The innermost of the abdominal muscles. Like those already referred to, it consists of a flat fleshy portion and a broad aponeurotic tendon.

Origin. - From the lower extremities of the false ribs, and from the transverse processes of the lumbar vertebrse.

Insertion. - Into the linea alba and the ensiform cartilage. The internal surface of this muscle is covered by peritoneum.

Action. - The same as the oblique muscles.