164 MARRIAGE AND DISEASE. 



of 148 pupils in the Deaf and Dumb Institution of 

 London, there was one in whose family there were 

 five deaf-mutes, one in whose family there were four, 

 eleven in each of whose families there were three, and 

 nineteen who each had a brother or sister similarly 

 afflicted with themselves. These figures Rlbot con- 

 siders in themselves conclusive proof of the frequent 

 hereditary character of the affection; and certainly 

 when we find in thirty-two out of 148 cases, almost 

 22 per cent. this evidence of the condition not being 

 confined to the individual, but present in other 

 members of the family the case in favour of the 

 hereditary origin of the affection is strong. But much 

 more positive evidence of the frequent hereditary trans- 

 mission of deaf -mutism is to be found in the article on 

 "Vital Statistics" in the Keport of the Irish Census 

 Commissioners. This writer discusses at considerable 

 length the subject of congenital deaf -mutism, and pro- 

 duces a mass of evidence which Sir William Turner, 

 in his address before the Anthropological Section of 

 the British Association in 1889, asserted "proves that 

 it is often hereditarily transmitted." 



This writer states that "in the Irish census for 

 1871, 3297 persons were returned as deaf-mutes, and 

 in 393 cases the previous or collateral branches of 

 the family were also mute. In 211 of these the con- 

 dition was transmitted through the father, in 182 

 through the mother." Here we have almost exactly 

 12 per cent, of direct transmission through one or 

 other parent. But this writer does not stop here ; he 



