When the object is not small enough to be embraced by the simple movements of the eye in its orbit, we bend and turn the head, or move the trunk to right or left; if that does not suffice, we move the whole body. Actors represent fear by exaggerating the attitude peculiar to one intently observing an object.
These movements are so spontaneous and natural, that it costs an effort to keep head and body still when looking at an object situated on one side of us. A feeling of profound contempt, hatred, or pride is necessary before we can pass close to a man with head stiff and erect.
Anyone who studies the parts of a machine can judge of the accuracy of its movements, because the structure of a machine represents its function; the dead organism is, therefore, no less important a field for observation and study to the physiologist than the living organism.
When we see, on opening the skull, that three nerves leave the brain to move the eye, and that six muscles are attached to this little ball weighing on an average seven grammes, we may conclude at once that perhaps no other organ has the same variety, independence, and rapidity of movement.
The eye is indeed unrivalled in the complication of its muscles and the number and variety of its nerves by any other organ except the tongue. This explains why both have their own language, and how they are able, by the infinite variation of their movements, to express every emotion of the mind.
The life of the eye lies entirely in its movement. A well-made glass eye which can follow the movements of the real eye can scarcely be distinguished from the latter when placed in the orbit, but when it remains motionless it gives to the countenance a dreadful, spectral appearance.
I have studied the expression of the eye in those born blind. These poor people, who could not even see dim shadows of objects, nor distinguish night from day, as though a sevenfold bandage covered their eyes, used to play instruments and be happy together, nor would anyone have thought that in them the eye was dead, insensible for ever to light; but it was only its movements which gave it an expression of joy and amiability, which inspired confidence and tenderness.