Plutarch Quaestiones Convivales 5.7.2

[2] True, said I, but methinks there is some small track to the cause of this effect, if you come to the effluvia of bodies. For smell, voice, breath, and the like, are effluvia from animal bodies, and material parts that move the senses, which are wrought upon by their impulse. Now it is very likely that such effluvia must continually part from animals, by reason of their heat and motion; for by that the spirits are agitated, and the body, being struck by those, must continually send forth effluvia. And it is probable that these pass chiefly through the eye. For the sight, being very vigorous and active, together with the spirit upon which it depends, sends forth a strange fiery power; so that by it men act and suffer very much, and are always proportionably pleased or displeased, according as the visible objects are agreeable or not. Love, that greatest and most violent passion of the soul, takes its be ginning from the eye; so that a lover, when he looks upon the fair, flows out, as it were, and seems to mix with them. And therefore why should any one, that believes men can be affected and prejudiced by the sight, imagine that they cannot act and hurt as well? For the mutual looks of mature beauties, and that which comes from the eye, whether light or a stream of spirits, melt and dissolve the lovers with a pleasing pain, which they call the bittersweet of love. For neither by touching or hearing the voice of their beloved are they so much wounded and wrought upon, as by looking and being looked upon again. There is such a communication, such a flame raised by one glance, that those must be altogether unacquainted with love that wonder at the Median naphtha, that takes fire at a distance from the flame. For the glances of a fair one, though at a great distance, quickly kindle a fire in the lover’s breast. Besides everybody knows the remedy for the jaundice; if they look upon the bird called charadrios, they are cured. For that animal seems to be of that temperature and nature as to receive and draw away the disease, that like a stream flows out through the eyes; so that the charadrios will not look on one that hath the jaundice; he cannot endure it, but turns away his head and shuts his eyes, not envying (as some imagine) the cure he performs, but being really hurted by the effluvia of the patient. And of all diseases, soreness of the eyes is the most infectious; so strong and vigorous is the sight, and so easily does it cause infirmities in another.