Spallanzani, Treviranus and others were dealing what we may call only the first of a long series of death blows to the hydra-headed theory of spontaneous generation, which was not eventually disposed of until the excellent work of Pasteur, over half a century later, and even now is often found lingering in popular scientific lore.
A consideration of these foregoing facts demonstrates to us that the greater number of these exact researches had been carried on in France and England. When now we turn with special interest to Germany, we find that her scientific thought had been fermenting in that powerful intellectual narcotic, the Naturphilosophie, which, under the great influence of Hegel at Heidelberg and Berlin, was stupefying every branch of accurate scientific research throughout Germany. Of the tendency of this movement to avoid the deductive method of research and to build up a conception of nature upon theoretical and speculative conclusions, we shall speak further. For the present, however, having gained some understanding of the condition of natural science, especially physiology, previous to the period of Müller's greatest activity, let us now consider more in detail Müller's relation to these movements, philosophical and otherwise.
Müller, as nearly every other investigator of his time, was a vitalist; but, as Verworn has said, "Müller's vitalism had an acceptable form." Although to him vital force was different from the forces of lifeless nature, its administration nevertheless followed certain physico-chemical laws. In this, Müller's conception seems to be modeled after the idea of Reil, the leader, as we have said, of the most rational form of the doctrine of vitalism in Germany. Müller maintained his position as a vitalist to the very end. He cherished to the last the thought of the existence of a "life energy." We well know how the activity of his pupils has apparently disproved forever this conception for natural science; and how it has led to the opposite extreme, the rather one-sided materialism of the present day.
When we turn to consider Müller's relation to the Natarphilosophie, we recall how he contracted this spirit while he was at Bonn, and how he was rescued, at least from its extreme influences, by Rudolphi at Berlin. Throughout his Berlin period, Müller devoted much of his thought to freeing natural science from the influence of the Naturphilosophie. The result was that not long after the death of Hegel, in 1831, the dangerous play with mystical words became gradually eliminated from the consideration of life phenomena. From this time on, the problems of living substance were furthered, especially by Müller, with the implements of comparative anatomy, of physics and of chemistry. In bringing about this condition, and in establishing the deductive scientific method as alone admissible in the realm of natural science, we must look upon Müller as a reformer whose work has been of enduring benefit to science. The nature of