In "Aphorism" works, it was noted that urine lacking color could indicate diseases of the brain – some today think that this author who made this statement was meaning to refer to chronic renal failure or even diabetes. It was also suggested that the appearance of blood within urine could indicate vessels of the kidney to have burst, potentially due to necrosis of blood arteries or vessels. Furthermore, doctors noted that if bubbles formed on top of urine, the kidneys were diseased and showed the potential of long-lasting disease.