Muscles are the active organs of motion, or locomotion, each being separated from the other by a thin delicate membrane made up of connective tissue, which forms a sheath for the muscle. A muscle is divided into two parts, viz.: muscular and tendinous. The muscular part is the larger of the two. It is sometimes called the belly of the muscle or flesh. This part is known as muscular tissue, and has a reddish, meaty color. At both ends of the muscle there is a tendinous part, or the hard, white portion of the muscle which becomes attached to the bone. All muscles are attached to two or more places of different bones, and when contracted, the joints of the body are moved. They are well supplied with nerves, which give strength and feeling, and also well supplied with small blood vessels, from which the muscle is fed. Muscles are found in separate groups, all of which have different actions to perform. There are two kinds of muscles--voluntary and involuntary. The voluntary muscles are under the control of the will of the animal; example--the muscles of the head, neck, back, hip and legs. The involuntary muscles are beyond control of the animal, and will act even though the animal were asleep--such as those of the heart, the large muscular curtain which separates the chest cavity from the abdominal cavity, which is one of the great muscles of breathing; also the muscles around the chest which assist in breathing. [Illustration: PLATE II. MUSCLES OF THE HORSE--SUPERFICIAL LAYER--AFTER MEGNIN.] EXPLANATION OF PLATE II. MUSCLES OF THE HORSE. This illustration shows the superficial muscles of the body after the skin and panniculus carnosis muscle has been carefully removed. This muscle is spread over the greater part of the body, which is related externally with the skin; internally with the superficial layer of muscles. Its action corrugates the skin, and thus enables the animal to expel or shake off insects and irritating bodies, its use being thus protective to some extent; it also supports and binds down the superficial muscles. SUPERFICIAL LAYER. The panniculus and tunica abdominalis are removed.