CHAPTER II. 

 INORGANIC SUBSTANCES. 



THE inorganic substances are present in the animal body in great 

 variety. Some of them, such as water and the salts of lime, con- 

 stitute a large proportion of the mass of the tissues and fluids in which 

 they are found ; others are in comparatively small quantity. Some of 

 them are found in all regions of the body, while others are met with 

 only in particular tissues or fluids ; but there are hardly any which do 

 not appear as constituents of several different parts. As their name 

 implies, these substances exist abundantly in the inorganic world, and 

 form a large part of the crust of the earth. But they are also essential 

 constituents of the animal frame, and necessary ingredients of the 

 food. No regimen would be capable of supporting life indefinitely 

 which did not contain them in due proportion. 

 This group includes the following substances : 



Water ; Potassium phosphate ; 



Sodium chloride ; Potassium sulphate ; 



Sodium phosphate ; Potassium carbonate ; 



Sodium biphosphate ; Lime phosphate ; 



Sodium sulphate ; Lime carbonate ; 



Sodium carbonate ; Magnesium phosphate ; 



Potassium chloride ; Magnesium carbonate. 



Beside the substances above named there are found, as constant in- 

 gredients of the incombustible residue of various parts of the human 

 body, iron, silica, and fluorine ; but it is not certainly known in what 

 form of combination these substances originally existed in the animal 

 solids and fluids. Sometimes, but not always, there are indications of 

 the presence, in minute quantity, of copper, manganese, and lead, also 

 in unknown forms of combination. 



The most important of the inorganic substances, considered in regard 

 to their quantity and their part in the vital phenomena, are the fol- 

 lowing : 



1. Water, H 2 0. 



Water is present in all the tissues and fluids of the body. It is 

 abundant in the blood and secretions, where it is indispensable in order 

 to give them the fluidity necessary to the performance of their functions. 

 For it is by the blood and secretions that new substances are introduced 

 into the body, and old ingredients discharged ; and it is a necessary 

 condition both of the introduction and discharge of solid substances 



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