Krogh, krawg, Schack August Steenberg (1874-1949), a Danish physiologist (scientist who studies how living things function), made important discoveries about the way that capillaries (small blood vessels) react when the body is doing muscular work. Krogh found that capillaries expand or contract in relation to the amount of blood that the body tissues require. An active muscle requires a larger number of open or enlarged capillaries than a less active muscle does. The additional open capillaries increase the surface area through which gases are exchanged. For his discoveries, Krogh was awarded the Nobel Prize in physiology or medicine in 1920.