His work on bile practically closes Schwann's career as an investigator. The seven years between twenty and {266} twenty-seven were so full of discovery that there seemed to be great promise for his mature years. Had Schwann died at thirty his biographies would have surely contained lengthy comments on the great discoveries that would undoubtedly have rewarded his efforts in the prime of his powers. Schwann's seeming inactivity has been a fruitful cause for conjecture. The fact of the matter is, however, that original work of a high order is accomplished mainly during the time when activity of the imagination is at its height. There are very few cases in which this acme of inventive effort has lasted more than ten years. Besides this there were certain more material factors that hindered original work. Schwann was a German, yet had to give his lectures at Louvain in French. For several years most of his efforts were devoted to acquiring facility in the language of his adopted country. Then Schwann was not such a teacher as Müller, but the true pedagogue who took seriously to heart the duty of teaching all his students. To do this meant, in the rapidly advancing science of that day, unceasing toil on the part of a conscientious professor. For it was a time of great discoveries succeeding one another with almost incredible rapidity. For ten years Schwann faithfully devoted himself to his teaching duties in the anatomical course at Louvain. He then accepted the chair of comparative anatomy and physiology at Liège, where he continued to lecture for thirty years. As the result of his stay at Louvain there has always been special attention given to biological studies at that university. At the present time there is published there a very well and favorably known biological journal, _La Cellule_, through which many important contributions from the professors and students of the university find their way before the public.