Claude Bernard wrote An Introduction to the Study of Experimental Medicine. Published in 1865, the book became one of the foundational statements of modern experimental physiology and medical research.
Bernard was a 19th-century French physiologist who emphasized testing ideas through controlled observation and experiment. He argued that medicine should move beyond relying solely on tradition, authority, or observations made without intervention. Researchers should formulate hypotheses, manipulate conditions, and compare results carefully. His approach helped establish physiology as an experimental science rather than merely a descriptive branch of anatomy.
Bernard also introduced the influential idea of the “internal environment,” later called the milieu intérieur. He showed that organisms actively maintain relatively stable internal conditions despite changes outside the body, a concept that helped lead to the modern understanding of homeostasis.
The other choices belong to important scientific traditions but are not the author of this book. Gregor Mendel studied inheritance in pea plants, Charles Darwin developed the theory of evolution by natural selection, and Louis Pasteur made major contributions to microbiology and germ theory. Bernard’s work is especially associated with experimental method, physiological regulation, and the relationship between hypothesis and evidence.