''From Victorian times well into this century, American magazines carried advertisements extolling the
advantages of 'silent flush' toilets. The idea was that if you were
playing bridge with friends at home and the urge to excrete came you
could excuse yourself with some polite lie about wanting to check on the
canary, attend to the horrid task, and then return to the table without anyone knowing where you've been.
In his Enviromental Design classic 'The Bathroom' (1976), Alexander Kira notes the the tendency to label any book that discusses elimination as 'humour'. Another aspect of scatological repression is its link to the middle class. In 'Let Us Now Praise Famous Men' (1941), James Agee discusses 'the middle-class worship of sterility and worship-fear of its own excrement', suggesting that in this country at least, middle-class people are more anal than their lower-or upper-class compatriots.''
(The RE/Search GUIDE TO BODILY FLUIDS, by Paul Spinrad)