The document discusses the muscles of the neck and trunk. It divides the neck into the anterior and posterior triangles, separated by the sternocleidomastoid muscle. It then describes various neck muscles including the sternocleidomastoid, trapezius, infrahyoid, suprahyoid, and lateral neck muscles. Regarding the trunk, it outlines the deep muscles of the back, deep muscles of the thorax, respiratory muscles, muscles of the abdominal wall, muscles that form the floor of the abdominopelvic cavity, muscles that act on the scapula, and muscles that act on the arm. The document stresses the importance of identifying these muscles through diligent study.