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MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. 



Table P. — Analysis of 22,4:1'2 cases of deaf -mutes tal-en frnm census returns, classified by periods of 



five years. 



[The number who became deaf in each quiuqueuuial period is reduced to a percentage of the whole on a basis of 



10,000 cases in all.] 



Table Q. — Analysis 0/22,472 cases from the census returns, classified by periods of five years, and 

 separating the congenital from the non-congenital cases. 



Table R. — Total number of deaf-mutes in the United States living June 1, 1880, classified according 



to race and sex. 



