However that may be, the fact was that under these alluring attractions Haeckel’s studies were drifting from the medical profession to an “impecunious art.” But as medical work had been chosen, if only as a temporary occupation, Haeckel had to tear himself away from the great magnet, at the Easter of 1855, by removing to a different place. He chose, as the least intolerable compromise, to return to Würtzburg. At all events we find him spending three terms there. I have already said that Rudolf Virchow was one of the distinguished Würtzburgers at the time who sought most keenly the solution of the new problems of biology on the medical side. Hence Virchow had to help him to find the bridge between the work he really loved and the work he was obliged to do. As a fact, Virchow directed the whole of his studies on this side in the three terms. Virchow was not so fascinating as Johannes Müller, even in his best years. But it was something to be initiated into medical science by such a man. A later generation has, unfortunately, grown accustomed to see mental antipodes in Virchow and Haeckel. In 1877 they had a controversy with regard to the freedom of science that echoed through the whole world of thought. Yet seventeen years afterwards Haeckel himself (who was first attacked by Virchow), looking back on the days he spent at Würtzburg, had nothing but grateful recognition to say of Virchow. “I learned,” he says in 1894, “in the three terms I spent under Virchow the art of the finest analytic observation and the most rigorous control of what I observed. I was his assistant for some time, and my notes were especially praised by him. But what I chiefly admired in him at Würtzburg was his wide outlook, the breadth and philosophic character of his scientific ideas.” The theory that Virchow put before his pupils was pure Monism, or a unified conception of the world without any distinction of physical and metaphysical. Life was defined, not as a mystic eccentricity in an orderly nature, but plainly as a higher form of the great cosmic mechanism. Man, the object of medical science, was said to be merely a higher vertebrate, subject to the same laws as the rest.