DEAF-MUTISM. 167 



doubted that the deaf-mutes occurring in the last two 

 generations of this family would have been set down 

 to some inexplicable freak of Nature. The parents 

 in each case were both of them normal, yet they 

 brought forth deaf and dumb children. A single 

 glance at the family tree shows from whence came 

 the imperfection. 



Unfortunately, in the histories of such families as 

 the above, we rarely know anything of the in-coming 

 so-called normal parents beyond the fact that they 

 can hear and speak. We do not know whether they 

 approach the normal type, or are members of families 

 as degenerate as those into which they marry. But 

 in such cases as that before us, in which deaf-mutism 

 or other defect appears generation after generation in 

 the children of normal members of the tainted family, 

 we are justified in assuming that the in-coming parents 

 are also tainted with degeneration, and that it is the 

 double parental taint which ensures the reappearance 

 of the pathological character. For instance, in the 

 family under review the deaf-mutism was only suffi- 

 ciently potent in the great-grandfather to reproduce 

 itself in one of his two children, yet we find it appear- 

 ing in his children's children, and in their children 

 again. We have already seen how readily reversion 

 to the normal takes place on the individual bearing 

 the lately acquired character "crossing" with the 

 normal. All through Nature this is the rule, and 

 when we find a character already latent in the indi- 

 vidual for want of prepotence reappearing in the 



