Old Feller wrote: "ominous rumbling in the bowels", a precursor, frankly, to a f*rt. Which proves, ladies and gentlemen, that you learn something new every day, particularly if you happen to make a visit to Cambridge university.
I wish I'd stayed at my studies instead of arsing around, Leeds Modern had a fast-track to Cambridge and I too could have been a professor of ominous stomach rumblings, wonderful stuff.