OUR ENVIRONMENT AND HOW WE USE IT 17 



mountain side or it may fall from the clouds as snow or 

 hail. 



In our own bodies hundreds of chemical and physical 

 changes are taking place every minute as the human 

 machine changes its position in walking, running, swim- 

 ming, driving, and even sitting or resting. Our mus- 

 cles are always at work, contracting, relaxing, thus 

 showing physical changes. And inside the body com- 

 plicated chemical changes are taking place : food is being 

 digested ; we breathe and the oxygen of the air unites with 

 the digested foods as we do work. Work done by the 

 muscles involves still more chemical changes. All life as 

 seen from the standpoint of the chemist and physicist is a 

 series of chemical and physical changes. And in the com- 

 plex environment of today more and new physical and 

 chemical changes are found as man makes use of new and 

 different helps in his everyday life. 



Man's Environment Much More Complex Than It Used 

 to Be. If we were to compare the life of Uncas, the 



Compare the living conditions of the Indian with those in a modern city, 

 what ways do they differ ? In what ways are they alike ? 

 H. & w. sci. 1 3 



In 



