246 THE TREND OF THE RACE 
that in some even of these five matings the normal parent had 
unknown deaf relatives. But if the hearing partner have deaf 
relatives then the proportion of resulting fraternities containing 
deaf mutes increases to 35 per cent.” 
Huth who has made a very useful compilation of data on the 
subject has tabulated returns from 52 institutions or observers 
with percentages of deaf mutes of consanguineous origin varying 
from o to 34.4, but with a general average of over 5 per cent in 
33 cases, of 10 per cent or over in 21 cases, and 25 per cent or 
over in 6 cases. Although the variability of these results was 
used as an argument against the réle of consanguineous marriages 
per se in the production of deafness, the data show that this defect 
arises from such marriages in an unusually large number of in- 
stances. 
The problem of the inheritance of deaf-mutism, like that of the 
transmission of feeble-mindedness, epilepsy and insanity, is com- 
plicated by the as yet insufficiently known influence of syphilis. 
Dr. Kerr Love has attempted to separate cases of syphilitic origin 
by the use of the Wassermann reaction. It is only by eliminating 
such cases, as well as those caused early in life, that the real mode 
by which deafness is transmitted can be revealed. 
Where people form inbreeding communities different traits are 
apt to become prevalent in different localities. According to 
Davenport, ‘‘consanguinity on Martha’s Vineyard results in 11 
per cent deaf mutes and a number of hermaphrodites; in Point 
Judith in 13 per cent idiocy and 7 per cent insanity; in an island 
off the Maine Coast the consequence is intellectual dullness; in 
Block Island loss of fecundity; in some of the ‘Banks’ off the 
coast of North Carolina, suspiciousness, and an inability to pass 
beyond the third or fourth grade of school; in a peninsula on the 
east coast of Chesapeake Bay the defect is dwarfness of stature; 
in George Island and Abaco (Bahama Islands) it is idiocy and 
blindness (G. A. Penrose, 1905). There is no one trait that re- 
sults from the marriage of kin; the result is determined by the 
specific defect in the germ plasm of the common ancestor.” 
Such evils of inbreeding as have been discussed may be re- 
