Ultra- Violet Rays, Test
A well-known school in England had the windows of one of its classrooms fitted with one of the new glasses permitting passage of the ultra-violet rays. In this room thirty boys between nine and eleven years of age conducted their regular school work for ten months. In another classroom not pro¬vided with such glass was a “control” group of boys, practi¬cally identical as to age and physical condition. During the ten months the average gain in weight of the “control” boys was 2.83 pounds, in height 1.22 inches, and in hemoglobin 7.53 per cent. But the boys in the experimental room made an average gain of 6.11 pounds in weight, 1.86 inches in height, and 16.14 per cent, in hemoglobin. This means that the class in the health-glass room gained 4.28 pounds, .64 inch in height, and 8.60 per cent, in hemoglobin more than the con¬trol class in the same ten months, with all other circumstances practically identical.