The drawing is reproduced by Ploss and Bartels, Das Weib, vol. i, Chapter XVII; many facts bearing on the ethnography of coitus are brought together in this chapter.
Onanoff (Paris Société de Biologie, May 3, 1890) proposed the name of bulbo-cavernous reflex for the smart contraction of the ischio-and bulbo-cavernosus muscles (erector penis and accelerator urinæ) produced by mechanical excitation of the glans. This reflex is clinically elicited by placing the index-finger of the left hand on the region of the bulb while the right hand rapidly rubs the dorsal surface of the glands with the edge of a piece of paper or lightly pinches the mucous membrane; a twitching of the region of the bulb is then perceived. This reflex is always present in healthy adult subjects and indicates the integrity of the physical mechanism of detumescence. It has been described by Hughes. (C. H. Hughes, "The Virile or Bulbo-cavernous Reflex," Alienist and Neurologist, January, 1898.)
Roubaud, Traité de l'Impuissance, 1855, p. 39.