THE FORMATION OF A DEAF VARIETY OF THE HUMAN RACE. 189 



Table XV. — Proportion of the non-congenitally deaf ivho hare deaf-mute relatives. 



Institutions. 



Ami'iican A.syliim 



Ni'xv Yorli Instiiiition 



Ohio Institiilioii 



Indiana Instiiiition .. 

 Illinois Institution. ... 

 Texas lustitntiou 



Total 



Niunlxn' of Niinibiir having | Percentage 

 non-congenital deaf-mnto rcl- having deaf-mute 

 deaf-mutes. atives. relatives. 



13.8 



Table XVI. — Fro])ortion of the congenitally deaf who have deaf nude relatives. 



Institutions. 



American Asylum 



New York Ins itutiou 



Ohio Institution 



Indiana Institution .. 

 Illinois Institution. .. 

 Texas Institution .. .. 



Total 



Number 



of congenitally 



deaf pupils. 



973 



488 

 208 

 149 

 418 

 26 



2,262 



Number having j Percentage 

 deaf-mute rel- having deaf-mute 

 atives. relatives. 



552 

 287 

 118 



72 

 194 



11 



1,234 



The above tables (Tables XIV, XV, aud XVI) sbow tbat of 2,262 congenital deaf-mutes^ more 

 than one-half^or 54:.5 jjer cent. — had deaf-mute relatives ; and that even in the case of those j)upils 

 who became deaf from apparently accidental causes, 13.8 per cent, had other members of their families 

 deaf and dumb. 



If we apply the.se results to the total retiirued by tbe Tenth Census, we obtain the following- 

 figures (Table XVII) as a probable api^roximation to the number of sporadic and non-sporadic 

 cases of deafness among the deaf-mutes of the country. 



Table XVII. — Estimate of the probable number of sporadic and non-sporadic cases ofdeafness among 

 the deaf-mutes of the United States in the year 1880. 



If to the estimated number of deaf-mutes who have relatives deaf and dumb we add the pre- 

 sumed uumber of sporadic cases amoug the congenital deaf-mutes we reach a total of 20,474 cases 

 where the deafness would probably tend to become hereditary by intermarriage. But these are 



