THE VARIATIONS OF THE SPECIFIC GRAVITY OF THE PLASMA OF THE BLOOD AND THE MEANS AVAILABLE FOR ALTERING IT

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Abstract
It has been demonstrated that the specific gravity of the plasma and (Moore and Van Slyke''s observations) the plasma proteins of normal individuals show remarkable constancy for short periods (days) provided the samples of blood are taken at the same time each day. In 5 patients suffering from heart disease who were in water balance the maximum and minimum daily variations in the specific gravity were 0.0004 and 0 respectively. In 2 normal individuals the variations were 0.0015 and 0.0011 over a period of 14 mos. There was corresponding variation in the protein content of the plasma. The specific gravity of the plasma of a normal individual varied 0.0007 in the course of a day. The protein content and the specific gravity of the plasma of arterial blood were found (in 7 cases studied for this point) to be uniformly less than those of venous blood. The intravenous injection into 2 dogs of normal salt solution resulted in decrease in the specific gravity of the plasma of the blood. The administration of water 1000 cc. by mouth to 2 human beings decreased the specific gravity of the plasma, however, only slightly. During "concentration tests" 2 patients exhibited increases (0.0013) in the specific gravity of the plasma of the blood. Hemorrhage in a dog was followed by decrease in specific gravity of the plasma, and a corresponding decrease in the plasma protein concentration. Return to the initial level occurred 4 days after bleeding. The intravenous injection of hypertonic solutions of glucose in 3 dogs resulted in decrease in the specific gravity of the plasma. The injection of gum acacia in glucose solution in an edematous patient increased the specific gravity of the plasma slightly, but the volume of fluid injected and the dilution resulting from the presence of hypertonic glucose solution decreased the protein concentration. Moore and Stewart conclude that the specific gravity and the protein content of the plasma of patients suffering from cardiac disease are within the range found in normal individuals. In those cardiac patients exhibiting edema as well as in those in whom this sign is not present, there is a linear relationship between the specfic gravity and the total protein content of the plasma which is expressed by the formula of Moore and Van Slyke. They remark that the anticoagulant used has an effect on the specific gravity of the plasma. If data are to be compared with those published by Moore and Van Slyke, heparin must in consequence be used.