Claude Bernard was a French scientist, physician and physiologist. During the early stage of his career, he worked in the laboratory of Francois Magendie, the dominant figure of physiology in France. Later Claude Bernard became professor at the College de France.
He is regarded as one of the most important figures of science of the 19th century. His major book, "L'introduction a l'etude de la medecine experimentale," (Introduction to the study of experimental medicine) appeared in 1865 and is a seminal contribution to the philosophy of science. Claude Bernard's works and methodology laid the foundation for modern experimental physiology. Claude Bernard was convinced that medical advances could be achieved through well-designed physiologic studies coupled with meticulous clinical observations.
Claude Bernard's extensive research studies included several areas of physiology such as the pancreatic function in lipid absorption, glycogenic function of the liver, gastric glands,toxicology with research on curare, and vasomotor nerve action. He also created the concept of "Milieu Interne" (internal environment or homeostasis).
His work on operative methods of research entitled, "lecons de physiologie operatoire," was published posthumously in 1879. The content of the book was based on the "lecons" delivered by Bernard at the College de France. In the preface, Claude Bernard described the division of the book into three sections:
The first section included the operative procedures to localize the different functional phenomena of the organism, meaning an anatomic approach with descriptive physiology. The second section dealt with research studies to explain these physiologic events including the study of physico-chemical properties of the organism. Finally the third section reported his studies on experimental pathology, therapeutics and toxicology.
Lecon 14 is devoted to the experimental studies of the circulatory system. In that chapter, Bernard described his techniques of cardiac catheterization in animal model.
The term cardiac catheterization ("catheterisme du coeur") appeared for the first time in this work.
He explained the different approaches to get access to the right and left sided cardiac chambers. He used the internal jugular vein for the right chambers and the carotid or femoral artery for the left chambers.
He then explained the surgical exposure of the vessels and his technique of catheterization using specially designed probes. He also described the difficulty to cross the aortic valve in order to enter the left ventricle.
These probes were designed to measure the pressure and the temperature in different parts of the circulatory system and within the cardiac chambers. In 1844, Bernard inserted a mercury thermometer into the carotid artery of a horse and advanced it into the left ventricle and measured the temperature of the blood. He also recorded the blood temperature in the right ventricle after the insertion of the thermometer into the jugular vein and studied temperature differences between the right and left ventricles. The results of these investigations were described in detail in his monongraph, "lecons de physiologie operatoire." Claude Bernard was the first to measure intracardiac pressures in the living animal in 1847.