424 



PHYSIOLOGICAL CHEMISTRY. 



ouDces) of butter will supply the quantities of solid food required in 

 a day by an active laborer : 



Bread Lean meat Butter 



(900 grammes). (340 grammes.) (57 grammes). 



74 grammes. 66 grammes. ... 



14 " 12 " 50 grammes. 

 460 



22 " 17 " 



Bread, meat, 

 and butter. 



140 grammes. 



76 " 

 460 " 



39 



Proteids ... 

 Fats ... 

 Carbohydrates . 

 Inorganic salts . 



In providing a diet, it must be borne in mind that the digestibility 

 of a food is more a measure of its nutritive value than its elementary 

 composition. Different foods show great differences in the rapidity 

 and completeness with which they are absorbed. Thus eggs, fresh 

 meat, white bread, and butter are absorbed and assimilated more 

 readily than pork, rye bread^ potatoes, green vegetables, and bacon. 



The relative proportions of nitrogenous and non-nitrogenous matter 

 in various kinds of food are shown in the following table : 



Nitro- Non-nitro- 



Nitro- 



Non-nitro 



Nutrition. In the process of nutrition five phases may be dis- 

 tinguished, viz. : Digestion, absorption, assimilation, destructive meta- 

 morphosis, and elimination of waste products. 



Digestion is the process of converting food material into dialyzable 

 compounds, or into other forms of matter capable of absorption. 

 Absorption is the mechanical process of transferring the digested 

 materials from the alimentary canal into the circulation. Assimila- 

 tion includes the changes taking place after they are absorbed until 

 they have become a part of living cells. Destructive metamorphosis 

 includes those changes which take place chiefly in consequence of 

 oxidation, the oxygen being supplied during the process of respira- 

 tion. Elimination of waste products is the discharge of that material 

 which is no longer needed in the system. 



Digestion. It has been stated before that foods are divided into 

 two classes, inorganic and organic, and that the latter are subdivided 



