Pavlov

Pavlov, Ivan Petrovich

ACHIEVEMENTS:

Pioneering studies in the physiology of the gastrointestinal system and the conditioned reflex

NICKNAME/ALIAS:

None

DATE AND PLACE OF BIRTH:

26 September 1849, Ryazan, Russia

DATE AND PLACE OF DEATH AND AGE AT DEATH:

27 February 1936, St Petersburg, Russia. Aged 87

DISCIPLINE:

Physiologist

FIELD:

Physiology

PARENTS:

Father: Peter Dmitrievich Pavlov

Mother: Vavara Ivanovna

SIBLINGS:

3 brothers: Dmitri,, Peter, Serge

1 sister: Lydia

SPOUSE:

Seraphima Vasilievna Karchevskaya

CHILDREN:

3 sons

l daughter

EDUCATION:

Church School, Ryazan

Ryazan seminary

University of St Petersburg

Medico-Surgical Academy

MAJOR WORK:

“Lectures on the Work of the Digestive Glands” (1897)

LIFE AND TIMES:

When he was a boy Pavlov read Charles Darwin’s* “Origin of the Species” which remained an inspiration throughout his life. He also came across a drawing of the digestive tract in “The Physiology of Common Life”, a book written by George Henry Lewes*, the lover of the novelist George Eliot.

Pavlov claimed that this was the origin of his interest in the digestive system. At the age of twenty-one he left his religious seminary and entered the university of St Petersburg where he studied chemistry and physiology and won a gold medal for his investigation of the nerves controlling the pancreatic gland.

In 1875 he accepted a job as assistant to the professor of physiology at the Military Medical Academy but resigned in protest when the professor’s appointment was revoked because he was Jewish. Pavlov then went to run a laboratory which had been set up by the most famous Russian clinician of his time, Dr S P Botkin, the director of the medical clinic of the Academy.

The laboratory was actually a wooden shed in the garden and Pavlov had no official salary but he began to make his name in medical circles when it was realized that all the theses coming out of Botkin’s clinic were based on Pavlov’s work. In 1877 Pavlov won a scholarship for post-graduate study and research at the Academy.

In 1881 he married a student, who knew Turgenev* and Dostoyevsky*, whom Pavlov admired. The Pavlovs lived in extreme poverty, largely because Pavlov wanted to concentrate only on preparing his doctrinal thesis on the nerves of the heart; when friends paid him to give them lectures as a way of providing him with food, Pavlov spent it on buying animals for dissection. He had taught himself to be ambi-dexterous as a child and was a brilliant dissector and surgeon, waving both hands about in what seemed a frenzy and operating at a speed no one else could keep up with. After receiving his doctorate in 1883, Pavlov was appointed lecturer at the Academy and in 1885 selected as one of three students who were sent abroad to study.

In Breslau he studied the gastrointestinal system and in Leipzig he worked in the laboratory of the cardiovascular physiologist Ludwig*. On his return to Russia, Pavlov worked in Botkin’s laboratory in St Petersburg investigating the cardiovascular and digestive systems.

He saw how much nervous excitation was involved in the circulation of the blood and in the digestive system and did everything he could to keep the dogs he used for his experiments in a healthy and stress-free condition. He was one of the first researchers to utilize antiseptic techniques in operations on animals and he also trained his dogs to accept the presence of a tube in the body as normal.

In 1890 he became professor of pharmacology at the Military Medical Academy and a year later was appointed directory of the physiological department at the Institute of Experimental Medicine.

He had perfected a technique by which he created a pouch in a dog’s gullet which received the food taken by the dog through its mouth. The ingested food passed out of the pouch without reaching the dog’s stomach. Meanwhile, any gastric secretions in the stomach could be drawn off for study, uncontaminated by ingested food. The dog could be kept in perfect health for years by being fed by a tube into its stomach.

Pavlov demonstrated that when a dog treated in this way was fed by mouth, it could eat for up to six hours (only stopping when its jaw muscles became exhausted), and its stomach – which had received none of the food – produced a pint and a half of digestive juices. He thus proved that the activity in the stomach was due to nervous stimulation rather than the belief that it was the action of the food on the stomach wall which stimulated production of juices.

The action which produced the most juice appeared to be not the taste, chewing or swallowing of the food, but the sight of the food. Pavlov showed that the vagus nerve was the secretory nerve of the gastric glands. He detailed the different gastric secretions involved in the digestion of varying foods such as meat, break and milk, and he demonstrated the inhibitory effect of fat on gastric secretion, and the ability of starch to stimulate a greater output of juice.

