Evening star. [volume] (Washington, D.C.) 1854-1972, 1891-03-14

suits, however, until verified by other OBJ
servers, should be received as probable only
and not certainly proved.
THE PROBABILITIES
Now" continued the speaker, "thsre is a
law Of heredity that may afford great comfort
to many of the deaf-the law Of reversion
There is a very strong tendency in offspring to
revert to the normal type of the race. 1t re-
qulres constant selection from generation to
generation on both sides to perpe,uate any alb
normal popularity. There will always. there
fore, be a tendency to produce hearing children
rather than deaf. excepting in cases where
both parties to marriage come from families
belonging to classes 2, 3 and 4.
Whatever may be the character Of the deaf
ness IN your own case, you will probably dimin-
minish your liability to have deaf offspring
l. BY marrying a deaf person mot born deaf
who has no deaf relatives, or a hearing brother
or sister OF such person. 2. By marrying q
hearing person in whose family there is no
deafness.
On the other hand, you will probably increase
your liability to have deaf offspring-1. By
marrying deaf person mot born deaf who
has deaf relatives, or a hearing brother or
sister OF such person. 2. By marrying a
tiyes, or hearing brother or sister of such a
person 8. By marrying deaf person (born
deaf who has deaf relatives, or q hearing
brother or sister of such person.
READIcArISa DEAFNESS
"Of course, if you yourself were born deaf
or have deaf relatives it is perfectly possible
that In any event some of your children may
be deaf Still, 1 am inclined to think that if
you marry member of family in which there
Is no deafness Cor only single case of non
congenltal deafness), you will not only have
fewer deaf children than if you married into q
family containing congeuital deaf mute or a
Leaf hnt fha <.f
your children will not tend so strongly to be
handed down to the grandchildren. The ten
dency to Inheritance will be weakened in the
one case and intensified in the other. That is
In the former case your deaf child will have q
less tendency to transmit his defect to his
children than You yourself possess; in the lat
ter case a greater tendency.
Take the case Of family in which three or
four children are born deaf. Now, suppose
that all the members of this family and their
deaf descendants are careful to marry only into
families which are free from deafness or which
contain only single cases of non-congenital
deafness. Then the probabilities are that at
each generation the percentage OF children
born deaf will be less and the proportion Of
hearing children greater, until finally the deaf
tendency disappears and all the descendants
viii hear. On the other hand suppose that the
members OF this family and their deaf de-
scendants marry into families containing a
congenital deaf mute or containing several deaf
persons Then the probabilities are that at
each generation the percentage of children
born deaf viii increase and the proportion of
hearing children will be less, until finally the
tendency To produce hearing offspring disap-
pears and all the descendants will be deaf
This family would then constitute deaf variety
OF the race, in which deaf offspring would be
the rule and hearing offspring The exception.
Now, the point that would impress upon you
all is the significance Of family deafness.
would have you remember that all the mem
beers of a family in which there are number
Of deaf mutes have liability to produce deaf
offspring the hearing members Of the family
as wen as the deaf members.-