Grotesques are a form of decorative sculpture often found in or on Gothic structures.
The term is used broadly for gargoyle, although traditionally a gargoyle serves as a drainage spout for rain water, while a grotesque can function solely as decoration. The term gargoyle is derived from the gurgling sound of water issuing from a spout. There are fifty grotesques flanking the North and South Arcades; these figures are ornamental, although you will see gargoyles along the exterior that do carry water.
Notice the grotesque with the protruding tongue just above the first set of spiral staircases. It was medieval practice to decorate column capitals and corbels of arches with grotesque heads. Architect Charles Parker ordered terra cotta casts of these figures from the Atlantic Terra Cotta Company in Staten Island, New York. He liked them so much that he created his own, and placed some in his home at the bases of exposed beams. After his death, his wife had them removed.