- and urine was an important component of the dyeing process - used as a mordant snce ancient times. I am led to believe that the Aztecs had public conveniences along the causeway from Mexico City to the mainland, and that people came out in boats to empty the contents thereof to use for just that purpose.

Sterility of urine was well-known in the ancient world, also. Wounds sustained in battle or whilst hunting were sterilised by pee-ing onto them. It is, of course, only sterile whilst abolutely fresh - urine attracts bacteria pretty swiftly [eek]