The method usually applied in the determination of blood volume is that worked out by ROWNTREE and his colleagues (1929). The principle of the method is that a dyestuff is injected intravenously and its degree of dilution determined.2 As the dye only mixes with plasma, the volume of the plasma alone is thus measured. The relative volume of corpuscles and plasma is determined with the haematocrit. To arrive a t the blood volume the volume of the corpuscles is added t o that of the plasma.

I n the study of the permeability of phase boundaries to ions usually an inorganic salt, the ions of which are to be investigated, is added to one of the phases and the time is measured after which a certain concentration of the salt can be ascertained in the other phase. The result of such experiments indicates, however, not the resistance which one kind of ions encounters when passing the phase boundary, but the resultant of the hindrance of both ions of the salt or, if a cation, for example sodium, present in one phase interchanges with potassium, for example, present in the other phase, it indicates the resultant of the hindrance of the passage of the sodium and of the passage of the potassium ion through the phase boundary. If one of the two ions encounters a great resistance when passing the membrane it will compel the other ion to move slowly as well.1 Furthermore, this method implies that the ion can accumulate in the second phase. The hindrance which an ion encounters when passing the phase boundary can be measured by measuring the rate a t which labelled and non-labelled ions interchange through the phase boundary. When one phase contains W a ions, the other phase besides 23Na ions also 24Na ions of negligible weight, we obtain by determining the rate a t which 24Na penetrates into the second phase a correct measure of the hindrance which sodium ions encounter when passing the phase boundary and, thus, a cor-The influence which the anions exercise on the rate of penetration of the ~~ cations is discussed on page 220. 13 -413286. d c t a phys. Scandimav. Vol. 3.

Summary.Solutions of labelled chloride, bromide, sodium, potassium, phosphate and deuterium oxyde were injected into the circulation of rabbits and the speed of the escape of the labelled ions from the plasma was determined. Potassium was found to penetrate at a much faster rate through the capillary wall than any other ion investigated.Information on the permeability of the muscle and brain capillaries were obtained by comparing the labelled sodium, phosphate and heavy water content of muscle and plasma, respectively brain and plasma. The muscle endothelium was found to be more permeable to sodium and to phospate than the endothelium of the brain. The partition ratio of labelled sodium between plasma and the chloride space of the brain amounts after the lapse of 11 min. only to 1/10 of the equilibrium value; during that time a proportional partition of labelled sodium between plasma and the chloride space of the muscle was obtained.In the course of an hour, somewhat less than 1/3 of the proportional partition of bromine between plasma and the grey brain substance was reached. Proportional partition of labelled water between plasma and the muscle water was reached after about half an hour.We wish to express our hearty thanks to Professor Niels Bohr for kindly putting numerous facilities at our disposal.

The Th2 cytokine IL-13 is involved in biliary epithelial injury and liver fibrosis in patients as well as in animal models. The aim of this study was to investigate IL-13 as a therapeutic target during short term and chronic intrahepatic cholestasis in an Abcb4-knockout mouse model (Abcb4−/−). Lack of IL-13 protected Abcb4−/− mice transiently from cholestasis. This decrease in serum bile acids was accompanied by an enhanced excretion of bile acids and a normalization of fecal bile acid composition. In Abcb4−/−/IL-13−/− double knockout mice, bacterial translocation to the liver was significantly reduced and the intestinal microbiome resembled the commensal composition in wild type animals. In addition, 52-week-old Abcb4−/−IL-13−/− mice showed significantly reduced hepatic fibrosis. Abcb4−/− mice devoid of IL-13 transiently improved cholestasis and converted the composition of the gut microbiota towards healthy conditions. This highlights IL-13 as a potential therapeutic target in biliary diseases.