How was Schack August Steenberg Krogh awarded the Noble Prize in Physiology or Medicine?

Name: Schack August Steenberg Krogh.
Country: Denmark.
Date of Birth: 15 November 1874.
Died: 13 September 1949.
Education: University of Copenhagen.
Subjects Of Study: Capillary Circulation Respiration.
Known as: Krogh’s principle.
Noble Prize Year: Nobel Prize for Peace in 1920, for his discovery of the capillary motor regulating mechanism.