28 SCIENCE PRIMERS. [§ HI. 



If you put one hand on the front of your other 

 upper arm, about half-way between your shoulder and 

 elbow, and then bend that arm, you will feel something 

 rising up under your hand. This is the muscle, which 

 bends the arm, shortening, or, as we shall learn to call 

 it, contracting. 



In your own arm, as in the limb of the rabbit 

 which you studied in your last lesson, the flesh is 

 arranged in masses or bundles of various sizes and 

 shapes, and each mass or bundle is called a muscle. 

 There are several muscles in the arm, but there is in 

 particular a large one occupying the front of the arm, 

 called the biceps. It is a rounded mass of red flesh, 

 considerably longer than it is broad or thick, and taper- 

 ing away at either end. It is represented in Fig. 3. 



You may remember that while examining the leg of 

 the rabbit you noticed that in many of the muscles, 

 the soft flesh, which made up the greater part of the 

 muscle, at one or both ends of the tnuscle suddenly 

 left off", and changed into much firmer material which 

 was white and glistening. This firmer white part you \v 

 were told was called the tendon of the muscle. The \ 

 rest of the muscle, generally called "the belly," is 

 made up of what you ?" accustomed to tall flesh, or 

 lean meat, but which you must now learn to speak of 

 as muscular substance. Every muscle, in fact, 

 consists in the first place of a mass of muscular sub- 

 stance. This muscular substance is made up 

 of an immense number of soft strings or 

 fibres, all running in one direction and done 

 up into large and small bundles. At either end 

 of the muscle these soft muscular fibres are joined 

 on to firmer but thinner fibres of connective or fibrous 



