DIGESTION OF THE CARBOHYDRATES 229 



intestine. Here the foodstuffs are very soon met by the alkaline 

 Pancreatic Juice, which reaches the intestine, in man, through the 

 common duct of the liver and the pancreas. 



The pancreatic juice contains an Amylase which completes the work 

 of the salivary amylase and furthermore, a Maltase which converts 

 the maltose, derived by the action of amylase from starch, into Glucose. 

 The glucose which is thus formed is very rapidly absorbed into the 

 portal circulation, and carried to the liver where it is converted into 

 Glycogen. The rapidity of this conversion is very great. Thus the 

 quantity of glucose derived from the polysaccharides in a single meal 

 may very readily exceed one hundred grams. Dissolved in all of the 

 blood in the body, which cannot exceed seven liters in a man of seventy 

 kilos, this would give a glucose concentration of no less than 1.5 per 

 cent. As a matter of fact even at the height of absorption during a 

 meal rich in carbohydrates the concentration of glucose in the blood 

 of a person in normal health never exceeds one-tenth of this. As 

 rapidly, therefore, as the glucose is taken to the liver by the portal 

 circulation, it is transformed into the colloidal anhydride, glycogen, 

 and held in reserve for future consumption. 



When, however, an extraordinary load is thrown upon this mechan- 

 ism, by the excessive ingestion of diffusible sugars, some slight degree 

 of Glucohemia or excess of sugar in the blood may nevertheless occur 

 and in these cases the glucohemia is relieved by the passage of sugar 

 into the urine. This type of glycosuria is known as Alimentary Glyco- 

 suria. The sugar which is found in the urine is usually Glucose, but 

 when cane-sugar or sweets made of cane-sugar have been ingested in 

 large quantities, Levulose may also be found in the urine, together 

 with traces of unhydrolyzed cane-sugar. Lactose is somewhat more 

 readily absorbed and excreted as such than cane-sugar. If either of 

 these sugars be injected intravenously, they appear unaltered and 

 quantitatively in the urine. 



It is an exceedingly remarkable fact that whereas amylase and 

 maltase are both present in the digestive juices, Lactase and Invertase 

 are usually completely absent, or if lactase is present its action is 

 inconspicuous. We have seen that the unaltered disaccharides, if 

 absorbed as such, are not utilized but are as promptly as possible 

 ejected from the circulation by the kidneys. Yet lactose is the sole 

 carbohydrate nutriment of suckling infants and cane-sugar is an exceed- 

 ingly important item in the dietary of modern peoples. As a matter 

 of fact, although the hydrolysis of these disaccharides cannot be 

 accomplished to any important extent by the secretions which are 

 poured into the alimentary canal by the various digestive glands, yet 

 the consequence of their ingestion is actually the appearance of in- 

 creased glucose in the portal circulation and enhanced storage of 

 glycogen in the liver. When partaken of in reasonable amounts they 

 are furthermore fully utilized for maintenance and the production of 

 energy in the body. At some point during their passage through the 



