On this day, 89 years ago, on February 27, 1936 (February 5, 1936, the famous Soviet physiologist Pavlov passed away. Pavlov Ivan Petrovich, a Soviet physiologist, proposed the concept of conditioned reflexes and was famous for it. He won the 1904 Nobel Prize in Physiology and Medicine for his research on digestive physiology. Pavlov was born in the family of a rural priest on September 26, 1846 (September 14, the Russian Old Calendar). He studied theology. In 1870, he entered St. Petersburg University to study chemistry and physiology. In 1883, he received a doctorate in medicine from the Imperial Academy of Medical Sciences. Later, he went to Germany to study under C. Ludwig and R. Heidenhain. 1890-1924 Professor of Physiology in 1999. Later, we studied digestive physiology and designed surgical methods such as the Pap's small stomach. With this method, people can observe the digestive juice secretion and other functions of unanesthetized animals for life. In 1897, he published "Lectures on the Function of Digestive Gland". It also started from the spiritual excitement of salivary glands to the study of higher nerve activities, and established the theory of conditioned reflexes. 1890-1930 During the years, he studied the physiological mechanism of cerebral cortex and subcortical central activities, functional mosaics of the cortex, sleep, and the causes of neurosis. It proves that speech functions are unique to humans and are conditioned reflexes of using words as stimuli. In 1930, he began to use his theory to explain and treat mental illness. He criticized the Soviet government many times before the early 1930s, but the government always supported his research work. He died on February 27, 1936.