testimony to that common source of their first stimulus and earliest enthusiasm, Johannes Müller.
Look as we will through the history of natural science, we do not find an instance where a single individual, gathering about himself a body of select disciples, has by the infusion of his spirit of work sent abroad influences that have ruled so large a part of the territory of natural science. No such influence emanated from Haller, busily engaged in his collections and accumulation of the facts and theories of a century of physiological activity. Nor could it come from Cuvier, excluding from his circle of labor, as he did, the whole field of physiology and embryology, and preoccupied with his foibles of nobility. Nor was such influence from Darwin, secreted in the recesses of his study, modestly content to think, but not to speak. Nor from the combative Huxley, ever at the cannon's mouth with his evolutionary arguments. Nor yet from our more familiar Agassiz, with his noble retinue of followers, and a leader in our own popular thought of natural history though he was. These men have, it is true, been pillars in the development of the biological structure of the present time; yet their fields of labor have been most limited. But it was the nature of the case that it must be so, for no human individual, coming after Müller, could have the same grasp on the ever-extending realm of biological knowledge. Since his time there are few who have become masters of even a single territory.
In these days, when the scientific spirit is throwing its ever-increasing impetus into all lines of human activity, man has little opportunity to look back "to the mountains whence cometh his strength." The source of his to-day's blessings is either wholly overlooked, or, upon special occasions and anniversaries, is (with that feeling which Macaulay has called the "furor biographicus") made to glow in the colors of the sunset. Having avoided, as it is hoped, both of these extremes, we may quickly summarize what, for Johannes Müller, must ever stand as the criterion of greatness: With an all-including glance he was a master of the whole realm of natural science, which he widened until it became too great for its own government. With the certain power of genius, he studied the field of physiology, cleared away the rubbish, breathed into the earth his own spirit, and, in the end, left in the hands of his followers the thrifty seedling of modern comparative physiology, nurtured in the soil of an exact natural scientific method for the investigation of all life phenomena.