426 MANUAL OF PHYSIOLOGY. 



while yet another group is devoted to setting free and utilizing 

 the energy of the various chemical associations. 



But all the food we eat is not assimilated ; indeed, the destiny 

 of the numerous ingredients of our complex dietaries is not easily 

 traced. Of food stuffs proper, the following classification may be 

 made, showing that even the same stuff may meet with a different 

 fate under different circumstances : 



1. Stuffs which never enter the economy (fteces). 



2. Materials absorbed and arriving at the blood are at once 



carried to certain portals of excretion (excess of salts). 



3. Substances which are broken up in the intestine to facili- 



tate their elimination (excess of proteid). 



4. Substances absorbed and carried along by the fluids, but 



not really united to the tissues (circulating albumin). 



5. Materials which, after their absorption, are really assimi- 



lated by the protoplasm of the tissues (a certain amount 

 of all food stuffs). 



6. Substances which, after their assimilation by the proto- 



plasm, reappear in their original form, and are stored 

 up (fats). 



The question of the exact amounts and materials required to 

 form the most economic and wholesome dietary is one of too great 

 practical importance to receive adequate attention in this manual. 

 As a rule, men, like other animals, partake of food largely in 

 excess of their physiological requirements when they can get it. 

 This may be seen by contrasting one's own daily food with the 

 amount which has been found to be adequate in the case of in- 

 dividuals who have not the opportunity of regulating their own 

 supplies of comestibles. 



An adult man should be well nourished if he be supplied with 

 the following daily diet : 



Albuminous foods, 100 grms. or 3.5 ozs. 



Fats, 90 " " 3.1 " 



Starch, 300 " " 10.7 " 



Salts, 30 " " 1.0 " 



Water, 2800 " " 5 pints. 



As a matter of fact, many persons do thrive on a much less 



