Have you heard the one about the musical bum? It's a real gas

At the opening of Fecal Matters in Early Modern Literature and Art (2004), Jeff Persels and Russell Ganim lament "the relative academic neglect of the copious and ubiquitous scatological rhetoric of Early Modern Europe, here broadly defined as the representation of the process and product of the elimination of the body's waste products (faeces, urine, flatus, phlegm, vomitus)". Their irreverent collection is pursued by Valerie Allen's fascinating and witty On Farting , a piece of sustained "butthole scholarship" that takes as its subject the re-inscription of laughter "at the centre of an epistemological relationship with the world that allows neither any safe distance between subject and object nor the collapse of difference between them".

Allen considers there to be a resonance between a period that exists as "the age median between classicism and Renaissance", that is, the Middle Ages, and the fart "which does not exist qua fart until it passes the anal threshold". This trembling incipience makes the fart trendily liminal and modishly presentist: "A fart comes into being in the moment of transition, in-between inside and outside, in-between cheeks."

While this evanescent quality might be devoutly to be wished for while snoozing under the duvet after a heavy night in the pub, in theory at least, its fleeting quality lends the fart an ethereal dimension that casts it as anything but oafish: "The medieval fart shape shifts continuously between smell and sound, air and vapour, always on the move between earthly elements, bodily senses, people and buttocks."

Allen's thesis is not especially original: "The domesticisation of waste and the birth of the modern subject are inextricably connected." Norbert Elias (1939) and David Inglis (2001) addressed the development of this modern faecal habitus in sociological terms, while Norman O. Brown (1959) discussed the excremental vision in terms of psychoanalysis and Mary Douglas (1966) dealt with the anthropology of dirt. John G. Bourke described various scatological rites as long ago as 1891.

But the strength of On Farting is its playful and evocative treatment of a number of scatological authors and episodes. The usual suspects - Rabelais, Chaucer and Dante - are here but also Robert Copland's account of Iyl of Braintford, who bequeathed a score of farts in her will, as well as Roland (aka Baldwin) le Pettour who, during the 13th century, performed a dance every Christmas Day, in which, in the words of the Elizabethan antiquarian William Camden, he would "puffe up his cheekes making therewith a sound, and besides let a cracke downeward." Section headings give an indication of the jouissance that Allen brings to her subject: "The musical bum", "The nose knows", "Better out than in" and her discussion of le Pettour cites his address as "Fartlands".

This often puerile rhetoric belies Allen's scholarly achievement. Her discussion of flatus as the inversion of the spiritus Dei is commanding and she deftly deploys such heavyweights as Augustine, Hippocrates and Galen in her erudite sifting of linguistic terms for gas, sacred and profane.

She describes anal eruptions as being symptomatic of post-lapsarian bodily disobedience, which, incidentally, is also the cause of unwanted erections. Her analysis of earthly music ( musica mundana ) is neatly placed between cosmological harmonies and the less celestial sounds of the human body: "the musical bum provides the occasion to [consider] the mystical alignment between body, soul and cosmos". This is a volume which will be profitably consulted by all those interested in the philosophy, art, medicine and literature of the Middle Ages.

Peter J. Smith is reader in Renaissance literature at Nottingham Trent University. He is currently writing Between Two Stools: Scatology in English Literature, Chaucer to Swift .