muscles. But if we dissect a limb, we find that the muscles are beautiful organs, adapted, as regards form and length and bulk, to the work each has to perform. This diagram will give you a conception of what we mean by a muscle. It shows the muscles of a frog's leg. You observe that, as a rule, a muscle springs from a bone, and is attached at the other end to another bone, a joint, sometimes two or more joints, intervening. One end of such a muscle as the gastrocnemius (Fig. 6) muscle terminates in what is called a tendon or sinew—
We may call the muscles the organs of movement. By an organ physiologists mean a part of the body devoted to a special use or purpose, or, as we say, a function. A muscle has its own work to do, in a sense as true as that the heart has its own work to do in acting as a force-pump to drive on the blood through the blood-vessels, or, in other words, to keep up the circulation. It is important to notice that a muscle may be regarded as an
