Fig. 11-8. A, Diagram to show the chief muscles producing extension and flexion of the fingers. ED., extensor digitorum; FD.P., flexor digitorum profundus; FD.5., flexor digitorum superficialis; I., interosseus; L., lumbrical. B, The Z-position of the hand, produced by the interossei and lumbricals. C, Claw hand, due to paralysis of the interossei and lumbricals (following section of the ulnar nerve). The unopposed extensor and flexors produce the opposite of the Z-position. Click for high resolution image.