I do not purpose to discuss here either _cunnilingus_ (the apposition of the mouth to the female pudendum) or _fellatio_ (the apposition of the mouth to the male organ), the agent in the former case being, in normal heterosexual relationships, a man, in the latter a woman; they are not purely tactile phenomena, but involve various other physical and psychic elements. _Cunnilingus_ was a very familiar manifestation in classic times, as shown by frequent and mostly very contemptuous references in Aristophanes, Juvenal, and many other Greek and Roman writers; the Greeks regarded it as a Phoenician practice, just as it is now commonly considered French; it tends to be especially prevalent at all periods of high civilization. _Fellatio_ has also been equally well known, in both ancient and modern times, especially as practiced by inverted men. It may be accepted that both _cunnilingus_ and _fellatio_, as practiced by either sex, are liable to occur among healthy or morbid persons, in heterosexual or homosexual relationships. They have little psychological significance, except to the extent that when practiced to the exclusion of normal sexual relationships they become perversions, and as such tend to be associated with various degenerative conditions, although such associations are not invariable. The essentially normal character of _cunnilingus_ and _fellatio_, when occurring as incidents in the process of tumescence, is shown by the fact that they are practiced by many animals. This is the case, for instance, among dogs. Moll points out that not infrequently the bitch, while under the dog, but before intromission, will change her position to lick the dog's penis--apparently from an instinctive impulse to heighten her own and his excitement--and then return to the normal position, while _cunnilingus_ is of constant occurrence among animals, and on account of its frequency among dogs was called by the Greeks skylax (Rosenbaum, _Geschichte der Lustseuche im Altertume_, fifth edition, pp. 260-278; also notes in Moll, _Untersuchungen über pie Libido Sexualis_, Bd. I, pp. 134, 369; and Bloch, _Beiträge zur Ætiologie der Psychopathia Sexualis_, Teil II, pp. 216 et seq.)