Any of three muscles, the first with its origin from the second metacarpal, and the second and the third with origin from the fourth and fifth metacarpals; the first with insertion into the index finger, and the second and the third with insertion into the ring and little fingers; with nerve supply from the ulnar nerve, and whose action adducts the fingers toward the axis of the middle finger. [ http://en.wikipedia.org/wiki/Palmar_interossei_muscles ]