[16] See Swale Vincent, _Internal Secretion and the Ductless Glands_, 1912; F.H.A. Marshall, _The Physiology of Reproduction_, 1910, ch. ix; Munzer, _Berliner klinische Wochenschrift_, Nov., 1910; C. Sajous, _The Internal Secretions_, vol. i, 1911. The adrenal glands have been fully and interestingly studied by Glynn, _Quarterly Journal of Medicine_, Jan., 1912; the thyroid, by Ewan Waller, _Practitioner_, Aug., 1912; the internal secretion of the ovary, by A. Louise McIlroy, _Proceedings Royal Society Medicine_, July, 1912. For a discussion at the Neurology Section of the British Medical Association Meeting, 1912, see _British Medical Journal_, Nov. 16, 1912. [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 Wesché, "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, Zoölogy, 1906. [18] Näcke now expresses himself very dubiously on the point; see, e.g., _Archiv für Kriminal-Anthropologie_, 1905, p. 186. [19] _Untersuchungen über 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.