[The introduction of thermodynamics in the theory of the microcirculation]

By application of thermodynamics on the theory of microcirculation in tissues one must implicate the fact that both phenomena convection and diffusion through semipermeable membranes take place in "non opened" compartments. Based on this precondition the present paper shows that the known calculations by Kedem and Katchalsky and others are insufficient in order to describe the above mentioned processes and that the reflection coefficient delta is not relevant to the real movement of molecules through capillary walls. Furthermore, the basic equation of the microcirculation is to be improved by a diffusion component in order to represent a better approximation of the exchange situation in tissues.