In 1864 Manet exhibited at the Salon a painting entitled An Incident in the Bullring. The work was savagely caricatured and criticized, one writer describing its subject as “a toreador of wood killed by a horned rat.” After the picture was returned from the Salon, Manet cut out two separate compositions from the canvas, possibly because he accepted the criticism as justified. The lower, larger section, now known as The Dead Toreador, is in the National Gallery, Washington. Both sections of the original canvas were subsequently reworked by the artist, the head of the bull being added to the Frick segment after the painting had been divided.
Source: Art in The Frick Collection: Paintings, Sculpture, Decorative Arts, New York: Harry N. Abrams, 1996.