As already shown, general sensibility, including in the term the sense of touch and the muscular sense, is of prime importance in equilibration, but it is unquestionable that the nerves of the other senses carry to the nerve-centre impulses from the external parts of the body which are necessary to the highest development of the function. The partially ataxic man can walk with his eyes open, although he does not feel the floor, because sight replaces touch. The blind man, certainly, cannot balance himself so well as he whose eyes are perfect. We all know that the sight of a yawning abyss or the gazing upon whirling objects is prone to produce giddiness.
Some experiments made by the English physiologist Crum Browne show that there must be guiding impulses which are connected with equilibration besides those already discussed. The observer mentioned found that if a blindfolded man lies on a table with a movable top placed upon a central pivot, he can judge in regard to the movements lateral or vertical, even if they be made so carefully and slowly that the man is perfectly quiescent. The subject under experiment is almost always able to decide correctly not only the direction of the motion, but also the angle through which the motion has extended. It is possible that the guiding impulses under these circumstances originate in all parts of the body. Thus, when we lie with the head downward we are at once sensible of a feeling of fulness or pressure due to the gravitation of the blood and other liquids of the body toward the head. Position undoubtedly affects the gravitation of liquids in all parts of the body: the man whose forces are reduced by a low fever gets a congestion of the back of the lungs if he lies too long upon his back. It may be that this flow of fluids toward any unusually dependent part of the body makes an impression upon the nerves of touch, which pass through all parts of the organism, and that in this way peripheral impulses are generated which reach the lower brain.