Most gracious King, The Heart of creatures is the foundation of life, the Prince of all, the Sun of their Microcosm, on which all vegetation does depend from whence all vigor and strength does flow. Likewise the King is the foundation of his Kingdoms, and the Sun of his Microcosm, the Heart of his Common-wealth, from whence all power and mercy proceeds. I was so bold to offer to your Majesty those things which are written concerning the Heart, so much the rather, because (according to the custom of this age) all things human are according to the pattern of man, and most things in a King according to that of the Heart; Therefore the knowledge of his own Heart cannot be unprofitable to a King, as being a divine resemblance of his actions (So us'd they small things with great to compare). You may at least, best of Kings, being plac'd in the top of human things, at the same time contemplate the Principle of Mans Body, and the Image of your Kingly power. I therefore most humbly entreat, most gracious King, accept, according to your accustom'd bounty and clemency, these new things concerning the Heart, who are the new light of this age, and indeed the whole Heart of it, a Prince abounding in virtue and grace, to whom we acknowledge our thanks to be due, for any good that England receives and any pleasure that our life enjoys. Your Sacred Majesties most devoted Servant, William Harvey.
Harvey's introduction seems a strange conflation of the medical, the spiritual, and the conservative. Harvey's circulation, which allowed for fluid theories of the nervous system, is framed here in terms of the heart's similarities to the King as a central, radiant object. The metaphorical relations between the heart, the King, the sun, and the body become quite complex as the King, who is like the heart, is invited to better acquaint himself with his own heart. Most interesting here is the way in which the most basic physical elements of sensibility, before they are even elaborated upon, are made political. The fundamental engine of feeling, the heart, is imagined into a conservative political context which turns feeling itself into the radiating influence of a benevolent dictator. The passage is further complicated by the fact that in 1653, the time of publication, Charles I, to whom the work is dedicated, is dead.