The next series of experiments, that with S. A. B., January 7 to 12, 1905, included a 4-day fasting experiment, followed by a food experiment of only one day, as the subject was unable to continue the diet longer.1 The results of this latter experiment are given in table 8. The food consisted of the somewhat unusual combination of a modified milk and orange juice, a diet insisted upon by the subject as a supposedly advantageous method of breaking a moderately long fast. As on the first day of fasting there was more muscular activity than usual, the values obtained on that day are not suitable for a base-line. The food values are therefore compared with those for the second day of the fast. On comparing the fasting and food values, we find that this experiment differs from that preceding in that here the digestive activity produced no increment in the metabolism, the values for the food day being lower than those for the second day of fast. On the other hand, when the fourth day is used as a base-line, there appears to be an increase in the metabolism after the food. It should be noted in this connection that the amount of energy in the diet from both protein and carbohydrates was small, the total fuel value of the food being only 1,698 calories. The only deduction which can be made from this experiment is that after 4 days of fast, the ingestion of 1,359 grams of food of the composition noted was not sufficient to raise the metabolism above the level of the second day of fast, although the values were somewhat increased by the food over those obtained for all the factors during the fourth fasting day, which immediately preceded the taking of the milk and orange juice.

Table 8. - S. A. B., January 8-12,1905. (24-Hour Periods, 7 A. M. To 7 A. M.) Milk And Orange Juice

Amount, 1,359 grams; nitrogen, 6.24 grams; total energy, 1,752 calories. Fuel value, 1,698 calories; from protein, 9 per cent; from fat, 73 per cent; from carbohydrates, 18 per cent.

1First day not included because of work done on bicycle ergometer.

1For the detailed results of this series, see Benedict, Carnegie Inst. Wash. Pub. No. 77, 1907, experiments Nos. 71 and 72.

Somewhat similar conditions exist in the next series of experiments with the same subject S. A. B., January 28 to February 5, 1905.1 This consisted of a 5-day fasting experiment, followed by a 3-day food experiment. (See table 9.) A mixed diet was used, consisting of modified milk, orange juice, a small quantity of apple, and a few graham crackers. This diet was somewhat above maintenance in energy, but small in nitrogen content. After 5 days of continuous fasting, the effect of the amount of food taken was not sufficient to bring the metabolism up to the values obtained on the first 2 days of the fast. Nor did the continued ingestion of the food materially alter the total metabolism in any way. The results of this experiment are in striking contrast to those obtained for A. L. L., on December 16 to 23, 1904 (see table 7, page 56), in which there was a continued increase in the values obtained on the food days. The fuel value of the food used for the experiment with A. L. L. was, however, about 25 per cent higher than that given to S. A. B. If the results for the fifth day of the fast are used as a base-line in this experiment with S. A. B., the metabolism on the food days will show a positive increment for all 3 days, although the increment on the second day is very small for both the oxygen consumption and the heat production. Indeed, the food experiment in this series seems to indicate simply a maintenance of the fasting value originally established at the end of the fifth day of fasting, for it is apparent that although the body requirement was only about 1,600 calories, the ingestion of food having a fuel value of about 2,000 calories was not sufficient to raise the metabolism to the initial level of the first two fasting days, i. e., 1,800 calories. In this, as in all other experiments, strict attention was paid to the necessity of securing comparable conditions of muscular activity. Such variations as were unquestionably present have been carefully discussed in detail in a previous publication.1 The data there given show that the energy of the estimated muscular activity was extraordinarily constant throughout the 5 days of fasting and the 3 days with food; the difference can not therefore be explained by differences in muscular activity.

Table 9. - S. A. B., January 28-February 5, 1905. (24-Hour Periods, 7 A. M. To 7 A. M.) Mixed Diet {Per Day)

Amount, 1,671 grams; nitrogen, 6.37 grams; total energy, 2,133 calories. Fuel value, 2,078 calories; from protein, 8 per cent; from fat, 65 per cent; from carbohydrates, 27 per cent.

1For the detailed results of this experiment, see Benedict, Carnegie Inst. Wash. Pub. No. 77, 1907, experiments Nos. 73 and 74.

Still another series of experiments was made with this subject March 4 to 14, 1905, in which the fasting experiment continued for 7 days and the food experiment 3 days.2 The diet in the food experiment consisted of milk, gluten crackers, an apple, orange juice, and a small quantity of a breakfast food. As shown in table 10, the average value for the heat production for the first 2 days was 1,767 calories.

Table 10. - S. A. B., March 4-14,1905. (24-Hour Periods, 7 A. M. To 7 A. M.) Mixed Diet (Per Day)

Amount, 1,274 grams; nitrogen, 6.45 grams; total energy, 1,841 calories. Fuel value, 1,788 calories; from protein, 9 per cent; from fat, 37 per cent; from carbohydrates, 54 per cent.

After the ingestion of the mixed diet, which had a fuel value of 1,788 calories, the metabolism returned to the level of the first 2 days, but was not raised above it. It was, however, about 200 calories higher than the metabolism on the seventh day of the fast. Thereafter the metabolism remained essentially constant, the progressive increment noted with A. L. L. being absent. We have here, therefore, the singular fact that this diet was sufficient to raise the metabolism after 7 days of fast to the initial level of the first 2 days of the fast, while in the experiment with the same subject on February 2 to 5, a diet containing about 300 more calories was not able to produce this effect. An analysis of the character of the diet shows that the percentage of protein was essentially the same in both instances, but that the carbohydrate contained double the amount of energy in this experiment, with a corresponding reduction in the proportion from fat. It is not impossible, therefore, that the action of the carbohydrate accounts for the apparent discrepancy between the two sets of results. Since even in this experiment there was no evidence of an increment if the first 2 days of fasting are taken as a base-line, we can consider the stimulating effect of the food as simply compensating for the decrease in the metabolism produced by the specific effect of the fasting. It is only when this depressing influence of fasting has been completely overcome that the stimulating action of the food is apparent. In the plan of experimentation thus far used it is clear that the problem is distinctly complicated by the conditions involving the depressant effect of a prolonged fast and by the attempt to superimpose the stimulating effect of the ingested food.

1Benedict, Carnegie Inst. Wash. Pub. No. 77, 1907, p. 486, table 234.

2For the detailed results of this experiment, see Benedict, Carnegie Inst. Wash. Pub. No. 77, 1907, experiments Nos. 75 and 76.