When describing Jurgis's miserable state in jail, the author employs verbal irony and an allusion to “The Ballad of Reading Gaol." This was a poem written by the British author Oscar Wilde, who was also unjustly imprisoned. The narrator ends the chapter with this enigmatic statement:
So wrote a poet, to whom the world had dealt its justice—
I know not whether Laws be right,
Or whether Laws be wrong;
All that we know who lie in gaol
Is that the wall is strong.
And they do well to hide their hell,
For in it things are done
That Son of God nor son of Man
Ever should look upon.
The allusion Sinclair makes here draws a parallel between Jurgis and Wilde. Wilde was imprisoned in England in the late 19th century because he was gay (homosexuality was criminalized by the bigoted government at the time). Wilde wrote and published this poem after his own imprisonment as a kind of social protest. He and Jurgis were both victims of unjust legal practices, and both "The Ballad of Reading Gaol" and The Jungle contain messages of social reform.
By invoking the poem, the author emphasizes the harsh reality of Jurgis's situation, the unfairness of the ruling that convicted him, and the inhumane conditions of the prison in which he's incarcerated. What's more, by suggesting that the world "deals its justice," the narrator uses verbal irony to underscore the unjust nature of a system that allows such hardships and suffering to persist. In moments like this, the reader is prompted to reflect on the flawed nature of early-20th-century criminal justice.