August Krogh Biography (1874-1949)


Schack August Steenberg Krogh (pronounced Krawg) was born on November 15, 1874, in Grenaa, Jutland. Throughout his life Krogh was active in both zoology and human physiology, accomplishing his major discoveries in the physiology ofrespiration.

Krogh attended school at the Gymnasium at Aarhus, and then went on to the University of Copenhagen in 1893. He first entered Copenhagen with the intentionof studying physics and medicine, but under the influence of zoologist William Sorensen, he changed to the study of zoology and physiology. So slash rensen had advised Krogh to attend the lectures of Christian Bohr, an expert in circulatory and respiratory physiology. After attending Bohr's lectures at Copenhagen, Krogh began to work in Bohr's laboratory in 1897, and after receiving his master of science degree in 1899, he became Bohr's laboratory assistant.

One of Krogh's earliest achievements was his invention of a microtonometer--an instrument that measures gas pressure in fluids--which he developed to helpin his research with a marine organism named Corethra. As a student Krogh had done research on the larvae of Corethra to determine how itsair bladders operated (he found that they worked like the diving tanks of submarines). Traveling in 1902 to Greenland, Krogh studied the amounts of oxygenand carbon dioxide dissolved in fresh and sea water. His research cast a newunderstanding on the role of the oceans in carbon dioxide regulation and atthe same time he was able to improve his techniques for measuring gas pressures in fluids.

In 1903 Krogh received a Ph.D. in zoology from the University of Copenhagen,where, in his doctoral dissertation, he demonstrated the difference between the skin and lung respiration of the frog. Whereas the frog's skin respirationwas constant and regular, Krogh found that the frog's lung respiration varied and was controlled by the autonomic system through the mechanism of the vagus nerve. Oxygen passed from the air sacs (alveoli) of the lung through a membrane to the capillaries and then to the blood stream where it formed carbondioxide after it was used by the different tissues in the body. The process then reversed when the blood carried carbon dioxide to the alveoli of the lungs, where it was exhaled.

Krogh was married in 1905 to Marie Jorgensen, a physiologist who also workedin Bohr's laboratory. (The couple would eventually have three daughters and one son.) In 1906 the first of Krogh's papers to receive international recognition, a work which showed that nitrogen is not involved in animal metabolism,was awarded the Seegen Prize from the Vienna Academy of Sciences. In 1907 Krogh received further international attention at Heidelberg, Germany, when hediscussed his findings on the diffusion of pulmonary gases at the International Congress of Physiology.

In 1908 Krogh made another trip to Greenland with his wife to study the Eskimo's meat-eating dietary habits and the effects it had on their respiration and metabolism. He was also given an associate professorship of zoo physiologyat the University of Copenhagen that year. Two years later Krogh and his wifewere given a laboratory at Ny Vestergade for physiological research. Krogh then became a full professor at Copenhagen in 1916.

From 1908 to 1912 Krogh was engaged in research to resolve the question of how oxygen was transferred in the lungs to the blood. Bohr and John Burdon Sanderson Haldane, along with other scientists, believed that the lung acted as agland in the alveolar transfer of oxygen to the blood; in other words, the lung secreted the oxygen. Krogh, in 1912, convincingly delivered the fatal blow to the secretion theory by first showing that in fishes there is no secretion of oxygen into the air sacs, and then by demonstrating that the amount ofoxygen in the blood always equalled the amount that should be provided by hisdiffusion theory.

It was not until 1916, however, that Krogh accomplished the work that would,in 1920, earn him the Nobel Prize for physiology or medicine. He showed thatmuscle tension was always slightly lower than the tensions in the capillaries, even when the muscle was at work. Noting that there were few open capillaries when a muscle was at rest, Krogh demonstrated that as soon as the muscle became active many capillaries began to open up. He was also able to show thatblood did not enter the capillaries through the pressure of the blood vessels but from the relaxed tonus (partial contraction) of the active muscle. Therelaxation of the muscle allowed the field of capillaries to open and the blood to flow in, thus providing more oxygen to the muscle, organ, or tissue.

Krogh's discoveries relating to gas exchanges in the lung and to the operation of the capillary system helped to develop medical techniques for breathingthrough the trachea. His work also improved surgical methods for open heart surgery, such as the procedure for reducing body temperature to below normal levels to slow down the rate of gaseous exchange.

In 1922 Krogh became interested in insulin (which had been discovered by Frederick G. Banting and John James Rickard Macleod the year before), partly because his own wife had diabetes. Besides being active in insulin research, Krogh helped to promote manufacturing facilities in Denmarkfor its production. Krogh also maintained his interest in zoology, writing about insects and becoming particularly attentive to theories about the way honey bees communicate.

Krogh died on September 13, 1949, in Copenhagen.

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