Riis goes to great lengths to depict the reality of the tenements—at least, his perception of them—to the reader through imagery and figurative language. While he succeeds in creating an empathetic image in some passages, certain others end up demonizing the very subjects Riis wishes to help. One can see this clearly in Riis's use of metaphor in the following passage from the introduction:
[The tenements are places] that throw off a scum of forty thousand human wrecks to the island asylums and workhouses year by year; that turned out in the last eight years around half a million beggars to prey upon our charities; that maintain a standing army of ten thousand tramps with all that that implies; because, above all, they touch the family life with deadly moral contagion.
Utilizing metaphor in this passage, Riis paints a picture of moral corruption as equivalent to a "contagion," likening evil and immorality to physical disease. This creates a connection between diseases like cholera and influenza (which spread quickly in the packed and unsanitary conditions of the tenements) and what Riis considers to be immoral behavior, which—from his perspective—spreads outward from the tenements just like physical disease. And this spread, he suggests, runs the risk of corrupting the surrounding society.
Throughout the book, Riis uses animalistic, demeaning language to describe tenement residents, more often than not speaking about them as a large, threatening group as opposed to as individuals with agency and identity. This imagery of the "swarms" or "hordes" of impoverished immigrants is so widely used in Riis's work that it becomes a motif, one he employs as early as the introduction, mentioning the "question" of "how to lay hold of these teeming masses in the tenements." He also uses the term "herd" in Chapter 1 to describe crowding in cities, noting that many other overcrowded cities were far less crowded than New York:
The utmost cupidity of other lands and other days had never contrived to herd more than half [the people who lived in New York tenements] within that same space.
Disturbingly, Riis also describes children in this manner in Chapter 4:
A horde of dirty children play about the dripping hydrant, the only thing in the alley that thinks enough of its chance to make the most of it.
This imagery, which Riis utilizes throughout his writing, generates a fear of the presumed degenerate masses that has its roots in the eugenics movement of the late 19th and early 20th centuries. This generation of fear and disgust surrounding large masses of people becomes a motif within Riis's work, surfacing often in the descriptive language he chooses.
