From these data, we see that per kilogram-meter of work less energy was required and less oxygen consumed with fat than with either of the other two foodstuffs; but practically, fat and carbohydrate as sources of muscle energy have about the same value. Much stress is ordinarily laid upon the importance of a large intake of proteid food whenever the body is called upon to perform severe, or long-continued, muscular work; but in view of what has been stated it may be questioned whether there is any real physiological justification for such custom. The pedestrian Weston,[48] who in 1884 walked 50 miles a day for 100 consecutive days, was found by Blyth during a period of five days to consume in his food 37.2 grams of nitrogen a day, while he excreted only 35.3 grams, leaving a balance of 1.9 grams of nitrogen per day apparently stored in the body. His daily food during this period was composed of 262 grams of proteid, 64.6 grams of fat, and 799 grams of carbohydrate, with an estimated fuel value of 4850 calories. Yet he performed this large amount of work daily, and still laid by a certain amount of proteid on a ration, the energy value of which would not ordinarily be considered high for the muscular work to be done. Fourteen years prior to this, Weston, while in New York, was carefully studied by Dr. Flint during a period of 15 days, on 5 of which he walked a total of 317 miles. His diet was essentially a proteid diet, consisting principally of beef extract, oatmeal gruel, and raw eggs. Nitrogen intake and output were carefully compared during the days of rest and during the days of work, with the results tabulated. [48] This and the following account of Weston are taken from Bulletin No. 98, U. S. Department of Agriculture, Office of Experiment Stations. The effect of severe and prolonged muscular work on food consumption, digestion, and metabolism. By W. O. Atwater and H. C. Sherman, p. 13.