Throughout time there have been numerous reports of the expulsion of fluids from the vagina by women during sexual arousal and/or orgasm. There are references to this by historical scientific figures such as Aristotle and Galen, discussing and identifying vaginal expulsions which did not have the appearance or smell of urine, and did not stain. The first modern description of both female genitalia and the matter of vaginal expulsions came from the 17th century Dutch physician, Reinier De Graaf, who in 1672 stated: "The urethra is lined internally by a thin membrane. In the lower part, near the outlet of the urinary passage, this membrane is pierced by large ducts, or lacunae, through which pituito-serous matter occasionally discharges in considerable quantities. Between this very thin membrane and the fleshy fibres we have just described there is, along the whole duct of the urethra, a whitish, membranous substance about one finger-breadth thick which completely surrounds the urethral canal. This substance could be called the "female prostatae". De Graaf's description of the prostatae in women in reference to the glands surrounding the female urethra represented conventional medical thought for almost 200 years.