This occurs only in persons who are subjects of Cystinuria. It appears as if, by a congenital derangement of the nutritive processes, such persons form cystine, to a certain extent probably in place of uric acid; and this peculiarity occurs frequently in several members of the same family. The urine, continuously or frequently, contains flat hexagonal crystals of cystine, and these may be already present in the urine at the time of evacuation, or may be deposited after the urine has stood for a time. The cystine may begin to be deposited in the uriniferous tubules so that calculi are formed in the pelvis of the kidney, or it may be deposited in the bladder. The stones are oval in shape and have a waxy consistence. The surface is brownish or greenish yellow in colour, and crystals can often be separated from it. The stone may be buried in a shell of phosphates. Cystine is soluble in alkalies, mineral acids, and oxalic acid.