Stamen Grigorov (1878–1945), a Bulgarian student of medicine in Geneva, first examined the bacteria in Bulgarian yogurt. In 1905 he said that it contained a round and a rod-like lactic acid-producing bacteria. In 1907 the rod-like bacteria was called "Lactobacillus bulgaricus" (now "Lactobacillus delbrueckii subsp. bulgaricus"). The Russian Nobel laureate biologist Ilya Ilyich Mechnikov, from the Pasteur Institute in Paris, was influenced by Grigorov's work and made a hypothesis that eating yoghurt regularly was the reason why Bulgarian peasants lived for so long. Mechnikov believed that "Lactobacillus" was needed for good health, and worked to make yoghurt popular through Europe.