The governing power exercised by the brain as a whole, or by certain centres in the nervous system, to make various muscles contract in harmony and so produce definite actions (instead of meaningless movements). Coordination is intimately bound up with the complex sense of localisation (see PROPRIOCEPTORS), which enables a person with their eyes shut to tell, by sensations received from the bones, joints and muscles, the position of the various parts of their body.

This power is impaired in various diseases, such as LOCOMOTOR ATAXIA. It is tested by making the patient shut their eyes, moving their hand in various directions, and then telling them to bring the point of the forefinger steadily to the tip of the nose – or by other simple movements.