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The accepted definition of postpartum haemorrhage is an estimated blood loss of at least 500 ml. after vaginal delivery. Estimation of blood loss is often unreliable, for few attendants have a clear appreciation of the appearance of 500 ml. of blood soaked into linen and the other accoutrements of delivery. Because of the failure to recognize the extent of haemorrhage, its true importance in maternal morbidity and mortality tends to be missed. Several methods have been used in attempts to measure blood loss accurately. Gatch and Little (1924) extracted haemoglobin and measured it as acid haematin by photometric comparison with a series of acid haematin solutions prepared by diluting the patient's venous blood. Pilcher and Sheard (1937) Controls.-(1) Five samples of fresh blood of known haemoglobin content and varying in volume between 100 and 300 ml. were allowed to clot in bins containing linen fabrics. The haemoglobin was recovered from each with errors of less than 2 %. (2) An excess of calcium ions was added to known quantities of haemoglobin in six samples of old stored blood varying in volume between 400 and 1,000 ml. These were spilt on the floor and on to fabrics, and again the errors of recovery were less than 2%. (3) Solutions of liquor amnii and of meconium in concentrations greater than would occur in the solution in the washing-machine bowl were not found to cause measurable absorption in the oxyhaemoglobin wave band. Determination of the Significance of the LossesThe blood losses recorded at the time of delivery were compared with the subsequent measurements.

We sampled fish and selected water chemistry variables (dissolved organic carbon, sulfate, and pH) in nine southeastern depression wetlands to determine relationships among wetland morphology (surface area and maximum depth), hydrology, water chemistry, and bioaccumulation of mercury (Hg) in fishes. We concentrated on three fish species representing the range of trophic levels occupied by fish in southeastern depression wetlands. Whole-body Hg concentrations were lowest in lake chubsucker (Erimyzon sucetta), a benthic detritivore, and highest in redfin pickerel (Esox americanus americanus), a top carnivore. However, variation in Hg concentrations among wetlands was greater than variation among species. Regression analyses indicated that maximum depth and hydroperiod accounted for significant portions of variation among wetlands in standardized lake chubsucker and redfin pickerel Hg concentrations. Maximum depth and dissolved organic carbon had a negative effect on standardized Hg concentrations in mud sunfish (Acantharchus pomotis). Path analysis confirmed the results of regression analyses, with maximum depth and hydroperiod having relatively large direct negative effects on Hg concentrations. Our results suggest that leaching of Hg from sediments during the drying and reflooding cycle and binding of Hg species by dissolved organic carbon in the water column are primary factors controlling the bioavailability of Hg in southeastern depression wetlands.

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