Perception, then, is due to the meeting of an element in us with the same element outside. This takes place when the pores of the organ of sense are neither too large nor too small for the “effluences” which all things are constantly giving off (fr. 89). Smell was explained by respiration. The breath drew in along with it the small particles which fit into the pores. From Aetios[637] we learn that Empedokles proved this by the example of people with a cold in their head, who cannot smell, just because they have a difficulty in breathing. We also see from fr. 101 that the scent of dogs was referred to in support of the theory. Empedokles seems to have given no detailed account of smell, and did not refer to touch at all.[638] Hearing was explained by the motion of the air which struck upon the cartilage inside the ear and made it swing and sound like a bell.[639] Footnote 637: Aet. iv. 17, 2 (_Dox._ p. 407). Beare, p. 133. Footnote 638: Beare, pp. 161-3, 180-81. Footnote 639: _Ibid._ pp. 95 sqq. The theory of vision[640] is more complicated; and, as Plato adopted most of it, it is of great importance in the history of philosophy. The eye was conceived, as by Alkmaion (§ 96),[641] to be composed of fire and water. Just as in a lantern the flame is protected from the wind by horn (fr. 84), so the fire in the iris is protected from the water which surrounds it in the pupil by membranes with very fine pores, so that, while the fire can pass out, the water cannot get in. Sight is produced by the fire inside the eye going forth to meet the object. This seems strange to us, because we are accustomed to the idea of images being impressed upon the retina. But _looking_ at a thing no doubt seemed much more like an action proceeding from the eye than a mere passive state. Footnote 640: _Ibid._ pp. 14 sqq. Footnote 641: Theophr. _de sens._ 26. He was quite aware, too, that “effluences,” as he called them, came from things to the eyes as well; for he defined colours as “effluences from forms (or ‘things’) fitting into the pores and perceived.”[642] It is not quite clear how these two accounts of vision were reconciled, or how far we are entitled to credit Empedokles with the Platonic theory. The statements which have been quoted seem to imply something very like it.[643] Footnote 642: The definition is quoted from Gorgias in Plato, _Men._ 76 d 4. All our MSS. have ἀπορραοὶ σχημάτων, but Ven. T has in the margin γρ. χρημάτων, which may well be an old tradition. The Ionic for “things” is χρήματα. See Diels, _Empedokles und Gorgias_, p. 439. Footnote 643: See Beare, _Elementary Cognition_, p. 18.