sence of deaf relatives. In cases where the
parents are not congenitally deaf and have no deaf relatives, the
proportion of deaf children is very low. When one or both parents are
congenitally deaf or have deaf relatives--when the deafness is inherited
or in the family--the likelihood becomes far greater, and greater still
when the two influences are in conjunction. In general, in respect to
the influences of heredity upon deafness, the main determinants seem to
be found in the existence in the parties, whether hearing or deaf, of
deaf relatives, and, to a less extent, in the existence in parties who
are deaf of congenital deafness.

POSSIBLE ACTION FOR THE PREVENTION OF CONGENITAL DEAFNESS

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