This we can learn only from physiology and hygiene.
The General Plan of the Human Automobile is Simple.

Complicated as our body-automobile looks to be, there are certain things about the plan and general build of it which are plain enough.

It has a head end, where fuel supplies are taken in and where its lamps and other look-out apparatus are carried; a body in which the fuel is stored and turned into work or speed, and into which air is drawn to help combustion and to cool the engine pipes.

It has a pair of fore-wheels (the arms) and a pair of hind-wheels (the legs), though these have been reduced to only one spoke each, and swing only about a quarter of the way around and back again when running, instead of round and round.

It has a steering gear (the brain), just back of the headlights, and a system of nerve electric wires connecting all parts of it.