He also defined the three phases of gastric secretion: the nervous, the pyloric and the intestinal. His findings were published in his “Lectures on the Work of the Digestive Glands” (1897).

In 1904 Pavlov was awarded the Nobel prize for physiology and medicine for his demonstration that secretion of the digestive juices in the stomach and the pancreas is controlled by the nervous system and in particular by the vagus nerve.

Pavlov had become interested in the subjective or psychical response of the dogs, as in the production of gastric juices at the mere sight of food. They also produced more saliva at the sight of dry food than at the sight of moist food, a fact which indicated the involvement of higher nervous activity than that related to digestion.

After discarding the possibility of a subjective measurement for his research into psychical behavior, Pavlov fixed on salivary secretion as a scientifically-valid quantitative measure. He used salivation as a way of detecting the presence of psychical nervous activity and of measuring its intensity. His work in this area led him to his formulation of the laws of conditioned reflex for which he is famous.

He had special sound-proof laboratories built where the dogs were isolated from each other and from all external stimuli save that introduced by the researcher in an outside room. In this way, the stimuli which triggered a reflex could be clearly differentiated. He found, for example, that a dog began producing saliva almost immediately after meat powder was put into its mouth.

When the feeding routine was changed and an object was rotated in front of the dog before the food was put in its mouth, it took only about five instances of this new routine before the dog began salivating when the object was rotated and before the meat powder was put into its mouth.

Pavlov named the first type of reflex, caused by the presence of food in the mouth, an unconditioned reflex, and the second type a conditioned reflex. He stated that unconditioned reflexes are innate, conditioned reflexes are acquired through experience. He found both types of reflex to be equally automatic and demonstrated that the conditioned reflex cannot be induced once the cerebral cortex is removed – thus proving the involvement of the brain in conditioned reflexes.

Pavlov also investigated the inhibitory reflex, as seen when his dogs were disturbed by an unaccustomed noise or smell and immediately stopped salivating despite the continued presence of the stimuli which normally induced salivation. He concluded that sleep was the spread of inhibition over the cerebral cortex and that hypnotism was a partial state of inhibition of the cerebral cortex. He also showed that sedatives do not calm excitation, they reinforce inhibitory action in the brain.

Pavlov’s work was interrupted by the Russian revolution and during the winter of 1917/18 many of his dogs died when food became scarce. In 1920 he met the British author H G Wells* who was visiting Russia and who noted the difficulties encountered by academics.

Pavlov was an outspoken critic of the new regime and even requested permission to work overseas. This was refused but Lenin* issued a decree ensuring Pavlov’s welfare in 1921. In 1923 he was granted leave to leave the country to meet scientific colleagues. In America he met the physiologist Cannon* with whom he kept in contact for the rest of his life.

At a scientific conference in Edinburgh Pavlov was given a standing ovation. In 1924 he resigned his chair of physiology in protest at discriminatory actions against the sons of priests, and in 1927 he wrote to Stalin criticizing the treatment of the Russian intelligentsia. Despite this provocation the Russian government continued to support his work which they rightly saw as adding esteem to the state and they built the famous Tower of Silence at the Institute of Experimental Medicine for his work.

From 1929 Pavlov attempted to apply his theories about the conditioned reflex to human behavior. His theory that the catatonic behavior seen in some mentally ill patients was an inhibitory protective reflex influenced psychiatric treatment in Russia where such patients were treated in quiet and non-stimulating environments. In the West, his theories influenced the work of the psychologist Skinner*.

ASSESSMENT: Pavlov’s investigations of the digestive process formed the basis of modern medical and surgical treatment for gastrointestinal disorders. He is better known generally for his formulation of the laws of conditioned reflex.

EXTRA CONNECTIONS: None

ONELINER: IP Pavlov, discoverer of the Pavlovian reaction

BIBLIOGRAPHY:

Barkin, B P, Pavlov, A Biography, Victor Gollanz Ltd., London 1951

Cuny, Hilaire, Ivan Pavlov, The Man and his Theories, Souvenir Press Ltd., London, 1964

Gray, Jeffrey, Pavlov, Harvester Press, Brighton, 1979

Sherwood, Elizabeth and Martin, Ivan Pavlov, Heron Books,Edito-Service, Geneva, 1970