How does this chapter work to further the basic ideas that Sinclair is conveying?

In Chapter Fifteen, Sinclair uses language that exemplifies the meaning of the book’s title. In the novel, the idea of “jungle” means several different things. In this chapter, the reader begins to see that one meaning is the issue of the devolving of characters. In several instances, Sinclair gives Ona and Jurgis animalistic traits. Ona is like a hunted animal. Jurgis, when going to attack the foreman that has raped Ona, acts like a tiger, and when he is imprisoned, he acts like an animal in a cage. The social atmosphere of Packingtown has created characters that now know they must kill or be killed. In this way, the “jungle” is society framed in the terms of natural selection.