=Laboratory Diagnosis.=—Other than the noting of evidences of malarial infection, rapid reduction in red-cell count and haemoglobin percentage there is little information to be derived from the blood which is thin and shows delayed coagulation time. It is difficult to make good blood smears. In the urine we note the granular sediment of débris of red-cell destruction with at times haematoidin crystals. Spectroscopically we get absorption bands of methaemoglobin and more rarely oxyhaemoglobin. [Illustration: FIG. 24.—The most important clinical spectra. (_Monographic Medicine._ D. Appleton and Co., New York.)] Albumin is present in quantity and urobilin is usually present in large amount. One can examine the urine for blood by the haemin-crystals, guaiac or benzidin tests. Burkitt has noted that his cases of blackwater have shown a very acid urine with large amounts of acetone bodies. The serum shows haemoglobinaemia and may show reduced alkalinity. PROGNOSIS So far as statistics go the mortality rate would appear to be influenced by the delicateness of the tests used for determining the presence of haemoglobinuria. When a diagnosis is only made with the presence of marked haemoglobinuria, showing porter-colored urine, the mortality rate is, of course, higher than when slight haemoglobinuria is taken into consideration. In cases treated with quinine, Deaderick, in statistics of various authorities, gives a death rate of 25.9%; in cases not so treated, of 11.1%. Marked and persistent vomiting and hiccough are very unfavorable signs. In particular, however, it is anuria that gives us our greatest concern in the care of a case. A severe attack is followed by a marked anaemia and convalescence is usually protracted. PROPHYLAXIS AND TREATMENT =Prophylaxis.=—The view now generally entertained is that where malarial prophylaxis is properly carried out there will not be any blackwater fever. In persons who have had a previous attack of blackwater fever quinine prophylaxis should be with quinine tannate or quinine base, avoiding the acid salts of quinine. In particular any exposure to chilling influences or conditions which lower resistance should be avoided. As blackwater fever is more prevalent among those who have been for 2 or 3 years in highly malarious, tropical regions than among recent arrivals, the former should exercise the greater care as to errors in diet, alcoholic excesses, exposure to wet and irregularity in quinine prophylaxis. =Treatment.=—There is less unanimity of opinion as to the advisability of giving quinine during an attack of blackwater fever than exists as to any other therapeutic measure.