METABOLISM OF CARBOHYDRA TE. 917 



which is unmistakably found in the circulating fluids and in the tissues 

 of the body. The path of absorption of carbohydrates is the same as 

 that of proteids, 1 the absorbed dextrose being taken up by the blood, 

 conveyed by the portal vein to the liver, and there stored. The portal 

 blood taken during digestion is, in fact, the only blood in the body in 

 which it can be conclusively shown that normally there is an excess 

 of sugar. If taken in the intervals of digestion, it contains the same 

 amount of sugar (one to two parts per thousand) as any other sample 

 of blood. 



The blood of the hepatic vein, on the other hand, although it is said 

 to contain an excess of sugar in the intervals of absorption of foods 

 containing carbohydrates (but vide infra, p. 923), does not, during the 

 actual process of such absorption, contain nearly as much sugar as the 

 blood of the portal vein ; we must therefore assume that the sugar 

 which is carried to the liver by the portal vein is arrested in that 

 organ. As a matter of fact, it is found that the immediate result of 

 the digestion and absorption of a meal containing much carbohydrate 

 food is to promote a considerable accumulation of glycogen in the liver, 

 and the same is found if in a fasting animal solution of dextrose is 

 slowly injected into a vein of the mesentery, 2 or if dextrose is injected 

 subcutaneously (in rabbits). 3 The same is even found if blood contain- 

 ing dextrose is perfused through the " surviving " liver of a dog. 4 The 

 amount of glycogen in the liver (which would contain in man at most 

 150 grms. of this substance) 5 is not sufficient to account for the storage 

 of the whole of the carbohydrate which is absorbed from a meal con- 

 taining much starch or sugar. A part of the absorbed carbohydrate, 

 when it is in excess, must therefore pass through the liver into the 

 general circulation. Here it is apparently taken up by the muscles, for 

 in a well-nourished animal, especially one nourished upon mixed food, 

 the muscles may contain as much as 1 per cent, or even more of 

 glycogen. Although this is not by any means as large a proportion as 

 may be contained in the liver itself, 6 the muscles may collectively hold 

 as much as is present in the liver. 7 Even, however, if we take into 

 consideration the whole of the glycogen in the liver, that in the muscles, 

 and that in other tissues in the body in which it might be stored, it will 

 still be found that the whole of the carbohydrates of a meal which 

 contains much of these substances is not represented in the body, 

 either by the glycogen of the organs or by the sugar present in the 



1 See this Text-book, vol. i. pp. 432-436. 



2 Bernard, "Lecons de physiol. exper.," Paris, 1855. 



3 G. Lusk (with Yoit), Ztsehr.f. Biol., Miinchen, 1892, S. 288. The ingestion or sub- 

 cutaneous injection of leevulose will also cause a production of glycogen ; galactose and 

 lactose do not (C. Voit, Ztsehr.f. Bid. , Miiuchen, 1 892, Bd. xxviii. S. 245). Kausch and Solin 

 (Arch. f. exper. Path. u. Pharmakol., Leipzig, 1893, Bd. xxxi. S. 398) obtained positive 

 results with lactose and galactose. Cf. also Creraer, ibid., 1893, Bd. xxix. S. 484 ; Haycraft, 

 Ztsehr.f. physiol. Ohem., Strassburg, 1894, Bd. xix. S. 141. Whether the kevulose is first 

 converted into dextrose, and this into glycogen, or whether the glycogen is formed directly 

 from laevulose, the ketone group of Irevulose must in either case become converted into an 

 aldehyde group (Neurneister, "Lehrbuch," Aufl. 2, S. 326). On the subject of the forma- 

 tion of glycogen from carbohydrates, see further, E. Voit, Ztsehr.f. Biol., Miinchen, 1889, 

 Bd. xxv. S. 551 ; C. Voit, ibid., 1892, Bd. xxviii. 



4 Luchsinger, Inaug. Diss., Zurich, 1875. 



5 Bunge, "Lectures," p. 383. 



6 Pavy found in rabbits and dogs fed with a large amount of carbohydrate-containing 

 food, that the amount of glycogen of the liver might rise as high as 17 per cent. (" Physio- 

 logy of Carbohydrates," p. 116). 



7 Bohm, Arch.f. d. gcs. Physiol,, Bonn, 1880, Bd. xxiii. S, 51. 



