Continuous pressure on a living structure weakens it, while intermittent pressure strengthens it; so the man who stands on his feet continuously develops a flat instep and a weak calf, while the professional dancer or runner acquires a high instep and a strong calf.

Now there are many occupations which involve prolonged standing and so induce the condition of flat foot: waiters, hall-porters, hawkers, policemen, shop-walkers, salesmen, and station officials are examples.

But the waiter's gait is characteristic--a quick, shuffling walk which enables him to carry liquids without spilling them.

This man walks with a long, swinging stride; he is obviously not a waiter.

His dress and appearance in general exclude the idea of a hawker or even a hall-porter; he is a man of poor physique and so cannot be a policeman.