It seems like such a simple thing for us to sniff something and smell it. But the process of smell, and the whole subject of odor, is quite a complicated thing. Man’s sense of smell is poorly developed compared to that of other creatures. Man’s organ of smell is located in the nose; at least; this is the place where the “messages” of smelling are received. This organ is quite small. Each side of the nose is only as large as a fingernail!
This organ is really a mucous membrane, containing ner•ve cells which are surrounded by nerve fibres, kept moist by mucous glands. Through the cells, delicate hairs stick out into the nasal cavity.
But the tips of these hairs are covered by a fatty layer of cells. If they become uncovered and dry, our ability to smell disappears. In ordinary breathing, the stream of air does not come in contact with the smelling area, so if we want to smell, we have to sniff. This sends the air to the right place.
The substance that we smell must actually be dissolved in the fatty layer that covers the hairs before we can it! This is why it takes us a bit of time to “get” a smell. It is also why substances that have an odor have to be both volatile, or able to move, and part of an oily substance that can dissolve in that layer that covers the “smelling” hairs.
The way a thing smells depends on certain groups of atoms that carry odors. So that odor depends on the chemical formula, and each type of odor has a different chemical formula. And it takes only a very tiny amount of an odorous substance to excite our sense of smell. There is a small smell center in the brain that receives the “messages” from the nerves in the nose and tells us what we are smelling
What Are The Four Basic Smells?
4. Woody and resinous.