Realism is a movement which described life as it was. It did not use "rose-colored" language like the Romantics to disguise the "ugly" in life. Instead, it celebrated the ugly. Realists acted as only observers, writing down life as it happened without interference. Naturalists were very similar to Realists. One great difference between the Realist and the Naturalist is that Naturalists believed nature to be the most powerful element in existence. Human beings possessed no free will and nature ruled their lives.
This defined, The Underdogs (by Mariano Azuela) possess an unpleasant scene which illustrates both Realism and Naturalism. In the opening chapter, Fortunata and Demetrio hear soldiers coming. Afraid, Fortunata suggest that Demetrio hides. Refusing to, Demetrio goes into the night to see what the dog is barking at. The dog runs out after him.
Immediately, a gun shot is heard and the dog quiets. Screaming at the men, Fortunata grans the dead dog and drags it into the house. Once in the house, she begins to tend to the fire.
This scene illustrates the realism of life in the country. People there accept what happens and simply move on. Given that death is a part of nature, the death of the dog symbolizes the Naturalistic perspective. The shooting of the dog, dragging of it into the house, and the tending of the fire (without grief) can prove to be unpleasant for some readers.