a compound belonging to the purine group, and the chief form in which nitrogen, resulting from the breakdown of protein during digestion, is excreted by reptiles and birds. Small quantities of uric acid (about 0.7 gram per day) are excreted by humans as a product of the breakdown of purines that are constituents of nucleoproteins. In persons suffering from gout (q.v.), however, the level of uric acid in the blood may be high. Minute quantities of a sodium salt of uric acid, precipitated in cartilage and bone, are the cause of gout.