A24 JOURNAL OF SCIENCE. 
TABLE VII. 
Tissot je of the dcubly defective who are also trebly defective. 
Of 493 blind deaf-mutes, 217, or 44.02 %, are returned as also idiotic. 
Of 493 blind deaf-mutes, 30, or 6.09 “%, are returned as also insane. 
Of 2,339 idiotic deaf-mutes, 217, or 9.28 %, are returned as also blind. 
Of 298 insane deaf-mutes, 30, or 10.07 %, are returned as also blind. 
Of 1,403 blind idiots, 217, or 15.47 %, are returned as also deaf and dumb. 
Of 558 insane blind persons, 30, or 5.38 %, are returned as also deaf and dumb. 
The tables seem to indicate that in case of deafness, blindness, 
idiocy, and insanity, some correlation exists; for persons having one 
of those 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, 240,816, or 0.4921 %, are defective. 
(b) Of 246, 816 defective persons, 4,597, or 1. 86 Joy are doubly defective. 
(c) Of 4,597 doubly defective persons, "947, or 5.37 %, are trebly defective, 
The results obtained above, I think, merit the consideration of 
scientific men, and are calculated to throw light upon the subject of 
correlated defects. 
Although the proportion of the insane who are deaf or seid is 
abnormally large, the evidences of a correlation between insanity and 
the other defects noted above are not well marked; but in regard to 
deafness, blindness, and idiocy, a marked correlation appears to exist. 
1. Deaf-mutes.—There are fourteen and a half times as many 
blind persons among the deaf and dumb in proportion to the popu- 
lation as there are in the community at large, and forty-six times as 
many idiotic. 
2. Alind.—There are fourteen times as many deaf-mutes among 
the blind in proportion to the population as there are in the 
community at large, and nineteen times as many idiots. . 
3. Idiotic.—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 blind. 
The apparent correlation between deafness, blindness, and idiocy, 
may possibly indicate that in a certain proportion of cases these defects 
arise from a common cause, perhaps arrested development of the 
nervous system. 
It is of course possible that some of the persons returned as 
‘blind deaf-mutes’ may have lost sight and hearing from the same 
disease. The returns have not yet been sufficiently analyzed to 
enable us even to separate the congenital from the adventitious cases. 
We cannot therefore tell at the pr resent time how far the evidences 
of correlation may be weakened by a closer inspection of details. 
The large number of deaf-mutes who have been classified as 
idiots, also suggests caution in accepting the returns. I recently met 
a young lady—one of the brightest and best pupils of the Illinois 
institution for the deaf and dumb—who commenced her school-life in 
an idiot asylum. She was there discovered to be simply deaf, and 
was transferred to the Insiitution for the deaf and dumb at Jackson- 
ville, where she not only received a good education, but was 
