/…/ Many years later we, former friends from the Sorbonne, met in Paris at a scientific conference. One day we gathered for dinner at Lapérouse’s near the Seine where we all used to celebrate our PhD’s. Now we are all professors. One of is at the Collège de France, the other one is at the Sorbonne, the three of them are in Strasbourg, one of them is in Marseille, one is in Lausanne etc. We laugh at our new roles and joke by calling each other „Monsieur le professeur!” because we feel that deep down we remained what we were. What is a man of science but an alumnus! Then, we used to study, read, research, think that we would discover something “big”; that is what we also think and do today. Then, we used to think that we knew more than we know today. (Discovery of the World II, 351p.)

• 1884.He was born on July 21 in L'Havre in Normandy, France. His mother, Delphine, was French and his father Bozidar was a naval captain from Dubrovnik.
• 1890.Djaja’s family returned to Serbia where he finished primary school and the First Belgrade High School For Boys.
• 1902-1903.He spent a year in France where he attended the Lycée Corneille in Rouen.
• 1903-1905.He studied natural sciences at the Sorbonne. In 1914 he became the first correspondent of Politika from Paris
• 1906.At the age of 22 he published his first scientific paper with two associates.
• 1909.Djaja earned his PhD on July 23 1909 after defending his thesis Study on ferments of glycosides and carbohydrates in mollusks and crustaceans” at the Sorbonne (Etude des ferments des glucosides et des hydrates de carbone chez les mollusques et chez les crustacés). Years later he published the following note: “When I earned my PhD degree and came to Onfler, on a Sunday afternoon my grandmother put on some smart clothes, took me by the hand, which she had never done, and we walked down the main street. My grandma was very short and it looked as she was almost hanging on my hand. It was much later that I understood the meaning of this walk, the last walk withthe good old lady: At the time a note entitled “University success of our fellow citizen” was published in the Onfler newspapers and the passers-by greeted us and congratulated us... Over time I realized that the greatest joy in one’s life is when he brings joy to others.” (Discovery of the World II, 352p.)
• 1910.He returned to Belgrade at the invitation of academician Zivojin Djordjevic . He became an assistant professor of physiology at the School of Philosophy of the University of Belgrade. He established the first Chair in Physiology in the Balkans and organized the first Serbian Institute for Physiology.
• 1912.He published his first monograph entitled “Ferments and Physiology”, for which he received an award from the Serbian Royal Academy of Sciences.
• 1914-1918.“When in 1913 I met my friends at the Congress of Physiology in Groningen (the Netherlands), they and many other unfamiliar people gathered around me to find out what the war was like. A year later they had a chance to find out themselves.” (Discovery of the World II, 351p.) In the summer of 1914 Djaja and Sima Lozanic visited university centers (Schools of Agriculture) in Prague, Berlin, Leipzig and Paris. When the war started he was in Vienna and he stayed there until December 1918.
• 1919.He became an associate professor of physiology and physiological chemistry at the School of Philosophy in Belgrade.
• 1921.He became full professor. He became a correspondent member of the Serbian Royal Academy of Sciences.
• 1923.He published his textbook “Fundamentals of Physiology”, the first of a kind in Serbia.
• 1932.He became a full member of the Serbian Royal Academy of Sciences.
• 1934.He was elected the rector of the University of Belgrade. He remained in that position for two years. He protested together with students against the police raid into the University building defending students and the autonomy of the University. According to the testimony of his daughter Ivanka, after the war he told Tito: “I protected them so that they could study and I considered their political rapture only youthful foolhardiness.“
• 1941-1945.During German occupation, in 1941 he was kept prisoner in a concentration camp in Banjica. After being released from Banjica he wrote: “At that time, we believed in the moral value of science. We believed in the permanent development of humankind and science as the most important aspects of advancement. We lived with the ideas of Encyclopedists, Renan, Pasteur and Berthelot. Today I have at least realized that science can serve barbarism of the worst kind. But I have always been convinced that it could inspire the elevation of men and one day that would happen.” (Discovery of the World II, 3510p.) He retired at his own request in 1942 and by the end of the war he led secluded life.
• 1945.He returned to research and scientific work. Since November 1945 he had been professor of physiology, physiological chemistry and general physiology at the School of Mathematics and he was the Head of the Department of Physiology and the Director of the Institute of Physiology. However, the postwar authorities saw Djaja as unsuitable and reactionary, so his file contained the following “he has bourgeoisie origin, he was not active enough during the occupation, he did not respect enough the Soviet science and achievements and he promoted the Western ones.”
• 1952.He became the correspondent member of the National Medical Academy in Paris.
• 1954.He received an honorary doctorate of the Paris University and in that way he became the third person from the territory of Yugoslavia (after Nikola Tesla and Jovan Cvijic) to have earned this academic degree.
• 1955.He became a member of the French Academy of Sciences. He retired for the second time.
• 1957.He died on October 1 at the age of 73.
• 2004.On march 19 the city council adopted a decision on changing the name of 22 streets on the territory of Stari grad and Vracar. One of them was Vlade Zecevica Street in Vracar which changed its name into Ivan Djaja Street.
• 2010.The Faculty of Biology of the University of Belgrade organized a symoposium “100th anniversary of the Ivan Djaja’s Belgrade School of Physiology”. On the occasion of this anniversary a memorial to Ivan Djaja, the work of the sculptor Djordje Arnaut, was set at the Ivan Djaja Street on September 10.

The literature used in this paper can be found in Bibliography and Web bibliography.