INTRODUCTION 3 



for the wind to blow us to and fro, or, like the pebbles by 

 the roadside, for somebody to move us. When we choose, 

 we can move from place to place. 



Indeed, it is true that every living animal, even the 

 tiniest creature that lives its brief life in a single day and 

 can be seen only with the help of the microscope, has the 

 power to move of itself. 



5. Animals are Warm. Even in the coldest day of mid- 

 winter, when the stones and trees are as cold as ice, our 

 bodies, except perhaps the tips of the fingers, the toes, 

 and the ears, are always warm. On a winter day we 

 sometimes put our cold fingers to the lips to warm them 

 with our breath. 



In fact, the bodies of all animals are more or less warm 

 so long as they are alive. On a wintry day we have all 

 seen the clouds of steam blown from the nostrils and rising 

 from the warm body of a hard-working horse. 



6. The Body compared to a Locomotive. The body is, in 

 some respects, like a locomotive. The bones and muscles 

 correspond to the machinery, and the food we eat to the 

 fuel that is used in running it. When the engine is to 

 be used, the fireman puts fuel into the furnace, and soon 

 the water in the boiler is heated and expands into steam. 

 The piston begins to work. This moves the connecting 

 rods and wheels. And so the locomotive is set going by 

 means of the fuel which was put into the furnace. 



Something not unlike the action of the locomotive occurs 

 in our bodies. We take food, and it passes into the stomach. 

 By means of that food we are kept warm, muscular force 

 is developed, and our limbs and other parts are made to 

 work, just as the parts of the engine are set in motion by 

 means of the fuel. 



