Why did Ivan Pavlov receive the Nobel Prize in Physiology or Medicine in 1904?

Ivan Pavlov was awarded the Nobel Prize in Physiology or Medicine in 1904 for his pioneering research on digestive secretions.12

His work in this field involved developing precise surgical procedures to study the gastrointestinal processes in animals. Most notably, he devised an operation to create a "miniature stomach" or pouch that was isolated from ingested food but maintained its vagal nerve supply. This innovative technique allowed him to observe and record digestive secretions in a normal animal over its entire life span, leading to the publication of his influential book, Lectures on the Work of the Digestive Glands, in 1897.23