The flexor muscles are situated at the back part of the leg, attached above to the back part of the elbow joint, passing downwards at the back part of the leg. About two or three inches above the back part of the knee joint they become tendinous, and from there down to the back part of the coffin bone, where two of the principle muscles are attached; these form what is known as the back tendons, or cords, of the leg. Some of them become attached to the back part of the knee, same as the muscles on the front part of the leg, while the other two principal tendons pass through a loop formed by ligaments, the same as those mentioned in the front part of the knee. In tracing these tendons down from the knee to the fetlock, notice that they pass through another larger loop or sheath formed at the back of the fetlock, where some of the fibers are attached, while others continue down at the back part of the pastern bones, and are attached to the os pedis or coffin bone. These tendons are important, because when they are strained the fact is spoken of as the strain of the back tendons. The action of these muscles is to flex the leg, bend the knee, pastern joints and fetlock. MUSCLES OF THE HIND LEG.--These are also divided into two groups, extensor and flexor. The extensor muscles are situated in front of the hind leg. They are attached above, around the stifle joint, and pass downward in front of the tibia, or thigh bone, one being attached to the front part of the hock. The other passes through sheaths, or loops, supplied by a synovial membrane, formed by ligaments, to hold the muscles firm in front while the leg is in action. In tracing them down, in front of the shin bone to the fetlock, note that they pass through loops, or sheaths, and continue down in front of the pastern bones to where they are attached. The action of these is to bring the leg forward.