Original article here: http://www.readworks.org/passages/through-nose
Adapted for use in my 8th grade science classroom as an introduction to how senses relate to memories.

Nasal cavity is covered by membranes (thin, filmy layers) dotted with smell receptors.
Humans have a fairly weak sense of smell, even with 5 million receptors.

If a dog's nasal membrane was unfolded, it would have the same surface area as its entire body!

With so many receptors, a significant part of their brain is devoted to decoding, analyzing, and storing smells. A dog's sniffing tells them a lot about their environment.

Dogs use their sense of smell to identify not only other dogs, but the moods of other dogs. They also recognize by scent their human owners and home.

Training= repeated exposure to certain stimuli.
Dogs trained to recognize explosives, drugs, and other dangerous materials are used by police, transportation authorities, and other agencies to find illegal and dangerous materials.