We come now to the consideration of the question of possible action for the prevention of congenital deafness. This examination naturally centers about the matter of the regulation of marriage, with due attention to the extent that action on the part of the state is to be regarded as desirable or feasible.
We have seen that congenital deafness may, hypothetically, be divided into three distinguishable classes: that in which consanguineous marriages are concerned, that in which there is antecedent deafness in the family, and that in which neither of these conditions occurs; and in our inquiry it has seemed best to take up each of these separately. It may be, however, that there is in fact no very radical difference between these several forms, and that with increased knowledge on the subject a more or less intimate relation will be found to exist.
Of that form of deafness in which neither consanguineous marriages nor antecedent deafness is involved, we are at present, as we have noted, able to say little definitely. In most cases we may be convinced that there exists in the parent some peculiar state of morbidity or other affection, latent or manifest, perhaps to some extent of hereditary influence, which has an effect on the organs of hearing of the offspring. A certain proportion is quite possibly due to recognizable defects both of physical and mental character. Our statistical evidence, however, in respect to this form of congenital deafness is too slight to warrant any positive deductions; and we will have to wait for further investigation to determine its nature fully. None the less, marriage of persons known to be liable to have ill effect on possible offspring is objectionable for not a few reasons, from the standpoint of the interests of society; and in their reduction there will probably be a greater or less diminution of congenital deafness.
With regard to consanguineous marriages and their effect on deafness we are on surer ground, so far as may be indicated by statistical data. This question is found in very great measure to be connected with that of deaf relatives in general. The matter appears to be largely a part of a law of wide application, namely, that in the blood relationship of parents the possibilities are intensified of the perpetuation of a certain strain, which holds true no less with the transmission of deafness. Consanguineous marriages are perhaps not of sufficiently frequent occurrence, so far as concerns the effect on deafness, to require special action; but in the consideration of such marriages in general, their part in the causation of deafness should have due weight; and whatever may be said regarding them in other relations, they are to be avoided if we wish to remove all chances of this kind of deafness resulting.
The problem of deaf relatives and their connection with congenital deafness is a very large one. Attention however, has mostly been focused upon it in relation to the intermarriage of the deaf and its effect upon their offspring. Indeed, in such unions there has already been more or less concern, and there has even been question whether it is a wise or unwise policy to allow the deaf to marry other deaf persons. The deaf, as we shall discover, not only find their companions for social intercourse among similar deaf persons, but a fortiori very often seek such persons for their partners in marriage—in fact, more often than they do hearing partners, nearly three-fourths of the married deaf being married to deaf partners.[56] Not only has it been feared that the offspring of such marriages might likewise be deaf, but there has also been apprehension lest in their encouragement there might result a deaf species of the race.[57]
From our discussion, however, we have found that in most of the marriages of the deaf we have but small reason for disquiet. If deafness in the parent is really adventitious, there is little possibility of its passing on to the offspring. When the deafness in the parent is itself congenital, the situation becomes more serious. If in such case there is no added risk from the existence of deaf relatives, the likelihood of transmitting deafness need not always be a matter of deep concern, though the hazard is materially larger than for adventitious deafness. When there are deaf relatives involved, the peril, made stronger if coupled with congenital deafness, is most pronounced; and, indeed, the existence of collateral deafness seems a more certain sign of warning than direct heredity itself. Finally, even in the marriage of the deaf with the hearing, the dangers are not in fact lessened if conditions otherwise unchanged are attendant.
What action should be taken in respect to that part of the deaf who may marry under conditions favorable to the production of deaf offspring is not at present clear. Legislation would not appear on the whole to be advisable;[58] and the exertion of moral suasion, so far as possible, in the individual cases concerned would seem a more acceptable course. The matter, however, really belongs in the province of eugenics, and we will probably do best to await the authoritative pronouncement of its decrees before full procedure is resolved upon.
Congenital Deafness as an Increasing or Decreasing Phenomenon
The final matter to be ascertained in respect to congenital deafness is whether it is relatively increasing or decreasing. The following table will show the number of the congenitally deaf in the censuses of 1880, 1890, and 1900, with their respective percentages and the ratios per million of population.[59]