Our Bodies 



331 



Scapula 



Humerus 



Radius. 



The greater part of the body outside of the framework, or 

 skeleton, is composed of the flesh, or muscles. Muscles are of 

 two kinds, voluntary and involuntary. Movements that are under 

 the guidance of the will, such as the movements of the arm or 

 the leg, are controlled by vol- 

 untary muscles. Movements 

 that are not under the guid- 

 ance of the will, such as the 

 beating of the heart or the 

 action of the stomach in diges- 

 tion, are caused by involuntary 

 muscles. 



Muscles are also distin- 

 guished as flexor and extensor. 

 Any muscle that bends a 

 limb is a flexor muscle and 

 any muscle that extends or 

 straightens a limb is an ex- 

 tensor muscle. 



We are not expected to 

 learn the names of all the mus- 

 cles of the body, but we should 

 know those of a few impor- 

 tant ones. The biceps muscle 

 that flexes or bends the fore- 

 arm, and the triceps muscle 

 that extends it, are examples 

 of voluntary muscles with 

 which every one should be 

 familiar. All muscles con- 

 nected with the bones are vol- 

 untary. The lieart is the best 

 example of an involuntary 

 muscle. The muscles of the THE SKELETON 



blood vessels, of the intes- The framework of the human bod y- 



tines, and of certain glands are other examples of involuntary 

 muscles. 



