. A text-book of animal physiology, with introductory chapters on general biology and a full treatment of reproduction ... Physiology, Comparative. 434 ANIMAL PHYSIOLOGY. The Uses of Glycogen.—Whether the blood of the hepatic vein contains more sugar than that of the portal vein has long been a subject of controversy. If the affirmative could be established, it would be pretty clear that glycogen stored in the liver-cells was transformed into sugar, possibly by a process of hydration. But, considering the rapidity of the blood-stream, it is easy to understand that a large amount of sugar might
. A text-book of animal physiology, with introductory chapters on general biology and a full treatment of reproduction ... Physiology, Comparative. 434 ANIMAL PHYSIOLOGY. The Uses of Glycogen.—Whether the blood of the hepatic vein contains more sugar than that of the portal vein has long been a subject of controversy. If the affirmative could be established, it would be pretty clear that glycogen stored in the liver-cells was transformed into sugar, possibly by a process of hydration. But, considering the rapidity of the blood-stream, it is easy to understand that a large amount of sugar might be conveyed Main verume trunk Bight awiole Vena cava Bepatie eefn-. Ijymph. gtana Portal system S'i ^^p'^-^^ Sg Blood vessel, tissue cells, &„(^m lympti-spaces Alimentary tract Fie. 329.—Diagram intended to illustrate the general relations of blood and lymph to metab- olism (nutrition); and the method by wmch the portal, lymphatic, and general venous systems are related to the alimentary tract. into the general circulation, and yet the blood, whether of the hepatic vein or of other parts, contain but a small quantity at any one time. The blood is kept of a certain fairly constant composition, both by the action of the excreting organs and by the withdrawal from it of supplies for the tissues. Moreover, that correlation of functional work on which we have already insisted, is not to be forgotten. One must not conceive of the liver-cells or any others doing their work independently of the condition of their fellow cell-units in the organic common- wealth. We mean to say that the amount of glycogen trans- formed to sugar will depend on a great many circumstances outside of the liver itself. Such aspects of the case have been rather overlooked. According to another theory, glycogen is an intermediate product between sugar and fat, but of this there is very little evidence indeed; and, besides, fat formation is otherwise well enough accounted for, though, of course, too m
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