To understand the significance of this comparison one should consider the relative difference which is shown between school children and delinquents in the statistics of health, defective sight, nose and throat obstructions, etc. The percentages of consecutive delinquents showing other defective or diseased conditions has never, so far as the writer is aware, been found to be double that among the school children generally when figured on a corresponding basis. Medical inspection shows that for other conditions than retardation the frequency of defects and disease found among representative groups of ordinary juvenile delinquents can often be equaled in the poorer schools of the city. To find a factor relatively twice as common among delinquents as among school children, when the frequencies are as great as with retardation, means a variation that is unquestionably significant. This is, of course, not an argument against the detection and treatment of handicaps that can be benefited by the physician. It only suggests the relative size of the two problems. In considering the frequency of school retardation among delinquents in Minneapolis, it will be noted that the most serious condition is clearly among the girls, 90% of whom are below grade as compared with the index of 35% for the corresponding group of school girls. One may estimate that the chance of a Minneapolis boy who is retarded in school getting into juvenile court is about 3½ times that of a boy who is up-to-grade. But the chance of a girl who is retarded in school getting into juvenile court is about 17 times as great as that of a girl who is up to grade. This calculation is easily made on the assumption that the indices of Table XIV are typical for a single year, knowing that about 194 in 10,000 school boys in Minneapolis get into the court annually and 21 in 10,000 school girls. The best measure of the difference in school attainment cannot be shown, however, without considering the _amounts_ instead of the frequency of retardation in the groups compared. We should regard two years retardation as twice as serious as one year and make a corresponding allowance for each additional year of retardation. Thus weighting our results we find in the indices of Table XIV that the boys 8-15 years of age in the Glen Lake Farm School group of delinquents have on the average lost 1.54 of a year through retardation in school attainment compared with the satisfactory standard of 7 in the first grade. The ordinary delinquent boys have lost on the average 1.27 of a year, while the indices for Minneapolis school boys of corresponding ages are—.54 and—.61 of a year respectively. Among the ordinary delinquent girls the average amount of retardation on the same basis is 2.29 years as compared with .64 of a year among the school girls of corresponding age distribution.