Recently, Professor Irving Fisher,[63] of Yale, has conducted an interesting experiment on the influence of a change in diet on endurance, having the co-operation of nine healthy students as subjects. The experiment extended through five months, with endurance tests at the beginning, middle, and end of the period. At the outset, the men consumed daily an average of 2830 calories, of which 210 were in the form of flesh foods, such as meats, poultry, fish and shell-fish; 2.6 calories of proteid being ingested for each pound of body-weight. At the close of the experiment, the per capita calories had fallen to 2220, of which only 30 were in flesh foods, and the proteid had fallen to 1.4 calories per pound of body-weight. In other words, the total calories of the daily ration had dropped off about 25 per cent, the proteid about 40 per cent, and the flesh foods over 80 per cent, or to about one-sixth of their original amount. [63] Through the kindness of Professor Fisher, the writer has had the opportunity of reading the report of this work, which at this writing is not published, and he has drawn upon it freely for the following statements of fact. To determine the endurance of the subjects, six simple gymnastic tests were employed, and one of mental endurance. The physical tests consisted of (1) in rising on the toes as often as possible; (2) deep knee-bending, or stooping as far as possible and rising to the standing posture, repeating as often as possible; (3) while lying on the back, raising the legs from the floor to a vertical position and lowering them again, repeating to the point of physical exhaustion; (4) raising a 5-lb. dumb-bell (with the triceps) in each hand from the shoulder up to the highest point above the head, repeating to the point of physical exhaustion; (5) holding the arms from the sides horizontally for as long a time as possible; (6) raising a dumb-bell (with the biceps) in one hand from a position in which the arm hangs free, to the shoulder and back, repeating to the point of physical exhaustion. This test was taken with four successive dumb-bells of decreasing weight, viz., 50, 25, 10, and 5 pounds respectively. The mental test consisted in adding specified columns of figures as rapidly as possible, the object being to find out whether the rapidity of performing such work tended to improve during the experiment. The following table shows the results of the three sets of physical tests made in January, March, and June: TESTS OF PHYSICAL ENDURANCE WITH THE NINE SUBJECTS