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558 pathological, and outlined a classification of new growths which is the basis of all present-day knowledge of tumors.

With his activities as anthropologist-archeologist we are not especially concerned except as they indicate the wide range of his interests. He was one of the founders of the German Anthropological Society, and later its president, and made expeditions with Schliemann to Troy, Egypt, Nubia and the Peloponnese.

Of vast importance to medicine, however, was his establishment of the first pathological laboratory, at the time he returned (in 1855) to Berlin from Würzburg after a political exile of eight years; an exile due to his sympathy with the revolutionary tendencies of 1848. This laboratory was the forerunner of the many which have been founded in the past fifty-five years in all parts of the world, and which have been found essential not only for the purpose of teaching and research, but also in the modern hospital. And again of importance is that influence exerted through his famous pupils such as Leyden, v. Recklinghausen, Cohnheim, Waldeyer, Kühne and Rindfleisch, to mention only the more prominent, who carried his views to other fields and continued his methods. Other great influences were to extend the territory of pathology, as, for examples, Cohnheim's conception of experimental pathology, Weigert's tinctorial methods for the differentiation of cells and tissues, Ehrlich's application of these methods to the study of the blood, Metchnikoff's studies in comparative pathology, and finally the science of bacteriology; but with Virchow remains the credit of having established pathology as a science of university rank.

The third of a century beginning in 1838 with the founding of Liebig's laboratory and ending in 1858 with the publication of Virchow's doctrine of cellular pathology, represents a greater advance in the science of medicine than the combined activities of all the preceding centuries. What was the influence of these advances on the art and practise of medicine? Medicine at the beginning of the century was still influenced by the metaphysical treatment of scientific subjects. The previous century had been one of schools and systems, those of Cullen and Brown in England, Broussais in France and Hoffman and Stahl in Germany. It was also the time of Hahnemann (1753-1844) and the rise of homeopathy. The prevailing tendency was to base disease on the study of symptoms, without regard to the underlying pathological changes causing the symptoms. A few quotations may bring this period of change from the old to the new prominently before you.

Helmholtz writes of the period of his student life: