August Krogh was a Danish professor who won the 1920 Nobel Prize in Physiology or Medicine for discovering the mechanism by which capillaries in skeletal muscle are regulated. His contribution to our understanding of the capillary system’s anatomy and physiology has been truly remarkable and noteworthy. Krogh, a prodigious child, demonstrated an early interest in natural sciences. A lecture by Christian Bohr inspired Krogh to pursue a career in physiology. He was a pioneer in the field of comparative animal studies. Additionally, he made numerous fundamental and revolutionary discoveries in the fields of physiology and is best known for developing the Krogh Principle. From 1916 to 1945, he was a professor at the University of Copenhagen’s department of zoophysiology. Interestingly, Krogh invented a number of instruments and machines during his lifetime to aid in his physiological research. His recording spirometer is still in use in a number of hospitals, his bicycle ergometer is one of the most highly regarded working machines, and his precision pipettes and respiration apparatus aided in the advancement of gas analysis methods. They reveal a more constructive side to Krogh that was hidden behind his outstanding scientific achievements.
Childhood and Adolescence
Schack Steenberg, August Krogh was born in Grenaa, Jutland, Denmark on November 15, 1874, to Viggo Krogh and Marie, née Drechmann. He was the son of a shipbuilder.
As a child prodigy, young Krogh developed an early interest in natural science. When boys his age were involved in sports, Krogh was immersed in experiments. He was an avid reader of botany, zoology, physics, and chemistry books.
Krogh attended a lecture on medical physiology by Professor Christian Bohr as a young man. Krogh decided to pursue a career in physiology after being impressed by the latter and inspired by his teacher friend William Sorenson.
Krogh enrolled as a student of medicine at the University of Copenhagen in 1893. He was unable, however, to abstain from studying zoology. In 1897, he began working at the Laboratory of Medical Physiology under the supervision of Professor Bohr. After passing his zoology examination in 1899, he was appointed an assistant to Professor Bohr.
Krogh earned his doctorate in 1903. His dissertation examined the oxygen and carbon dioxide exchanges in the lungs and skin of frogs.
Career of August
Following his doctorate, Krogh developed a keen interest in the gas exchange processes of living organisms. He submitted a paper on nitrogen exchange in the lungs in which he demonstrated that no free nitrogen was involved in respiratory exchanges. He substantiated his findings through meticulous experiments involving chrysalides, eggs, and mice in a temperature-controlled apparatus. The work earned him the Austrian Academy of Sciences’ Seegan Prize.
Krogh developed his own method of investigation and expanded his research on respiration to include other animals. Krogh believed that pulmonary exchanges occurred during this time period via secretory processes regulated by the nervous system. He also invented a tonometer and a device for gas microanalysis.
In 1904, he co-authored a paper with Bohr and K. A. Hasselbalch on the relationship between blood’s carbon dioxide tension and oxygen association. His initial belief that the lung secreted oxygen into the bloodstream was later abandoned in favor of the new fundamental that pulmonary gas exchange was purely diffusion-dependent.
Following the establishment of the fact that oxygen absorption and carbon dioxide elimination from the lungs occur via diffusion, a number of articles appeared criticizing this new perspective and highlighting the problems. Krogh spent the next decade publishing works on the flow of blood through the lungs.
In 1908, Krogh was appointed to a special associate professorship of zoophysiology at the University of Copenhagen. Krogh left Bohr’s laboratory to pursue new discoveries and research in the field. In 1916, it was replaced with a standard chair.
Without a laboratory of his own, Krogh converted his residence into a laboratory. He invented numerous instruments to assess the function of blood flow and respiration, including the rocker spirometer, the electromagnetic bicycle ergometer, and a gas analysis apparatus with an accuracy of 0.001%.
Krogh’s focus shifted in 1915 to the mechanism by which blood capillaries delivered oxygen to muscle cells and removed carbon dioxide during exercise. This study established that blood capillaries remained open during work and closed during rest.
Krogh finally demonstrated the opening and closing of blood capillaries with the aid of extensive microscopical and histological methods. He established that metabolic control of the capillaries existed. This became the pinnacle of his career, bringing him unprecedented success. In 1920, his work earned him the coveted Nobel Prize in Physiology or Medicine.
Krogh published ‘The Anatomy and Physiology of the Capillaries’ in 1922. He emphasized in it the fact that nerves and hormones both influence capillary movement, a study he conducted in collaboration with a large number of foreign scientists. Interestingly, the book continues to exert a strong influence on cell metabolism, water balance, inflammation, and disease.
In 1922, Krogh traveled to America to deliver a lecture. There he learned about the then-newly discovered insulin for the first time. Upon his return to Denmark, he organized the manufacture of insulin with internist H.C. Hagedorn. Nordisk Insulinlaboratorium and Nordisk Insulinfond were founded by the duo. He even collaborated with A. M. Hemmingsen on the standardization of insulin.
The Rockfeller Institute was founded on the Rockfeller Complex in 1928. Additionally, the complex housed two other institutes: the institute of medical physiology and biophysics and the institute of gymnastics theory.
Krogh conducted research on heavy muscle work at the Rockfelller Institute. He developed novel techniques for determining the total osmotic tension of blood and conducted research on the balance of insensible perspiration. During this time period, he also demonstrated an interest in the physiological problems associated with house heating.
He resigned from his academic duties in 1934 and officially retired from the university in 1945. This did not, however, mean the end of his career. He continued his research and studies in his home laboratory on a private basis. Following his retirement, he focused on the flight of insects and grasshoppers. He even investigated the bud development process in trees.
Krogh published over 200 research articles in international journals during his lifetime. He studied aquatic animals’ water and electrolyte homeostasis and authored two books on the subject, ‘Osmotic Regulation’ and ‘Comparative Physiology of Respiratory Mechanisms.’
Though Krogh rose to new academic heights in the field of physiology, he never lost his passion for marine biology, insect physiology, and the osmotic relationship between plants and animals. He returned repeatedly to vigorously read about each of the fields and kept abreast of new research works.
Significant Works of August
Krogh’s most significant contribution as a scientist and professor of zoophysiology was his discovery of the mechanism by which capillaries in skeletal muscle are regulated. The work contributed to a better understanding of the capillary system’s anatomy and physiology. Additionally, it earned him the 1920 Nobel Prize in Physiology or Medicine.
Krogh was the inventor of the ‘Krogh Principle,’ which stated that ‘for such a large number of problems, there will be some animal of preference, or a few such animals, that can be studied most conveniently’. Until recently, the concept has dominated those branches of biology that rely on comparative methods, such as neuroethology, comparative physiology, and functional genomics.
Awards and Accomplishments
In 1920, Krogh was awarded the prestigious Nobel Prize in Physiology or Medicine for his discovery of the mechanism by which gas is regulated in blood capillaries of muscles.
He was conferred with honorary doctorates by a number of universities worldwide, including Edinburgh, Budapest, Lund, Harvard, Göttingen, Oslo, and Oxford.
He was elected to the Danish Academy of Sciences. Additionally, he was elected a foreign member of a number of academies and societies, including The Royal Society of London. He was made an honorary citizen of Grenaa in 1939.
In 1945, he was presented with the Baly medal by the Royal College of Physicians in London.
Personal History and Legacies
In 1905, Krogh married Birte Marie Jörgensen, a medical student who later became a scientist. The couple had four children together, a son and three daughters. Their son was appointed Prosector of Anatomy at Arahus University.
Marie passed away in 1943. August Krogh died in Copenhagen on September 13, 1949, at the age of 74.
Estimated Net Worth
The net worth of August is unknown.