ABSTRACT
Olfactory life begins at the nose sometimes with a sniff, but usually with just a breath. Odour molecules progress through the two nasal cavities called nares (singular = naris), commonly known as the nostrils, and into the two nasal vaults, which are separated by a fleshy bit of cartillage, the nasal septum. The nose warms the air and also acts as a filter, keeping out unprepossessing organisms. It also constricts and dilates asymmetrically which leads to changes in airflow to, and mucal concentration in, the different nostrils (a phenomenon possibly under the control of the hypothalamus which is described in a later section). Sniffing, which increases the rate of airflow and, therefore, the transport of more molecules, also increases the response of the olfactory system (Mozell et al., 1991). The percentage of the air we breathe that reaches the olfactory cleft is estimated to be 10–15 per cent (Hahn et al., 1993).
