Presence of certain type of bacteria in intestinal tract can also affect the color of human stools. Salmonella, a type of bacteria, if enters in human intestine or digestive tract, could disturb its functioning and result in change in color of stools. This could be easily treated with antibiotics.
Many critics have suggested that there is no clear distinction between realism and its related late nineteenth-century movement, naturalism. As Donald Pizer notes in his introduction to The Cambridge Companion to American Realism and Naturalism: Howells to London, the term realism is difficult to define, in part because it is used differently in European contexts than in American literature.
Pizer suggests that whatever was being produced in fiction during the 1870s and 1880s that was new, interesting, and roughly similar in a number of ways can be designated as realism, and that an equally new, interesting, and roughly similar body of writing produced at the turn of the century can be designated as naturalism (5).