CHAPTER VIII 

 PASSAGE OF OXYGEN THROUGH THE BODY 



WHAT is the nature of oxygen ? What is its purpose in 

 the body and how does it serve this purpose ? How is the 

 blood able to take it up at the lungs and give it off at the 

 cells ? What becomes of it after being used ? These are 

 questions touching the maintenance of life and they 

 deserve careful consideration. 



Nature of Oxygen. To understand the relation which 

 oxygen sustains to the body we must acquaint ourselves 

 with certain of its chemical properties. It is an element 1 

 of intense affinity, or combining power, and is one of the 

 most active of all chemical agents. It is able to com- 

 bine with most of the other elements to form chemical 

 compounds. A familiar example of its combining action 

 is found in ordinary combustion, or burning. On account 

 of the part it plays in this process, oxygen is called the 

 supporter of combustion ; but it supports combustion by 

 the simple method of uniting. The ashes that are left and 

 the invisible gases that escape into the atmosphere are 

 the compounds formed by the uniting process. It thus 

 appears that oxygen, in common with the other elements, 

 may exist in either of two forms : 



1 An element is a single kind of matter. Those substances are classed as 

 elements which cannot be separated into different kinds of matter. Two or 

 more elements combined in definite proportions by weight form a compound. 

 The elements are few in number, only about eighty being known. Compounds, 

 on the other hand, are exceedingly numerous. 



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