pattern formation The direction given to cells to
form a specific three-dimensional structure in shaping
the development of an organism and its parts.
pattern recognition The identification of patterns in
large data sets using appropriate mathematical method-
ologies.
Pavlov, Ivan Petrovich (1849–1936) RussianPhysi-
ologist Ivan Petrovich Pavlov was born on September
14, 1849, in Ryazan, to Peter Dmitrievich Pavlov, a vil-
lage priest. He was educated first at the church school
in Ryazan, the Ryazan Ecclesiastical High School, and
then at the local theological seminary.
Pavlov abandoned religion for science when he
was inspired by the progressive ideas of the Russian
literary critic D. I. Pisarev, by Ivan M. Sechenov, the
father of Russian physiology, and by the works of
Charles Darwin. In 1870 he enrolled in the physics
and mathematics faculty to take the course in natural
science.
Pavlov became interested in physiology. While tak-
ing the course in natural science, he and a fellow stu-
dent wrote a treatise on the physiology of the
pancreatic nerves that won wide acclaim, and Pavlov
was awarded a gold medal.
In 1875 Pavlov received the degree of candidate of
natural sciences. However, his overwhelming interest in
physiology forced him to continue his studies and
attend the Academy of Medical Surgery. Pavlov won a
fellowship at the academy, and with a position as direc-
tor of the physiological laboratory at the clinic of the
famous Russian clinician, S. P. Botkin, he was able to
continue his research work. In 1881 Pavlov married
Seraphima (Sara) Vasilievna Karchevskaya, a teacher,
the daughter of a doctor. They had four sons and a
daughter. In 1883 he presented his thesis, entitled “The
centrifugal nerves of the heart,” and laid down the
basic principles on the trophic function of the nervous
system. Pavlov showed that there existed a basic pat-
ternin the reflex regulation of the activity of the circu-
latory organs.
In 1890 Pavlov organized and directed the depart-
ment of physiology at the Institute of Experimental
Medicine and spent the next 45 years making it one of
the most important centers of physiological research.
Also, in 1890 he was appointed professor of pharma-
cology at the Military Medical Academy, and five years
later he was appointed to the then-vacant chair of
physiology, which he held until 1925.
Between the years 1891 and 1900, Pavlov did
the bulk of his research on the physiology of diges-
tion at the Institute of Experimental Medicine and
demonstrated that the nervous system played the
dominant part in regulating the digestive process.
Pavlov promoted his research in lectures that he
delivered in 1895 and published under the title Lekt-
sii o rabote glavnykh pishchevaritelnyteh zhelez
(Lectures on the function of the principal digestive
glands) in 1897.
His research on the physiology of digestion led to
the development of the first experimental model of
learning, called classical conditioning. Pavlov’s research
into the physiology of digestion led to the study of con-
ditioned reflexes. In a now-classic experiment, he
trained a hungry dog to salivate at the sound of a bell,
which was previously associated with the sight of food.
He implanted small stomach pouches in dogs to mea-
surethe secretion of gastric juices produced when the
dogs began to eat.
In 1901 he was elected a corresponding member of
the Russian Academy of Sciences, and in 1904 he was
awarded a Nobel Prize for his work in digestion. In
1907 he was elected academician of the Russian Acade-
my of Sciences, and in 1912 he was given an honorary
doctorate at Cambridge University. He held many other
honorary memberships of various scientific societies
abroad. Finally, upon the recommendation of the Med-
ical Academy of Paris, he was awarded the Order of
the Legion of Honor (1915).
After the Russian Revolution, a special government
decree signed by Lenin on January 24, 1921, noted
“the outstanding scientific services of Academician I. P.
Pavlov, which are of enormous significance to the
working class of the whole world.”
The Communist Party and the Soviet government
gave Pavlov and his collaborators unlimited scope for
scientific research and built him a laboratory. Pavlov
summarized his discoveries in his book, Conditioned
Reflexes.Pavlov died in Leningrad on February 27,
1936.Pavlov, Ivan Petrovich 261