BIOLOGY 



her of elements, nine chemical elements being ordinarily pres- 

 ent in living things, four of which predominate, while the other 

 four are present only in small quantities. They are as follows : 



Oxygen, a colorless, odorless gas, forming about one-fifth 

 of the atmosphere. 



Carbon, a solid at ordinary temperatures. Charcoal, graphite, 

 lampblack, and diamond are examples of almost pure carbon. 



Hydrogen, a gas, the lightest of all known substances and 

 highly inflammable. 



Nitrogen, a colorless, odorless gas which comprises about 

 four-fifths of the atmosphere. 



Sulphur, phosphorus, calcium, iron, and potassium consti- 

 tute the other chemical elements that are found in living 



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FIG. 1. DIAGRAM SHOWING THE RELATIVE PROPORTIONS 



OF THE CHIEF ELEMENTS MAKING UP A LIVING BODY 



things. Only very small amounts of these elements are present, 

 although calcium is found in animals in considerable quantities 

 in the bone. Figure 1 shows diagrammatically the relative 



