+--------------------------+--------+---------+---------+--------+-----------------+ | Heat of Combustion of | (d) | (e) | (f) | | Heat Measured | | Food and Excreta as | Avail- | Total |Estimated| Heat | Greater or | | Determined by Bomb | able | Energy | Energy |Measured| Less than | | Calorimeter. | Energy |from Body| from | by | Estimated. | +--------+--------+--------+ from |Material | Material|Respira-+--------+--------+ | (a) | (b) | (c) | Food. |Gained or| Oxidized| tion | | | | Food. | Excre- | Urine. | a-(b+c)|Lost.[34]| in the | Calor- | Amount.|Propor- | | | ment. | | | | Body. | imeter.| | tion. | | | | | | | d-e | | | | +--------+--------+--------+--------+---------+---------+--------+--------+--------+ |calories|calories|calories|calories|calories | calories|calories|calories|per cent| | 2569 | 149 | 103 | 2317 | +229 | 2088 | 2113 | +25 | +1.2 | +--------+--------+--------+--------+---------+---------+--------+--------+--------+ [34] In the experiment, the body lost 29.16 grams of proteid = 165 calories, but gained fat and glycogen = 393 calories. Hence, there were 229 calories gained from body material. As is seen from the above figures, the total fuel value of the food was 2569 calories. The fuel value of the unoxidized portion of the food contained in the excreta was 149 + 103 calories, leaving as the available energy of the food 2317 calories. This must be further corrected by the fact, mentioned in the footnote, that a portion of the food was stored as fat and glycogen, while the body lost at the same time a small amount of proteid. Making the necessary correction for these causes, we find 2088 calories as the energy from material oxidized in the body. The actual output of energy as measured by the calorimeter was 2113 calories, only 1.2 per cent greater than the estimated amount. By aid of the respiration calorimeter, many important questions in nutrition can be more or less accurately answered, especially such as relate to the total energy requirements of the body. The law of the conservation of energy obtains in the human body as elsewhere, and if we can measure with accuracy the total heat output, with any energy liberated in the form of work, and at the same time determine the total excretion of carbon dioxide, water, nitrogen, etc., together with the intake of oxygen, it becomes not only possible to ascertain the energy requirements of the body under different conditions, but, aided by data obtainable through study of the exchange of matter, we can draw important conclusions concerning the sources of the energy, _i. e._, whether from proteid, fat, or carbohydrate.