io6 HEREDITY AND EUGENICS 



former had twenty-eight normals to sixteen affected 

 offspring. The condition is transmitted by both 

 sexes, and shows a tendency to become less marked 

 in later generations. 



Hawkes (191 4) has compared different t^^pes of 

 human foot as regards the relative lengths of the 

 first and second digits. From an examination of the 

 feet of 2,300 persons, chiefly children, he finds the 

 " L " type of foot, with the great toe longest and 

 the other toes sloping back in an oblique line, the 

 commonest. The '' S " type, in which the second 

 toe is longer than the great toe, is much less common. 

 Not very rarely one foot will be of the L type, and 

 one of the S type. This is in hetero zygotes, but 

 some persons with both feet L are heteroz3^gous. The 

 " E " type, in which digits I and II are of equal 

 length, is very unusual. The L t3^pe of foot shows 

 irregular dominance over the S t3^pe in inheritance, 

 but the S type occurs more commonty in females than 

 in males, and is commonest in the foetal stage. The 

 male heteroz}^gote tends to be L, and the female to 

 be S, in foot pattern. Occasionalh^ digit III is 

 longer than digit II, and this condition is also found 

 to be hereditar}^ 



Various Abnormalities. 



Lundborg (1920) concludes that hereditary deaf- 

 mutism is due to one Mendelian recessive factor, and 

 rejects Plate's h^^pothesis of two factors. Acquired 

 deaf-mutism ma\^ be either intra- or extra-uterine 

 in origin. Hence congenital deafness is not always 

 hereditar\^. Irish statistics of the ^xar 1891 register 

 congenital deaf-mutism as "jG per cent, of all cases. 

 In Norwa^^ (1897) the number was estimated at 50-9 

 per cent., in Sweden (1904) at 40-8 per cent., and in 

 the Malmohus district of Sweden (191 9) at only 

 28-2 per cent. (108 in 383). Meningitis and scarlatina 



