FOOD 207 



a pleasant taste which may assist digestion, and to stimulate 

 the secretion of digestive juices. Used to excess, how- 

 ever, all these drinks injuriously affect the nerves, and 

 the condiments may irritate the sensitive lining membrane 

 of the alimentary canal, besides impairing the delicacy of 

 the sense of taste. 



296. Food Values. The nutritive value of a diet lies 

 chiefly in the amount of nitrogen and carbon derived from 

 it. A man of moderately active life will give off, mainly 

 from the lungs as carbon dioxide, from eight to nine 

 ounces of carbon each day. If he is engaged in severe 

 muscular effort, he will give off much more carbon. The 

 amount of nitrogen passing from the body (chiefly as urea) 

 during a day is from .47 to .56 ounce, and with the 

 increase of muscular activity it does not increase to nearly 

 so great a degree as does the carbon. 



In order to repair the daily waste of the tissues, the 

 proportions of carbon and nitrogen contained in the food 

 should be the same as in the excretions, viz. about 16.6 to 

 1. While the proteids contain carbon, they contain only 

 about 3.5 parts of carbon to 1 of nitrogen, hence other 

 groups of food elements must be depended upon to supply 

 the necessary carbon. 



The oxygen contained in food, being already combined 

 with other elements, cannot be used in oxidation, so that 

 from the lungs alone comes the needful supply of that 



Since the slow combustion within the body sets free the 

 same amount of energy as does the rapid combustion of 

 the same substances, by burning a quantity of food equal 

 to that which a man eats in a day and measuring the heat 

 given off, the amount of energy which that food can sup- 

 ply may be estimated. In that way it has been shown 



