Elements of biology; a practical Elements of biology; a practical text-book correlating botany, zoology, and human physiology elementsofbiolog00hunt Year: [c1907] CIRCULATION 357 requires from twenty to thirty seconds only for the blood to make the complete circulation from the ventricle back again to the starting point. This means that the entire 0^'^^^^=^^^^^'^^ volume of blood in the human body passes three or four thousand times a day through the various organs of the body.^ Portal Circulation. — Some of the blood, on its return to the heart, passes by an indirect path through the spleen,
Elements of biology; a practical Elements of biology; a practical text-book correlating botany, zoology, and human physiology elementsofbiolog00hunt Year: [c1907] CIRCULATION 357 requires from twenty to thirty seconds only for the blood to make the complete circulation from the ventricle back again to the starting point. This means that the entire 0^'^^^^=^^^^^'^^ volume of blood in the human body passes three or four thousand times a day through the various organs of the body.^ Portal Circulation. — Some of the blood, on its return to the heart, passes by an indirect path through the spleen, pancreas, and other organs of the body cavity, to the liver. Here the vein which carries the blood (called the portal vein) breaks up into capil- laries around the cells of the liver. We have already learned that the liver is a great storehouse of animal sugar called glycogen. This glycogen is a food that may be easily oxidized to release energy, and is stored for that purpose. The sugar that becomes glycogen is carried to the liver directly from the walls of the stom- ach and intestine, where it has been absorbed from the food there contained. From the liver, blood passes directly to the right auricle. The fortal system, as it is called, is the only part of the circulation where the blood passes through two sets of capillaries. Changes in Blood within the Body. — We have already seen that blood loses much of the carbon dioxide it has taken from the tissues, ^ See Hough and Sedgwick, The Human Mechanism, page 136. Diagram of the course of the blood in the circulation.
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