It is, however, plain that the mouth is at first concerned only with the gratifying of the hunger instinct; later the desire for a repetition of pleasurable experience gained in this way is separated from the need of taking nourishment, thereby transforming this mucous surface into an erogenous zone.
"Studies in Forensic Psychiatry"
Bernard Glueck
Low erogenous puffs of dust are swathed by passing feet.
"Eyeshine"
Paul Cameron Brown