How is olfactory appeal used?

All fiction writers try to make the reader feel that he is present in the setting and experiencing what one or more characters--usually the viewpoint character--is experiencing. The best fiction writers, such as Ernest Hemingway and Guy De Maupassant for example, try to achieve this purpose by appealing to all of the reader's senses--sight, sound, touch, taste, and smell. It is very easy to appeal to the senses of sight and sound. Sound can be handled just with dialogue, sight with good description. Taste is usually appealed to by having the characters eat or drink something. This can be seen in Maupassant's famous story "Boule de Suif" and in Ernest Hemingway's "Hills Like White Elephants," in which the man and woman drink cold beer and then try a drink called Anis del Toro that tastes like licorice. In "The Invalid's Story" Mark Twain seems to be amusing himself by focusing on the sense of smell, which is the hardest of the five senses to evoke in the reader. In Mark Twain's story the smell is overpowering. Not only does the cheese smell up the railroad car, but the imaginary odor of a decaying corpse makes the smell seem even worse. Furthermore, the things the two men try to do to disguise the most offensive smell only makes that smell worse, especially when they light a bonfire of chicken feathers and other things. Everybody in Mark Twain's day was familiar with the unmistakable smell of burning chicken feathers. It could permeate the air in an entire small town.
The story, as the title suggests, is told from the point of view of the Invalid. The reader is drawn into the story by identifying with this character, who is the protagonist. The reader will almost always identify with a character by being drawn into that character's point of view and empathizing with his problem. The initial problem is just to transport a friend's corpse to his family home for burial. But the problem becomes inordinately complicated by the overpowering smell of the Limburger cheese, which both the protagonist and the expressman assume to be emanating from the corpse. Then they make the problem worse by desperately trying to cover it up with other smells.
The effect of the whole story, including its sardonic, homespun humor, is based on the highly unusual device of appealing to the reader's olfactory system, or sense of smell. Mark Twain was not only amusing the reader but amusing himself by making up such a bizarre tale. The reader can be amused by the story because he can imagine being there in the railroad car but doesn't really have to endure what the narrator and the expressman are experiencing. This story might be described as "experimental," or as a "tour de force," or even as an "etude." It gives the aspiring writer a lesson from a master in how to appeal to a reader's senses.