226 Human Albinism [CH. 



records among 761 cases, 228 are said to have been offspring 

 of consanguineous marriages. It is not in dispute that the 

 condition may be produced by various specific causes also, 

 but the heredity through consanguineous marriages creates 

 a presumption that a group of cases may be of a recessive 

 nature. 



It should perhaps be pointed out categorically that 

 nothing in our present knowledge can be taken with any 

 confidence as a reason for regarding consanguineous mar- 

 riages as improper or specially dangerous. All that can 

 be said is that such marriages give extra chances of the 

 appearance of recessive characteristics among the offspring. 

 Some of these are doubtless bad qualities, but we do not 

 yet know that among the recessives there may not be 

 valuable qualities also. 



From what is known of the genetics of albinism in other 

 types we should on analogy expect it to be recessive in 

 man. There is no reasonable doubt that this description 

 is true so far as it goes, but obvious complications are 

 met with. No union of two albinos is on record so far 

 as I know, but the frequency with which the albinos have 

 proved to be offspring of related parents, especially of first 

 cousins, justifies us in definitely inclining to the view that 

 albinism is in man a recessive character. The families 

 available for numerical comparison are scarcely well enough 

 reported for a proper analysis to be made, but it is clear 

 that they exhibit again the difficulty met with before in 

 human pedigrees, namely, that the affected are far in excess 

 of expectation (on the hypothesis that they are ordinary 

 recessives). For example, from a set of figures derived 

 from various sources* I get the numbers 115 albinos and 

 174 normals, where the expectation is only 72 to 216. 

 There are reasons for thinking these records of albinos too 

 high, and those of normals too low, but the discrepancy is 

 too large to be accounted for thus. 



Human albinism differs from that of our domestic 

 animals in the fact that it shows many gradational forms 

 which connect it with the normal. There are also several 



* I am especially grateful to Dr V. Magnus of Christiania for a series 

 of 10 albino pedigrees. One of these contains an extraordinary family of 

 which seven are stated to be albinos and only one pigmented. 



