Loeb, Jacques (1859–1924), a German-American experimental biologist and physiologist. In 1899 Loeb succeeded in fertilizing eggs of sea urchins artificially, using chemicals instead of male sperm. In his experiments, Loeb sought to test his theory that the behavior of all living things can be explained in chemical terms. He showed that certain machinelike reactions, which he called tropisms, are made by animals as well as plants in response to certain stimuli. Loeb believed that tropisms were often mistaken for expressions of will and purpose.
Loeb was born in Germany. He received a medical degree from the University of Strassburg (Strasbourg) in 1884. After coming to the United States in 1891, he taught at the University of Chicago (1892–1902) and the University of California (1902–10). In 1910 he joined the Rockefeller Institute for Medical Research.