"From this we may further conclude, that as the Soul acts not immediately upon Bone, Flesh, Blood &c. nor they upon that, so there must be some exquisitely small Particles, that are the Internuncii between them, by the help of which they manifest themselves to each other."
— Mandeville, Bernard (bap. 1670, d. 1733)
Misom. All these latter Conclusions I grant: The Internuncii you speak of, are the Animal Spirits, and that they are the intermediate Officers between the Soul and the grosser parts of the Body no Man denies; but that the Spirits, which compose the Stomachick Ferment, should be of a finer sort than those by whose Musculary Motions and other actions of force are perform'd, is not only a supposition, but in my Opinion a strangely odd one, that has not a shadow of Reason or probability in it.
Do you think it a natural consequence from what we know of all manner of flitring, or straining, that some of the Animal Spirits must infinitely differ from others in fineness and subtilty?
Mandeville, Bernard. A Treatise of the Hypochondriack and Hysterick Passions vulgarly call'd Hypo in Men, and Vapours in Women; in which the Symptoms, Causes, and Cure or Those Diseases are Set Forth after a Method entirely New (London: Printed and Sold by D. Leach, 1711). <Link to ECCO>