Ernest Henry Starling laid the groundwork for our modern understanding of how the interstitial fluid, which he referred to as ‘lymph', is regulated. Together with his colleague, William Bayliss, he provided the crucial insight into how fluid is driven out of the capillary to form interstitial fluid. That was to measure (estimate) the capillary pressure in different parts of the circulation and to relate changes in these pressures to altered lymph formation. In addressing how interstitial fluid re-enters the circulation, he was able to show that this occurs not only via the lymphatics, but also by re-entering the capillaries, mediated by the oncotic pressure of the plasma proteins. Starling's discoveries put to rest all notions that the processes of filtration and reabsorption of fluid are mediated by the ‘vital activity' of cells. They could be explained entirely on the basis of physic-chemical forces. Based upon his insights from animal experiments, he was able to explain the genesis of edema (dropsy) in a number of disease states, including venous obstruction, cardiac disease and inflammatory conditions.