It is evident from what has been said that both of these non-nitrogenous foods, fat and carbohydrate, play a very important part in nutrition, because of their ability to maintain in a measure the integrity of tissue proteid. When we recall that a diet of pure proteid, such as meat or eggs, must be excessive in quantity in order to meet the energy requirements of the body, and that the stimulating action of proteid food serves to whip up body metabolism, we can appreciate at full measure the great physiological economy which results from the addition of carbohydrate and fat to the daily diet. The establishment of nitrogenous equilibrium is made possible at a much lower level by the judicious addition of these two non-nitrogenous foodstuffs. The same principle may be illustrated in another way, viz., by noting the effect on tissue proteid of withdrawal of a portion of the fat or carbohydrate of the intake, in the case of a person nearly or quite in nitrogen balance. The following experiment[30] affords a good example of what will occur under such treatment: [30] An experiment by Miura, quoted from A. Magnus-Levy in v. Noorden’s Handbuch der Pathologie des Stoffwechsels, 1906, p. 331. +-------+---------------------------------------++---------+----------+ | | Income. || |Balance of| | +---------+-----+-------------+---------+|Output of| Nitrogen | | |Nitrogen.| Fat.|Carbohydrate.|Calories.||Nitrogen.| in Body. | +-------+---------+-----+-------------+---------++---------+----------+ |Av. of | grams |grams| grams | || grams | | |3 days | 15.782 |40.47| 289.6 | 1955 || 14.927 | +0.862 | |Nov. 30| 15.782 |40.34| 177.3 | 1493 || 14.959 | +0.830 | |Dec. 1| 15.782 |40.34| 177.3 | 1493 || 17.546 | -1.757 | | 2| 15.782 |40.34| 177.3 | 1493 || 18.452 | -2.663 | +-------+---------+-----+-------------+---------++---------+----------+ | Average of the last two days -2.210 | +---------------------------------------------------------------------+