Medical language – like all forms of living language – is subject to change. The ‘scientific currency’ (de Almeida Reference de Almeida1991: 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 Reference Lawrence2004; see also Beddoes Reference Beddoes1795; Bynum & Porter Reference Bynum and Porter1988). 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.

Although Brunonianism’s experimental basis was problematic in several ways, its author seems to have become convinced of his system through experimenting on himself. This was an approach regularly adopted by later Romantic scientists such as Humphry Davy (see further Holmes Reference Holmes2009, especially ch. 6). Brown suffered from gout, but reported that abstention from meat and alcohol, as recommended by an anonymous medical adviser, was ineffective. (The adviser was possibly the great William Cullen, who had once been Brown’s mentor, but with whom he had quarrelled.) He therefore decided to go to the opposite extreme, ingesting ‘liberally’ (Lawrence Reference Lawrence2004) not only substantial quantities of food and drink but also opium, with, it seems, satisfactory results. His approach to medicine was promulgated through a series of university lectures, and subsequently published as Elementa Medicinae Brunonis (1780), and (anonymously) as Observations on the Principle of the Old System of Physic (1787). His views achieved considerable acclaim from many contemporaries, including students attracted by his charismatic manner of teaching: ‘[i]n Edinburgh, espousing Brunonianism was often the choice of young Turks whose medical radicalism might be matched by a socio-political radicalism’ (Bynum & Porter Reference Bynum and Porter1988: ix). However, the system remained controversial, not least because of Brown’s perceived personal faults. Thomas Beddoes (1760–1808), the radical (and teetotal) chemist and physician, who had also attended Cullen’s lectures in Edinburgh, offered the following anecdote in his hostile ‘Observations on the Character and Writings’, prefixed to his posthumous translation of Brown’s Elementa:

Beddoes’s considered views on the author of the Elements were summed up by the dedication of his translation: ‘To the ingenious, the candid, and humane, the following production of unfortunate genius is inscribed by the editor.’ Brown’s influence was nevertheless widely felt, notably in Germany and – as Professor Tanturri has shown – in Italy.

Brown’s excitability, and the related form excitant, are both derivatives of the verb excite, from Latin excitāre (‘to set in motion’). Other related words include excitancy, excitation, excitative, excitator, and excitatory. According to the Oxford English Dictionary (OED), the earliest specifically medical usage of any of these terms dates from Middle English, where excite simply refers to the process whereby a purge is induced. John Trevisa’s translation of Bartholomaeus Anglicus’s encyclopaedia De Proprietatibus Rerum (1398) describes how ‘It is generall medycyne to excyte spewinge’, and that the form has no special medical significance is confirmed by its usage in the near-contemporary Three Kings of Cologne: ‘Þe deuyll […] excited […] among þe pepil diuers opynyouns of heresy.’

More relevant to the later development of the term is its appearance in Sir Thomas Browne’s Pseudodoxia Epidemica (1646), where magnetism is referred to: ‘If an iron or steele not formerly excited, be held perpendicularly or inclinatorily unto the needle, the lower end thereof will attract the cuspis or southerne point.’ Magnetism fascinated contemporary writers; Sir Thomas was said to have been drawn to his wife Dorothy ‘by a kind of Natural Magnetism’ (Lawrence Reference Lawrence2004), and magnetism was a trope for metaphysical poets such as John Donne, used to refer to both profane and sacred love. Indeed, interchange between scientific and religious meanings of these words is characteristic of this early usage. Excitant, for instance, is first recorded in the OED in the puritan preacher Richard Crakenthorpe’s A sermon of sanctification (1608): ‘Gods grace in our conversion is not onely an excitant, but a viuificant grace.’ Interestingly, the OED classifies the citation from Crakenthorpe, glossing excitant as ‘That rouses, excites, or stimulates; exciting, stimulating’, alongside a 1774 reference to the Royal Society’s Philosophical Transactions: ‘Cushions […] covered with silk […] are much more powerfully excitant.’

The physiological meaning of excitability seems to emerge from these earlier usages, both religious and secular, and underpinned Brown’s extension of the term’s meaning. The OED shows how swiftly the term became current in contemporary scientific discourse, for example in the writings of Brown’s contemporary Erasmus Darwin (1731–1802), an Edinburgh-trained physician as well as polymath who, in addition to favouring Brown’s ‘strong interventions’ such as opium (though not alcohol), used ‘swinging machines’ (Lawrence Reference Lawrence2004). Darwin’s Phytologia (1800) refers to how ‘The buds of vegetables […] possess irritability, and sensibility, and voluntarity, and have associations of motion […]. But […] the three latter kinds of excitability are possessed in a so much less degree by vegetable buds.’ Darwin was hugely influential on Romantic writers. Mary Shelley, for instance, seems to have been inspired to write Frankenstein after a discussion with Lord Byron and her husband Percy about ‘the experiments of Dr Darwin’ (1831: ix–x).

Fascinatingly, as Romantic thinking developed it seems to have sustained a broad approach to the notion of excitability, and here the key figure is the poet and philosopher Samuel Taylor Coleridge (1772–1834). Numerous citations from Coleridge relating to the term and its congeners appear in the OED. Coleridge was clearly aware of the scientific sense of these words, accompanied by a good understanding of Brunonian principles. As Neil Vickers has pointed out, Coleridge is on record – in a letter to his publishers of 1819 – as ranking Brown ‘alongside Cicero, Luther, Giordano Bruno, Milton, Dryden, Wolfe, Hunter and Wordsworth, as a “man of great Genius and original Mind”’ (1997: 48). It is no surprise to learn that Coleridge was close to Beddoes, who encouraged him to travel to Germany in 1798–1799 to develop his philosophical education (in 1799 Coleridge was to enrol as a student at Göttingen). An OED quotation from Coleridge’s Table-Talk (1833), which catches something of the poet’s inspired casual conversation, reads as follows: ‘The English affect stimulant nourishment—beef and beer. The French excitants […] alcohol, champagne.’ And excitability is used in a less flippant way in Coleridge’s much more serious, and highly influential, Aids to reflection in the formation of a manly character on the several grounds of prudence, morality, and religion (1825): ‘Pleasure […] consists in the harmony between the specific excitability of a living creature, and the exciting causes correspondent thereto.’ Coleridge, in truly Romantic fashion, clearly saw the connexion between physical and metaphysical approaches to the world, reminding us incidentally why science used to be referred to as ‘natural philosophy’. It is intriguing in this context that excitability and excitant continue to be current terms in neurology (see for instance Izhikevich Reference Izhikevich2000, with 1,876 citations to date in Google Scholar).