A section concerning one particular effect of eating onions may be found in the Physiologia crepitus ventris (The Physiology of Ventral Crepitation) of Rudolphus Goclenius père (1547-1628), professor of Physics, Logic, Mathematics and Ethics at the University of Marburg, eclectic philosopher, polymath and poet. The text was first published in Frankfurt in 1607, and later included (with the title Problemata de crepitu ventris - Questions concerning Ventral Crepitation) in the Amphitheatrum Sapientiae Socraticae Joco-Seriae of Caspar Dornavius (Hanau, 1619), where it appears alongside the De peditu eiusque speciebus, crepitus et visio, Discursus methodicus in Theses digestus (On Farting and its Species, the Noisy and the Silent, Methodical Discourse divided into Theses), ascribed to a certain Sclopetarius, an otherwise unknown and possibly pseudonymous author. The authors of the Bibliotheca Scatologica (Paris, 1848) fulsomely describe the two tractates as follows: "L'un est l'alpha, l'autre l'omega de la matière, et tous deux il forment le nec plus ultra de ce que pourront jamais inspirer de plus ingénieux les soupirs abdominaux."
Question VII of the Problemata ("Why is it that the Vandals by eating onions fart frequently?") is both ethnological and physiological in scope, and concerns the onion-eating habit of the barbarous Vandals, who sacked Rome in AD 455, and its less than civilised effects:
Cur Vandali ex ceparum esu frequentius pedunt? An quia sunt Dioscoridi πνευματωτικαι et δηκτικαι hoc est, inflandi atque erodendi seu commordendi vim habent, quae in pituita redundante multos spirituosos flatus gignunt, maxime si cepae longae, ruffae, siccae et crudae fuerint. Vandalos autem cepis vel quotidie victitare, notissimum est, quibus ventris crepitus gratissimi sunt.
Thus, the reason can be none other than that the onion is apt to cause flatulence (πνευματωτικός). Onions are piquant (δηκτικαι) and produce a superabundance of wind (flatus) in the body's excess phlegm, especially if the legumes in question are of the long, red, dry and raw variety (longae, ruffae, siccae et crudae). It is notorious that the Vandals eat onions as their everyday victuals, and so breaking wind is most agreeable to them.
(c) Alistair Ian Blyth, Bucharest 2009