Physiology -- the branch of biology that deals with the normal functions of living organisms and their parts -- gained prominence and became a science unto itself thanks to the contributions of Danish scientist August Krogh. Krogh was one of the most influential physiologists in the early 20th century, who defined comparative physiology, epithelial transport and exercise physiology as independent disciplines.
Schack August Steenberg Krogh was born on November 15, 1874, in Grenaa, Djursland, Denmark, to shipbuilder Viggo Krogh. He studied at the Aarhus Katedralskole, and attended the University of Copenhagen, completing his MSc in 1899 and PhD in 1903. As a pioneer in comparative physiology, Krogh wrote a thesis on respiration through the skin and lungs in frogs: ‘Respiratory Exchange of Animals, 1915’. In 1908, he began lecturing at the University of Copenhagen, attaining the role of full professor by 1916, by which time he also began to head the first laboratory for animal physiology (zoophysiology).
Zoophysiology, or animal physiology, refers to the study of internal physical and chemical functions of an organism, and how these functions are regulated by hormonal and neuronal signals. In 1920, Krogh was awarded the Nobel Prize in Physiology or Medicine for “the discovery of the mechanism of regulation of the capillaries in skeletal muscle”.
He was the first to describe “the adaptation of blood perfusion in muscle and other organs according to demands through opening and closing the arterioles and capillaries”. He developed ‘Krogh’s Principle’, which states that “for such a large number of problems there will be some animal of choice, or a few such animals, on which it can be most conveniently studied”.
In later years, he carried out research on water and electrolyte homeostasis of marine animals and published seminal works: Osmotic Regulation (1939) and Comparative Physiology of Respiratory Mechanisms (1941). He also published over 200 research articles in international journals. As a constructor of scientific instruments of practical importance, he created a spirometer and an apparatus to measure basal metabolic rate. Krogh passed away at 74, on September 13, 1949, in Copenhagen. Besides his contributions to physiology, Krogh co-founded what is today the Novo Nordisk pharma company.