Fio.12. 



Lboenb.— Distribntion according to age (1) of the whole population o( 

 the United States, (2) of the congenital deaf mute population, and (3) of 

 deaf mutes who are the children of deaf mutea. 



The ordinates of the cnrves represent the percentage of the whole who 

 were born in the decades indicated by the abscissa;. 



represents population of the United States. 



represents congenital deaf mutes of the United States. 



represents deaf mutes who are the children of deaf 



mutes. 

 vepresentsportion of rhcciirrcs Icnownto be unreliable 



on account of incoinjilete returns. 



)_m 



31 



mi-178 



1781-1^70 



1791-1800 



I80I-I8I0 



1811-1820 



1821-1830 



IB3I-I8S0 



1841-1850 



1851-1860 



1861-1670 



1671 - 1880 



