Flight is the most 'perfect and unconstrained form of animal motion; it is also the most widespread, since it offers the most favourable conditions of survival in the struggle for existence. Animal species losing the power of flight, are an easy prey for their enemies, and speedily become extinct.

Man, having achieved the power of mechanical flight by technical skill, has now introduced the art of flying in his own struggle for existence, as abundantly proved by the history of the past thirty years. Research, and not engineering research alone, has stood in the forefront of this development: filling the rôle of the advanced reconnaissance unit in development, experimentation, and the tactical application of the power of flight.

Man, aircraft-borne, now flies higher (record altitude 17,000 m.), faster (speed record 755 km./h.), and farther (long-range distance record over 12,000 km.), than any other animal. This raises a query as to the effect of flight on the human organism.