+------+---------------+---------------+-------------+ | | Fuel Value of | Fuel Value of | Total | | Day. | the Proteid | the Fat | Fuel Value. | | | metabolized. | metabolized. | | +------+---------------+---------------+-------------+ | | calories | calories | calories | | 3 | 303 | 1916 | 2220 | | 4 | 320 | 1781 | 2102 | | 5 | 339 | 1684 | 2024 | | 6 | 341 | 1651 | 1992 | | 7 | 286 | 1684 | 1970 | +------+---------------+---------------+-------------+ These somewhat general statements, with the illustrations given, will serve in a brief way to emphasize some of the essential features of metabolism in the fasting individual; where there is no income of energy-containing material, and where the body must draw entirely upon its store of accumulated fat and proteid to keep the machinery in motion, maintain body temperature, and do the tasks of every-day life. When it is remembered that persons have fasted for periods of thirty days or longer without succumbing, it is evident that the body of the well-nourished man has a large reserve of nutritive material, which can be drawn upon in cases of emergency. At the same time, the facts presented show us that in the early days of fasting the actual amounts of tissue proteid and body fat consumed are not large. In Cetti’s case, on the sixth day of fasting the metabolized nitrogen amounted to 10 grams, which implies a loss of 62.5 grams of proteid. At this rate of loss, one pound of dry proteid matter in the form of tissue proteid would meet the wants of a man of 130 pounds body-weight for seven and a half days, provided of course there was a reasonable stock of fat to help satisfy the energy requirements. Finally, we may again emphasize the fact that the loss of nitrogen in the fasting man is by no means a measure of the minimal proteid requirement. By feeding fat, or carbohydrate, or both, the output of nitrogen can be materially diminished, although naturally we cannot establish a nitrogen balance by so doing, since the income is free from nitrogen; but we can postpone for a time the approach of nitrogen starvation.