BASAL METABOLISM. 55 



olism. The evidence as a rule indicates an increment in metabolism, 

 but certain experiments, as we have seen in the summary of the liter- 

 ature on this subject (see page 40), have at least suggested a depression 

 of the basal metabolism. 



Furthermore, with the 24-hour period it is practically impossible to 

 detect slight increases, which may actually occur but be lost in the 

 daily quota. These increases could be demonstrated if the maximum 

 effect could be obtained by means of measurements in short periods 

 immediately following the ingestion of food. In a study on the influ- 

 ence of food upon metabolism it would therefore be expected that the 

 24-hour type of experiment could be satisfactorily used only when 

 studying classes of foods which produce a considerable increment in 

 metabolism rather than for securing evidence regarding foods which 

 cause but a slight increase in metabolism. 



DISCUSSION OF RESULTS OF FASTING AND FOOD EXPERIMENTS 



ON THE 24-HOUR BASIS. 



In view of the results obtained in the fasting studies carried out at 

 Wesleyan University and later in the Nutrition Laboratory, the selec- 

 tion of a suitable basal value to be used for the 24-hour food experi- 

 ments has been a subject of much consideration. As will be shown 

 later, in our discussion of the experiments and in our conclusions as 

 to the use of this type of experiment, the length of the fast influences 

 the increment in the metabolism due to the ingestion of food. In 

 discussing the basal metabolism in this special group of 24-hour experi- 

 ments, therefore, it has seemed desirable to give the detailed results 

 obtained after the taking of food, presenting only those fasting values 

 which have been selected for the base-line. The data for the food ex- 

 periments, when significant, will later be included in abstract in several 

 tabular presentations of final results and in the discussion of special food 

 topics. They are presented here primarily as material for a critical 

 study of the general principle of the use of 24-hour periods. In giving 

 the data for these experiments, the fuel value of the diet, i. e., the heat 

 of combustion less the unoxidized portion of the protein excreted in 

 the urine, has been used in all cases. For the method employed in 

 calculating these values, see page 334. 



The first series of experiments on the 24-hour basis is that for A. L. L., 

 December 16 to 23, 1904. 1 In this series 4 fasting days preceded the 

 ingestion of milk and plasmon. In table 7 the average of the first 

 2 days is used as a base-line, these values being the best available for 

 comparison, as will be shown later (see page 70). The average excre- 

 tion of nitrogen for the first 2 days of fast was 12.18 grams, the carbon- 

 dioxide production 649 grams, the oxygen consumption 615 grams, and 



'For the detailed results of this aeries gee Benedict, Carnegie Inst. Wash. Pub. No. 77, 1907, 

 experiments Nos. 69 and 70. 



