Russia's contribution to the broader life sciences, from agriculture to biology to medicine, is remarkable. A hundred years ago, the Russian life sciences reached their peak, and world-class physiologist Pavlov and immunologist Metznickov appeared. Then, especially after Lysenko's pseudoscience overwhelmed science with politics, Russia produced other pseudosciences, but since then the most important work in the frontier of life sciences has been basically extinct, and because the discovery of the double helix structure of DNA in 1953 has promoted the life sciences of the world, Russia has so far been a country where the life sciences are basically insignificant. Today's Russian life sciences lag far behind China's. Such a journey is more memorable for pavlov, the greater of digestive physiology and neurophysiology. His work on conditioning also influenced psychology and people's general understanding of themselves.
Written by | Liu Yingying
Editor-in-charge | Li Shanshan
Pavlov, Russian physiologist (courtesy of the National Library of Medicine)
Ivan Petrovich Pavlov was a Russian physiologist and psychologist who constructed the theory of conditioned reflexes and was one of the most influential figures in the development of psychology. In 1904, Pavlov was awarded the Nobel Prize in Physiology and Medicine for his pioneering achievements in the physiology of the digestive system, and he was the first Russian scientist to win the Nobel Prize. Since then, he has still not stopped the pace of research, and has continued to break ground in the world of science, with remarkable achievements. It is no exaggeration to say that Pavlov devoted his life to the scientific research he loved until the last moments of his life.
I am willing to devote all my life to scientific research to contribute to the motherland and people who gave birth to me and nurtured me.
—Pavlov
Childhood and education
Pavlov was born in 1849 in the small city of Ryazan in central Russia. His father was a village priest and his mother was the daughter of a priest. Pavlov was the eldest of eleven children in the family. As the eldest son, pavlov the younger was very sensible, taking the initiative to share the burden of the family, helping his mother with housework, and sometimes taking care of his younger siblings.
From childhood, Pavlov showed curiosity and unusual energy, which he called the "research instinct." Since his father loved to read, there were many progressive writings in the family like Herzen, Chernyshevsky and others. Under the influence of his father, he climbed to the attic as soon as he had time and read his father's collection of books. In addition, he has a wide range of hobbies, such as gardening, cycling, boating, swimming, and these activities occupy all his time every holiday. Although he could go to school at the age of seven, at that time, the mischievous little Pavlov fell off a high wall and was seriously injured, so he did not start formal education until he was 11 years old.
Pavlov Jr. first entered the Ryazan Ecclesiastical School, and four years later entered the Ryazan Seminary. However, inspired by Charles Darwin's theory of evolution and the ideas of Ivan Mikhailovich Sechenov, a famous Soviet physiologist at the time, he abandoned theological research and instead entered the world of science.
Getting Started: "Papa's Little Stomach"
In 1870, Pavlov, who had not graduated, decided to leave the seminary, and at the age of 21, he entered the Department of Physics and Mathematics of St. Petersburg University with an acceptance letter and began to study natural sciences.
At that time, Shechenov was a professor of physiology here, while the young Mendeleev was a professor of chemistry. Pavlov had a mediocre performance in the first two years of university, and in his third year of university, he took the physiology taught by Professor Ilya Cyon, became interested in physiology and experimentation, found the discipline he wanted to major in, and thus threw himself into the arms of physiological research.
Pavlov studied very hard, and in order to make the experiment handy, he constantly practiced with his hands, and gradually he was able to do quite delicate surgeries well and quickly. Mr. Zion admired his talents and often asked Pavlov as his assistant. Under Zion's direction, in 1874 he and his classmate Afanasyev completed their first scientific paper, On the Nerves That Innervate the Pancreas, and won the Gold Medal for Research.
In 1875, at the age of 25 Pavlov completed the course with outstanding grades and received a bachelor's degree in physiology. Out of a keen interest in physiology, Pavlov decided to continue his studies and enrolled at the Imperial Academy of Medical Surgeons, where Pavlov spent more than 40 years. In the physiological laboratory of the famous surgeon Portkin, Pavlov began research on the nerves of the heart. In 1883, Pavlov published "The Efferent Nerves of the Heart", a paper that used the heart nerves he found as an example to illustrate the position of nerves in physiological activity. At the same time, he also found that due to reflexes, circulatory organs can achieve self-regulation, which is an unprecedented discovery. Pavlov was also awarded a doctorate in medicine, a lecturership and a gold medal.
After receiving his doctorate, Pavlov went to Leipzig, Germany, for 2 years to study and worked in the Heidelheim laboratory. At this time the laboratory was using the dog stomach in vitro to study the digestion methods of dogs. Pavlov perfected the technique, using surgical methods to cut out a small sac at the bend of the dog's stomach and open it to the skin, this small stomach does not fall into the food, but still retains the visceral nerves and blood flow supply, so that when the stomach digests food, the activity and secretion of the stomach will be clearly demonstrated through the small stomach, which is the famous "Pap small stomach" technology.
