Tongue surface. Light micrograph of a section through a tongue surface, showing taste buds (round purple/white bodies, upper frame) in a circumvallate papilla. The papilla is one of the tongue structures responsible for the sense of taste. It is set into the surface of the tongue and surrounded by a cleft (white, across centre). The epithelial lining of the cleft contains the taste buds, which are stimulated when food dissolves in a fluid secreted into the cleft by aggregations of glands (not seen). Magnification unknown.