The fable is a variant of stories recorded since antiquity of which there is scarcely one version that concerns the same pair of animals. It is included as one of Aesop's Fables and numbered 181 in the Perry Index,Aesopica site and other Greek sources also pair a donkey and a mule, while the story is told of an ox and a donkey in the Mediaeval Latin version of Ademar of Chabannes. In the former the overburdened donkey asks its companion for help in carrying its load and dies when this is refused; the other is then forced to carry not only the original load but the dead animal's skin as well. In Ademar's story the two animals are yoked together but the ass refuses to pull its weight; after the ox dies of the strain, the ass is forced to continue pulling and also dies.
