On the basis of the strict exclusion of the vis vitalis, the demand was raised by Carl Ludwig, Helmholtz, Du Bois-Reymond, and Brucke for a physiology which was causal-analytical and physically and chemically experimental. If, out of these four investigators, we pick Ludwig as the actual founder of modern physiology, the grounds for this must be justified specifically. That modern physiology is not to be contemplated without the works of the three great students of Johannes Muller is explicitly emphasized. However, Carl Ludwig occupies a special position for physiology.