represented as corresponding with the media that communicate the qualities of odour. It is therefore composed of air and water, and it cannot act except we simultaneously draw in the breath if we exhale or restrain the breath, smell cannot operate'. The sense which has been just described stands midway between the elementary sensations with which we started and those sense-functions which remain to be discussed. While touch and taste act apparently by actual contact, odours are perceived by the intervention of some medium or other-a mode of operation which is still more prominent in sight and hearing. And while touch and taste are indispensable conditions of animal existence, the sense of smell is almost as it were a luxury in life-an appendage to the faculties which are essential to vitality itself. Still more is this true of the two remaining senses. Sight and hearing play an important part in our higher cognitive development. But they do so to different degrees. Sight, as the sense which reveals the greatest number of differences in objects, is indeed directly the most intellectual sense: but hearing, by the knowledge which it brings of others' minds, is incidentally the most important factor in our spiritual knowledge: so that, adds Aristotle, the blind are generally more intelligent than the deaf3. Hearing is discussed by Aristotle with less detail than the importance of the sense itself would seem to merit. It would almost seem, in fact, as if, as Trendelenburg suggests, the Treatise on Sense had lost a section which would have explained the character of sound and hearing in accordance with the statement of the Genesis of Animals. But at the same time Aristotle's analysis of hearing and its object is comparatively full. The real object of hearing, Aristotle would seem to hold, is that vibration of the air which we describe as sound or noise. 1 4255; 42114. * De Sensu, 1, 437 15, διόπερ φρονιμώτεροι οἱ τυφλοὶ τῶν ἐνεῶν καὶ κωφών. De Gen. Animal. v. 7, 78623; 788*3+. Hence then it is air which forms the essential element in enabling us to hear. "Every object so constituted as to set in movement the air extending continuously in one stream until it reach the hearing is sonorous'." Air then is the medium of sound: and hearing is the result of a movement in the air within the ear communicated by a movement of the air which lies outside. Closely connected with this is the explanation Aristotle gives of the distinction between high notes and low. High or sharp notes, he explains, are those which move the sense of hearing to a great extent within a short period of time-that is they are those which offer a great number of vibrations: low notes on the contrary are those which move the ear but slightly in a larger space of time-that is they are those which present a less number of vibrations. Shortly in fact high notes are the result of rapid, low or grave notes the result of slow vibrations. perhaps the most interesting section of Aristotle's chapter on hearing is the distinction which he draws between mere sound or noise and actual speech. Mere sound, he points out, may be made by the tongue and in other ways: for voice, on the contrary, the organ striking must be animate and accompanied by some mental image (uerà pavтasías Tivos): voice being in fact sound possessed of meaning (Vódos onμavtikós)3. But Sight', as might be expected from the important place it occupies in the economy of knowledge, is discussed by Aristotle at greater length than any of the other senses. Beside the chapter devoted to it in the Psychology itself, it occupies the greater portion of the Treatise on the Senses, and there is a special Tractate on the collection of qualities which constitute its object 1 4203. 2 De An. 11. 