[The theory of microcirculation. 4: The movement of molecules through semipermeable membranes]

The movement of the molecules through semipermeable membranes does not only follow thermodynamical principles but it is also in keeping with the classical mechanics of particle movement. Hence, in presence of chemical potentials a simple diffusion at semipermeable membranes is impossible because of additional convective fluid transport, which influences the process. Reversely, every solution passing through semipermeable membranes generates a certain pattern of chemical gradients. These findings are important for the calculation of protein distributions in tissues. The current view of application of thermodynamics on microcirculation includes several misinterpretations concerning the movement of molecules through semipermeable membranes, because it does not take into consideration the special preconditions. The present paper shows, that it is necessary to reinterpretate the current concept of this field of the microcirculation.