26 FOOD INGESTION AND ENERGY TRANSFORMATIONS. 



with food the average carbon-dioxide excretion increased to 0.569 

 gram. The authors conclude that after a mixed diet or a diet composed 

 of carbohydrates a greater excretion of carbon dioxide with a more 

 active ventilation begins about an hour after the ingestion of food and 

 reaches its maximum from 2| to 3 hours afterwards. 



Zuntz and Magnus-Levy, 1891. In studying the digestibility and 

 nutritive value of bread, Zuntz and Magnus-Levy, 1 employing a Zuntz- 

 Geppert respiration apparatus, made a number of experiments on them- 

 selves, not only in the post-absorptive condition but likewise after 250 

 to 300 grams of bread and 60 grams of butter. Although recognizing 

 the fact that their data need amplification, they tentatively conclude 

 that bread causes a fairly considerable increase in the oxygen consump- 

 tion, the increase in the first hour amounting to about 25 per cent of 

 the fasting value. Subsequently the oxygen consumption decreases 

 and at the end of 3 to 5 hours reaches practically the basal value. 

 They further conclude that, in general, the increase above the fasting 

 value is, with bread, about 15 per cent during the first 6 hours, but that 

 on the 24-hour basis the increase due to digestion would be not less than 

 10 per cent of the total oxygen consumed during rest. Frequently, 

 in reporting an increase due to metabolism, writers confuse an increase 

 obtained for a short time, i. e., a "peak" increase, with that obtained 

 in a 24-hour period. Apparently Zuntz and Magnus-Levy were the 

 first to make a sharp distinction between these increases. This prac- 

 tice could well be followed by modern writers. 



Hanriot, 1892. The interesting series of observations on the effect 

 of taking glucose, reported by Hanriot in 1892, 2 are of greater signifi- 

 cance as regards the influence upon the respiratory quotient than as to 

 the effect upon the total metabolism. Hanriot's paper emphasizes 

 the fact that the respiratory quotient may attain a value as high as 

 1.30. Under these conditions there is a transformation of carbohydrate 

 into fat, and the values do not lend themselves easily to a computation 

 of the increased metabolism due to the digestion of the glucose, for 

 apparently the oxygen values determined by Hanriot are given with 

 some reserve. 



In Hanriot's article published in 1893, 3 which is a continuation of his 

 first paper published in 1892, emphasis is laid primarily on the respira- 

 tory quotient and on the transformation of carbohydrates into fat. 

 Of special interest in view of our own contrary findings is Hanriot's 

 statement that with 50 grams of glucose dissolved in 500 c.c. of water the 

 quotient always rises to about 1.25. The paper concludes with an 

 extensive discussion of the theoretical points involved in the trans- 

 formation of carbohydrate into fat. 



'Zuntz and Magnus-Levy, Arch. f. d. ges. Physiol., 1891, 49, p. 438. 

 2 Hanriot, Compt. rend., 1892, 114, p. 371. 

 'Hanriot, Arrh. de Physiol.. 1K93, 25, p. 248. 



