The jungle

From the text:

Under the system of rigid economy which the packers enforced, there were some jobs that it only paid to do once in a long time, and among these was the cleaning out of the waste barrels. Every spring they did it; and in the barrels would be dirt and rust and old nails and stale water—and cartload after cartload of it would be taken up and dumped into the hoppers with fresh meat, and sent out to the public's breakfast. Some of it they would make into "smoked" sausage—but as the smoking took time, and was therefore expensive, they would call upon their chemistry department, and preserve it with borax and color it with gelatine to make it brown. All of their sausage came out of the same bowl, but when they came to wrap it they would stamp some of it "special," and for this they would charge two cents more a pound.