V
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.
How eloquent is the eye of a dying friend looking at us for the last time, and seeming to reflect all the sadness of an existence fading while still full of hope and aspirations! The eye does not change for many hours, but when you come back to look at the cold semblance of your friend, and bid him a last farewell, the immovable look, the staring eye of death arrests you on the threshold; in it you read the anguish of pain, the horror of an overwhelming misfortune.
There are also in the pupil of the eye vivid expressions which are almost entirely unknown. It is curious to note in the eye of a dog, when quiet, how the pupil dilates and contracts at every emotion. This cannot arise from his looking at near or distant objects. The iris, like the blood-vessels, reflects every little emotion. We do not know these delicate shades in the language of the emotions, because the analysis of physical facts accompanying the expression of the passions has not yet become sufficiently minute and accurate. Between the maximum dilatation of the pupil, so characteristic of fear, and its greatest contraction in sleep, perfect calm and weariness, is the whole intermediate series of movements in which the passions are revealed. There are little alterations in the diameter of the pupil which pass unnoticed, unless one can look closely at the eye, but, by attentively observing a great number of persons, I have convinced myself that it is possible to read the effects of the passions in the movements of the pupil. When the edge of the iris grows narrower and the middle of the eye blacker and larger, it is a sign that we are agitated by a strong emotion which we try in vain to conceal, because the eye, as the poets say, is the window of the soul, through which we look into the depths of the heart.