We are now to examine what traces there may be of deafness in a family by noting what proportion of the deaf have deaf relatives, and are to attempt to see what may be its bearings upon the question of heredity. In the census investigations,[47] we find that out of 34,780 deaf persons who answered, there are 10,033, or 28.8 per cent, who have deaf relatives of some kind, direct or collateral, 8,170, or 23.5 per cent, having deaf brothers, sisters or ancestors. In all of these we can without difficulty discover the influence of heredity. In the congenitally deaf the trace of a physical defect is even more clearly indicated. Of these 40.1 per cent have deaf brothers, sisters or ancestors, and 46.2 per cent have also deaf uncles, cousins, etc.[48] It is thus evident that there are certain families in society deeply tinged with deafness, that it sometimes passes from parent to child, from generation to generation, and that like a cloud it hangs over a section of the race. THE OFFSPRING OF DEAF PARENTS All this argument leads up to one most pertinent question: Are the statistics which we have indicative that this deafness which passes so remorselessly in certain families will be found all the stronger in the children of deaf parents? Have we ground to believe or fear that this deafness will crop out far more surely than in the children of parents not deaf? And can we determine to what extent possibilities are increased of the offspring of deaf parents being likewise deaf? Let us now consider the statistics which we have in this matter, first examining the results of the census investigation.[49] Of the 8,022 married deaf persons for whom statements are made, we find that there are 190 who have deaf offspring, or 2.4 per cent. Of the 4,116 deaf persons who are married to deaf persons, 137 have deaf children, or 3.3 per cent; and of the 3,906 deaf persons married to hearing persons, 53 have deaf children, or 1.4 per cent. Of the married deaf having deaf children, 52.5 per cent have deaf relatives of some kind, and 54.7 per cent are congenitally deaf, the proportion of those having deaf relatives who are also congenitally deaf being 66.7 per cent. Of the deaf married to hearing partners, who have deaf children, 26.4 per cent are congenitally deaf, while 50.9 per cent of the partners in such marriages have deaf relatives of some kind. From the census statistics, then, it appears that the married deaf as a class do not have a large proportion of deaf children, and that this proportion is only a little more than twice as great when the deaf are married to the deaf as when they are married to the hearing. It appears also, however, that when there are deaf relatives involved in either kind of marriages, or when there is congenital deafness in the deaf parent, the effect is quite marked in the offspring.