The famous Pap small stomach technique (Source, Front. Physiol, 18 September 2019）
Pavlov then returned to Russia and helped form the Department of Physiology at the Institute of Experimental Medicine of st. Petersburg University, where Pavlov remained the leader for 45 years. Today, the institute has become one of the most important physiological research centers in the world.
"Science requires a double effort from one person, and assuming that each of you has two lives is not enough for you. You have to work with enthusiasm, to carry out your scientific explorations." This is Pavlov's testimonial and a portrayal of his life.
The Nobel Prize is well deserved
In the 1890s, Pavlov chose the subject of studying the physiological condition of the digestive system. In the beginning he studied the stomach of dogs, through the saliva glands to study the saliva secretion of food in dogs under different conditions. In experiments, he noticed that dogs began to secrete saliva before food was brought into their mouths, and began studying what he called "soul secretion." He thought these phenomena were more interesting than the chemical composition of saliva, so he changed the focus of his research and began to observe the digestive activity in animals for a long time.
In order to study the conditions of gastric secretion, Pavlov pioneered the famous pseudo-feeding experiment. He first surgically cut off the dog's esophagus and then left the dog hungry for a while. A day later, Pavlov placed a plate of fresh meat in front of the hungry dog. When the dog saw the fresh meat, he greedily swallowed it. However, after a while, the swallowed meat fell into the plate again. This is because the dog's esophagus has been cut off and meat cannot enter the stomach. After the dog was still greedily eating for four or five minutes, a strange phenomenon appeared, and a large amount of gastric juice flowed out of a rubber tube leading to the dog's stomach.
Gastric juice is constantly secreted, which is caused by the dog's Xth impulse to the cranial nerve, the vagus nerve. Pavlov drew a silk thread on the dog's vagus nerve, and by controlling the thread, he blocked the connection between the brain and the stomach. As a result, although the dog was constantly swallowing fresh meat, the secretion of gastric juice stopped. This is the famous "pseudo-feeding" experiment, which allows people to observe the secretion of the digestive glands of dogs.
Such creativity and skill allowed Pavlov to obtain first-hand information that no one else could obtain. After long-term observation, Pavlov found that the movement of the digestive tract, the secretion of digestive glands, the blood supply of digestive tubes and receptors are all innervated by nerves, and these findings have greatly enriched people's understanding of digestive physiology and neuromodulation. In 1897, the Lecture Notes on the Activity of the Main Digestive Glands was published, an academic work summarizing Pavlov's 20 years of research that soon made him famous all over the world.
In 1904, the Swedish Karolin Medical School awarded Pavlov the Fourth Nobel Prize in Physiology and Medicine, explicitly stating "in recognition of his work in digestive physiology." Through Pavlov's work, the knowledge of digestive physiology was transformed and expanded." This was the first time a physiologist had won a Nobel Prize, and Pavlov was also the first Russian scientist to win a Nobel Prize.
Pavlov experimented with dogs in a laboratory in 1902 (Courtesy Wellcome Library, London)
"Pavlov's Dog"
Who would have thought, however, that these discoveries were merely a prelude to Pavlov's seminal work?
In his study of digestive physiology, Pavlov found that laboratory animals often began to increase the secretion of digestive juices when they saw and smelled food. From the beginning of the 20th century, Pavlov began to study the higher activity of the nerves, and for the first time discovered the activity of the cerebral cortex function. This time, he made a small hole in the dog's gills and placed a thin catheter on one of its salivary glands. When a dog eats and saliva flows, a portion of the saliva flows out through the catheter. Pavlov found through experiments that as soon as food falls into the dog's mouth, it will secrete saliva. This reflexive activity is innate to dogs and all other animals, and Pavlov calls it unconditioned.
In later experiments, it was found that in addition to food stimulation of the mouth will cause the dog's saliva secretion, other food-unrelated stimuli, such as light, sound and other stimuli, can also cause the dog's saliva secretion. The classic experiments that Pavlov did in dogs are believed to be familiar to everyone: from "food - saliva secretion" to "rattle + food - saliva secretion" to "rattle - saliva secretion", the concept of conditioned reflex is still talked about today, and the word "reflex" also appears frequently in everyday language. Pavlov proved that people who have eaten lemons will unconsciously drool when they see or hear the language of the word lemon again, and this drooling reflex is conditional. He calls this "conditioned reflex.".
Pavlov never stopped exploring. Later, in order to deepen the mechanism of the study of the rational reflex in the brain, he observed the laboratory animals that removed the cerebral cortex, confirmed the position of the higher center of the brain in the conditioned reflex, and proposed the concept of nervous system excitation-inhibition. On this basis, Pavlov divided dogs into four neural types according to the differences in dog reaction activity, similar to the "temperament theory" of humans, and explored the differences between different nerve types in the process of neurosis. This brought Pavlov one foot into the threshold of psychology, and although he often expressed his dislike for the "unproven," untouchable kind of psychology, and even trumpeted in the laboratory those who called him a psychologist, his work had a profound and lasting impact on the science of thought and behavior.
