HEREDITARY TRANSMISSION 

 OF GENOTYPICAL DEAF-MUTISM 



BY H. LUND BORG 



THERE are various diseases and abnormalities in the human 

 race, e. g. epilepsy, idiocy, deafness etc., which are of two 

 quite .different kinds though, as syndroms (or phenotypically), they 

 may appear homogeneous. These are partly due to heredity, in 

 part they are modifications arising through previous diseases, i. e. 

 acquired consecutive diseases or after-effects of these, respectively. 

 The latter kind is of course not inherited. Acquired deaf-mutism 

 may be both of intra- and extra-uterine origin (it may take its 

 rise partly in the womb, partly after birth). Consequently, »con- 

 genital deafness» is not always of an inheritable nature. In former 

 times no strict distinction was made between these various forms 

 of deaf-mutism, and this being the case, it is of course easy to un- 

 derstand that no answer to the riddle concerning the course of 

 heredity of deaf-mutism has been found. Uncertain statements of 

 the problems can give nothing but obscure results. Only during the 

 past few decades have serious attempts been made to distinguish 

 between genotypical and phenotypical deafness. 



Scientific research has clearly shown that the inheritable form 

 is not of so frequent occurrence as was formerly supposed. The 

 great Irish statistics of the year 1891 for instance register congeni- 

 tal deaf-mutism in as much as 76 % of the whole number of cases. 

 UcHERMANN, on the other hand, in his great work (De dövstumme 

 i Norge [The deaf-mutes in Norway], Christiania 1897) estimates 

 the number of those born deaf at 50,9 %. In 1904 Englund in 

 Sweden estimates their number as only 40,8 % . Ebbr Bergh, ^ who 

 has made investigations concerning the deaf-mutes in the district 

 of Malmöhus in Sweden, rates the number of those born deaf at 

 108 out of the total 383 examined, which only constitutes 28,2 %. 

 Bergh, being himself an ear-specialist, has made a careful analysis 



^ Ebbe Burgh, Studier over dövslumheten i Malmöhus län. Doktorsavhand- 

 ling (Studies in Dcaf'-mutism in tlie district of Malmöhus. M. D. thesis). 

 Stockholm 1919. 



