Darwin, in his chapter on dog lineages talked of a “turnspit” breed of dog.  I checked it out and learned that it is apparently an extinct breed of dog that ages ago was trained to walk continuously like a mouse in a wheel cage to turn a spit for cooking meat in a fire.  I did not know that til I read about it in Chapter I, “Domestic Dogs and Cats,” in “The Variation of Animals and Plants under Domestication, Volume I, 1897.  The “monstrosity” of the shape of the legs and the body is noted in the paragraph beginning with “Some of the peculiarities.”