+-----------------+-------------+-------------+-------------+ | | Breithaupt. | Cetti. | Succi. | | Day of Fasting. | 59.9 Kilos. | 56.5 Kilos. | 62.4 Kilos. | +-----------------+-------------+-------------+-------------+ | | grams | grams | grams | | 0 | 13.0 | 13.5 | 16.2 | | 1 | 10.0 | 13.6 | 13.8 | | 2 | 9.9 | 12.6 | 11.0 | | 3 | 13.3 | 13.1 | 13.9 | | 4 | 12.8 | 12.4 | 12.8 | | 5 | 11.0 | 10.7 | 12.8 | | 6 | 9.9 | 10.1 | 10.1 | | 7 | ... | 10.9 | 9.4 | | 8 | ... | 8.9 | 8.4 | | 9 | ... | 10.8 | 7.8 | | 10 | ... | 9.5 | 6.7 | +-----------------+-------------+-------------+-------------+ In Succi’s case, the fasting was continued for thirty days. The daily average loss of nitrogen from the 11th to the 15th day was 5.8 grams; from the 16th to the 20th day, 5.3 grams; from the 20th to the 25th day, 4.7 grams; and from the 26th to the 30th day, 5.3 grams. A daily loss of 5.3 grams of nitrogen means a breaking down, or using up, of 33 grams of proteid, or a little more than one ounce. On the sixth day of fasting, all three of these subjects showed essentially the same daily loss of nitrogen; viz., 10 grams, which implies a using up of 62.5 grams of proteid material. We must not be led astray by these figures, however, or draw too hasty conclusions therefrom regarding the requirements of the body for proteid food. Noting the close agreement in the nitrogen output of the three subjects on the sixth day, combined with the fact that their body-weight was essentially the same, we might infer that 62.5 grams of proteid matter represents the amount of nitrogenous food necessary to maintain nitrogen equilibrium and keep the body in a condition of balance. Such a conclusion, however, would be quite erroneous for several reasons. First, a man fasting, if he was in an ordinary condition of nutrition prior to the fast, has in his tissues a large store of fat. It is considered that in fasting only about 10–12 per cent of the total energy of the body is derived from tissue proteid; the major part comes from the fat stored up. When there is no income to make good the loss, the body must naturally draw upon its own store. A certain amount of proteid must be used up daily, but in addition there are the energy requirements to be considered. These are met mainly by fat and carbohydrate, and so long as fat endures proteid will be drawn upon only, or mainly, to meet the nitrogen requirement; but if the fat gives out, then proteid must be used in