INTRODUCTION. 9 



an average of 10 C. to the temperature of the body, or 37 C., with an 

 expenditure of 81 calories. 1 



The feeling of warmth following the ingestion of food, familiar to 

 all, is not without significance as being a crude index of a scientific 

 fact which has been well established since the days of Lavoisier and 

 Jurine, i. e., that after food ingestion there is an increase in the metab- 

 olism or heat output. At present the main subjects for discussion 

 with physiologists are not as to there being an increase in the heat 

 output, but first, as to its quantitative relations to the ingesta; second, 

 as to the cause of the increase in the heat output. 



After an historical examination of the evidence with human sub- 

 jects which has thus far been accumulated to show that there is an 

 increased heat production following food, the results of an extensive 

 series of observations made under the auspices of the Carnegie Institu- 

 tion of Washington, first in the Department of Chemistry of Wesleyan 

 University, Middletown, Connecticut, and later in the Nutrition 

 Laboratory in Boston, will be presented. These observations, cover- 

 ing a period of 10 years, were made with a variety of methods and 

 somewhat changing technique, so that they are not strictly compar- 

 able in all instances. The evidence is, however, so extensive as to 

 throw general light upon the metabolism following ingestion of food 

 and justifies a consideration of the quantitative relations between the 

 energy intake and character of the ingesta and the quantitative increase 

 in the metabolism of man following the ingestion of the various diets. 



'Benedict and Joslin, Carnegie Inst. Wash. Pub. No. 136, 1910, p. 230. 



