new, it is often only necessary to go back to the work of Rokitansky to find that he had observed and accurately described it." (Councilman.) Although he encouraged the development of pathological histology, pathological chemistry and experimental pathology, he took no active part in these subdivisions of pathology and used the microscope but little. He seems to have been content with the establishment of pathological anatomy as a descriptive science.
Between Rokitansky's work and Virchow's cell theory there is no obvious connection. Between Morgagni, Bichat and Virchow we have an interesting link, that formed by the successive theories which placed disease in the organs, the tissues and the cell, respectively. Rokitansky worked with the organs and tissue and had no influence in carrying the quest on to the cell. The influences which led Virchow to the latter are wholly those we have discussed in the story of physiology and its beginnings, the personal influence of Johannes Müller, Schwann's writings and the results of the application to medicine of the methods of physics and chemistry. That he appreciated the importance of the relations of pathology, on the one hand, to physiology, and on the other to clinical medicine is shown in the title of his Archives established in 1847. It is not surprising, therefore, that he was not satisfied with the pathology as merely the descriptive and classifying science of Rokitansky and that he was the first to recognize that pathology was the study of life under abnormal circumstances, and that chemistry, physiology and embryology had a direct bearing on pathology and that the methods of all the other natural sciences should be applied to the elucidation of the problems of pathology and thus to those of medicine.
Virchow's "cellular pathology," as announced in its final form in 1858, must be considered as a general biological principle as important in the field of its application as Darwin's "Origin of Species" published one year later.
It is said that Virchow first began the observations which culminated in his doctrine of cellular pathology in his student days, while serving as an assistant in the eye clinic of the Berlin Hospital. Here he became interested in the fact that in keratitis and wounds of the cornea healing took place without the appearance of plastic exudate. This led to an investigation which indicated the occurrence of repair by the multiplication of preexisting cells. These studies led eventually to his theory, which Lord Lister has described as the "true and fertile doctrine that every morbid structure consists of cells which have been derived from preexisting cells as a progeny." In this theory he brought pathological processes into relation with normal growth, hence his axiom "omnis cellula e cellula." This was the underlying principle, which, following Rokitansky's work in classification, gave pathology a place among the biological sciences. With his cell doctrine as a guide he made many important contributions to histology both normal and
