90 HUMAN PHYSIOLOGY. 



The carbohydrate principles, after digestion, are absorbed as dex- 

 trose and temporarily stored up in the liver as glycogen. The inter- 

 mediate stages which sugar passes through and the combinations into 

 which it enters between its absorption and its elimination are but 

 imperfectly understood. That it contributes to the accumulation of 

 fat is probable, though it is doubtful if it is ever converted into fat. 

 A large percentage of the sugar absorbed is at once oxidized. The 

 reduction of fat and sugar to carbon dioxid and water, under which 

 forms they are eliminated from the body, is accompanied by a dis- 

 engagement of a large quantity of heat. 



Water is present in all the fluids and solids of the body. It pro- 

 motes the absorption of new material from the alimentary canal ; it 

 holds the various ingredients of the blood, lymph, and other fluids 

 in solution ; it hastens the absorption of waste products from the 

 tissues, and promotes their speedy elimination from the body. 



Sodium chlorid is present in all parts of the body to the extent 

 of no gm. The average amount eliminated daily is 15 gm. Its 

 necessity as an article of diet is at once apparent. Taken as a con- 

 diment, it imparts sapidity to the food, excites the flow of the di- 

 gestive fluids, promotes the absorption and assimilation of the al- 

 bumins, influences the passage of nutritive material through animal 

 membranes, and furnishes the chlorin for the free hydrochloric acid 

 of the gastric juice. In some unknown way it favorably promotes the 

 activity of the general nutritive process. 



The potassium salts are also essential to the normal activity of 

 the nutritive process. When deprived of these salts, animals become 

 weak and emaciated. When given in small doses, they increase the 

 force of the heart-beat, raise the arterial pressure, and thus increase 

 the action of the circulation of the blood. 



The calcium phosphate and carbonate are utilized in imparting 

 solidity to the tissues, more especially the bones and teeth. Many 

 articles of food contain these salts in quantities sufficient to restore 

 the amount lost daily. 



The vegetable acids increase the secretions of the alimentary canal, 

 and are apt, in large amounts, to produce flatulence and diarrhea. 

 After entering into combination with bases to form salts, they stimu- 

 late the action of the kidneys and promote a greater elimination of 

 all the urinary constituents. In some unknown way they influence 

 nutrition ; when deprived of these acids, the individual becomes 

 scorbutic. 



