Now, it can easily be understood that if by some fault in the organism the oxidation of albumen is not completed and carried on to the final production of urea, but stops short at the production of a less highly oxidised substance, namely, uric acid, there will be a disturbance of the ordinary course of action in the body {vide chapter xxviii., page 166). This uric acid is not, moreover, soluble like urea, and cannot be carried off by the kidneys with the same facility, being an insoluble and intractable substance. It exists in the form of small pointed crystals, which cause irritation of the urinary passages. Circulating in the blood, uric acid enters into combination with the sodium of the serum, and forms acicular crystals of urate of sodium, which are deposited in the membranes of the joints, giving rise to the well-known symptom of gout, namely, chalk stones. The attacks of gout are caused by an effort of nature to get rid of these deposits of a foreign substance in the joints; the joint becomes acutely inflamed, there is an increased flow of blood to the part, and urate of sodium is discharged into the blood current.