CHAPTER XII. 



DEAF-MUTISM. 



" Ordinary deaf -mutism is closely allied to idiocy, and is one of 

 the hereditary neuroses. To me it is a physiological sin that 

 marriages between such persons should be legal." CLOUSTON.* 



THERE is still some difference of opinion as to the 

 hereditary character of deaf-mutism, and some might 

 even demur to its being given a place in a work 

 treating solely of hereditarily transmitted affections.' 

 This difference of opinion depends largely upon the 

 want of discrimination with which cases are collected 

 and classified. To understand the part played by 

 family predisposition in the production of this con- 

 dition, all cases of deaf-mutism should be divided with 

 great care into two classes. First, those in whom 

 the deafness is the result of congenital defect; and 

 second, those in whom deafness follows some injury 

 to the auditory apparatus before or shortly after the 

 power of speech has been attained. Nearly the whole 

 of the cases making up the first class we shall find 

 dependent upon parental taint; whereas in the second 

 * Op. dt., p. 286. 



