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 tapering 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 muscle suddenly left off, and changed into much firmer material which was white and glistening. This firmer white part you were told was called the tendon of the muscle. The rest of the muscle, generally called “the belly,” is made up of what you are accustomed to call 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 substance. =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 tissue. And these thinner but firmer fibres make up the cord or band of tendon with which the muscle finishes off at either end. =It is by these tendons that the soft muscles are joined on to the hard bones, or to some of the other firm textures of the body.= The tendons are sometimes round and cord-like, sometimes flat and spread out. Sometimes they are very long, sometimes very short, so as to be scarcely visible. But always you have some amount of the firmer fibres of connective tissue joining the soft muscular fibres on to the bones, and generally the tendons are not only firmer but much thinner and more slender than the belly of the muscle. The muscular belly of the biceps is placed in the front of the upper arm. Some little way above the elbow-joint it ends in a small round strong tendon which slips over the front of the elbow and is fastened to, _i.e._ grows on to, the radius at some little distance below the joint (Fig. 3, P). The upper part of the muscular belly ends a little below the shoulder, not in one tendon but in two[1] tendons (Fig. 3, _a_), which gliding over the end of the humerus are fastened to the shoulder-blade (or =scapula= as it is called), into which the humerus fits with a joint.