THE FORMATIOX OP A DEAF VARIETY OF TUK HITMAN RACE. 



215 



In Table T of the Appendix I liave classified 215 cases of deaf-mutes who are the offspiins' 

 of de;if iiintes according to their i>eri()d of birth, separating those who have one parent deaf from 

 those wlio Juive both. The results are shown graphically in Fig. 11. 



Fig. 11. — The dark Hue indicates the deaf-mutes who have both parents deaf. The lower light line represents those who have one parent 

 deaf, and the upper line the total number of deaf-mutes returned who have one or both parents deaf. 



No deaf-mute having both parents deaf has been returned who was born before the year 1832. 

 It seems probable, therefore, that the oldest deaf-mute in the country whose parents were both 

 deaf-mutes Is only now a little past middle age. We have therefore received into our institutions 

 only #7(6 ^rsijrentfrrtiioM of deaf-mutes born from the intermarriage of deaf-mutes. The apparent 

 decrease in the number born since 1861 does not necessarily indicate a real decrease, for many of 

 the deaf-mutes born in the decade 1861 to 1870 have not yet been admitted to institutions for the 

 deaf and dumb. Those portions of the curves that we know to be unreliable from this cause 

 are represented in dotted lines. 



In concluding this portion of my subject it may be well to institute a comparison between the 

 deaf-mute population and the total population of the country as returned by the census of 1880. 



