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SCIENCR 



[Vol. XVII. No. 424 



of no value or sig-niflcance. This, however, is not the case; 

 for the imperfection of the statistics assures us that the 

 figures given are all underestimates, the true number of 

 deaf children in every case being greater than that men- 

 tioned. As a matter of fact, all the statistics since collected 

 by others have shown larger percentages. 



While it is believed that the true percentages are larger 

 than those given, it is probable that they are proportionately 

 larger; so that we may conclude with probable accuracy that 

 persons belonging to Class 4 are more liable to have deaf 

 children than those belonging to Class 3, those of Class 3 

 more liable than those of Class 2, and those belonging to 

 Class 1 are the least liable of any, to have deaf offspring. 

 The relative liabilities are probably represented by the per- 

 centage flgures. 



The results are imperfect from another cause. The insti- 

 tution j-eports from which the statistics were compiled did 

 not give details concerning both the parties to a marriage. 



It would be stated that Mr. So-and-so " married a deaf- 

 mute;" but no information would be given as to whether his 

 wife was born deaf or not, or whether she had or had not 

 deaf relatives. I have only been able, therefore, to classify 

 the marriages by one side. For example: the results noted 

 for Class 1 give the summation of all marriages of persons 

 not born deaf who have no deaf relatives, quite regardless 

 of the fact that some of them married congenital deaf-mutes, 

 others semi-mutes, and still others hearing persons. We 

 may deduce, however, from the figures, that, if the husband 

 belongs to Class 1, his liability to have deaf offspring will 

 he greatest if his wife belongs to Class 4, and least if she 

 belongs to Class 1, etc. 



Now that Professor Fay has taken up the subject, I hope 

 that we may obtain statistics of greater accuracy and im- 

 portance than any yet compiled. 



^When we obtain statistics classified by both parties to the 

 marriage, I think it will be found, that, where persons be- 

 longing to Class 1 marry persons also belonging to 

 Class 1, there will be no deaf oH'spring, or, at least, that 

 the percentage of deaf offspring will be insignificant; for 

 surely accidental deafness is no more liable to be 

 inherited than the accidental loss of an arm in battle, for 

 instance. If, however, a person born without an arm should 

 marry a person also born without an arm, some of the chil- 

 dren would probably exhibit the same defect. In a similar 

 manner, persons belonging to Classes 2, 8, and 4 exhibit a 

 decided tendency to transmit deafness to their offspring. 



Now, there 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. It requires constant selection from 

 generation to generation on both sides to perpetuate any ab- 

 normal peculiarity. There will always, therefore, be a ten- 

 dency to produce heariag children rather than deaf, except- 

 ing in cases where both parties to a marriage come from 

 families belonging to Classes 2, 3, and 4. 



Probabilities for Your Guidance. 



Whatever may be the character of the deafness in your 

 own case, you will probably diminish your liability to have 

 deaf offspring (1) by marrying a hearing person in whose 

 family there is no deafness; (2) by marrying a deaf person 

 (not born deafj who has no deaf relatives (Class 1), or a hear- 

 ing brother or sister of such a person. 



On the other hand, you will probably increase your liabil- 

 ity to have deaf offspring (1) by marrying a deaf person (not 



born deaf) who has deaf relatives (Class 2), or a hearing 

 brother or sister of such a person; (2) by marrying a deaf 

 person (born deaf) who has no deaf relatives (Class 3), or a 

 hearing brother or sister of such a person; (3) by marrying 

 a deaf person (born deaf) who has deaf relatives (Class 4), 

 or a hearing brother or sister of such a person. 



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, I am inclined to think, 

 that, if you marry a member of a family in which there is 

 no deafness (or only a single case of non-congenital deaf- 

 ness), you will not only have fewer deaf children than if 

 you married into a family containing acongenital deaf-mute, 

 or a number of deaf persons, but the deafness of your chil- 

 dren will not tend so strongly to be handed down to the 

 grandchildren. The tendency to inheritance will be weak- 

 ened in the one case, and intensified in the other: that is, in 

 the former case your deaf child will have a less tendency to 

 transmit his defect to his children than you yourself possess; 

 in the latter case, a greater tendency. 



Take the case of a family m 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 de- 

 scendants will hear. 



On the other band, suppose that the members of this fam- 

 ily and their deaf descendants marry into families containing 

 a congenital deaf-mute, or containing several deaf persons. 

 Then the probabilities are that at each generation the per- 

 centage of children born deaf will increase, and the propor- 

 tion of hearing children will be less, until finally the tendency 

 to produce hearing offspring disappears, and all the descend- 

 ants will be deaf. This family would then constitute a deaf 

 variety of the race, in which deaf offspring would he the 

 rule, and hearing offspring the exception. 



Now, the point that I would impress upon you all is the 

 significance of family deafness. I would have you remem- 

 ber that all the members of a family in which there are a 

 number of deaf-mutes have a liability to produce deaf off- 

 spring, the hearing members of the family as well as the deaf 

 members. 



This, I think, is the explanation of the curious fact that 

 the congenitally deaf pupils of the Hartford Institution who 

 married hearing persons had a larger percentage of deaf chil- 

 dren than those who married deaf-mutes. It is probable that 

 many of the hearing persons they married had brothers or 

 sisters who were born deaf. 



Cases will constantly arise in which a proposed marriage 

 will appear undesirable and desirable both at the same time. 

 For example : a semi-mute having no deaf relatives may form 

 an attachment for a congenitally deaf person in whose fam- 

 ily deafness may be hereditary. Of course, I have nothing 

 to say as to what the young people should do: that is a mat- 

 ter for them to decide. I cannot even undertake to advise. 

 The semi mute will have no tendency to have deaf children 

 if he or she will marry a person of similar kind (Class 1), or 

 marry a hearing person belonging to a family in which there 

 is no deafness: hence this person, by marrying a congeni- 

 tally deaf person iu whose family deafness is hereditary, 

 will create a liability to have deaf offspring which would not 



