The idea that maggots were produce by rotting meat is an example of spontaneous generation. Spontaneous Generation is an old fashioned thought about the formation of a living organism without descent from similar organism. They thought that maggots could be produce from the body of dead fish or a flea could arise from a dust. This idea was coherently synthesized by Aristotle. He expanded the work about the appearance of organism. According to his theory, Living things comes from nonliving things because they contains Pneuma.