CHAPTER XVI. 



THE ALIMENTARY TRACT AS AN ABSORPTIVE SYSTEM 



(Continued). 



8. The Absorption of Carbohydrates. The carbohydrates 

 which are of chief importance in the physiology of alimenta- 

 tion in so far as they are found in any ordinary mixed meal, 

 are the polysaccharides starch, glycogen, and cellulose, the 

 disaccharides cane-sugar, malt-sugar, and milk-sugar, and 

 the monosaccharides dextrose, laevulose, and galactose. Of 

 the polysaccharides the starches make up not only the bulk 

 of this class of food, but of all the carbohydrates that are 

 enjoyed in an ordinary diet. The consumption by an ordi- 

 nary individual of several hundred grams of starch a day in 

 the form of bread, potatoes, beans, etc., is not uncommon. 

 A few grams of glycogen enter into the ordinary daily diet as 

 constituents of lean meat, liver, etc. Cellulose is obtained 

 through the vegetable constituents of the diet, more particu- 

 larly celery, string beans, tufnips, carrots, beets, etc. 



Sucrose (cane- or beet-sugar) as the ordinary sugar of com- 

 merce and the recognized sweetening agent of our food makes 

 up the bulk of the disaccharides which we consume, though 

 the exact amount consumed in a day is subject to the widest 

 individual variations. Malt-sugar is obtained in small 

 amounts through beverages and " breakfast foods/' into the 

 composition of which sproufed grains enter. Milk-sugar 

 comes to us through milk and certain of its derivatives; only 

 rarely as a distinct addition to an ordinary mixed diet. 



Dextrose and Isevulose are found in certain fresh and dried 



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