330 



Our Surroundings 



Extensors of Fingers 

 ^Flexors oi Fln^ars 



both have special parts capable of transforming energy into 

 various kinds of work; both may be rendered useless by over- 

 work or accident and both must get rid of wastes. On the other 

 hand, the human body differs from an engine in some respects. 

 It has the power of self-repair, is conscious of various sensations, 

 and is capable of transforming food into energy without help. 

 The human body, to be fully efficient, must have proper food and 

 water, good air, necessary clothing, shelter, exercise, rest, and 

 sleep. The lack of any of these is a handicap. 



Functions of Relation Sensation and Motion. Indi- 

 viduals relate themselves to the outside world by means of the 



organs of sense and of motion. 

 All knowledge reaches the brain 

 through the agency of the five 

 senses : sight, hearing, touch, 

 taste and smell. 



Muscles. The organs of 

 motion are the muscles. In order 

 to appreciate their use we should 

 give a brief consideration to the 

 general structure of the body. 

 The knowledge of this structure 

 should be learned from the obser- 

 vation of our own bodies, supple- 

 mented by the use of a skeleton, 

 or of charts showing the most 

 important parts : the head, neck 

 and trunk, the backbone or spinal 

 column, the ribs, the sternum, the 

 pelvis, the pectoral girdle, or 

 bony arch supporting the arms, 

 the bones of the arm and of the 

 leg, and the shoulder and elbow 

 joints. There are more than two 

 hundred bones in the body. The 

 movements of the bones and of all parts of the body are controlled 

 by muscles, of which there are over five hundred. 



SURFACE MUSCLES 



