But those bodies which are composed of larger particles, since they yield with difficulty to the agent and transmit their motions to the whole, feel pleasures and pains— pains when they suffer alteration, and pleasures when they are restored to their original state. And all those bodies which undergo losses of substance and emptyings that are gradual, but replenishings that are intense and abundant, become insensitive to the emptyings but sensitive to the replenishings; consequently, they furnish no pains to the mortal part of the soul, but the greatest pleasures—a result which is obvious in the case of perfumes. But all those parts which undergo violent alterations, and are restored gradually and with difficulty to their original condition, produce results the opposite of those last mentioned; and it is evident that this is what occurs in the case of burnings and cuttings of the body. And now we have given a fairly complete statement of the affections which are common to the body as a whole, and of all the names which belong to the agents which produce them. Next we must try, if haply we are able, to describe what takes place in the several parts of our bodies, both the affections themselves and the agents to which they are ascribed. Firstly, then, we must endeavor to elucidate so far as possible those affections which we omitted in our previous account of the flavors, they being affections peculiar to the tongue. It is evident that these also, like most others, are brought about by means of certain contractions and dilationsCf. 64 E.; and, more than other affections, they involve also conditions of roughness and smoothness. For all the earthy particles which enter in by the small veins—which, extending as far as to the heart, serve as it were for testing-instrumentsThe function of the nerves is here assigned to the veins. of the tongue,—when they strike upon the moist and soft parts of the flesh and are melted down, contract the small veins and dry them up; and these particles when more rough appear to be astringent, when less rough harsh. And such as act on these veins as detergents and wash out all the surface of the tongue, when they do this excessively and lay such hold on the tongue as to dissolve part of its substance—and such, for example, is the property of alkalies,— are all termed bitter; while those which have a property less strong than the alkaline, being detergent in a moderate degree, seem to us to be saline, and more agreeable, as being devoid of the rough bitterness.

And those which share in the heat of the mouth and are made smooth thereby, when they are fully inflamed and are themselves in turn burning the part which heated them, fly upwards because of their lightness towards the senses of the head and cut all the parts on which they impinge; and because of these properties all such are called pungent. Again, when particles already refined by putrefaction, entering into the narrow veins, are symmetrical with the particles of earth and air contained therein, so that they cause them to circulate round one another and ferment, then, in thus fermenting they change round and pass into fresh places, and thereby create fresh hollows which envelop the entering particles. By this means, the air being veiled in a moist film, sometimes of earth, sometimes of pure moisture, moist and hollow and globular vessels of air are formed; and those formed of pure moisture are the transparent globules called by the name of bubbles, while those of the earthy formation which moves throughout its mass and seethes are designated boiling and fermenting; and the cause of these processes is termed acid. An affection which is the opposite of all those last described results from an opposite condition. Whenever the composition of the particles which enter into the moist parts is naturally akin to the state of the tongue, they oil its roughened parts and smooth it, contracting the parts that are unnaturally dilated or dilating those that are contracted, and thus settling them all, so far as possible, in their natural condition; and every such remedy of the forcible affections, being pleasant and welcome to everyone, is called sweet. For this subject, then, let this account suffice. Next, as regards the property of the nostrils, it does not contain fixed kinds. For the whole range of smells is a half-formed class, and no kind possesses the symmetry requisite for containing any smell; for our veins in these organs are of too narrow a construction for the kinds of earth and of water and too wide for those of fire and air, so that no one has ever yet perceived any smell from any of these, but only from substances which are in process of being moistened or putrefied or melted or vaporized. For smells arise in the intermediate state, when water is changing into air or air into water, and they are all smoke or mist; and of these, the passage from air to water is mist, and the passage from water to air is smoke whence it is that all the smells are thinner than water and thicker than air.

