no HEREDITY AND EUGENICS 



Maine showing the trait through three generations. 

 It is not, hke haemophiha, sex-hnked. It manifests 

 itself by spontaneous bleeding at the nose almost 

 daily, beginning at the period of adolescence and 

 continuing until eighteen or twenty. Individuals 

 showing it are vigorous in health and grow rapidly, 

 often feeling discomfort if the bleeding does not 

 take place. 



Diseases like haemophilia (abnormal tendency to 

 bleeding), Gower's disease (saltatory spasms), and 

 colour-blindness are well known to be sex-linked in 

 their inheritance, but with complications in the last 

 instance. Bulloch and Fildes (1910) bring together 

 a vast amount of information concerning haemophilia, 

 with many pedigrees. Nasse in 1820 asserted that 

 it is transmitted entirely by unaffected females to 

 their sons. Of the 171 recorded instances of trans- 

 mission, belonging to forty-four families, sixty conform 

 to the " law of Nasse." In the eleven other families, 

 in some of which inheritance from father to son was 

 supposed to have taken place, there is no good evidence 

 that this ever took place. Such apparent cases are 

 found to be explained by intermarriage of " bleeder " 

 families or in other ways. In the forty-four families 

 studied there were 644 males to 464 females — a great 

 excess of males . The marriage-rate of males in bleeder 

 families is ver}^ much lower than of females (9-6 per 

 cent. : 36-8 per cent.). The disease is rare. Lenz 

 (191 2) gives an extensive bibliography of haemophilia. 



Among recessive conditions are alkaptonuria* and 

 albinism. The most extensive pedigrees of cataract 

 have been those collected by Nettleship {cf. Bateson, 

 1909). They show that various forms of cataract 

 are usually transmitted as dominants. Harman 

 (1910) classifies cataracts as lamellar, axial, stellate, 



* A condition in which alkaptan (probably a derivative of 

 tyrosin) is present in the nrine. 



