ABSTRACT
The third organ disturbed under weightlessness is the vestibular apparatus. Although it plays an essential role in everyday life, few people are aware of its existence. This is easily explained: whereas human beings are continuously made conscious of the world around them through sight, hearing, olfaction and touch detectors, the vestibular apparatus is an automatic system, sending subconscious information to the brain. Only pathological manifestations, for instance vertigo or motion sickness caused by a rocking ship, remind us of its presence.