Their nature is made clear whenever there is some block in the respiration and a man draws in his breath forcibly; for then no accompanying smell is strained through, but the breath passes in alone by itself isolated from the smells. So for these reasons the varieties of these smells have no name, not being derived either from many or from simple forms, but are indicated by two distinctive terms only, pleasant and painful of which the one kind roughens and violently affects the whole of our bodily cavity which lies between the head and the navel, whereas the other mollifies this same region and restores it agreeably to its natural condition. The third organ of perception within us which we have to describe in our survey is that of hearing, and the causes whereby its affections are produced. In general, then, let us lay it down that sound is a stroke transmitted through the ears, by the action of the air upon the brain and the blood, and reaching to the soul; and that the motion caused thereby, which begins in the head and ends about the seat of the liver, is hearing; and that every rapid motion produces a shrill sound, and every slower motion a more deep sound; and that uniform motion produces an even and smooth sound and the opposite kind of motion a harsh sound; and that large motion produces loud sound, and motion of the opposite kind soft sound. The subject of concords of sounds must necessarily be treated in a later part of our exposition.Cf. 80 A. We have still remaining a fourth kind of sensation, which we must divide up seeing that it embraces numerous varieties, which, as a whole, we call colors. This consists of a flame which issues from the several bodies, and possesses particles so proportioned to the visual stream as to produce sensation; and as regards the visual stream, we have already statedCf. 45 C ff. merely the causes which produced it. Concerning colors, then, the following explanation will be the most probable and worthy of a judicious account. Of the particles which fly off from the rest and strike into the visual stream some are smaller, some larger, and some equal to the particles of the stream itself; those, then, that are equal are imperceptible, and we term them transparent; while the larger and smaller particles—of which the one kind contracts, the other dilates the visual stream—are akin to the particles of heat and cold which affect the flesh, and to the astringent particles which affect the tongue, and to all the heating particles which we call bitterCf. 65 E. with these white and black are really identical affections, occurring in a separate class of sensation, although they appear different for the causes stated.

These, therefore, are the names we must assign to them: that which dilates the visual stream is white and the opposite thereof blackCf. 45 C ff.; and the more rapid motion, being that of a different species of fire, which strikes upon the visual stream and dilates it as far as to the eyes, and penetrating and dissolving the very passages of the eyes causes a volume of fire and water to pour from them, which we call tears. And this moving body, being itself fire, meets fire from the opposite direction; and as the one firestream is leaping out like a flash, and the other passing in and being quenched in the moisture, in the resultant mixture colors of all kinds are produced. This sensation we term dazzling and the object which causes it bright or brilliant. Again, when the kind of fire which is midway between thesei.e., between the kinds of fire which produce blackness and brightness. reaches to the liquid of the eyes and is mingled therewith, it is not brilliant but, owing to the blending of the fire’s ray through the moisture, it gives off a sanguine color, and we give it the name of red. And bright color when blended with red and white becomes yellow. But in what proportions the colors are blended it were foolish to declare, even if one knew, seeing that in such matters one could not properly adduce any necessary ground or probable reason. Red blended with black and white makes purple; but when these colors are mixed and more completely burned, and black is blended therewith, the result is violet. Chestnut comes from the blending of yellow and grey; and grey from white and black; and ochre from white mixed with yellow. And when white is combined with bright and is steeped in deep black it turns into a dark blue color; and dark blue mixed with white becomes light blue; and chestnut with black becomes green. As to the rest, it is fairly clear from these examples what are the mixtures with which we ought to identify them if we would preserve probability in our account. But should any inquirer make an experimental test of these facts, he would evince his ignorance of the difference between man’s nature and Gods—how that, whereas God is sufficiently wise and powerful to blend the many into one and to dissolve again the one into many, there exists not now, nor ever will exist hereafter, a child of man sufficient for either of these tasks. Such, then, being the necessary nature of all these things, the Artificer of the most fair and good took them over at that time amongst things generated when He was engendering the self-sufficing and most perfect God; and their inherent properties he used as subservient causes, but Himself designed the Good in all that was being generated.