REQUISITES OF DIET l8l 



DIETETICS. 



The appetite, under normal conditions, may be depended 

 upon to regulate both quantity and quality of diet in a fairly 

 satisfactory manner. Different peoples require different pro- 

 portions and amounts of the various food stuffs and the 

 same is true of any given individual for varying conditions 

 of temperature, exercise, etc. But in any case the object of 

 eating is to prevent the loss, in aggregate, of proteid tissue, 

 fat, etc. to replace the wastes, and that in the most conveni- 

 ent and economical way. 



When the ingesta exceed the excreta the animal is gaining 

 in weight ; when opposite conditions obtain he is losing ; when 

 there is a balance between the two the body equilibrium is 

 being maintained. 



Determination of the Requisites of a Diet. The usual 

 method of determining, in a scientific manner, the requisites 

 of a normal diet for persons in general is to estimate the 

 amount of the various excretions from the bodies of a lim- 

 ited number of persons in health, and from this knowledge 

 to calculate the amount and kind of food which will supply 

 the demands in the most satisfactory way, it being assumed 

 that these excretions represent the normal and necessary 

 metabolism going on in the body. The results of such ex- 

 amination are found to correspond with the actual demands 

 of the system. 



It has been seen that the organism demands some fifteen 

 or more chemical elements for use to keep itself in good run- 

 ning order ; it has been seen also that its demands, so far as 

 quantity is concerned, are chiefly confined to carbon, hydro- 

 gen, oxygen and nitrogen. The other elements deserve no 

 attention here since they (excepting sodium chloride) are 

 unconsciously introduced with the ordinary foods in amounts 

 sufficient to satisfy the requirements of the system. More- 

 over, the air we breathe and the water we drink furnish an 

 ample supply of hydrogen and oxygen when to this supply is 



