FOODS. 121 



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

 to its physiologic activity. 



Water is promptly absorbed after ingestion and becomes a part of the 

 circulating fluids blood and lymph. In the digestive apparatus 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 blood and 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. 



Sodium 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 deprivation 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 maintaining 

 the solidity of the bones and teeth, replacing the amount metabolized 

 daily. Inasmuch as the metabolism of these two tissues is slight, there is 

 not much need in the adult for lime as an article of food. In young animals 

 lime is essential to the solidification and development of bone. When 

 deprived of it, the skeleton pidergoes a defective development similar 

 to the pathologic condition known as rickets. Lime is present in milk to 

 the extent of 0.15 per cent., as well as in eggs and peas in relatively large 

 quantities. 



Iron is contained in both animal and vegetable foods, not, however, 

 in the form of inorganic iron, nor in the form of an organic salt, but as a 

 compound with nuclein, thus forming an integral part of the proteid molecule. 



