Thomas Willis, Two Discourses concerning The Soul of Brutes, Which is that of the Vital and Sensitive of Man (1683), pp. 188, 192-193

Melancholy. . . is a complicated Distemper of the Brain and Heart: For as Melancholick people talk idly, it proceeds from the vice or fault of the Brain, and the inordination of the Animal Spirits dwelling in it; but as they become very sad and fearful, this is deservedly attributed to the Passion of the Heart. . . . But we cannot here yield to what some Physicians affirm, that Melancholy doth arise from a Melancholick humour. . . . Melancholy being a long time protracted, passes oftentimes into Stupidity, or Foolishness, and sometimes also into Madness. . . .

Willis, against the notion that sadness is connected with a single bodily fluid, is concerned with bringing melancholy, madness, and general feeling under the jurisdiction of the body's most basic mechanisms. If melancholy is at times a function of both the heart and the brain, then sensibility becomes connected with both the vital soul of the blood and the sensitive soul of the nerves. In other words, after Harvey's circulation, feeling is always in motion, always moving us.

Related terms:

a dictionary of sensibility
term list
source bibliography
critical bibliography