John's favorite artist - and inspiration for how he plays his harmonica - is Jimi Hendrix. There is no doubt that he heard Hendrix's cover of Howling Wolf's "Killing Floor" when he was first getting into his music. From the Blues-L FAQ:

Particularly in the Chicago Stockyards area, where many black newcomers from the South found jobs during the twenties, thirties, and forties, this was the slaughtering room, where animals were brought to be killed. Symbolically being on the "Killing Floor", then, meant being in trouble with little way out, or being so depressed (primarily by the loss of a lover) that he (generally) feels like he is going to die."

Reminiscent of a line from "The spider and the fly", a 19th-century poem by Mary Howit: "'Will you walk into my parlor?' said the spider to the fly". In it, a spider attempts to lure a fly into his web and finally succeeds by flattering her endlessly until she enters. Interestingly, the liner notes for this album simply list the portion between "let me do my thing" and the final chorus as simply "impromptu rap". When sung live, this part is omitted and is, in fact, an impromptu rap.

John can faintly be heard singing this line from the previous track twice during the quiet part just before the ending.