Superficial muscles of the chest, including pectoralis major (Gray 1918)
Pectoral muscles (colloquially referred to as "pecs") are the muscles that connect the front of the human chest with the bones of the upper arm and shoulder.
Deep muscles of the chest, including pectoralis minor, serratus anterior, and subclavius (Gray 1918)
Pectoralis major is a thick, fan-shaped muscle, which makes up the bulk of the chest muscle. It lies under the breast. It serves to flex, extend, and rotate the humerus, the long bone of the upper arm.
Pectoralis minor is a thin, triangular muscle located beneath the pectoralis major. It attaches to the ribs, and serves to stabilize the scapula, the large bone of the shoulder.