This pamphlet contains the text of a lecture on Canto XII of the Inferno given by Mazzoni in Florence. The characters inhabiting the bloody circle of Hell in Canto XII include the raging Minotaur, tyrants such as Alexander and Attila, and the noble but terrifying Centaurs. Mazzoni read the canto and his essay on it in the "Sala di Dante" in Orsanmichele, a room which served as the venue for the long-established Dante lecture series that Mazzoni took part in on February 21, 1906.