The term "cause" seems to be rather loosely used in this study. The author says concerning this, "Dealing with physical defects first, although they amount in the aggregate to 53 per cent (omitting defective speech, which is a secondary condition), in 10 percent only do they represent the whole cause. This is made up of those cases where the defect is of such intensity as to produce retardation in otherwise ordinary children, and of other cases of less intensity, but sufficient to weigh down the balance against those near the level of what we may call for convenience the lower limit of normal intelligence." How he determines, without removing a defect, what the child's intelligence would be without it he does not explain. The following table compares the physical condition of two groups, one comprised of children examined in the regular routine examinations during the year 1912,--the other a group of retarded school children, given a special examination:--[10] [10]: Transactions of the International Congress on School Hygiene, 1913, The Physical Condition of Retarded School Children. Group I Group II No. of children examined 287,456 1,541 No. with physical defects 206,720--71.9% 1,383--89.8% No. of defects found 226,639 2,986 Defect No. % No. % Anaemia 335 23 Malnutrition 8,303 2.9 557 36.1 Defective vision 21,078 9.3 536 34.7 Defective hearing 1,206 0.5 47 3 _Defective nasal breathing_ _21,931_ _7.6_ _316_ _20.4_ _Hypertrophied tonsils_ _30,021_ _10.4_ _297_ _19.2_ Defective teeth 142,168 49.4 796 51.6 Pulmonary disease 335 0.1 47 3.0 Cardiac disease 1,597 0.5 35 2.3 Average No. of defects per child 1.1 2.5 In an investigation of 3,587 exempt and 1,418 non-exempt children in the Philadelphia schools,[11] Dr. Newmayer found the following percentages of defect: [11]: Ayres: "Laggards in Our Schools." 1909. Exempt Children Non-exempt Children