66 HEREDITY AND EUGENICS 



to correlation between albinism and mental derange- 

 ment. 



In Scotland loo to 150 living albinos were recorded 

 from about half the population. This indicates a 

 frequency of i in every 15,000 to 25,000 inhabitants. 

 Moreover, less satisfactory records are available from 

 many other countries and races. It appears that 

 albinism occurs as a mutation in the absence of cross- 

 ing of races, both in the dark and white races, but 

 it also frequently arises, as we have seen, a generation 

 or two after a mixture of races has taken place. The 

 piebald, apparently arising only from cross-breeds, 

 is far rarer than the complete albino. 



Pearson also considers the pathological condition 

 known as leucoderma (white patches on the skin), 

 and finds there is no physiological differentiation from 

 albinism, the two being distinguishable only by the 

 inheritance of the latter. Pearson distinguishes 

 between spotlings and piebalds, the former including 

 those wdth white miarkings which do not extend to 

 extensive areas on the trunk. The extent of the 

 leucosis is probably hereditary, but there is no sharp 

 line between spotlings and piebalds. The spothng 

 of one generation may be the father of a piebald in 

 the next. Albinism, piebaldism, and leucoderma are 

 probably all to be accounted for by the same meta- 

 bolic defect. Leucoderma, however, is not necessarily 

 inherited. 



A family in which albinism was carried as a reces- 

 sive for five generations is described by Sedgwick 

 (1861). The pedigree of this famil}' is given in 

 Fig. 12. One of the original great -grandparents 

 must have been carr3dng albinism as a recessive. 

 The wife of No. II. i must have been in the same 

 condition. Their daughter, Josephine (III. i), was 

 the only descendant of this son to show albinism. 

 The two grandsons, III. 2 and III. 3, married sisters. 



