138 TEXT-BOOK OF PHYSIOLOGY. 



portion contributes to the formation of, if it is not directly converted 

 into, fat. As the carbohydrates form a large portion of the food, they 

 contribute materially to the production of energy. 



The inorganic principles, though not playing apparently as active 

 a part in the metabolism of the body as the organic, are nevertheless 

 essential to its physiologic activity. 



Watty is promptly absorbed after ingestion and hasgmes a part 

 of the circulating fluids blojo^jindj^ph. In the digestive appa- 

 ratus it favors the occurrence of those chemic changes in the food 

 necessary for their absorption, it promotes absorption of the. food, 

 holds various constituents of the bloodlincf other fluids in solution, 

 hastens the general metabolism of the body, holds in solution various 

 products of metabolic activity, and, leaving the body through the 

 excretory organs, promotes their elimination. 



Sgdium chlorid is absorbed into the blood and, unless taken in 

 excess, is utilized in replacing that which is lost to the organism daily. 

 The exact r61e which sodium chlorid plays in the nutritive process 

 is unknown ; but, as it is present as a necessary constituent in all the 

 fluids and solids of the body, and as it is instinctively employed as 

 a condiment, it may be assumed to have a more or less important 

 function. 



When taken as a condiment, it imparts sapidity to the food and 

 excites the flow of the digestive fluids; it ultimately furnishes the 

 chlorin for the hydrochloric acid of the gastric juice. Judging from 

 the impairment of the nutrition as observed in animals after depriva- 

 tion of salt for a long period of time, it favorably influences the growth 

 and functional activity of all tissues. 



It is well known that herbivorous animals, races of men as well as 

 individuals who live largely on vegetable foods, require a larger addi- 

 tional amount of sodium chlorid than carnivorous animals, or human 

 beings who live largely on animal foods, even though the two classes 

 of foods contain relatively the same amounts. The explanation is 

 that the vegetable foods contain potassium salts which, meeting in 

 the blood with sodium chlorid, undergo decomposition into potassium 

 chlorid and sodium carbonate or phosphate, all of which, when in 

 excess, are at once eliminated by the kidneys. The blood, therefore, 

 becomes poorer in sodium chlorid, one of its necessary constituents. 



Potassium phosphate and carbonate are also essential to the 

 normal composition of the solids and fluids. They impart a certain 

 degree of alkalinity to the blood and lymph, one of the conditions 

 necessary to the life and activity of the tissue-cells bathed by them. 

 When administered in small doses, they increase the force of the 

 heart, raise the arterial pressure, and increase the activity of the 

 circulation. 



Calcium phosphate and carbonate are partly utilized in maintain- 



