The founding father of modern physiology, Claude Bernard, was born on 12 July 1813 in Saint-Julien en Beaujolais in France. This year, we mark his 200th birthday. When Claude Bernard started exploring metabolism and diabetes, strange hypotheses were circulating in the medical community. One of them, formulated by Mialhe, was that glucose was transported by the lymphatic system into the blood and burned there. Some assumed that the lung was the place where this “burning” occurred. In 1845, Claude Bernard wrote in his red notebook, “The digestion of carbohydrates takes place in two steps; first: transformation into glucose, second: glucose is burned in the lung. If this doesn’t happen, diabetes occurs.” Claude Bernard asked, “Is this true?” Quoting Claude Bernard’s own words, let us explore the steps leading to his major discovery: > To clarify this question, I had to find the sugar in the blood, and to look for the sugar from the vessel of the intestine where it is absorbed to find finally the place …