As a successor to the School of Natural Philosophy came the School of Natural History (1831-1850). which made important concessions to realism; its most prominent members were from South Germany. This school was based{250} partially upon the philosophy of Nature, and expired almost suddenly. One of its most eminent exponents was Krukenberg, whose therapeutic creed was that "Physicians should be filled with pious reverence toward Nature; the organism is a whole, and must be contemplated in this sense; medical art is, undoubtedly, capable of decisive action, but let us not mistake that in many cases its activity is quite superfluous, in very many null and inadequate, and in many injurious." This school was the expression of the turn medicine was compelled to take in order to escape the after-effects of the one-sided, ideal, systematizing tendency of the eighteenth century (whose final outcome was natural philosophy), and to square itself with the realism and positivism of the nineteenth. Schonlein (1763-1874), of Bamberg, outlined a system that taught pathological and anatomical revelations as concrete expressions of the independent entity disease, whose relation to the organism is as that of a parasite sojourning temporarily in it; he also constructed a classification of diseases, something after the manner of the botanical classification of de Candolle. One of his best-known pupils was Canstadt (1807-1850), whose _Jahresbericht_ has preserved his name. Siebert, of Jena, famous as a diagnostician, and Haeser, the medical historian, belonged to this school.