A paper by v. Ardenne and Reitnauer [1974] is commented with the aim to refer to already known theoretical and experimental results of critical O2 supply in tumor tissue of DS-carcinosarcoma. This summarizing representation shows that the findings by v. Ardenne and Reitnauer [1974] essentially correspond with previous results. (1) The Po2, values in tumor tissue reveal a frequency distribution tilted to the left and dependent on the tumor age. (2) The mean Po2 in the tumor tissue depends on the tumor weight in a logarithmical regression. (3) The time constants of O2 responses after sudden changes of arterial Po2 depend on the initial Po2 values in the tumor tissue. (4) The critical O2 supply radii in tumor tissue can be calculated by diffusion laws, all boundary conditions taking into consideration. (5). The reaction kinetics of the respiratory enzymes at very low O2 pressures can be taken into account by means of an analogue computer. So as slightly improved O2 supply situation in capillary networks is evident.