ME TABOLISM 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 bloodj 
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 ii cm 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 througji 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-hook, vol. i. pp. 432-436. 
2 Bernard, "Lecons de physiol. exper.," Paris, 1855. 
3 G. Lusk (with Voit), Ztsehr.f. Biol., Miinchen, 1892, S. 288. The ingestion or sub- 
cutaneous injection of laevulose will also cause a production of glycogen ; galactose and 
lactose do not (C. Voit, Ztsehr.f. Biol. , Miinchen, 1892, Bd. xxviii. S. U45). Kausch and Solin 
{Arch. f. exper. Path. u. Pharmakol., Leipzig, 1893, Bd. xxxi. S. 398) obtained positive 
results with lactose and galactose. Cf. also Cremer. ibid., 1893, Bd. xxix. S. 484 ; Haycraft, 
Ztsehr.f. physiol. C'hem., Strassburg, 1894, Bd. six. S. 141. Whether the lsevulose is first 
converted into dextrose, and this into glycogen, or whether the glycogen is formed directly 
from laevulose, the ketone group of la±vulose must in either case become converted into an 
aldehyde group (Xeumeister, "Lehrbuch," Aufl. 2, S. 326). On the subject of the forma- 
tion of glycogen from carbohydrates, see farther, E. Voit, Ztsehr.f. Biol., Munehen, 18S9, 
Bd. xxv. S. 551 ; C. Voit, ibid., Is92, Bd. xxviii. 
4 Luchsinger, Inaug. Diss., Zurich, 1875. 
5 Bunge, '"Lectures," p. 383. 
a 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 Bulvru, Arch.f. d. yes. Physiol., Bonn, 1880, Bd. xxiii. S. 51. 
