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THE PSYCHOLOGY OF PERCEPTION 147 modern optics which recognises the dependence of visual sensation on the energy of ligbt and the presence of a colouring matter behind the lens, and treats the retina as the organ of vision.'
The cutaneous sense (tvak) is the source of touch-sensations and temperature-sengations. It is constituted by the physical element air, because, like the air, it manifests the quality of touch. The locus or the end-organ of the sense of touch is the whole skin of the body, from head to foot, outside and inside its surface ? From a common-sense standpoint no distinction is here made between the different sensations of touch or pressure and those of warmth and cold. In truth, the cutaneous sense is highly complex. Many psychologists distinguish between four cutaneous senses, namely, those of pressure, warmth, cold, and pain. The Naiyāyıkas do not go so far in their account of the cutaneous sense, but describe both pressure and temperature as touch sensations. Nor do they subscube to the view that the sense of touch is the primitive sense, from which the other external senses develop by increasing differentiation. “Touch,” Aristotle observed, “is the mother of the senses." Modern psychologists also think that “ starting from this mode of sensibility as a basis the other senses develop by processes of increasing complexity and refinement." 4 The Naiyāyikas oppose this hypothesis on the ground that the sense of touch cannot, in any degree, perform the function of the other senses in those who are deprived of them."
The auditory sense (śrotra) is the source of sensations of sound. It has its seat in the drum of the ear. It is possess
1 Ibid 2 TB , pp 20, 24 3 Titchener, op cit. 4 Hollingworth, Psychology p 456. 6 NB., 3.1 51-63
