Since Ireland is strongly Roman Catholic, the proportion of consanguineous marriages is probably small, so that the percentage of deafmutes derived from consanguineous marriages, varying from 5.86 to 11.56 is very much greater than the percentage of these marriages in the general population. The average number of deaf children to a family in Table XXIV varies less than any other part of the table, and clearly shows a much higher average number of deaf children where the parents were cousins. They reveal the interesting fact that the occurrence of two or more deafmutes in a family is more than twice as probable where the parents are related as where they are not. Table XXV still better illustrates this point. Of the families where there was but one deaf-mute, only 4.3 per cent were the offspring of cousin marriages; where there were two in a family 12.9 per cent were of consanguineous parentage; three in a family, 13.3 per cent; four in a family, 19.0 per cent; more than four in a family, 21.1 per cent. TABLE XXV. _Number of Congenital Deaf mutes to a Family in Ireland._ ---------------------------------------------------------------- | | Families in which deaf-mutes numbered. | |---------------------------------------- Year.| Parentage. | 1. | 2. | 3. |4.|5.|6.|7.|8.|9.|10.|11. ---------------------------------------------------------------- 1851 | Parents cousins | 127| 45 | 20 |10| 5| 2|..| 1|..|.. |.. 1871 | Parents cousins | 91| 38 | 24 | 5| 3| 1| 1|..|..|.. |.. 1881 | Parents cousins | 63| 30 | 13 | 6| 1|..|..|..|..|.. |.. 1891 | Parents cousins | 82| 38 | 19 | 9| 1| 3| 1| 2|..|.. |.. 1901 | Parents cousins | 79| 34 | 23 | 7| 1|..| 1|..|..|.. |.. 1851 | All families[A] |2963|347 |158 |35|13| 5|..| 1|..|.. |.. 1871 | All families[A] |2460|305 |167 |47|20| 5| 1|..|..|.. |.. 1881 | All families[A] |2080|281 |162 |39|18| 6|..|..|..| 1 |.. 1891 | All families[A] |1473|273 |134 |40|12| 6| 1| 2|..|.. | 1 1901 | All families[A] |1219|231 |122 |34|10| 4| 2|..|..|.. |.. ---------------------------------------------------------------- [A] Number of the "Deaf and Dumb" to a family, "as far as could be ascertained."