Introduction 5 



7. The Metabolism of the Body. The process of build- 

 ing up the materials of the body from simpler materials is 

 called anabolism. 



The breaking down of the materials of the body into 

 simpler substances is known as katabolism. 



The entire series of changes that take place in the living 

 body, beginning with the building up of its materials and 

 ending with the casting out of wastes, is included in one 

 word, metabolism. 



The reduction of complex to simple substances results 

 in the setting free of energy in the forms of heat and 

 mechanical motion. Thus a complex substance, like a 

 piece of muscle, or lean meat, is built up of many millions 

 of molecules, each composed of a number of atoms arranged 

 in a definite way. Force or energy was, of course, required 

 for this regular arrangement of the atoms. 



Now when this material is reduced by the process of 

 oxidation to substances consisting of simpler molecules, 

 such as carbon dioxide, urea, and water, the force stored 

 up in the muscle as potential energy becomes manifest and is 

 used as kinetic energy, or active life force. 



8. Technical Terms defined. All living organisms may 

 be studied from two points of view : first, as to their form 

 and structure ; second, as to the processes which go on 

 within them. 



The science which treats of all living organisms is called 

 biology. It has naturally two divisions : 



Morphology, which treats of the form and structure of 

 living beings. 



Physiology, which investigates their functions, or the 

 special work done in their vital processes. The word 

 physiology is from two Greek words ((^ucrt? and ^0709) and 

 means literally a talk or discourse about nature. 



