We humans do have one nose with two nostrils. We use it for breathing as well as smelling. But, did you know nature has separate plans for slugs?
Slugs have two noses. One for breathing and one for smelling. Nature has made slugs' body architecture quite different. Not, only it made them sluggish but also gave them two noses. One fore breathing and another for smelling.
People do think that the slugs have four noses but it is not true, the slugs have two nose only each one dedicated to something. One is located on tail and one on head.
The slug use the nose located on head for the purpose of breathing air and nose located on the tail for the purpose of smelling. Quite a wide business. Lol.