Prevalence of insanity--Imperfect adjustments of the brain mechanism inheritable--Many mental defectives married-- Disproportionate increase in number of mental defectives--Protests voiced by alienists--Examples of hereditary feeble-mindedness-- Difficult to secure accurate data--Feeble-mindedness and insanity not the same--Many types of insanity--Not all insanities of the same eugenical significance--Difficulties of getting genealogies of specific forms of insanity--Certain forms of insanity seem to behave as Mendelian recessives--Grades of feeble-mindedness--About two-thirds of feeble-mindedness inherited--Some results of non-restraint of the feeble-minded--Not all cases of mental deficiency inherited--Epileptics--Feeble-mindedness probably a recessive--Many apparently normal people are carriers of neuropathic defects--Tests for mental deficiency--The backward child in school--The exceptionally able child--Cost of caring for our mentally disordered--Importance of rigid segregation of the feeble-minded--Importance of early diagnosis of insanity--Opinion of competent psychiatrists essential--Some insanities not hereditary--Importance of heredity in insanity not appreciated. IX CRIME AND DELINQUENCY 263 Heredity and environment in this field--Feeble-mindedness often a factor--Many delinquent girls mentally deficient--Institutional figures misleading--Many prisoners mentally subnormal--Inhibitions necessary to social welfare--The high-grade moron a difficult problem--Degenerate strains--Intensification of defects by inbreeding--Vicious surroundings not a sufficient explanation in degenerate stocks--Not all delinquents defectives--No special inheritable crime-factor--What is a born criminal?--Epileptic criminal especially dangerous--The mental disorders most frequently associated with crime--Bearing of immigration on crime and delinquency--Sexual vice--School instruction in sex-hygiene-- Mere knowledge not the crux of the sex problem--Early training in self-restraint an important preventive of crime and delinquency-- Multiplication of delinquent defectives must be prevented. X RACE BETTERMENT THROUGH HEREDITY 289