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S ummary Surface tension values of human sera were determined, figures for freshly separated material being compared with samples from the same sources that had been stored at either 4°C or at — 20°C. Blood for these investigations was obtained from normal individuals as well as from antenatal, diabetic and myeloma patients. Comparisons were performed at 15, 20, 25, 37 and 45°C. Freezing of sera, whether normal or abnormal, resulted in the lowering of surface tension values by a maximum of 3 dynes/cm. Such a reduction was computed to be symptomatic of a partial denaturation, the most likely component involved being a lipoprotein. Human γ‐globulin and human serum albumin were hardly affected by freezing but reconstituted lyophilized serum and reconstituted lyophilized plasma showed the same surface tension depression values as denatured sera. Sera subjected to freezing and thawing displayed increased opalescence as well as increasing the pH value from 7.2 to 7.8 on increased exposure to freezing. It is advocated that the surface tension parameter be included with osmotic pressure and hydrostatic pressure in the consideration of plasma transport and transvascular fluid and solute transport.
S. Lewin (Mon,) studied this question.