Like the muscle last described, the internal oblique muscle is flat, and comprises a thick, fan-shaped fleshy portion spreading out from above forward and terminating in a broad aponeurotic tendon. It is situated in the region of the flank, and its fibres proceed from behind downward and forward, and in so doing cross those of the external oblique muscle as they pass backwards.

Origin. - From the external angle of the ilium or haunch-bone, and the contiguous fibres of Poupart's ligament.

Insertion. - Into (1) the symphisis pubis, (2) the linea alba, (3) and the cartilages of the last four or five ribs.

Action. - The same as the external oblique.