192 ORGANIC AGRICULTURAL CHEMISTRY 



hydrate food, glucose is very much in excess of the other two 

 digestive products. In the case of infants, galactose is also 

 present in equal amounts with the glucose. By the process of 

 absorption or assimilation, these three monosaccharoses are 

 taken up by the blood capillaries of the small intestine and they 

 are all found in that part of the blood circulatory system which 

 leads to the portal vein. After a meal rich in carbohydrate food 

 the amount of glucose, or of the three hexoses together, may be 

 as much as 0.2 per cent, which is double the normal amount. 

 The portal vein leads to the liver, and the three products of 

 carbohydrate digestion are thus carried to this organ. 



Glycogen. — In the liver, due probably to enzymatic action, 

 the first metabolic change occurs. This change is anabolic in 

 character, and the result is the conversion of the three hexoses 

 found in the portal vein into the polysaccharose glycogen. This 

 glycogen is stored in the liver cells and in some cases may 

 amount to as much as 10 per cent of the liver itself. 



The blood which is brought to the liver by the portal vein 

 leaves the liver by the hepatic vein and passes thus into the 

 general venous blood stream which reaches by means of fine 

 capillaries the muscle cells of the whole body. It is a striking 

 fact that while the glucose content of the portal vein varies in 

 its amount with the supply of assimilated carbohydrate food 

 the glucose content of the hepatic vein and general venous 

 system remains constant at o.i per cent. 



Conversion of Glycogen into Glucose. — Furthermore, while 

 the portal vein, which receives its supply of sugar from the 

 absorbed food, may contain all three of the hexoses mentioned, 

 the hepatic vein contains only glucose. This constant supply of 

 glucose is maintained by the katabolic conversion of the liver glyco- 

 gen into glucose. This change, also occurring in the liver, is like 

 the preceding anabolic change of glucose, fructose and galactose 

 to glycogen, without question brought about by enzymes. 



Amount of Glycogen in the Liver. — The amount of glycogen 

 stored in the liver, like the amount of hexose sugars present in 

 the blood of the portal vein, increases with the increase of ab- 



