1-OODS AND THEIR PHYSIOLOGICAL VALUE. 317 



While these are the main mineral ingredients a chemical 

 examination of the body would reveal small traces of quite 

 a number of additional inorganic salts, which may be omit- 

 ted here. Not only are these salts needed to build up the 

 mineral constituents of tissues, such as bone or enamel, but 

 they are also needed to make possible the proper working 

 of the tissues. Thus it is known that animals from which 

 common salt ha^s been kept will become materially deranged, 

 suffering what is called a " salt craze," and the continued 

 withholding of the salt may finally induce fatal results. The 

 exact manner in which this salt figures will be treated fur- 

 ther on. 



6. Water. On account of its abundance and free access 

 everywhere, water is not classed as a food, but is such in 

 an essential way, although of course no energy can be di- 

 rectly derived from the same ; but as an agent for dissolving 

 other foods, as an ingredient forming by far the largest 

 amount of all the tissues, it plays a first role in digestion 

 and nutrition. 



A MIXED DIET. 



Very few of the foods as they are served to us on the 

 dinner table belong wholly to one or another of these 

 classes. In nearly every case they are mixtures of some or 

 all of them, and their dietetic value will depend upon the 

 relative proportions in which they contain these classes as 

 ingredients. The multitude of dishes ranging from the 

 highly flavored and seasoned ones of tables of plenty, down 

 to the simpler foods of the peasant's meal, are but mixtures 

 in varying proportions. The different character which the 

 varying dishes possess is usually much more a matter of 

 flavor or condiment than it is a matter of nutritive value. 



In order to fully understand the nutritive value of the 

 food then, and leaving out entirely the matter of flavor, the 

 influence of which ceases with the palate, it is necessary to 



