The anatomy and physiology of the capillaries.

Silliman Lectures. Krogh was first to describe the adaptation of blood perfusion in muscle and other organs according to demands through opening and closing the arterioles and capillaries.

In 1920 Krogh received the Nobel Prize in Physiology or Medicine "for the discovery of the mechanism of regulation of the capillaries in skeletal muscle." 

Besides his contributions to medicine, Krogh was one of the founders of the company known today as Novo Nordisk.