THE CRANIAL SENSES
Gustatory sense-data are usually called tastes. We speak of the "taste" of food or drink; of a "sweet taste", a "bitter taste", a "metallic taste", etc. The elementary tastes, simple gustatory data, or gustatory seintienda, are of four qualities only: sweet, salt, bitter and sour. All other tastes, that is, all tastes having qualities other than one of these, are fusions of two or more of these elementary tastes. Bitter sweets, sour salts and bitter sours are more familiar than salt sweets, salt sours and salt bitters, although all of these fusions are possible. Fusions of three of the simple tastes also occur; for example, the sweet-bitter-sour of ripe grape- fruit is well known.
The gustatory data also fuse with tactual and dermal data and with olfactory data to produce flavors. In all the varieties of flavors of foods and drinks only the four taste qualities occur, the other components in the flavor--frequently the most important components--being odors, warmth, cold and touch.
The qualitative relationships of the four gustatory sentienda to each other and also the possibilities of fusion are represented by the taste tetrahedron in Fig. 1.18
In this figure, representing a solid or three dimensional scheme, each of the four elementary tastes is represented at one of the four vertices of the tetrahedron. The lines joining these points represent the fusions of the simple tastes in pairs. For example, points along the line joining sweet (Sw) and bitter (B) represent fusions of these two in varying proportions, from the slightly sweetish bitter, through a balanced proportion, to a slightly bitterish sweet. Mixtures of three of the sentienda; for example, sweet, bitter and sour, would be represented by points in the surface determined by____________________
Intensity relationships are not included, as a four-dimensional scheme would be required for this purpose.