45 



which, as we have seen, may be most acute, or so weak as 

 to merge into blindness, so the sense of hearing may include 

 every gradation from the most sensitive and acute to insen- 

 sitive or deafness. Opinions seem to differ as to whether 

 deaf-muteness is transmissible or not; but Dr. Meniere, 

 whilst admitting, that in some cases, the hereditary element 

 has been admitted, says : " Nevertheless, these facts must 

 be held to constitute a rare exception ; habitually deaf-mutes 

 married to deaf-mutes beget children who hear and speak. 

 This is, of course, still more the case when the marriage is 

 a mixed one, that is, when only one of the couple is deaf 

 and dumb though in this case there are well-attested cases 

 of heredity." As Ribot points out : " The returns of the 

 Deaf and Dumb Institution of London, from its foundation 

 to the present time, are conclusive in favour of heredity. 

 Amongst 148 pupils in the Institution at one time there was 

 one in whose family were five deaf-mutes ; another in whose 

 family were four. In the families of eleven of the pupils 

 there were three each, and in the families of nineteen two 

 each." May not the commonly observed non-inheritance of 

 deaf-mutism be explained by the fact that when both parents 

 present the same characteristics, heredity may acquire such 

 power as to destroy itself? In this way Sedgwick seeks to 

 account for the fact that two deaf-mute parents often give 

 birth to children that can hear and speak ; but after all, 

 these facts go only to show by what "concurrence of 

 fortuitous circumstances, and accidental causes, nature 

 produces diversity." 



I have taken pains to make it clear that hereditary trans- 

 mission does not entirely verify the truth of the axiom that 

 " Like produces like," which would be a realisation of the 

 unattainable ideal law, but concerns itself specially with the 



