Memory, 19 per cent with 8 losses and 19 gains. Spontaneous association, 42 per cent with 2 losses and 25 gains, Addition, 35 per cent with 1 loss and 26 gains. Controlled association, 29 per cent with 0 losses. Perception-attention, 69 per cent with 0 losses. Average gain for all tests, 57 per cent. Unfortunately, Wallin was unable to form a control group, so that it is impossible to estimate accurately how much of this gain is due to the treatment of the defect, and how much to other causes, such as growth, etc. "But," the writer adds, "if we concede that one-half of the gain--and that is, I believe, a sufficiently liberal concession--is due to a number of extrinsic factors, such as familiarity, practice and increased maturity, the gain solely attributable to the heightened mentation resulting from the physical improvement of the pupils would still be very considerable. There is corroborative evidence to show that there was a general improvement in the mental functioning of these pupils. This evidence is supplied by the examination of the pedagogical record of scholarship, attendance and deportment. Most of the members of this experiment squad were laggards, and repeaters, pedagogically retarded in their school work from one to four years, but during the experiment year only one pupil failed of promotion, while six did thirty-eight weeks of work in twenty-four weeks, and one boy finished two years of work within the experimental year." The second investigation was equally careful in its method. It was pursued by the Rockefeller Foundation, under the direction of E. K. Strong, with the purpose of examining the "Effects of Hookworm Disease on the Mental and Physical Development of Children." The children were divided into five groups and tested at intervals of three and one-half months. The tests used were opposites, calculation, logical memory, memory span, hand-writing, form-board, and Binet-Simon. After the first test-series was given, the five groups were divided into sub-groups on the basis of this initial performance, so that the improvement was compared only for those sub-groups in which this was equal. The improvement of Group A--uninfected children--proved to be greatest, and was taken as 100 per cent. On this basis, Group B--infected children not treated--showed the least improvement,--only 34 per cent. Group C--children completely cured of infection--improved 60 per cent. Group D--severely infected children, treated but not completely cured--improved 38 per cent, and Group Du--an older sub-group of D--improved 9 per cent as much as the normal children, and much less than the untreated younger children. Dr. Strong reaches the following conclusion: