In jaundice arising from melanotic cancer of the liver, the recognition of the presence of melanine in the urine would be an important aid to the diagnosis. Care must be taken not to confound the dark olive-green urine occasionally met with in other forms of jaundice, with the melanotic urine just described, or both {70} patient and doctor may become unnecessarily alarmed.[21] [Footnote 21: While I was Resident Physician in the Royal Infirmary of Edinburgh, in 1850, a woman, aged 28, was admitted with a universal and bright jaundice of three weeks' standing. Her urine was high coloured, and of a specific gravity of 1022. It contained a small quantity of albumen, and became perfectly black on being boiled with nitric acid. In this case there was no reason to suspect malignant disease of the liver; the colour of the urine was, therefore, most probably due to the bile pigment being more than usually oxidized. After a six weeks' stay in the hospital, I dismissed the patient as cured.] _Urea, Uric Acid, and Sugar._ The presence, and quantity of certain other substances met with in the urine of jaundice, although not peculiar to that condition, nevertheless afford us important information, not only as to its cause, but also as to its probable mode of termination. Firstly, a correct knowledge of the quantity of urea, and of uric acid passed in the twenty-four hours is of great value; and, secondly, the presence, or absence of sugar is a fact which ought never to be lost sight of. The value of this statement, as well as of several of the preceding, will, I think, be better appreciated by giving a short account of a case of obscure disease (where a correct diagnosis, and prognosis could not have been arrived at without the application of the chemical knowledge referred to), than by any mere abstract {71} treatment of the question. I shall, therefore, at once proceed to relate the brief history of the case.