ENERGY RELATIONSHIPS. 349 



mental evidence for any of the three current theories. It is of signifi- 

 cance that popcorn and bananas, with their large content of fiber 

 material, increase the metabolism, a fact which tends to support the 

 Verdauungsarbeit theory. The well-known increases in peristalsis sub- 

 sequent to the ingestion of pure sugars, especially levulose, would also 

 probably be considered by the advocates of the Verdauungsarbeit 

 theory as sufficient explanation of the increment noted with sugars. 

 On the other hand, the results of the two studies previously referred to, 

 in one of which excessive peristalsis was induced by the administration 

 of Glauber salts and agar-agar to man, and in the other a study was 

 made of the metabolism of dogs having defective assimilation due to 

 ablated pancreas, strongly disprove the Verdauungsarbeit theory. 



GENERAL CONCLUSIONS. 



Many of the conceptions as to the influence of the ingestion of food 

 upon the heat production have long been held and need no material 

 modification. But as most of such evidence was obtained in experi- 

 ments with animals rather than with men it seemed desirable for us to 

 undertake a research upon the influence of the ingestion of food upon 

 the metabolism of man. In making these experiments we have been 

 greatly indebted to the earlier investigators, more especially to Magnus- 

 Levy 1 and to Johansson and his school, 2 as their researches were in large 

 part with men. It has been impracticable in our discussion to cite 

 adequately the numerous observations made upon animals, particu- 

 larly the classic experiments of Rubner and the more recent work of 

 Lusk and his associates in New York. Believing that our problem was 

 sufficiently extended if confined primarily to man, we have therefore 

 intentionally omitted in this publication a review of practically all 

 experiments made upon animals. In the decade or more that the 

 results have been accumulating, numerous papers by other investi- 

 gators have appeared, many of them reporting experiments with men. 

 These we have considered carefully in our digest of the literature, as 

 well as in the discussion of the several chapters. 



The experimental evidence in this book as a result of our research 

 presents little that is startlingly new. The mechanical work of chewing 

 has been found to produce a definite increase in the metabolism. The 

 drinking of liquids, especially in large amounts, likewise has been 

 shown to increase the metabolism, although these increases are usually 

 relatively small. The fact that the ingestion of all kinds of food in any 

 amount results in an increment in the metabolism seems very clearly 

 established. No conclusive evidence of a metabolism depressed below 



Magnus-Levy, Arch. f. d. ges. Physiol., 1894, 55, p. 1. 



2 Johansson, Skand. Arch. f. Physiol., 1897, 7, p. 29; same journal, 1902, 13, p. 251; same journal, 

 1904, 16, p. 263; same journal, 1908, 21, p. 1. 



