SCIENCE PRIMERS. 



PHYSIOLOGY, 



INTRODUCTION. § I. 



I. Did you ever on a winter^s day, when the ground 

 was as hard as a stone, the ponds all frozen, and every- 

 thing cold and still, stop for a moment, as you were 

 running in play along the road or skating over the ice, 



to wonder at yourself and ask these two questions : 



"Why am I so warm when all things around me, the 

 ground, the trees, the water, and tlie air, are so cold ? 

 How is it that I am moving about, running, walking, 

 jumping, when nothing else that I can see is stirring 

 at all, except perhaps a stray bird seeking in vain for 

 food ? " 



These two questions neither you nor anyone else 

 can answer fully ; but we may answer them in part, 

 and the knowledge which helps us to the answer is 

 called Physiology. 



2. You can move of your own accord. You 

 do not need to wait, like the boughs or the leaves, till 

 the wind blows upon you, or, like the stones, till 

 somebody stirs you. . The bird, too, can move of its 





