Liquid yellow
When the opportunity to write a piece on urine arose, I thought "wonderful, here's something we can all relate to". I had no idea, however, where it was going to lead me: from Hippocrates, uroscopy and the tradition of Hebridean waulking to alchemy, quacks and The Pisse Prophet, a 17th century satire. Very early on, physicians took a keen interest in what each one of us exudes at least twice a day. Gradually, urine became a sort of medical manual per se in which the overall state of health of its host could simply be read - so much so that physicians began to feel that it was unnecessary to even meet their patients. Still today, urine tests help doctors form their diagnoses, but they certainly do not exclude carrying out other tests or talking to their patients. Urine has many tales to tell - depending on its colour, its scent, its molecular composition. In healthy individuals, it is usually a shade of pale yellow owing to the yellow pigment found in it: urobilin. Urobilin is just another component of the total waste product that forms urine and whose presence depends on an enzyme of bacterial origin: biliverdin reductase.
