There’s a funny (and actually educational) thread at APUG about using urea, a component of urine, as an accelerator for film developers. Check it out.

This is bizarre: This picture of a patient who had alkaptonuria (Fig. 1) was taken by my father, Dr. Ian Maxwell, in 1957 and was developed using the patient’s own urine [emphasis added]. Alkaptonuria was the first described “inborn error of metabolism.” This rare (< 1 per 250 000 births) hereditary recessive disorder is characterized [...]