330 FOOD INGESTION AND ENERGY TRANSFORMATIONS. 



results of the group of experiments under consideration, it is neces- 

 sary to draw conclusions not from the detailed results, which were based 

 in some cases upon defective values, but from the general picture pre- 

 sented. This general picture shows that the ingestion of a large amount 

 of liquid, such as water, coffee, or beef tea, is followed by a measurable 

 increase in the metabolism. 



Following the ingestion of food materials a pronounced increment in 

 the metabolism was almost invariably found. We may therefore dis- 

 regard possible inaccuracies in the base-line and discuss the experiments 

 on the general assumption that the basal values were determined with 

 sufficient accuracy to warrant quantitative deductions from the incre- 

 ments actually measured, although we freely admit that whenever 

 practicable a carefully determined base-line each day prior to the inges- 

 tion of food is highly desirable, if not, indeed, absolutely essential. 



The observed increment in the metabolism as a result of the ingestion 

 of food is in accordance with the experience of nearly all of the other 

 investigators in this field. The increase was especially pronounced 

 with protein, carbohydrates, and mixed diets, and less pronounced 

 when diets with a preponderance of fat were used. 



GENERAL QUANTITATIVE RELATIONS. 



The fact that different amounts of the several foodstuffs produce 

 varying increases in metabolism would make it appear that the estab- 

 lishment of definite mathematical relationships between the amounts of 

 food ingested, the character of the food ingested, and the increments 

 would be relatively simple. This, however, on close analysis, proves to 

 be far from the case. 



To establish a quantitative relationship between the various foods 

 ingested and the increase in the basal metabolism it is necessary to note 

 first the length of the experimental period to be considered. If the 

 total increment due to the ingestion of food is desired, the period of 

 measurement must be extended until the increment due to the ingestion 

 of food has disappeared and the metabolism has again reached the basal 

 level. For instance, if the basal heat production is 70 calories per hour 

 and the metabolism increases after the ingestion of food to 100 calories 

 per hour for one or two hours, obviously no complete mathematical 

 relationship can be established unless the measurements are continued 

 until the basal value of 70 calories per hour is again obtained. This is 

 somewhat difficult, especially when the stimulus effect is prolonged, as 

 it is with protein. 



The first quantitative relationship to be considered is the increment 

 in the metabolism above the basal level, to find how far it is possible to 

 increase the basal metabolism by the ingestion of nutrients. This is in 

 reality a measurement of the absolute maximum increment due to the 

 ingestion of food, somewhat similar to the "peak " effect in the load of a 



