Hemorrhagic cerebro-vascular accidents were simulated in dogs by injecting their own blood in the subarachnoidal space. Gathering daily samples of cerebrospinal fluid during 14 days the evolution of the concentrations of oxyhemoglobin and bilirubin using the spectrosphotometric method was studied. The author defines hemoglobin coefficient as being the relatinship between the oxyhemoglobin concentration and the sum of the cerebrospinal fluid pigments and the hemoglobin-bilirubin index as the relationship between the oxyhemoglobin and the bilirubin concentration. After statistical treatment the author concludes that both permit to calculate the time span between the subarachnoidal hemorrhage and the examination of the cerebrospinal fluid. Some suggestions on the practical applicability of these indexes in Clinical Neurology and Preventive Medicine are discussed.