Giaja’s first papers were in the field of physiological chemistry with an emphasis on enzymology and comparative physiology. He focused on mammals and birds, as well as lower animals, particularly marine organisms. His interest in marine animals stemmed from a study visit to the marine laboratory of professor Yves Delage at the Marine Station in Roscoff. He wrote in 1914 of his interest in the chemical phenomena of life and energy of living beings. With this work, Giaja built a foundation of experimental physiology and physiological chemistry (now biochemistry). In his view, the physiology of man and animal were not separate. Thus, he also introduced the principle of physiological studies of phenomena that are common to all living beings, as well as the studies of particular mechanisms that are unique to certain organisms. These studies actually led to the foundation of General Physiology that is taught even today in Giaja’s Institute at the University of Belgrade School of Biology. Some of the major problems that interested him in this period were pancreatic coenzymes, fermentation and digestion processes and the chemistry of carbohydrate metabolism. He also suggested a new rationale for a nomenclature of enzymes.
Andjus PR, Stojilkovic SS, Cvijic G. Ivan Djaja (Jean Giaja) and the Belgrade School of Physiology. Physiol Res. 2011;60 Suppl 1:S1-13. Epub 2011 Jul 19. [link]