Beginning such a study of the causative factors of crime and taking account of deviation from the normal among the criminalistic, we immediately see that mental defect looms very large. Just how extensive this factor is we are unable to say, because thoroughgoing examinations of delinquents have not yet been registered in sufficient numbers. Sutherland, who has had a large experience and has well considered the matter, states in his work on Recidivism (p. 50) that it is not wide of the mark to say that one-third of criminal recidivists are pathological specimens, “suffering from physical and mental degeneracy characterized by mental warp, instability and feeblemindedness,” and that of petty offender recidivists it is equally safe to hold that two-thirds are pathological in the same sense. The British Royal Commission for the study of the feebleminded looked at 2,300 prisoners in cursory fashion and without mental tests decided that they could determine about ten per cent. to be feebleminded. Incomplete work from many sources testifies to considerable proportions of feebleminded among criminals. We ourselves, in our Chicago Institute, are for several reasons doing fairly intensive work, and I would at once disclaim that our figures have much statistical value. Yet of 620 cases of youthful repeaters carefully studied by us and classified in a scale of mental ability and peculiarity, twenty-six per cent. grade distinctly below the class which we call poor in native ability. We found: Mentally subnormal--a class above the ordinary institutional 51 feebleminded types, but still well below the normal. Dull from physical causes, including epilepsy. 36 Feebleminded of the upper or moron group. 48 Feebleminded of the imbecile group. 5 Psychoses (various types of mental disease). 22 --- 162 Scattered for the most part through these classes we found 7-1/2 per cent. of the total 620 to be definitely epileptic.