[17] Since this was written I have come across a passage in Hampa (p. 228), by Rafael Salillas, the Spanish sociologist, which shows that the analogy has been detected by the popular mind and been embodied in popular language:  “A significant anatomico-physiological concordance supposes a resemblance between the mouth and the sexual organs of a woman, between coitus and the ingestion of food, and between foods which do not require mastication and the spermatic ejaculation; these representations find expression in the popular name papo given to women’s genital organs.  ‘Papo’ is the crop of birds, and is derived from ‘papar’ (Latin, papare), to eat soft food such as we call pap.  With this representation of infantile food is connected the term leche [milk] as applied to the ejaculated genital fluid.”  Cleland, it may be added, in the most remarkable of English erotic novels, The Memoirs of Fanny Hill, refers to “the compressive exsuction with which the sensitive mechanism of that part [the vagina] thirstily draws and drains the nipple of Love,” and proceeds to compare it to the action of the child at the breast.  It appears that, in some parts of the animal world at least, there is a real analogy of formation between the oral and vaginal ends of the trunk.  This is notably the case in some insects, and the point has been elaborately discussed by Walter Wesche, “The Genitalia of Both the Sexes in Diptera, and their Relation to the Armature of the Mouth,” Transactions of the Linnean Society, second series, vol. ix, Zooelogy, 1906.

[18] Naecke now expresses himself very dubiously on the point; see, e.g., Archiv fuer Kriminal-Anthropologie, 1905, p. 186.

[19] Untersuchungen ueber die Libido Sexualis, Berlin, 1897-98.

[20] Moll adopts the term “impulse of detumescence” (Detumescenztrieb) instead of “impulse of ejaculation,” because in women there is either no ejaculation or it cannot be regarded as essential.

[21] I quote from the second edition, as issued in 1881.

[22] This is the theory which by many has alone been seen in Darwin’s Descent of Man.  Thus even his friend Wallace states unconditionally (Tropical Nature, p. 193) that Darwin accepted a “voluntary or conscious sexual selection,” and seems to repeat the same statement in Darwinism (1889), p. 283.  Lloyd Morgan, in his discussion of the pairing instinct in Habit and Instinct (1896), seems also only to see this side of Darwin’s statement.

[23] In his Variation of Animals and Plants under Domestication, Darwin was puzzled by the fact that, in captivity, animals often copulate without conceiving and failed to connect that fact with the processes behind his own theory of sexual selection.

[24] Beaunis, Sensations Internes, ch. v, “Besoins Sexuels,” 1889.  It may be noted that many years earlier Burdach (in his Physiologie als Erfahrungswissenschaft, 1826) had recognized that the activity of the male favored procreation, and that mental and physical excitement seemed to have the same effect in the female also.