Physiology and the medicalized body played a crucial role in the development of literary and cultural sensibility. G. S. Rousseau, in his essay, "Nerves, Spirits, and Fibres," describes the development of sentiment and sensibility in terms of a series of Kuhnian paradigm shifts beginning in the seventeenth century. After William Harvery's discovery of the blood's circulation in the 1620's, it became more and more possible to imagine not only the blood, but other spirits moving and carrying information throughout the body. Nervous theories of all sorts were suggested: some said nerves were hollow tubes that could transport "animal spirits" from one part of the body to another. Newton suggested a musical metaphor, linkng the nervous sytem to a vibrating stringed instrument. Others, like Thomas Willis, complicated this idea, suggesting, in his case, that the nerves were conductors rather than hollow tubes and that the animal spirits moved about the body more mysteriously than water in plumbing. Willis also suggested that there were different sorts of spirit or soul in the body: the vital, which was transported in the blood, and the sensitive, which resided in the nerve juices. This increasingly complicated picture of the body described a unpredictable sort of mechanism whose delicate balance of fluids allowed for a belief in a mechanistic body which might still excercise free will.
The argument follows that these scientific, medical discoveries influenced other thinkers; Locke learned from Willis, allowing him a scientific backing for his repudiation of the Cartesian mind/body split; Richardson had as his close friend and medical advisor Dr. Cheyne, whose medical advice was based on the motion of the various spirits and involved complicated excercise machines such as the "Chamber Horse":
Actually a chair "set on a long board, which must have acted like a joggling board, supported at both ends and limber in the middle, with hoops to brace the arms and a footstool to support the feet," the horse promised "all the good and beneficial Effects of a hard Trotting Horse except the fresh Air." (Flynn, 147)
So, the intersection of the scientific, the popular cultural, and the high literary contributed to an environment which spoke familiarly about what remained, at its most basic level, absolutely unfamiliar. The manner in which the animal spirits moved one and the nerves themselves remained invisible.
The sense that beneath the skin, a set of universal human mechanisms were transporting and recoding sense data and feeling and emotion suggested a possibility of transcontextual solidarity based in a community of the flesh. If one is familiar enough with the body, one becomes familiar with the soul.
This community is, however, sometimes undercut by a classed, nationalized sense of sensibility, where the individual nervous system might be more or less sensitive depending on where one is from or how much money one has.