Common chemical sense, olfaction

The chemical senses are composed of stimuli from the external environment which act on specialized cells. They are conmonly divided into three classes 1) olfaction, 2) gustation, and 3) the common chemical sense. Olfaction permits reception of distant airborne volatile substances often at very diluted concentrations while gustation generally requires contact with the chemical stimulant source. Irritants are the main stimulants for the common chemical sense and involve little specificity. 

Tester, A. L. (1963). Olfaction, gustation and the common chemical sense in sharks. Sharks and Survival 8,255-282. 

Dichorhinic mixtures, where one component enters one nostril and the other component enters the other nostril, offered a useful way to discover whether the inhibitory interaction derived from a fortuitous choice of stimuli that just happened to interfere with one another at the mucosa. If inhibition occurred in the dichorhinic case, then it would establish two things 1) that the interaction depended less on a particular pair of odorant and irritant than on the activation of olfaction and the common chemical sense by any suitable stimuli, and 2) that the interaction probably took place in the brain. Figures 8B,D reveal that dichorhinic mixtures did indeed exhibit the interaction. Further experimentation indicated that this interaction, almost indistinguishable from that seen in physical mixtures, occurred in the brain (11). 

Cain, W. S. Olfaction and the common chemical sense some psychophysical contrasts. Sensory Processes, 1976, 1,... 

Individuals exist within an environment, and its impact upon the chemical senses becomes obvious with simple testing. Exposure to an odorant results in adaptation to the odorant i.e., individuals lose sensitivity to the odorant often to the point where they can no longer perceive its presence. This is a common, everyday experience. What many individuals fail to appreciate are the broader impKcations of such changes in olfaction. For example, exposure to one odorant may affect sensitivity to other odorants, whether the additional odorant smells similar to the first odorant or not. This is an example of cross-adaptation (see Fig. 17). 

Odor or odor (commonly referred to as smell) can be described as the property of a substance that is perceptible by the sense of smell. An odor is caused by one or more volatilized chemical compounds, generally at a very low concentration, that humans or animals perceive by the sense of olfaction. Odors are also commonly called scents and can be pleasant or unpleasant. The terms fragrance and aroma are used primarily by the food and cosmetic industries to indicate a pleasant odor, and are sometimes used to describe perfumes, hi contrast, malodor, stench, reek, and stink are used specifically to describe unpleasant odors. 

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