defects appear more liable to the others than persons normally constituted, and doubly defective persons appear to be more liable to be otherwise defective than persons having a single defect. For instance : -(a) Of 50,155,783 persons in the United States, 246,816, or 0.4921 per cent., are defective. (6) Of 246,816 defective persons, 4,597, or 1.86 per cent., are doubly defective. (c) Of 4,597 doubly defective persons, 247, or 5.37 per cent., are trebly defective. The most marked correlation

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... ms to exist between deafness, blindness, and idiocy. There are fourteen and a half times as many blind persons among the deaf and dumb in proportion to the population as among the community at large, and fortysix times as many idiotic. There are fourteen times as many deaf-mutes among the blind in proportion to the population as there are among the community at large, and nineteen times as many idiots. There are forty-three times as many deaf-mutes among the idiotic in proportion to the population as there are in the community at large, and eighteen times as many idiotic.