On the Vital Principle/Book 2/Chapter 10
The sapid object is a kind of tangible object, and this is the reason why it does not require, in order to be perceived, any other medium than the body, for the Touch requires no other. The body in which is savour, is the gustable body, and the matter of savour is in fluid, and fluid is something tangible. Thus, were we in the water, and were any thing sweet cast into the water, we should be sensible of the sweetness, not through the water as a medium but, from its having been mixed with the water as with a potable fluid. Colour, however, is not thus made visible from having been mixed with anything, nor is it made visible by emanations; and as the medium, in the case of colours, plays no part and colour is the visible, so is savour the gustable. No object, however, without humidity can impart the sense of savour; and, therefore, every sapid object contains humidity, in an active or a potential state, as does salt; for salt is readily moistened and liquefied by contact with the tongue.
Now, vision is perceptive of the visible and the invisible (for darkness, although invisible, is still judged of by vision), and a very bright light (which is also invisible, although in a manner different from darkness), and so hearing is equally perceptive of sound and silence, of which that is audible and this inaudible, as well as a very loud sound, just as vision is of a very bright light; for as a very low sound is, in a certain sense, inaudible, so is a very loud and crashing sound. On the other hand, the term invisible, used absolutely, is analogous to the term impossible upon other subjects, and which may be significant of something generated without parts or with parts ill formed for their office, as an animal without feet, or a fruit without a kernel. So, too, the taste in its turn is perceptive both of what is sapid and insapid; and the insapid implies whatever has a faint or nauseous savour, or a savour altogether perversive of taste. The potable and the impotable seem alike to be the origin of taste, for they both are sapid; but then the first has a nauseous savour, and is perversive of taste, while the last is genial to the sense; the potable is common, besides, to the touch and taste. Since whatever is sapid is humid, it follows that the organ of taste may neither be humid really, nor yet be incapable of becoming humid; for the taste suffers impression by the sapid body, in so far as it is sapid. It is, therefore, necessary that the sentient organ, if not moist, should, for its function, be capable of becoming so: and, as proof of this, the tongue, when very dry or very moist, is not sensible of sapid impressions—as in the former instance, it is a tangible rather than a sapid impression which is made by a fluid when first tasted; and when very moist, it is sensible only of the fluid already present, just as it happens when, after tasting something pungent, we proceed to taste a different fluid. It is thus that all savours appear to the sick to be bitter, because the tongue, with which they taste, is charged with a moisture having that savour.
Kinds of savour are, like shades of colour, simple when in broad contrast—as the sweet and bitter with their sequences, of the former the oily and of the latter the brackish; and intermediate to these are the pungent, rough, astringent, and sour, which seem to include almost all the varieties of savour.
In fine, the sapid sense, when in potentiality, is such as is the sapid object; and the sapid object, when in reality, is productive, in the sense, of its own savour.
Notes
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Note 1, p. 114. Colour, however, is not thus made visible.] The opinion here objected to originated with Democritus. Aristotle[1] held it to be absurd to suppose that colour and vision could be a process of emanation from the eyes; for colour produces sensation, he observes, not by emanation but, by contact, and so it is better, at once, to admit that vision is produced by the action of the medium. There are[2], it is said, seven distinctions of colour and as many of savour; and in another work[3] seven vowels, seven pleiads, and seven chords.
Note 2, p. 114. No object, however, which is without humidity.] This is little more than a repetition of what had been said concerning sapid substances. Aristotle[4] seems to have adopted a theory, derived from mechanics, for explaining the solubility of objects--Whence comes it, he asks, that an earth is both melted and moistened by fluid (καὶ τήκεται καὶ τέγγεται) while soda (τὸ δὲ νίτρον) is melted but not moistened? The answer is, because there are pores throughout the soda which cause its parts to be, at once, separated by the fluid; while the pores in the earth are in alternate rows, so that the influence of the fluid, in whatever way it may gain access, cannot but be different.
Note 3, p. 114. As vision is perceptive, &c.] The argument here is interrupted and obscured by parenthetical explanations; but the purport is, that the senses are the sole judges of sentient impressions through all their degrees of intensity, and that, as sensibility is a mean, they cannot discriminate such as are far above or below the allotted medial standard. There is a seeming discrepance, however, in employing the term invisible as analogous to impossible on other subjects, as vision is not altogether lost in any darkness; but a creature without feet could not continue its existence, nor a fruit without the kernel continue its species.
Note 4, p. 115. The impotable as well as the potable, &c.] The impotable implies, of course, whatever is neither moist nor capable of becoming moist, and every such substance must, necessarily, pain—be very disagreeable to, that is—and pervert the Taste. All these passages, however, while proving that moisture is required for savour, point to a want of knowledge of the salivary and mucous glands which were yet to be discovered. But over and above the due conditions of moisture, there was still required the knowledge of the nervous system to account for the many perversions of Taste which are manifested, both in sick and well; and manifested, at times, without any apparent cause. It will occur to many, besides, how differently the Taste is affected by the same substance, as sugar for instance, in different persons, and even, at times, in the same person.
Note 5, p. 116. Kinds of savour are like shades of colour, &c.] There must ever be difficulty in fixing upon terms for savours or other sentient qualities, and still greater difficulty in settling what are the exact equivalents for such terms in another, and that not a cognate tongue; for although some savours, as bitter and sweet, may be supposed to have an universal acceptation, there are others which, being far less definite, are subject to variation, according to climate and race. So that, with the exception of bitter and sweet, it can hardly be pretended that the other terms, as oily, pungent, rough, astringent, &c., are perfect representatives of those in the text.
Note 6, p. 116. In fine the sapid sense, &c.] This passage does but repeat what has been already insisted upon, that the sense, in potentiality, that is, when inactive, is identical with that which is to act upon it; but that, having been acted upon, it is brought into the state of reality, and then becomes perceptive of the qualities of the excitant.