The speaker remembers a homemade childhood museum where three animal skulls, two cows and a mule, held pride of place among shells, coral, fossils and old medicine bottles. The children found the skulls in the woods, along with other bones, and carried only the heads home. An elderly neighbor even remembered the mule's name, Charlie, which quietly gives the animal a past the kids never considered.
The tone is warm and nostalgic, with a little dry humor, as in the comparison of missing teeth to strip-mined mountains. The speaker admits that as children they ignored death and the animals' working lives; the skulls were "live enough." What mattered was their strange perfection, the zigzag seams and the hinged jaws. The ending is playful but a bit eerie: even a bored kid would lift the mule's jaw and make him talk, giving the dead a voice, if only a borrowed one.