4 STUDIES IN PHYSIOLOGY 



The term biology is usually employed, however, when we 

 are comparing the processes carried on in both of these two 

 great kingdoms of animate bodies. If we confine our study 

 to the structure and activities of plants alone, we call this 

 part of the science botany. Zoology, on the other hand, treats 

 of the anatomy and physiology of animals. Human physi- 

 ology discusses man, the highest type of the animal king- 

 dom ; hence it is a branch of the science of zoology, which 

 in turn is one of the subdivisions of the study of biology. 



The Relation of Chemistry and Physics to Physiology We 



saw in a previous section that a complete explanation of the 

 action of a locomotive requires some knowledge of physics 

 and chemistry. This is far more true in animal physiology. 

 We may study the various parts of the human body, and we 

 may watch the activities of these parts, but we cannot begin 

 to understand the processes that we see until we know some- 

 thing of the chemical composition of lifeless as well as of 

 living things, and something of the chemical changes that 

 are constantly taking place all about us as well as within 

 us. Our next chapter will therefore be devoted to a con- 

 sideration of some simple experiments in chemistry. 