8, 420b3. Cp. Timaeus, 67 B, öλws μèv ovv øwrijv Oŵμev Tηy di' wτ WP ὑπ' ἀέρος ἐγκεφάλου τε καὶ αἵματος μέχρι ψυχῆς πληγὴν διαδιδομένην, τὴν δὲ ὑπ' αὐτῆς κίνησιν, ἀπὸ τῆς κεφαλῆς μὲν ἐρχομένην, τελευτώσαν δὲ περὶ τὴν τοῦ ἥπατος ἕδραν, ἀκοήν· ὅση δ ̓ αὐτῆς ταχεία, ὀξείαν, ὅση δὲ βραδυτέρα, βαρυτέραν. 3 II. 8, 420 31. Cp. and contrast Polit. 1. 1, 1253 10 where Aristotle distinguishes between φωνή and λόγος: ἡ μὲν οὖν φωνὴ τοῦ λυπηροῦ καὶ ἠδεός ἐστι σημεῖον· ὁ δὲ λόγος ἐπὶ τῷ δηλοῦν ἐστι τὸ συμφέρον καὶ τὸ βλαβερόν. + De An. 11. 7; De Sensu, 2. 3. -viz. colour (TEρì xрwμȧτWV). Colour itself is a secondary quality (to adopt Locke's phraseology) which has the power of throwing the actually pellucid into movement': for it is this excitation of the pellucid or diaphanous and no material emanation (a óppoia) which explains the visibility of colour. What then, we have to ask, is this pellucid (diapavés)? It is that which is not visible by itself but becomes visible only through a foreign colour (di àλλóтpiov xpâμa). So, for instance, air or water are pellucid: they are so, because apart from their specific properties they contain the same quality as inheres within the upper air or aether: pellucidity in fact is an attribute of no definite body or elements except the aether. Now this pellucid substance is, as potential, colourless, and dark: it becomes actual through fire or some such agency. But this presence of fire in the pellucid is just what produces light, just as its absence on the other hand produces darkness. Light therefore may itself be defined as the actual expression or full play of the pellucid as pellucid: practically we may describe light as the colour of the pellucid. Colour then is the quality which sets the actually pellucid into motion: so that since this actually pellucid matter is so actual by means of light, it follows that colour is not visible without the help of lightlight, that is to say, is a condition of vision. This account of colour cannot certainly be said to be distinguished by lucidity. At times it seems a mere see-saw between two terms-colour and pellucidity-which are made in turn to explain each other. But we shall not perhaps be misrepresenting Aristotle's doctrine if we regard colour as an intensification of light. This view of colour seems at least to correspond with Aristotle's second definition. Colour, he says, is the limit of the pellucid, the increased expression of transparency which shews itself upon the surface of a body. So understood, colour at once gives us two primary hues-white 1 418431, πᾶν δὲ χρῶμα κινητικόν ἐστι τοῦ κατ ̓ ἐνέργειαν διαφανοῦς. Cp. 41039. * D: Sensu, 3, 43911, ὥστε χρώμα ἂν εἴη τὸ τοῦ διαφανοῦς ἐν σώματι ὡρισμένῳ πέρας. and black-corresponding to the light and shade which play upon the surfaces of substances-and from these two primary colours all the others may easily be derived. Into the manner in which Aristotle conceives the other colours to be formed from this primary white and black it would be out of place to enter here. But the student of the physics of Aesthetics will find much that will repay him in the pages of the Tract on Sense which discuss this subject, and may find some similarity between the theories there enunciated and those of Goethe's Farbenlehre. The media by which the qualities of coloured objects are transmitted need not detain us long. Air and water are the two which Aristotle enunciates. They act as such in virtue of that pellucid quality which they share in common with the upper aether. At the same time they are themselves colourless and thus well adapted by their neutral character to transmit the colours of material objects. Aristotle accordingly rejects entirely that theory of sensible emanations with which he has been sometimes so strangely credited. Rather in fact he may be thought to have anticipated in some respects the undulatory theory of light and vision. The