CHAPTER XVII 



C/ovnr/e 



MUSCLES 



While the skeleton is the hardest part of the body, it is not 

 the most abundant tissue and does not require so large a part 

 of the food materials for its building or maintenance as do 

 the muscles. The skeleton gives the body its general shape, 

 but the bones are of use only because of the muscles attached 

 to them. Life, of course, could not continue if we lacked 

 the ability to move, and even though the internal organs of 

 breathing and circulation are in good condition, there is no 

 more pitiful sight than that of a person whose limbs are 

 withered or whose muscles are paralyzed. 



Muscles make up the heaviest part of the arms and legs, 

 of the shoulders and hips. They occur in the trunk of 

 the body, both in 

 front and behind. 

 The heart, arteries 

 and veins are chiefly 

 composed of muscle 

 tissue; the tongue, 

 oesophagus, stomach 

 and intestine are also 

 largely muscular. In 

 short, about 44% of 

 the whole body is 

 made of muscle cells, 

 and most of the food 

 taken into the body 

 is used in building them up, and in furnishing them ma 

 terials on which they constantly draw while doing work. 



273 



FIG. 137. THE ARM (SEMI-DIAGRAMMATIC) 



Showing the relations of the biceps muscle. From 

 the figure it is evident that if the muscle contracts 

 slightly the fore arm will be lifted over a great 

 distance. 



