526 



SCIENGK 



[N. S. Vol. XII. No. 301. 



genitally deaf or a hearing partner, 111, or 21 

 per cent, resulted in deaf oflfspring ; and 20 per 

 cent, of the children, or one in each five, were 

 deaf; while of 1,155 marriages where one 

 partner was adventitiously deaf and the other 

 adventitiously deaf or hearing, only 40, or 3J 

 per cent. , resulted in deaf offspring ; and only 

 2 per cent, of the children, or one in each fifty, 

 were deaf. 



If it were possible to draw this line with 

 rigorous accuracy, and to divide all the deaf 

 into these two classes, all deaf persons with a 

 marked probability of deaf children would be 

 found in the first class, while the members of 

 the second class, the adventitiously deaf, would 

 have little reason to fear the transmission of 

 their deafness to posterity ; but, as a practical 

 matter, it is not possible to draw this line with 

 scientific exactness. Deafness is not usually 

 discovered until the child has reached the age 

 when children usually begin to talk ; and it is 

 difficult to determine whether the hearing has 

 been destroyed during this period or has been 

 deficient from the first. If the child has suffered 

 from some disease which is known to frequently 

 result in deafness, the case is regarded as ad- 

 ventitious, although it may possibly be con- 

 genital. If, on the other hand, no such disease 

 has been observed, the case is likely to be 

 regarded as congenital ; but it is, perhaps, just 

 as likely that hearing has been lost in conse- 

 quence of some unnoticed inflammation of some 

 part of the auditory apparatus, occurring at 

 some time before the deafness was discovered. 

 In fact, one who, having heard, afterwards be- 

 comes deaf as the effect of disease, may be an 

 example of congenital deafness. When deafness 

 is said to be inherited, it is not actual deafness, 

 but some constitutional weakness or suscepti- 

 bility to disease that is transmitted, and a child 

 who has heard and has afterwards lost its hear- 

 ing may, while regarded as a case of adven- 

 titious deafness, have the same significance in 

 inheritance as one born deaf. 



The term ' congenitally deaf usually means 

 'supposed to be congenitally deaf,' and 'ad- 

 ventitiously deaf ' often means ' supposed to 

 be adventitiously deaf.' Some more accurate 

 method of classifying the deaf must be em- 

 ployed before we can clearly express the prob- 



ability of deaf children in any given marriage 

 of the deaf. 



It is well known that deafness often prevails 

 in families ; that deaf persons often have deaf 

 relatives ; and the arrangement of the deaf- 

 married persons, according to the existence or 

 non-existence of deaf relatives gives results 

 which are most instructive. 



In 437 marriages of deaf persons where both 

 partners in marriage had deaf relatives, more 

 than 25 per cent., or one in four, resulted in 

 deaf ofispring ; and more than 20 per cent., or 

 one child in each five, were deaf. In 471 mar- 

 riages where neither partner had deaf relatives, 

 only 2 J per cent, resulted in deaf children, and 

 only one child in each hundred was born deaf 

 (IJ per cent.). When we consider how few 

 persons especially in America, where changes 

 of residence are frequent, are acquainted with 

 the condition of all their relatives, it is not im- 

 probable that there were unknown or unre- 

 ported deaf relatives in some of these marriages 

 and that marriages of this class are even less 

 likely to result in deaf oflfspring than the tables 

 indicate. 



Indeed, Professor Fay is led to the conclusion 

 that even when deafness is congenital, it should 

 not be regarded as a bar to marriage if neither 

 of the partners in marriage has deaf relatives 

 since the tendency to transmit deafness if it ex- 

 ists at all, is very slight. On the other hand, 

 the marriage of a deaf person to a hearing per- 

 son with deaf relatives is much more hazardous 

 than the intermarriage of deaf persons without 

 deaf relatives. In fact, careful study of the 

 tables indicates that the marriage of two hear- 

 ing persons who have deaf relatives is just as 

 likely to result in deaf offspring as the inter- 

 marriage of two deaf persons who have deaf 

 relatives. Taking all the marriages of a year's 

 standing or longer of which the results have 

 been reported, where both the parents had deaf 

 relatives, more than 25 per cent, of the mar- 

 riages resulted in deaf oflfspring, and the pro- 

 portion of deaf children born to them is 20.9 

 per cent. ; where one of the parents has deaf 

 relatives while the other has not, the propor- 

 tion of marriages resulting iu deaf offspring is 

 6.6 per cent. ; where neither of them had deaf 

 relatives only 2.3 per cent, of the marriages 



