The human body is not a machine but it is subject to mechanical law. That is to say it is weight-bearing and the lines of stress are present in the living organism as they are present in every object on this earth-plane. Parallel, non-parallel and curved, the lines are arbitrary in operation, having a direction and magnitude that will only by denied at the expense of the body and no amount of corrective treatment will suffice in many cases if the stress remains.
The base-line, the axis of symmetry, the centre of gravity, the polygon of forces, the upper and lower triangles have been fully established and the accuracy of this scientific data is beyond question. The curved lines bring a new set of problems, representing the dynamics of the moving body of which the central ‘double arch’ or ‘power house’ of the spinal column, is the most important factor.
Certain vertebrae act as pivots and others as keystones and the balance of the arches is of special significance in the maintenance of recovery power from the effects of stress.