CL BOWMAN LECTURE. 



(j) Proportion of Females Carrying Disease in Certain 

 Sex-limited Affections. 



In a disease transmitted only by unaffected females the number of 

 sisters in any childship who carry it can, Avith our present knowledge, 

 be known only if they all have children. The following are the only 

 examples I have been able to find, and even in them the evidence must 

 be regarded as incomplete for such of the sisters as had very few 

 children : 



(1) Discontinuous retinitis |)igmentosa: Fig. 36, IV6,* contains 5 

 sisters, 1 of whom dies single ; of the others 2 have 12 children in all, 

 some of whom have the disease ; the other 2 have 4 children in all (only 

 3 of these are shown in the Figure), none of whom have the disease. 



(2) Discontinuous night-blindness : Fig. 42, IVa, contains 4 sisters ; 

 2 of them have 9 children in all, some affected ; the other 2 have 4 in all, 

 all normal. 



(3) Discontinuous night-blindness (R.L.O.H., xvii, p. 419: Fig. 175), 

 II, contains 4 sisters ; 2 of them have in all 5 children, some affected ; 

 the other 2 have in all 3 children, all normal. 



(4) Discontinuous night-blindness (ibid., xvii, p. 422: Fig. 178, III&), 

 contains 2 sisters ; 1 has 4 children, some affected ; the other 2 children 

 both normal. 



(5) Leber's disease (this Appendix: Fig. 108, Ilia), contains 2 sisters, 

 both of whom had affected issue. Note that of their 7 brothers 6 had 

 the disease. 



(6) Leber's disease (ibid. : Fig. 94), the two small childships Ila 

 and b, contain 3 females, 2 of whom married, and both had some affected 

 children. 



(7) Leber's disease (ibid.) : Fig. 143, II, contains 2 sisters, of whom 

 one certainly bore affected issue. 



(8) Leber's disease (ibid.) : Fig. 166, Ilia, contains 2 sisters, of whom 

 one bore three children, one of them affected; the other had an only 

 child who was affected. 



In these eight instances we have 24 sisters, of whom 21 certainly had 

 children (1 died childless and 2 others appear to have been unmarried 

 at date of record). Of these 21, 13 had amongst them rather more than 

 51 children (exact number in one case not given), containing 18 affected. 

 The remaining 8 had amongst them only 14 children, all normal. 



* IV6. The letter b signifies the second eligible childship in Gen. IV 

 counting from the left ; the first is a. These letters are not marked on 

 the Figure. The same explanation applies to the other relevant Figures. 



