The Danish physiologist Schack August Steenberg Krogh (1874-1949) is noted for his classic researches on the anatomy and physiology of the blood capillaries and his contributions to respiratory physiology, marine biology, and cell physiology.

August Krogh was born on Nov. 15, 1874, in Grenaa, Jutland. As a boy, he read widely in botany, zoology, physics, and chemistry, but he was uncertain at first whether to specialize in physics or zoology. He attended lectures on medical physiology by Christian Bohr, father of the physicist Niels Bohr, and decided forthwith to follow a career in physiology. In 1899 Krogh was appointed assistant in Christian Bohr's laboratory, and in 1903 he received a doctorate for his analysis of respiratory exchanges of oxygen and carbon dioxide in the lung and skin of frogs.

With his own new methods Krogh extended his studies of respiration to other animals, including man. At the time he started research, it...