The phrase — The Philosophy of Hats and other things in General — does not appear in the original French text: instead this seems to be a poetic adornment of the uncredited translator who is responsible for my 1910 English edition from Societe des Beaux-Arts. My hat’s off to you, uncredited translator!
Sources:
Murger, Henri. Bohemians of the Latin Quarter. Paris: Societe des Beaux-Arts, 1910.