10 ADVANCED PHYSIOLOGY 



questions are constantly arising as to the proper means for 

 preserving health. Even country life is ceasing to be the 

 simple, natural life that it was once, and the smaller com- 

 munities are facing many of the problems of the large 

 cities. With each succeeding year we realize more fully the 

 need of understanding the laws of life in order to maintain 

 both individual and public health. All this makes a con- 

 stantly increasing demand for the study of those subjects 

 which teach us how to keep our bodies and minds in a 

 state of highest efficiency; and the study of physiology and 

 hygiene has come to be recognized as one of the necessities 

 of education. 



Normal and Experimental Physiology. Physiology is the 

 science of the activities of living things. It may refer to the 

 activities of animals or plants, of the whole animal or its 

 parts, of the whole plant or its parts, or even of whole 

 groups of animals or plants. If observations are made 

 upon animals under healthy, normal conditions, while they 

 are acting under their own ordinary impulses, the study 

 is called normal physiology. Sometimes, however, an animal 

 or a plant or parts of either may purposely be put under 

 unnatural conditions and the result noted. We may change 

 the food supply, the temperature or moisture of the sub- 

 stance in which it lives, we may try the effects upon it of 

 drugs and poisons, or we may artificially stimulate it to 

 action. In these cases the study is termed experimental 

 physiology. 



The term physiology, as commonly understood, refers 

 to the study of the activities or functions of the different 

 parts of the human body under normal conditions. Although 

 thus primarily a study of activities, some attention must 

 also be paid to structure; for if one is to understand 

 thoroughly the working of any machine, he must know the 

 form and position of its parts. The study of the structure 

 of the body is called anatomy. Anatomy and physiology 



