Locomotory organs of mammals: New mechanics and feed-back pathways but conservative central control

The dynamic stability of quadrupedal mammalian locomotion from small to med ium body size is based on limbs which follow a couple of rather simple mech anical rules (zigzag configuration of equally proportioned segments, 'panto graph behaviour' (see p. 7), position of scapular pivot and hip joint at th e same height and consecutively the same functional length of fore- and hin d limbs, clear functional separation of a propulsive proximal segment from distal joints used for fine tuning of ground contact, position of forelimb touch down just below the eye). Intra- and inter limb kinematics are the ob vious expression of activities of central and peripheral control systems. D uring cyclic locomotion muscles act mainly against gravity, stabilise and p osition the three-segmented therian limb. The intrinsic mechanical properti es of the locomotory organs especially muscles reduce the need for control. Furthermore, muscles control their stiffness themselves by a afferent feed back system which modulates external effects. Adaptive mechanics and seemin gly unique feedback pathways in therian mammals deal with highly conservati ve spinal rhythmogenic flexor- and extensor centres.