An oxygen diffusion through the mucosa of the colon into the vessels of the submucous coat was provable after rectal insufflation of an oxygen-gas mixture by animal experimental investigations in rabbits. Significantly higher pO2 values in the blood of the mesocolon veins, the portal vein, in the arterial and venous mixed blood of the liver parenchyma, and in the arterial vessels of the mesocolon are measurable after rectal application of oxygen during a time of 40 minutes. The oxygen therapy after rectal oxygen insufflation is established by animal experiments.