INGESTION OF CARBOHYDRATES. 247 



acter of the metabolism, this fact being indicated by a great rise in the 

 respiratory quotient. If we apply a rough correction of 3 points for 

 the conversion of these quotients to non-protein quotients, we should 

 find that none of the quotients would reach 1 with dextrose and lac- 

 tose, but with levulose the non-protein quotients would be either 1 or 

 above for the first 1\ hours of the experiment, while those for sucrose 

 would appear for the first \\ hours. The general course of the respira- 

 tory quotient shows, therefore, that the effect on the character of the 

 metabolism parallels the effect upon the total metabolism; that is, it is in 

 large part confined to the first hours after the taking of carbohydrate. 



GENERAL DISCUSSION OF RESULTS OBTAINED WITH PURE 



CARBOHYDRATES. 



The increase in the respiratory quotient subsequent to the ingestion 

 of carbohydrate is in practically all instances due to a pronounced rise 

 in the carbon-dioxide production rather than to a decrease in the 

 oxygen consumption; the latter is also increased in the majority of 

 instances. This increase in the carbon-dioxide production, which is 

 the only factor measured in Johansson's experiments, certain experi- 

 ments of Gigon, and a large number of Rubner's, does not indicate 

 accurately the effect upon the metabolism itself as measured either 

 directly in calorimeter experiments or by indirect calorimetry when 

 botn the carbon-dioxide and oxygen determinations are made. The 

 increase hi the carbon-dioxide production observed after carbohydrate 

 ingestion may have three explanations: 



As can be inferred from the average basal respiratory quotient, the 

 katabolism during the post-absorptive period is a protein-fat-carbo- 

 hydrate katabolism. When carbohydrate has been ingested, fat may 

 be completely excluded from the katabolism, and we then have a 

 protein-carbohydrate katabolism; under these conditions the propor- 

 tion of carbon dioxide produced will be larger than that when fat is 

 used in the production of a like amount of energy. Hence one explana- 

 tion of the increase in carbon-dioxide production may be that it is due 

 simply to a replacement of fat by carbohydrate in the metabolism. 



Second, the increment in carbon-dioxide may be derived in appre- 

 ciable amounts from a cleavage of carbon-dioxide from carbohydrate in 

 the formation of fat. The formation of fat as a result of excessive 

 carbohydrate feeding is no longer in question, for the experiments of 

 Meissl 1 and of Bleibtreu 2 on swine and geese, to say nothing of the 

 many experiments with man and other animals than swine and geese, 

 have shown this conclusively. With the ingestion of 100 grams of 

 pure carbohydrate, there is immediately made available 380 to 400 

 calories, while the basal requirement may not exceed 70 to 90 calories 

 per hour. The sugar ingested would therefore logically suffice for the 



Weissl, Zeitschr. f. Biol., 1886, 22, p. 63. 

 2 Bleibtreu, Arch. f. d. ges. Physiol., 1901, 85, p. 345. 



