One point deserves special attention in the above list. It is that where there are no deaf relatives (i.e. where there has not been a history of deafness in the family) only one child out of twenty-four is deaf, even when the parents were both born deaf themselves. Where there were deaf relatives already in the family on both sides, and the parents were born deaf, the percentage of deaf children is seven and a half times as great. This seems to show that there are causes of congenital deafness which are, comparatively speaking, unlikely to be transmitted to future generations, while other causes of congenital deafness are so liable to be perpetuated that one child in every three is deaf. We conjecture that one original cause of congenital deafness which reappears in a family is consanguinity--for instance, the intermarriage of first or second cousins (hearing people) in some previous generation. Out of the 2245 deaf persons who were born deaf, 269 had parents who were blood relations, according to Fay. And perhaps many more refrained from acknowledging the fact. Eleven had grandparents who were cousins. This theory calls for investigation, and while the marriage of deaf people is not encouraged, it is fair to ask those who so strenuously oppose such unions whether they may not be spending their energies on trying to check an effect instead of a cause, and if that cause may not really be consanguinity,--witness the percentage of deaf people among Roman Catholics, Protestants and Jews before noticed. On the principle that prevention is better than cure it is the intermarriage of cousins and other relations which should be discouraged. The marriage of deaf people is inadvisable where there has been deafness in the family in former generations, but the same warning applies to all the other members of that family, for the hearing members are as likely to transmit the defect of which deafness is a symptom as the deaf members are. We are more concerned to discover the primary cause of the defect, and take steps to prevent the latter from occurring at all. Those who have no dissuasions for hearing people, who might perhaps cause the misery, and only give counsel to those among the transmitters of it who happen to be deaf, are acting in a manner which is hardly logical.