While reflecting on 'Negroes' and how "they" behave in The Sound and the Fury, Quentin remembers hearing or reading about the "brothel full of them in Memphis" who ran naked into the street during "a religious trance" (170).
To get to the site of the bridge where he plans to commit suicide and later to get back to Harvard from the picnic site Quentin takes an "interurban" train rather than the city streetcars that he takes before and after this trip out of Cambridge. Though both interurbans travel close to the river, they don't seem to follow the same route - at the end of his ride back to Cambridge he must take a trolley that crosses the river and takes him almost back to the post office where his travels had begun that morning.