Medical science in the 2nd half of the 19th century proceeded in a stepwise fashion, when the development of new techniques permitted the evaluation of living processes by direct microscopic or endoscopic inspection, as well as by quantitative measurements of the underlying physical and chemical forces. Ludwig, Henle, Helmholtz and DuBois-Reymond all contributed in different ways to the evolution of medicine and physiology into natural sciences, freed from romantic, philosophic speculation. Nephrology benefitted from this development and from the contributions of the non-nephrologists to natural science.