From the neuromodulation of low-level physiological activities to the regulation of higher-level neural activities, from "unconditioned reflexes" to "conditioned reflexes", Pavlov has experienced a long and arduous experimental process, and has achieved one amazing result after another with persistent enthusiasm and rigorous academic attitude, laying an important theoretical foundation for digestive physiology.
Even in times of very difficult living conditions, Pavlov placed scientific research at the utmost importance. During the Soviet war, Gorky was entrusted with comforting Pavlov and asking if there was anything that could be done to help or provide. Pavlov replied, "Dogs are needed, dogs!" The situation was so critical that my colleague had to go out on the street to catch a dog! Without mentioning the difficulties of life at home.
Pavlov in the laboratory in 1913 (Source: saint-petersburg)
Missed big finds
True endocrinology was born by William M Bayliss and Ernest H Starling through experiments of 1902-1905, who pointed out the presence and mode of action of secretin. It can be said that Pavlov is only one step away from revealing this basic phenomenon. Because as early as 1894, Pavlov's student Russian physiologist Dolinsky had discovered a phenomenon of secretion beyond innervation. After stripping away a certain concentration of hydrochloric acid in the duodenum of all the innervated nerves, it actually triggered a large amount of secretion of pancreatic juice. But Pavlov always believed that this phenomenon was caused by the nerves not being stripped clean, and still insisted that this was a neural reflex.
After that, the god of chance took care of him again, and another pavlov student, Popielski, cut off the dog's bilateral vagus nerve, bilateral visceral nerve, and damaged bulbar, and the reaction still appeared. He envisions the possibility of a "peripheral reflex center" secreting pancreatic fluid.
In 1901, Papilski discovered that even if all the nerves that connect the dog's pancreas were removed, the hydrochloric acid solution could still cause pancreatic juice to secrete. Papilsky had to revise his own past assumptions as a "local short reflex" and find ways to move the results of the experiment closer to "neurology." Life is always full of regrets, and such an important scientific phenomenon still did not cause Pavlov to think further, and he still insisted that neuromodulation was at work, completely missing the opportunity to reveal the regulation of bodily fluids.
In 1902, after Baylis and Stalin published their discovery of insulin-stimulating, it aroused great interest among physiological scientists around the world and also caused great shock to Pavlov's laboratory workers. This new concept shook the neurotic idea that the digestive glands, which the latter had long enshrined as Guizhang, secreted entirely by neuroregulation, making it difficult for them to accept for a while. On the one hand, they tried to collect the existing evidence to refute this chemical regulation theory, and on the other hand, they carefully repeated the experiments of Bay and Sie. However, insulin is objectively existing and can stand the test of practice.
One of Pavlov's pupils, B.P. Babkin, wrote pavlov's biography with this vivid description: "Pavlov asked one of his students to repeat the experiments of Baylis and Stalin, and Pasteur himself and the other students stood quietly and watched." When pancreatic juice secretion appeared (caused by the extract), Pap walked out of the experimental site and returned to the study without a word. After half an hour, he returned to the laboratory and said with deep regret, "Naturally, people are right." It is clear that we have lost an opportunity to discover the truth."
Pavlov was busy... Pavlov is dying
Few scientists like Pavlov have been able to achieve great success in every field he is committed to. In his more than 60-year scientific career, Pavlov has made remarkable achievements in physiology and psychology: his discoveries on the physiology of digestion have earned him the Nobel Prize; the "conditioned reflex" doctrine he founded has a profound influence, leading directly to the birth of behaviorist psychology; and "Pavlov's dog" has evolved into an idiom for those who do things only instinctively without going through the brain.
For Pavlov, the Nobel Prize, the highest honor in science, summed up only a small part of his work. Pavlov's outstanding achievements have earned Pavlov an extremely high reputation. Pavlov is regarded as a leader by the international physiological community, and the academies of science in 22 countries elect Pavlov as an academician. In 1935, at the age of 86, Pavlov presided over the 15th International Congress of Physiology in the former Soviet Union. At this congress, Pavlov was awarded the title of "Patriarch of Biology of the World".
Pavlov at the 15th International Congress of Physiology in 1935 (source, valentinagurarie)
Pavlov died on February 27, 1936, at the age of 86. A solemn funeral was held for him, his laboratory was preserved as a museum in his honor, and in honor of the great scientist, asteroid 1007 Pawlowia and lunar crater Pavlov were also named after him.
At the time of his death, Pavlov remained sane and continued his research. In the last hours of his life, Pavlov kept a close eye on the deteriorating physical condition, constantly dictate to his assistants sitting next to him the feeling of the decay of life, and he wanted to leave more sensual material for the scientific cause he loved all his life. Pavlov is said to have refused those who came to care for him, "Pavlov was very busy... Pavlov is dying".
Pavlov really managed to devote his whole life to scientific research, to put his words into practice with his actions. He was a great scientist and an immortal legend.