52 FOOD INGESTION AND ENERGY TRANSFORMATIONS. 



olism and the metabolism after food were determined on separate days, 

 but later in the research the food was frequently given after several 

 hours of fasting and the measurements continued for the remainder of 

 the 8 hours. Thus, in these later experiments, the basal metabolism 

 and the metabolism after food were determined on the same day. In 

 the short-period experiments the basal metabolism was measured on 

 the same plan as that used in most of the later 8-hour experiments, i. e., 

 in several periods preceding the ingestion of food. 



Both the 24-hour experiments and the 8-hour experiments were 

 carried out with respiration calorimeters, by means of which not only 

 the carbon-dioxide production and the oxygen consumption could be 

 measured, but also the heat production. The short-period experi- 

 ments, in which the individual periods were approximately 15 minutes 

 long, were made with respiration apparatus which gave measurements 

 of only the carbon-dioxide production and the oxygen consumption. 

 The heat production was calculated by the indirect method. 



The main object in all these experiments w r as essentially the same, 

 namely, to secure a constant base-line upon which could be superim- 

 posed the factor of the ingestion of food. With the 24-hour base-line 

 it was necessary to assume that the metabolism was constant from day 

 to day; with the earlier 8-hour base-line, that it was constant on differ- 

 ent days; and in the experiments in which the base-line was determined 

 on the same day as the metabolism after food (the later 8-hour experi- 

 ments and the short-period experiments), that the metabolism was 

 constant from hour to hour throughout the day. From a consideration 

 of these plans of experimenting it is easily seen that the probability 

 of constancy in muscular activity is not the same for all types of 

 experiments. The advantages and disadvantages of each method may 

 therefore be discussed more in detail in connection with the results 

 obtained in the determinations of the basal metabolism. 



EXPERIMENTS OF 24 HOURS' DURATION. 



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. 0. 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 inges- 

 lion of food. This was done in the belief that a knowledge of the 



