Krogh, Schack August Steenberg (1874–1949)

Danish physiologist who was awarded a Nobel Prize for Physiology or Medicine in 1920 for his discovery of the mechanism regulating the dilation and constriction of blood capillaries.

Krogh was born at Grenaa, Jutland, and went to school in Århus. He graduated and completed a doctorate in zoology at Copenhagen University, specializing in marine biology, an interest that he maintained all his life, although his most important work was in human physiology. He twice travelled to Greenland to research the metabolism both of the Inuit inhabitants and of Arctic marine mammals. For many years he worked on the absorption of oxygen into the body, showing that diffusion, rather then secretion, accounts for all oxygen taken into the blood. His later experiments on frogs' tongues allowed him to identify the characteristics of capillaries; he concluded that a physiological mechanism must regulate their action in response to the body's needs.