The earliest experiments included in this study, which were made with the respiration calorimeter at Wesleyan University, Middletown, Connecticut, used the 24-hour day as a unit. This was in accordance with the usage of the Munich school of Carl Voit, in which Professor W. O. Atwater of Wesleyan University obtained his introduction to metabolism experiments; practically all of the researches with the large calorimeter at Wesleyan University which have been published since 1897 have been based upon the 24-hour day.

A study of the metabolism during inanition was first attempted with the idea of using the results of the fasting experiments as a base-line in a supplementary study of the effect upon metabolism of the ingestion of food. This was done in the belief that a knowledge of the gaseous metabolism and energy transformations during prolonged fasting would be of fundamental importance, and furthermore, that after such a fast ideal conditions would be present for studying the superimposed factor of the ingestion of food.

These fasting experiments varied in length from 1 to 7 days. To obtain like activity in the basal periods and in those following food, it was the custom to watch the subject continuously during the fasting period and to record each movement. A program was then prepared, duplicating in every detail the movements of the fasting period, and in the comparison food experiment the subject was requested to follow this program faithfully. It was assumed that the narrow confines of the chamber and the routine program would so restrict the muscular activity of the subject on the food days that the degree of intensity would approximate that of the fast days.

The experiments as planned included one or more periods of observation when the subject was lying, presumably asleep, inside of the respiration chamber; it was believed that these periods would give ample opportunity for studying the most quiet metabolism of the fasting individual. At that time evidence was not secured regarding the constancy in the degree of muscular repose during these sleeping periods, aside from the reports of the subjects themselves as to their condition during the night. It was almost invariably reported that the subject slept moderately well. Certainly the men did not at any time leave the couch and the muscular activity, if there were such, did not cause a sufficient heat disturbance to attract the attention of the physical observer.

The influence of the ingestion of food was determined by noting the basal metabolism in 24 hours without food and comparing it with the metabolism during a 24-hour period in which a particular diet was ingested, the increment in the metabolism showing the increase due to the ingestion of the food.

Critique Of 24-Hour Method

This method of determining the metabolism in 24-hour periods has been regularly employed by many investigators. It was used by Johansson and his associates1 in the Stockholm laboratory in considering the effects of food following a 5-day fast. In Johansson's experiments the food ingestion immediately followed or immediately preceded the fasting days. In the experiment of 5 consecutive days reported by Rubner,2 on the first day there was hunger and rest, on the second protein diet and rest, on the third protein diet and work, on the fourth sugar diet and rest, and on the fifth sugar diet and work.

1Johansson, Landergren, Sonden. and Tigerstedt, Skand. Arch. f. Physiol.. 1897. 7, p. 20. 2Rubner, Siuber. K. Preuss. Akad. Wiss., 1910. p. 316.

Theoretically the measurement of the basal value during a 24-hour fast, to be immediately followed by a day in which the prescribed food intake is given, is an ideal method for studying the influence of the ingestion of food, inasmuch as it includes the activities of a complete normal day. The subject is thus awake during the major part of the 24-hour period and asleep the normal time, the movements being restricted to those possible inside a respiration chamber, such as dressing and undressing, drinking water, telephoning, urinating, and similar activities. By means of the program prepared for the subject, this daily cycle of normal activity could be approximately duplicated in comparison experiments without difficulty. In some respects the longer periods are pleasanter for the subject, as more freedom is allowable in the routine and strict muscular repose is not necessary.

As the total amounts of carbon dioxide given off and oxygen consumed are relatively large in a 24-hour experiment, the experimental errors are practically eliminated; the chemical and physical measurements thus have a greater degree of manipulative accuracy than is the case in short periods.

Furthermore, the continuance of food experiments for 24 hours insures a complete measurement of the effect of food, especially with certain diets, for undoubtedly the influence lasts at times longer than the 12 hours usually assumed to establish post-absorptive conditions. Finally, the long-period experiment allows the ingestion of food at the regular times of the day and in the regular amounts, thus permitting a summation effect and the obtaining of information as to the influence of the diet upon the basal metabolism for the whole day.

On the other hand, the 24-hour period can not give a minimum metabolism value for the subject, since it necessarily includes so much extraneous muscular activity. Although the method used to secure comparable activity in the experiments was as satisfactory as was then possible, it could give only an approximate control, with no assurance of perfect uniformity. Ocular evidence of the activity is at best more or less unreliable, as observers vary widely in their estimates of the quantitative relationships of various minor muscular movements.

The 24-hour type of experiment has yet another disadvantage, for although the deprivation of food for 24 hours is by no means so great a hardship as would ordinarily be supposed, yet the enforced abstinence from food for this length of time is not borne so cheerfully by the majority of individuals as is the short-period fasting.