Final answer:
In Upton Sinclair's 'The Jungle,' the common practice in the Packingtown factories was combining spoiled meat with other meat and selling it.
Step-by-step explanation:
In the Packingtown factories described in the excerpt from Upton Sinclair's 'The Jungle,' combining spoiled meat with other meat and then selling it was a common practice. The book exposes the unsanitary conditions and unethical behavior of the meatpacking industry in Chicago in the early 1900s. The narrative includes descriptions of rats and even human body parts falling into the meat grinder, which became part of the contaminated sausages that were sold.