Born on September 14, 1849, in Ryazan, Russia, Pavlov was the son of a village priest. He planned to follow family tradition by becoming a priest himself. While at a theological seminary, however, Pavlov read Charles Darwin's Origin of the Species and found he really wanted a career in science instead. Soon afterward, in 1870, Pavlov transferred from the seminary to St. Petersburg University. There his professors included two renowned Russian chemists, Dmitri Mendeleev and Alexander Butlerov (1828-1886). Pavlov studied both chemistry and physiology. He obtained a medical degree from St. Petersburg Military Medical Academy in 1879, and a Ph.D. in 1883.

For the next few years, Pavlov studied cardiovascular and gastrointestinal physiology in Germany, then returned to the Medical Academy, where he was appointed Professor of Physiology and also conducted most of his research investigations. Pavlov's first major studies centered around the physiology of digestion. He was particularly interested in working...