Abstract for research narrative: A review of the evolution of the senses shows a clear distinction between the chemical senses -- presumably occupied with the acquisition of food -- and the physical senses, which seem to derive from the needs for alarm and escape. The most direct evidence comes from the effects of sensory overload: nausea, for taste and smell; and pain, for sight, touch and hearing. A physical force applied to the sensory end organs will evoke a perception of light, touch, or hearing from the physical end organs, but will not evoke a sense of taste or smell at the tongue or nose. On the other hand, simple chemical stimulation, short of overt irritation, does not evoke a sensation of sight, touch, or hearing. Moreover it appears that the tactile sense is the most primitive of all senses. Stimulation of the lateral-line organ in fish and primitive reptiles produces a response from the contralateral organ and a crossover through the central nervous system. Stimulation of tactile neurons adjacent to the lateral line produces only a surface reaction in primitive creatures. Whereas Bekesy has shown that a person will interpolate between coincident tactile stimuli applied to one side of the body, interaction with the contralateral side has not been demonstrated.