STRUCTURE OF THE MUSCLES.--If we take a piece of lean beef and wash out the red color, we can easily detect the fine fibers of which the meat is composed. In boiling corned beef for the table, the fibers often separate, owing to the dissolving of the delicate tissue which bound them together. By means of the microscope, we find that these fibers are made up of minute filaments (_fibrils_), and that each fibril is composed of a row of small cells arranged like a string of beads. This gives the muscles a peculiar striped (striated) appearance. [Footnote: The involuntary muscles consist generally of smooth, fibrous tissue, and form sheets or membranes in the walls of hollow organs. By their contraction they change the size of cavities which they inclose. Some functions, however, like the action of the heart, or the movements of deglutition (swallowing), require the rapid, vigorous contraction, characteristic of the voluntary muscular tissue--FLINT.] (See p. 276.) The cells are filled with a fluid or semifluid mass of living (protoplasmic) matter. FIG. 15. [Illustration: _Microscopic view of a Muscle, showing, at one end, the fibrillæ; and, at the other, the disks, or cells, of the fiber._] The binding of so many threads into one bundle [Footnote: We shall learn hereafter how these fibers are firmly tied together by a mesh of fine connective tissue which dissolves in boiling, as just described] confers great strength, according to a mechanical principle that we see exemplified in suspension bridges, where the weight is sustained, not by bars of iron, but by small wires twisted into massive ropes. FIG. 16. [Illustration: _Tendons of the Hand._] THE TENDONS.--The ends of the muscles are generally attached to the bone by strong, flexible, but inelastic tendons. [Footnote: The tendons may be easily seen in the leg of a turkey as it comes on our table; so we may study Physiology while we pick the bones.] The muscular fibers spring from the sides of the tendon, so that more of them can act upon the bone than if they went directly to it. Besides, the small, insensible tendon can better bear the exposure of passing over a joint, and be more easily lodged in some protecting groove, than the broad, sensitive muscle. This mode of attachment gives to the limbs strength, and elegance of form. Thus, for example, if the large muscles of the arm extended to the hand, they would make it bulky and clumsy. The tendons, however, reach only to the wrist, whence fine cords pass to the fingers (Fig. 16).