42 PLAIN FACTS FOR OLD AND YOUNG 



a human being. In another chapter we speak more fully 

 upon this point. 



This flexibility of the bony framework of the body 

 in early life, clearly indicates the imj^ortance of train- 

 ing the body to a correct and symmetrical development 

 during the years of childhood and youth, while it is 

 developing and being molded into its permanent form. 

 The subject of exercise and physical development will 

 receive special attention in another chapter, which it 

 is hoped the reader will carefully peruse. 



Five Hundred Muscles.— Beefsteak or mutton- 

 chop is a portion of the muscle of an ox or sheep. The 

 lean meat of all animals is composed of muscular tis- 

 sue, which also makes up the great bulk of the fleshy 

 portion of our own bodies. A piece of lean meat that 

 has been salted, after being boiled may be separated 

 into bundles, each one of which may be divided into a 

 large number of delicate threads. If one of these is 

 placed under a microscope, it may be divided into 

 fibers almost too small to be seen with the naked eye. 



How a Muscle "Works.— Each one of these minute 

 fibers, several hundreds of which would be required to 

 cover an inch in space, if laid side by side, possesses 

 the power to contract and then to return again to its 

 natural length. By the combined action of the thou- 

 sands of these little living threads which constitute 

 each muscle, these organs are enabled to do the work 

 assigned them in the body, which is that of producing 

 motion by contraction. 



The total number of muscles in the body is about 

 two hundred and fifty pair, which, with very few ex- 

 ceptions, are arranged symmetrically, each side of the 

 body being provided with muscles exactly like those 

 of the opposite side. 



