This is a thin, broad sheet of muscular tissue spread over a large extent of the surface of the body, especially the sides of the shoulder, chest, and belly, the front of the neck, and the sides of the face. It is connected above and below with considerable aponeurotic tendons, which attach it to the dorsal and lumbar spines, the flank, the inner side of the arm, the neck, and the abdominal tunic.
Insertion. - By its fleshy fibres into the under surface of the integument. It is this muscle which imparts that vigorous movement to the skin when flies or other matters irritate it and require to be dislodged.