268 



THE HUMAN MACHINE 



The Skin. — Covering the body is a protective structure called 

 the skin. Covered on the outside with dead cells, yet it is provided 

 with delicate sense organs, which give us perception of touch, taste, 



smell, pressure, and temperature. 

 It also aids in getting wastes out 

 of the body by means of its sweat 

 glands and plays an important part 

 in equalizing the temperature of 

 the body. 



Bones and Muscles. — The body 

 is built around a framework of 

 bones. These bones, which are 

 bound together by tough ligaments, 

 fall naturally into two great groups, 

 the bones of the body proper, verte- 

 bral column, ribs, breast bone, and 

 skull, which form the axial skeleton, 

 and the appendages, two sets of 

 bones which form the framework 

 of the arms and legs, which with 

 the bones which attach them to the 

 axial skeleton form the appendicular 

 skeleton. 



To the bones are attached the 

 muscles of the body. Movement 

 is accomplished by contraction of 

 muscles, which are attached so as 

 to cause the bones to act as levers. 

 ~p/ Bones also protect the nervous 

 system and other delicate organs. 

 Thej^ also help to give form and 

 rigidity to the body. 



Hygiene of Muscles and Bones. 

 — Young people especially need to 

 know how to prevent certain defects 

 which are largely the result of bad 

 habits of posture. Standing erect 



cramum ; 

 sternum ; 

 vertebral 



Skeleton of a man. CR 

 CL., clavicle ; ST., 

 H., humerus; V.C., 

 column; R., radius; U., ulna; 

 P., pelvic girdle; C, carpals; 

 M., metacarpals; Ph., phalanges; 

 F., femur ; Fi., fibula ; T., tibia ; 

 Tar., tarsals; MT., metatar- 

 sals. 



