Situated behind the one last described, of which it seems to be a continuation. It is composed of a flat or aponeurotic tendon and a number of fleshy segments.

Origin. - From the spinous processes of the seven posterior dorsal vertebrae and the two anterior lumbar.

Insertion. - Into the outer surfaces and posterior borders of the eight or nine last ribs.

Action. - To pull the ribs backwards and assist in expiration.