Medical language – like all forms of living language – is subject to change. The ‘scientific currency’ (de Almeida 1991: 13) of the late eighteenth and early nineteenth centuries differs from our own. One word in English that had special meanings at the time, as identified by Professor Alberto Tanturri, is excitability, and the linked terms excite, excitant, and so on, which in the late eighteenth century came to develop specifically physiological meanings. This usage seems to derive from the writings of John Brown (1735–88), an Edinburgh physician of the Scottish Enlightenment whose biography is conveniently available in the Oxford Dictionary of National Biography (Lawrence 2004; see also Beddoes 1795; Bynum & Porter 1988). Brown, the founder of an eponymous innovative nosographic system known as Brunonianism, held that excitability was the fundamental feature of living bodies, being triggered by interaction with the environment to produce excitement; that is, the life force. Brunonianism thus pointed forward to Vitalist and Romantic notions of the operation of the body, going beyond the dominant earlier eighteenth-century conception that living bodies could be understood as the outcome of mathematical or physical laws alone.