Terrestrial animal locomotion

The structure of animals moving on the surface of the ground reflects their locomotion habits. Arthropods and vertebrates tend to move by walking or running, using the legs to support the body off the surface and to propel it forward. Stability is maintained during this process by a functional sequence of limb movements which in the fastest case are asymmetrical in the case of vertebrates (four-legged) and symmetrical in the case of arthropods (six-legged or more) which are consequently less rapid. Movement by saltation (hopping) is also used by some vertebrates and arthropods which necessarily have larger hind legs; four patterns of saltation may be distinguished. Movement by crawling is used by some invertebrates (using peristaltic locomotion or contract-anchor-extend locomotion) and by limbless vertebrates. The latter use one of four patterns: serpentine locomotion (simultaneous lateral thrusts against solid projections by a body in a series of sinuous curves), concertina locomotion (used when there is not enough frictional resistance for the serpentine form), sidewinding locomotion (used over friable sand, such that only portions of the body remain in contact with the ground), and rectilinear locomotion (using movement of scales beneath the body in contraction waves from head to tail).

The structure of praxis-oriented groups or individual personalities reflects their mode of movement over social terrain. To reduce resistance to such movement, the group may only interface with its programme through a succession of complementary policies. These may each be discarded once their immediate objectives have been achieved but may be reimplemented in a modified form to achieve subsequent objectives. Stability is maintained by appropriately ordering the process of implementing and abandoning such complementary policies. An alternative procedure, rather than maintaining continuous contact with the social terrain and its constraints, is to undertake a discontinuous succession of policy leaps thus by-passing obstacles which might otherwise prove impassable. Another alternative is to ensure that all parts of the group are in continuous contact with the terrain and to coordinate the manner in which they each act on it in order to move the group forward.

The manner in which support, propulsive and stabilizing functions are distinguished and coordinated.

In China official use has been made of the metaphor of 'walking on two legs' as well as of the 'great leap forward'. But in general there is little understanding of how the relationship between contrasting policies is to be coordinated. It is as though the different legs win in competition for the right to move forward. This is a guarantee of instability and discontinuity in two-party systems and of confusion in multi-party systems. This clarifies the frequent repeat that society can only advance at a 'crawling' pace. The metaphor also throws light on the debate between those who favour organizations in which all sections deal with practical issues and those favouring specialized sections for such contact.

Contrast between the evolutionary relationship between different forms of movement and the effectiveness of particular forms in particular environments.