January i8, 1889.] 



SCIENCE 



39 



increase due to greater accuracy of enumeration : for, when the 

 whole population of the United States are classified according to 

 their age in 1880, the proportion of deaf-mutes among the younger 

 persons is seen to be greater than among the older ; indeed, it is 

 proportionally greater as the age is younger, until quite young 

 children are reached. 



The following are the number of the deaf-and-dumb returned in 

 the Tenth Census : — 



Classification of these cases according to their age in 1880 shows 

 that there has been an enormous increase of recent years in the 

 numbers of the non-congenitally deaf ; but this need hardly be 

 considered as a permanent condition, for it appears to be due to an 

 epidemic of cerebro-spinal meningitis, which will probably die 

 away, as former epidemics have done. 



The following table shows the percentage of the whole popula- 

 tion of the United States born at each decade, and also the per- 

 centage of the congenitally deaf population : — 



These results are shown in graphical form in the following dia- 

 gram. The continuous line indicates the percentage of the general 

 population, and the broken line that of the congenitally deaf popu- 

 lation, born at each decade. 



The indications are that the congenital deaf-mutes of the country 

 are increasing at a greater rate than the general population. 



The great and sudden decrease in the numbers of deaf children 

 born in the last decade (1871-80) is probably due to imperfect re- 

 turns of deaf-mutes under ten years of age : for, though 54 per cent 

 of all the deaf-and-dumb were deaf from birth, only 30 deaf infants 

 were reported in the census of 1880, and only 49 between the ages 

 of one and two, out of a total deaf-mute population of 33,878. 



Statistics in my possession show that in the year 18 19 deaf- 

 mutes began to marry partners who were themselves deaf-and- 

 dumb. 



The percentage of intermarriages hascontinuously increased, un- 

 til now not less than 90 per cent of all deaf-mutes who marry, 

 marry partners who are themselves deaf-and-dumb. 



The latest statistics collected by me include 1,443 cases of mar- 

 riage. Of these 1,443 deaf-mutes, I find that 71 (or 5 per cent) 

 had married hearing persons, and 1,372 (or 95 per cent) had inter- 

 married among themselves. 



In 1828 a deaf-mute child was born of a deaf-mute father and 

 mother, and now such cases can be numbered by the hundred. My 

 statistics are based upon a list of 528 deaf-mutes, mostly young, who 

 have one or both parents deaf. 



Some of these children have already married deaf husbands or 

 wives, and deaf offspring have appeared in the third generation. 



I can cite families in which the deafness has been handed down 

 through four generations, and can give in minute detail particulars 

 relating to a family in Maine in which congenital deaf-mutes have 

 appeared for five successive generations in increasing numbers, and 

 in which the younger deaf-mutes are marrying deaf-mutes. 



My list of deaf children of deaf parents (all, excepting one, born 

 before 1880) comprises 528 cases (mostly young), 91.6 of whom 

 were deaf from birth. 



Upon the assumption that 528 such cases were living when the 

 Tenth Census was taken, we obtain the following results: i. 

 One person in every 1,480 of the general population was deaf- 

 and-dumb, and one person in every 64 of the deaf-mute population 

 was a child of deaf-mute parents ; 2. One person in every 2,736 of 

 the general population was deaf from birth, and one person in every 

 38 of the congenitally deaf population was a child of deaf-mute 

 parents. 



The laws of heredity indicate, that, if these deaf children should 

 marry congenitally deaf husbands or wives, an increased propor- 

 tion of deaf offspring will appear in the next generation ; and that 

 the continuous interm.arriage of congenital deaf-mutes from gener- 

 ation to generation may ultimately result in the formation of a deaf 

 variety of the human race in America, in which all or most of the 

 children will be born deaf. 



In these conclusions I am supported by the following American 

 men of science, all members of the National Academy of Sciences, 

 and most of these experts on the subject of heredity. These gen- 

 tlemen are Professor Edward D. Cope, editor of the American 

 Naturalist ; Professor Alpheus Hyatt of Harvard University ; Pro- 

 fessor William H. Brewer of Yale University ; Dr. Bowditch of 

 Harvard University ; Professor Simon Newcomb of Washington, 

 D.C. ; and Professor W. K. Brooks of Johns Hopkins University. 



I would therefore urge upon the United States the importance of 

 examining in'the next census the marital relations of defective per- 

 sons, and the extent to which their defects have been inherited by 

 their offspring. 



The enumeration of the defective classes is always found to be 

 itself defective. 



However perfect the classification may be, the returns of these 

 classes will always be incomplete, on account of a natural objection 

 to expose the defects of relatives, especially when these are very 

 young. 



Accuracy of enumeration will be promoted by eliminating from 

 the census schedules (as far as may be possible) every question that 

 could wound the feelings of parents or friends of afflicted persons. 

 For example : if the enumerator approached the subject of defects 

 by asking whether the persons enumerated were perfect in sight, 

 hearing, mind, and body, he would be more likely to secure the in- 

 formation desired than if he asked a fond mother whether her child 

 was "blind, deaf-and-dumb, idiotic, insane, maimed, crippled, bed- 

 ridden, or otherwise disabled." 



There are degrees in every defect, and the lesser forms are more 



