Casts were first discovered by Henry Bence Jones. They are microscopic cylinders of Tamm-Horsfall protein that have been precipitated in the kidneys and then released into the urine; we know now these casts are normal findings unless they contain cells within them; these cellular casts indicating an abnormality in the kidneys. A prevalent idea in the 18th and early 19th centuries was that illness was a result of the condition of the whole body. The environment and the activity of the patient thus played a large part in any treatment. The epitome of this kind of thinking was the concept of the vital force, which was supposed to govern the chemical processes within the body. This theory held that organic compounds could only be formed within living organisms, where the vital force could come into play. This belief had been known to be false ever since Friedrich Wöhler succeeded in synthesising urea from inorganic precursors in 1828. Nevertheless, the vital force continued to be invoked to explain organic chemistry in Bird's time. Sometime in the middle of the 19th century, a new way of thinking started to take shape, especially among younger physicians, fuelled by rapid advances in the understanding of chemistry. For the first time, it became possible to identify specific chemical reactions with specific organs of the body, and to trace their effects through the various functional relations of the organs and the exchanges between them. Among these younger radicals were Bird and Snow; among the old school was William Addison (a different person from Bird's superior at Guy's). Addison disliked the modern reliance on laboratory and theoretical results favoured by the new generation, and challenged Richard Bright (who gave his name to Bright's disease) when Bright suggested that the source of the problem in oedema was the kidneys. Addison preferred to believe that the condition was caused by intemperance or some other external factor, and that since the whole body had been disrupted, it could not be localised to a specific organ. Addison further challenged Bright's student, Snow, when in 1839 Snow suggested from case studies and laboratory analysis that oedema was associated with an increase in albumin in the blood. Addison dismissed this as a mere epiphenomenon. Bird disagreed with Snow's proposed treatment, but his arguments clearly show him to be on the radical side of the debate, and he completely avoided whole-body arguments. Snow had found that the proportion of urea in the urine of his patients was low and concluded from this that urea was accumulating in the blood, and therefore proposed bloodletting to counter this.