178 PRINCIPLES OF STOCK-BREEDING. 



tionsliip came by the mother's side, there were in 

 cases of congenital mutism eight cases where three 

 cousins were deaf and dumb, and fourteen instances 

 where two cousins were thus affected. In the case 

 of two mutes in the same family, we find that .... 

 in one case three cousins, and in four cases two 

 cousins, labored under the like defect .... and 

 .... where three mutes occurred in the same fami- 

 ly .... two cases presented of two cousins also deaf 

 and dumb." 



These facts, upon their face, appear to be conclu- 

 sive as to the alleged influence of consanguineous 

 marriages in producing the defects in question. In 

 collecting them, however, a number of important 

 points have been neglected, which seriously detract 

 from the force they would otherwise be entitled to. 

 Endemic conditions, we have already observed, have 

 a decided influence in producing similar malforma- 

 tions, and an inherited tendency of the parents to a 

 diseased condition of the system of another form 

 would likewise aid in their production. 



In this connection it will be well to examine the 

 facts in relation to the heredity of deaf -mutism. Dr. 

 Joseph Adams, 1 in noticing the statistics furnished 

 by the Deaf and Dumb Institution of London, says : 

 " Of one hundred and forty-eight scholars upon the 

 foundation of this institution, one is of a family 

 where there are five deaf and dumb (himself in- 

 cluded); one where there are four; eleven where 

 there are three ; and nineteen where there are two. 



" Of the scholars, fifty-seven are girls, and the rest 



1 " Hereditary Diseases," p. 66. 



