Smell

Smell, sense that enables humans and animals to perceive and identify odors. The organ of smell is the nose. Respiratory air is drawn into the nostrils and passes across a specialized receptor surface—the olfactory epithelium. Receptor cells detect the tiny concentrations of odors in the airstream and stimulate nerve impulses that pass to olfactory centers in the brain for coding and perception. It is not possible to classify odors in the same way as the primary colors in vision, and it is probable that pattern recognition is more important. Certain animals depend mainly on the sense of smell, while humans are predominantly visual animals. But with training, humans can achieve sensitive detection and discrimination of odors.