organ of sight is of course the eye. But the perceptive power is not located in the external organ. Apart from that reference to the heart which we will notice afterwards, it is particularly the inner chamber or kop which receives the impressions transmitted by the intervening medium from the coloured object'. The internal substance of the eye is therefore composed of water, a view corroborated empirically by the fact that when the eye is injured water is seen to gush forth from it. But Aristotle's analysis of the visual organ does not end with this description of it as composed of water. He explains that this water is produced by the brain, and refers to various ducts (Topo) by which it is conveyed to the inner chamber of 1 De Part. An. 11. 8, 65325; Hist. An. 1. 8, 491b20, TO 8' EVTOS тoû ¿¿ðaλμœî, τὸ μὲν ὑγρόν, ᾧ βλέπει, κορή. * De Sensu, 2, 4330, καὶ εὐλόγως τὸ ἐντός ἐστιν ὕδατος· διαφανὲς γὰρ τὸ ὕδωρ, τὸ δὲ περὶ τοῦτο μέλαν, τὸ δ ̓ ἐκτὸς τούτου λευκόν. the eye. It would be however an entire mistake to suppose that Aristotle viewed the act of vision as dependent on the brain or had any knowledge of the optic nerves. It is the heart and not the brain which Aristotle regards as the ultimate organ of vision, and he would seem to have formed no conception of the functions which the optic nerves discharge'. Aristotle's analysis of the single senses may be readily allowed to be possessed of more than merely antiquarian interest. Compared with the account of sense-perception given in the Timaeus of Plato, Aristotle's results mark a real advance in physiological observation. Plato had indeed (Timaeus 67 C) grasped to some extent the dependence of sound on oscillations of the air, but instead of shewing how the physiological structure receives and retains those oscillations he makes hearing simply a "vibration which begins in the head and ends in the liver." To Plato, in fact, the senses are, as Prof. Jowett says, "not instruments, but rather passages through which external objects strike upon the mind. The eye is the aperture through which the stream of vision passes, the ear is the aperture through which the vibrations of sound pass. But that the complex struc The chief passages bearing on this subject are as follows: De Gen. An. 11. 6, 74495, ὁ δ ̓ ὀφθαλμὸς σῶμα...ὑγρὸν καὶ ψυχρὸν καὶ οὐ προϋπάρχον ἐν τῷ τόπῳ ἀλλ' ἀπὸ τῆς περὶ τὴν ἐγκέφαλον ὑγρότη τητος ἀποκρίνεται τὸ καθαρώτατον διὰ τῶν πόρων οἱ φαίνονται φέροντες ἀπ' αὐτῶν πρὸς τὴν μήνιγγα τὴν περὶ τὸν ἐγκέφαλον. De Gen. An. 11. 6, 743 35, αἴτιον δ' ὅτι τὸ τῶν ὀφθαλμῶν αἰσθητήριον ἐστὶ μὲν ὥσπερ καὶ τὰ ἄλλα αίσθη τήρια ἐπὶ πόρων. Hist. Αn. Ι. II, 492021, περαίνουσι δὲ καὶ οἱ ὀφθαλμοὶ εἰς τὸν ἐγκέφαλον καὶ κεῖται ἐπὶ φλεβίου ἑκάτερος. Hist. An. 1. 16, 495311, φέρουσι δ ̓ ἐκ τοῦ ὀφθαλμοῦ τρεῖς πόροι εἰς τὸν ἐγκέφαλον, ὁ μὲν μέγιστος καὶ ὁ μέσος εἰς τὴν παρεγκεφαλίδα, ὁ δ ̓ ἐλάχιστος εἰς αὐτὸν τὸν ἐγκέφαλον. De Sensu, c. 2, 438 12, ἤδη γάρ τισι πληγεῖσιν ἐν πολέμῳ παρὰ τὸν κρόταφον οὕτως ὥστε ἐκτμηθῆναι τοὺς πόρους τοῦ ὄμματος έδοξε γενέσθαι σκότος, ὥσπερ λύχνου ἀποσβεσθέντος, διὰ τὸ οἷον λαμπτῆρά τινα ἀποτμηθήναι τὸ διαφανὲς καὶ τὴν καλουμένην κόρην. Sprengel, in his History of Medicine, tried to identify the ópo of Aristotle with the nerves, and of the three ópo mentioned the first might be thought to represent the ramus ophthalmicus, the second the optic, and the third the oculo-motor; but, as Bona Meyer says (p. 432), Aristotle had at least no idea of the function of nerves in the Tópo he mentions. And similarly Dr Ogle in his note on Parts of Animals, 11. 10, thinks that in Gen. An. 11. 6, Aristotle is speaking of optic nerves, and so also in De Sensu, c. 2, but considers that as Aristotle speaks also of tópo in relation to other sense-organs, it is unlikely he can have understood the office of the nerves in general. |