Carl Friedrich Wilhelm Ludwig’s career began with an article on the process of urinary secretion. While that may not sound like an illustrious start, Ludwig went on to become a prominent German professor and one of the most important names in the history of physiology.

Born December 29, 1816 in Witzenhausen, Germany, Ludwig studied medicine at Erlangen before receiving his medical degree at Marburg in 1839. An active fencer during college, Ludwig carried a deep scar above his upper lip thanks to the sport. That incident was a rare blemish in Ludwig’s time in Marburg, where he spent 10 years climbing the ranks as a professor and publishing influential articles.

Ludwig’s first article, published in 1842, demonstrated the relationship between urinary secretion and other chemical and thermal reactions in the body. It was one of the first scientific articles to draw a distinction between human anatomy and function. Also in the realm of secretion, Ludwig revealed a new class of secretory nerves that control the salivary glands. He showed that even when an animal is decapitated, its salivary glands continue to secrete when the nerves in question are stimulated. He also showed that organs could be kept alive outside an animal by pumping blood or saline solution into the excised part.

Ludwig was also interested in circulation and respiration. In 1847 he invented a device called the kymograph that used a mercury manometer tube and a revolving drum to graphically record blood pressure variations and other vital signs. The device, along with later modifications, became a standard tool for recording results of experiments. With a student, in 1859 Ludwig designed a mercury pump that separated and measured oxygen and carbon dioxide in the blood. His 1867 stromuhr measured the flow of blood. In addition to his inventions and scholarly articles, Ludwig also wrote the first modern physiology textbook.

This physiological research was part of a scientific revival that took place in the mid-19th century in Germany. Around 1840, young medical doctors began arguing the idea that “medicine = science;” medicine had previously been considered an art rather than a science. Medical schools began focusing on scientific breakthroughs in the way the body works, such as new research in the life of cells. Physiology became an accepted science as Ludwig and his colleagues worked to prove the idea that chemical processes rather than a “vital life force” control functions in living things.

In the mid-19th century, the first laboratories of physiology were set up. No laboratory of physiology existed in the Netherlands in 1848, but by 1866 all Dutch universities had a department and laboratory building for physiology. The mid-19th century also saw the birth of scientific journals in Germany, which eventually spread to the rest of Europe and the United States. Previously, scientists had discussed findings via personal letters. German scientific journals helped expose the scientific community to Ludwig’s groundbreaking ideas.

In 1849 Ludwig became the professor of anatomy and physiology at Zurich, and six years afterwards he went to Vienna as professor in the Josephinum school for military surgeons. In 1865 Ludwig was appointed to the newly established chair of physiology at Leipzig. Under his tutelage, many of his students went on to make further discoveries in physiology. One of Ludwig’s first American students later helped found the American Physiological Society. When the Johns Hopkins School of Medicine was opened in 1893, three of the four professors were pupils of Carl Ludwig: William H. Welch in pathology, Franklin P. Mall in anatomy, and John J. Abel in pharmacology. Ludwig continued his position at Leipzig until his death on April 23, 1895.

Ludwig often worked with his students to put together research papers, but rarely took credit for them, which could be one reason his name is not generally recognizable today, even in Germany. His name does live on at the Carl Ludwig Institute of Physiology at the University of Leipzig, which he founded in 1864, and since 1932, the German Society for Cardiology has awarded the Carl Ludwig Honorary Medal to outstanding cardiovascular researchers.