecessivedue to the absence of a factor which produces normal colour-vision.
Cambridge:PRINTED BY JOHN CLAY, M.A.AT THE UNIVERSITY PRESS.