As a result of the somewhat unsatisfactory experience with fairly long preliminary fasts, the experimental plan was altered so as to include fasts of only 2 days' duration in an attempt to minimize the depressing influence of the fasting and yet to secure a suitable baseline for determining the influence of food. Several experiments were made on this plan. The fasting data have already been published for most of these experiments,1 but the results are repeated in abstract here.

The first series of experiments on this later plan was made with H. R. D., December 5 to 8,1905, there being 2 days of fasting followed by 1 day with a mixed diet. The metabolism on the 2 days of fasting was remarkably constant, with an average heat production of 1,910 calories. On the food day the heat production increased practically 190 calories after the ingestion of food having a fuel value of 2,086 calories. In this instance, therefore, the fasting did not so depress the metabolism as to make it unresponsive to the stimulus of the ingested food. It should be noted that the percentage of energy from protein was somewhat larger than in the experiments thus far considered and the proportion from carbohydrates was likewise large. The details are given in table 11.

A series of experiments was also made with N. M. P., December 9 to 12, 1905, in which a mixed diet was given. (See table 12.) The fasting experiments do not show so close an agreement as was found in the preceding series with H. R. D., the individual values being 2,109 and 2,305 calories for the heat production, with an average of 2,207 calories. The food was taken at the usual meal times and the quantities were so adjusted that a large amount could be eaten by the subject. The metabolism was considerably increased by the food, the increment in the carbon-dioxide production being 180 grams, in the oxygen consumption 104 grams, and in the heat production 379 calories. That this increase was coincidental with the ingestion of a large amount of nitrogen and with a considerable part of the fuel value coming from carbohydrate is not surprising. The fuel value of the total diet was practically twice the daily requirements in the fasting period. The noticeable increase in the nitrogen excretion on the day with food is explained by the high nitrogen content of the diet.

1Benedict, Carnegie Inst. Wash. Pub. No. 77, 1907, p. 222.

Table 11. - H. R. D., December 5-8, 1905. (24-Hour Periods, 7 A. M. To 7 A. M.) Mixed Diet1

Amount, 2,010 grams; nitrogen, 12.66 grams; total energy, 2.197 calories. Fuel value: Total, 2,086 calories; from protein, 16 per cent; from fat, 35 per cent; from carbohydrates, 49 per cent.

1The food was eaten mostly in three portions, at 9 a. m., 2 p. m., and 6 p. m.

Table 12. - N. M. P., December 9-12, 1905. (24-Hour Periods, 7 A. M. To 7 A. M.) Mixed Diet1

Amount, 3,098 grams; nitrogen, 23.54 grams; total energy. 4,690 calories.

Fuel value: Total, 4,486 calories; from protein, 14 per cent; from fat, 30 per cent; from carbohydrates, 56 per cent.

1The food was eaten in four portions, at 8 a. m., 1 p. m., 6 p. m., and 10h30mp. m.

A series of experiments was carried out with D. W., January 10 to 14, 1906, which was similar in plan to those with H. R. D. and N. M. P., except that the food experiment was continued for a second day. The data are shown in table 13. The two fasting days gave results which agree fairly well with each other. After the ingestion of a mixed diet with a fuel value of only 943 calories, the metabolism on the first day after fasting was very slightly increased - hardly more, indeed, than would be expected as the limit of error. On the second day, with the same diet, the metabolism showed a very perceptible increase of 184 calories, a distinct indication of the influence of the ingestion of food. The results of this experiment are not unlike those found in the food experiments with A. L. L. - the first 24-hour experiment discussed - in which there was a continually increasing metabolism on the days following fasting. In the former case, however, the fuel value was sufficiently large to supply the daily requirements, while in this experiment the fuel value of the food was less than half that of the body needs. Inasmuch as this man was subsisting on an insufficient diet, the experiment with D. W. can hardly be termed an experiment with food, but is more properly classified as an experiment with partial inanition. In this experiment, as in the others, every attempt was made to secure uniformity in the activity. An examination of the records of the physical observer for the second day and of the figures for the total heat production show that the excess heat on this day was given off during the night between 11 p. m. January 12 and 7 a. m. January 13. This heat output can not, therefore, be considered as a digestive function, for the subject reported a very wakeful night; the records also show that he telephoned twice; although on the first day he had not done this. It is thus probable that the increment on this second day may in large part be accounted for by the difference in the muscular activity of the two days, especially during the wakeful night, and hence the results are not comparable.

Table 13. - D. W., January 10-14, 1906. (24-Hour Periods, 7 A. M. To 7 A. M.) Mixed Diet {Per Day)L

Amount, 616 grams; nitrogen, 5.11 grams; total energy, 988 calories.

Fuel value: Total, 943 calories; from protein, 14 per cent; from fat, 20 per cent; from carbohydrates, 66 per cent.

1Breakfast cereal and milk; eaten in three portions each day.

All of the food experiments thus far considered were made with a mixed diet. As it seemed desirable to study specific food substances, an experiment was made with one subject, A. H. M., in which an exclusively fat diet was given. The basal values for comparison were drawn from a 2-day fasting experiment with the same subject, carried out December 3 to 5, 1906, which was a duplicate of an experiment made on November 21 to 23, 1905. This repetition was due to the fact that, in a complete survey of the figures obtained with the subjects of the short fasts at Wesleyan University, it was found that A. H. M. gave indications of having stored glycogen during the November experiment, and it was thus desirable to find if this subject consistently gave abnormal values for katabolized glycogen. The results of the first fasting experiment have been given in full in an earlier publication,1 but the second experiment was made over a year afterward and too late to include in that report. As the results for the fasting experiment December 3 to 5, 1906, have not heretofore been published, the data are given in considerable detail in this publication.2