HUMAN PHYSIOLOGY 



LESSON I. 



THE GENERAL BUILD OF THE HUMAN BODY. 



THE word physiology is derived from the two Greek words phusis, 

 nature ; and logos, a discourse. Literally speaking, therefore, the 

 subject embraces all the various branches of natural science. 

 But the term physiology is now generally applied only to the 

 study of the functions of living beings. 



Animal physiology deals with the functions of animals, but 

 the term is now usually restricted to the study of man ; and 

 accordingly the object of this work is to give a brief and simple 

 outline of the life-processes of the human body. 



Of course it is impossible to understand the functions or uses 

 of the various parts of the body without a knowledge of their struc- 

 ture ; hence that branch of science which is called anatomy (Gr. 

 ana, up, and temno, I cut) must go hand in hand with physiology. 



The most obvious division of the human body is into head, 

 trunk, and limbs or extremities. 



The head includes the face, and a bony box called the cranium 

 which encloses the brain. 



The trunk encloses a large cavity which contains the parts that 

 are engaged in the circulation of the blood, respiration, digestion, 

 etc. The upper portion of the trunk is called the thorax or chest, 

 and the lower portion the abdomen or belly. These two parts 

 are separated by a fleshy partition called the diaphragm ; hence 

 we speak of the cavity of the chest as distinct from the cavity of 

 the abdomen. 



The limbs are arranged in two pairs the arms, or upper ex- 

 tremities, and the legs, or lower extremities. 



The body is made up of a large number of parts, each of 



