STUDIES IN PHYSIOLOGY 



ANATOMY AND HYGIENE 

 CHAPTER I 



INTRODUCTION 



The Study of an Engine. If we wished to make a careful 

 and scientific study of a railroad locomotive, it would, per- 

 haps, be best for us first to go to a machine shop where 

 engines are built and repaired. There we could see the 

 construction of each separate part and could also find how 

 these various parts are put together to form a completed 

 engine. 



But if we had never before seen an engine, the whole 

 machine would probably have little meaning or interest for 

 us until we had watched it in action. We should then 

 learn how the locomotive is supplied with water and coal. 

 We should see that the burning coal converts the water 

 into steam, and that energy or power is thus furnished by 

 which the pistons cause the drive wheels to revolve. All 

 the pipes, cranks, levers, and rods we should find to be 

 specially adapted for starting the locomotive, for keeping it 

 in motion, or for stopping it. 



To understand thoroughly, however, the action of this 

 complicated mechanism we should need to go still farther 

 in our study. Considerable knowledge of the principles of 

 levers would be required. We should have to investigate 

 the processes involved in the burning of coal and in the 

 change of water into steam, and we should seek an expla- 



B 1 



