Concerning the oxygenation of tissues and cells

The hypothesis that our tissues are oxygenated by 'pure' diffusion is rejected because diffusion is never 'pure' in living tissues-it is everywhere contaminated by the 'impurity' of convective or agitative 'flow'. The suggested alternative hypothesis is that tissue cells breathe by 'convection + diffusion' like all other aquatic organisms and that all aquatic respiration is identical. This change alters the interrelationship between Cell Theory, Membrane Theory, and Diffusion Theory: it also invalidates the premises of Krogh's tissue oxygenation model (Krogh's Cylinder), and his conclusions. The presumption that cell respiration is active (rather than passive, as is implicit in classical theory) has wideranging consequences: the following are only a few: -cells must work to procure oxygen, and - the ratio of work done to oxygen procured must depend on the oxygen content of the ECF. -since pO2 is only one of many factors determining oxygen content, it cannot be more than one of many factors determining the adequacy or efficiency of cell oxygenation: etc.