THE FOEMATION OF A DEAF VARIETY OF THE HUMAN RACE, 



201 



We have here n clear iiidifatiDn that a hereditanj tendency Inirards denfncftfi, as indicated Inj the 

 possession of deaf relatives, is a most itiijiortant element in determining the production of deaf of' 

 spring. ThefoUoicing table shoirs that it may cren he a more important element than the mere fact of 

 congenital deafness in one or hoth of the parents. 



Table XXX. — Ueafmulc offspring of deaf-mute marriages. 



Llirsiilts ilediii^ed t'ldin the tables in the appendix, coiiihiiiin;; the figures obtained from the reports of the American 



Asylum and Illinois Institution. ] 



De.scri)ition (if married couples. 



(1) Father known to be a deaf-mnte (siunmation of all cases where the cause of 

 father's deafness is stated): 



(n) Father recorded to be con}j;eni tally deaf 



{b) Father reeorde<l to be non-cougeni tally deaf 



(•2) Mothir known to be a deaf-mute (snniniation of all cases where the cau.se of 

 mother's deafness is stated): 



(«) Mother recorded to lie cougenitally deaf 



{b) Mother recorded to be uoneongeni tally deaf 



(3) Father known to be a de:if-nmte (sninmatiim of all such eases): 



(«) Father known to have deaf-mute relatives 



(h) Father recorded as a sporadic c;ise 



(4) Mother known to be a deaf-mnte (summation of all such eases) : 



(a) Mother known to have deaf-mute relatives 



(6) Mother recorded as a sporadic case 



(5) One parent known to be a deaf-mute (summation of all cases where the cau.se 



of deafness was stated): 

 (n) Deaf-mute parent recorded to be congeuitally deaf 



(b) Deaf-nnite jiarent recorded to be nou-congenitally deaf 



(6) One parent known to be a deaf-mnte (summation of all cases): 



(«) Deaf-mnte parent known to have deaf-mute rehitives 



(/>) Deaf-mute parent recorded as a sporadic case, 



(7) One parent recorded to be congeuitally deaf (summation of all cases): 



(n) (Cougenitally deaf parent known to have deaf-mnte relatives 



(b) Congeuitally deaf jiareut lecorded as a sporadic case 



(8) One parent recorded to be nou-congenitally deaf (summation of all cases): 



(a) Non-cougenitally deaf parent known to have deaf-mute relatives 



(6) Nou-congenitally deaf parent recorded as a sporadic case 



(9) Both parents known" to be deaf-mutes (summation of all cases): 



(a) One parent known to have deaf-mute relatives 



(fc) One parent recorded as a sporadic case 



(10) Both ]iarents kuown to be deaf-mutes and one recorded as congeuitally 



deaf: 



(a) Congeuitally deaf parent kuown to have deaf-mnte relatives 



(6) (Jongenitally deaf parent recorded as a sporadic case 



(11 ) Both parents knowu to be deaf-mutes, aud oue recorded as non-congeuitally 



deaf: 



(a) Non-cougenitally deaf parent kuown to have deaf-mute relatives 



{h) Xon-congenitally deaf parent recorded as a sporadic ca.se 



(12) One parent known to bi' a deaf-mute and the other presumed to be a hear- 



ing person (summation of all cases): 



(rt) The deaf-mute parent known to have de.af-mute relatives 



(i) The deaf-mute parent recorded as a sporadic case 



(13) One parent recorded to be a congenital deaf-mnte, the other presumed to be 



a hearing person: 



(a) Congeuitally deaf parent known to have deaf-mute relatives 



(6) Congeuitally di-af parent recorded as a sporadic case 



(14) One parent recorded to be a nou-congfuital deaf-mute, the other presumed 



to be a hearing jierscin : 

 (o) Non-congenital deaf-mute parent knuwn to have deaf-mute relative 

 (li) Non-congeuilal deaf-iiiuti- parent ri-c-mdcd as a sporadic case 



(15) General resulis (summation of all cases of marriage recorded) : 



Average ^16 



82 



10.0 



*The perceutages arc giveu as deduced from the institution reports, 

 greater, hat proportioiiaVii greater. 



S. Mis. 110 I'O 



The true percentages are probably much 



