smell

smell sense that enables an organism to perceive and distinguish the odors of various substances, also known as olfaction. In humans, the organ of smell is situated in the mucous membrane of the upper portion of the nasal cavity near the septum. It is made up of the olfactory cells, which are actually nerve cells that function as receptors for the sense of smell. The free ends of the cells project outward from the epithelial tissue in the form of numerous hairlike processes. These fibers are buried in the mucus that coats the inner surface of the nasal cavity and are stimulated by various odors. Nerve fibers extend from the olfactory cells to an area of the brain called the olfactory bulb. Any disturbance of the nasal cavity—such as the common cold—in which the olfactory hairs are covered with excess mucus or other material, interferes with the sense of smell. Most physiologists agree that although a substance must be volatile to be sniffed by the nose, it must subsequently be dissolved in the mucous lining of the nasal cavity to be smelled. It is also believed that there are only a few basic odors (perhaps about seven), and that all other odors are a combination of these. Attempts at classifying the so-called primary sensations of smell have not yet been successful. The sense of smell is not as strongly developed in humans as in many other vertebrates, particularly carnivores which employ olfactory organs to locate food and detect dangerous predators. To many invertebrates (especially insects) as well, smell is a highly developed sensory mechanism, necessary in obtaining food, in finding mating partners, and in recognizing other animals.

smell See olfaction.

smell smell a rat begin to suspect trickery or deception.
smell blood discern weakness or vulnerability in an opponent.
smell of the lamp show signs of laborious study and effort; the reference is to an oil-lamp, and according to Plutarch the criticism was once made of the work of Demosthenes, ‘His impromptus smell of the lamp’, meaning that his speeches were written rather than spoken orations.
smell the roses in North American usage, enjoy or appreciate what is often ignored.

See also fish and guests smell after three days, money has no smell, wake up and smell the coffee.