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Historical Book of the Week: The Work of the Digestive Glands (1902)


Ivan Pavlov, The Work of the Digestive Glands, translated by William H. Thompson. London: Charles Griffin & Compa-ny, Limited, 1902, p. 13.

Figure depicting the stomach, in Ivan Pavlov’s The Work of the Digestive Glands.[1]

Ivan Pavlov, the Accidental Psychologist

By Matt Grieser

Most who have heard the name Ivan Pavlov (1849-1936) have some vague memories of dogs and bells, having encountered the name in a psychology class at one point or another. Most know the Russian scientist for illustrating the phenomenon of performing two different things together many times, until doing only one of them produces the response usually associated with the other. This came to be known as Classical Conditioning. The story goes, Pavlov fed a dog while ringing a bell until, eventually, just ringing the bell made the dog’s mouth water. This discovery showed future psychologists that responses to stimuli could be “trained.”

What most people don’t know is that Pavlov never meant to get involved with psychology. Pavlov’s laboratory focused on physiology. Specifically, he investigated how the parts of the digestive system of dogs responded to different foods and stimuli. The methods his lab are best known for creating long-term access to different parts of the system to monitor what was getting secreted and when. The laboratory workers did this by surgically placing tubes and other collection devices on various places in dogs. Some of these tubes were in the dog’s stomachs, some were in their small intestines, and some were even in the dog’s mouths.

Pavlov was a skilled surgeon. His technical skill allowed him to put these tubes into the digestive tract of dogs and let them continue eating and digesting relatively normally. This access allowed observation of the working system unlike ever before possible. This access helped Pavlov to discover and describe the mechanism of action of many digestive enzymes.

Some of the surgeries required were quite complex. One of them involved separating layers of the stomach while leaving critical nerves intact, and creating a pouch from which to obtain secretions. This pouch allowed the scientists to collect the secretions without getting any contamination from the food coming in from above (see image).

The tubes placed in the dogs’ mouths would collect saliva that the dog would secrete before, during, and after eating. Pavlov and his lab’s researchers noticed that dogs would start salivating at the sight of the worker who usually fed them. Since these were not in response to anything physically in the digestive tract, Pavlov and his team referred to these as “psychic secretions.”[1] Pavlov was fascinated by the fact that a process in the dog’s brain could result in a physiological change in its digestive tract. Pavlov described psychic secretions as conditional responses, which writers mistranslated as conditioned responses.[2] The difference in that suffix is important—one means the salivation was dependent on the worker’s presence, and the other means that the worker’s presence absolutely trains the salivation—but the mistranslation stuck.

Pavlov summarized the era of his work on digestive physiology leading up to the description of psychic secretions in a collection of nine lectures. These lectures were transcribed and eventually translated by William H. Thompson in 1902.[3] The Work of the Digestive Glands collected in writing most of the work that would earn Pavlov a Nobel Prize in 1904[4]. The Leo J. McCarthy, MD, History of Medicine Room and Collection at the Ruth Lilly Medical Library of the IU School of Medicine is fortunate to have a copy of this English translation on its shelves. It is lovely to feel the pages of this 116-year-old book and think of all the physicians and students this book has helped. After all, the idea that the nervous system is what ultimately controlled digestion opened the doors to psychological study. If a conditional reflex could affect the conditions of the digestive tract, what other psychic reflexes could influence our physiology? Pavlov paved the way for description and treatment of anxiety disorders and emotional disorders, such as post-traumatic stress disorder.[5]

Winning the Nobel Prize transformed Ivan Pavlov into a scientific celebrity in the Russian Empire and abroad. This fame gave him extraordinary freedom in what he studied and with whom he exchanged information.[6] He was able to maintain scientific ties with people all over the world, at a time when the world was not so connected. It allowed him to shift the focus of his work from the physiology of digestion to focus on these newly described psychic secretions.

Pavlov’s laboratory was efficient and prolific. Daniel Todes described it as a “physiology factory.”[7] His laboratory system worked well and was replicated in America by Dr. Horsley Gantt, who created the Pavlovian Society. Over his 62 years of scientific life, Pavlov published 204 scientific articles.[8] Along with his extensive publications on physiology and psychology, and his lasting legacy in Russia, the Pavlovian Society in America serves to continue the tradition of the Pavlovian system.

Ivan Pavlov’s contributions to psychology are significant and vital, but it’s essential to remember physiology was his first love. It was in this field that he received his highest scientific award. The celebrity he gained from this award allowed him to enjoy scientific and personal freedom granted too few in his time. Pavlov’s ability to specialize and shift the focus of his research from Physiology to Psychology is analogous to Jean-Martin Charcot (Neurology/Psychology), Sigmund Freud (Neurology/Psychoanalysis), and Pierre Janet (Psychology/Psychiatry). In his lifetime, Pavlov was able to describe much of what we know about the enzymes of digestion, win a Nobel Prize with the help of his laboratory, lay the foundation for a new direction in psychological conditioning, and develop a system of research that could be passed down for generations. 


This post was written for the course HIST H364/H546 The History of Medicine and Public Health (Instructor: Elizabeth Nelson, IUPUI School of Liberal Arts).



[1]            Buser, Pierre. “Slowly Forgetting the Pavlovian Adventure?” Comptes Rendus Biologies 329, no. 5 (May 2006): 398–405. doi:10.1016/j.crvi.2006.03.010.

[2]            Cambiaghi, Marco, and Benedetto Sacchetti. “Ivan Petrovich Pavlov (1849-1936).” Journal of Neurology 262, no. 6 (June 2015): 1599–1600. doi:10.1007/s00415-015-7743-2.

[3]            Pavlov, Ivan Petrovich. The Work of the Digestive Glands. Translated by William H Thompson. London: Charles Griffin & Company, Limited, 1902.

[4]            Nobel Media AB. “The Nobel Prize in Physiology or Medicine 1904.” (accessed October 7, 2018).

[5]            Cambiaghi, Marco, and Benedetto Sacchetti. “Ivan Petrovich Pavlov (1849-1936).” Journal of Neurology 262, no. 6 (June 2015): 1599–1600. doi:10.1007/s00415-015-7743-2.

[6]            Tansey, E M. “Pavlov at Home and Abroad: His Role in International Physiology.” Autonomic Neuroscience : Basic & Clinical 125, no. 1 (April 2006): 1–11. doi:10.1016/j.autneu.2006.01.013.

[7]            Todes, Daniel P. “Pavlov’s Physiology Factory.” Isis 88, no. 2 (1997): 205–46. Pavlov, 1902.

[8]            Markov, A G. “Bibliographic Analysis of the Scientific Publications of Academician I. P. Pavlov.” Neuroscience and Behavioral Physiology 38, no. 9 (November 2008): 883–86. doi:10.1007/s11055-008-9065-7

[1] Ivan Pavlov, The Work of the Digestive Glands, translated by William H. Thompson. London: Charles Griffin & Company, Limited, 1902, p. 13.

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Jason Lilly