For a time, in his younger years, Müller appears to have been not all unaffected by the materialistic tendencies so rife in the science of the time. His early anatomical investigations seem to have clouded somewhat his faith in things spiritual. One of the expressions attributed to him before his twenty-fifth year is that nothing exists in the human being which cannot be discovered by the scalpel. It was not long, however, before Müller repudiated this expression and came back to a realization of the importance of the immaterial. Another expression attributed to him, "Nemo psychologus, nisi physiologus," "No one can be a psychologist, unless he is a physiologist," has been often repeated as if Müller meant it in an entirely materialist sense. As a matter of fact, however, it is intended to convey only the idea that no one can really exhaust the science of psychology unless he knows the physiology of the brain, the organ which the mind uses in its functions in this life. The expression is really the foundation of the modern physiological psychology, which is by no means necessarily materialistic in its tendency, and has become a favorite subject of study even with those who appreciate thoroughly the importance of the immaterial side of psychology. Müller seems never to have gotten so far away from the Church as that other great physiologist of the succeeding generation in France, Claude Bernard, who for many years allowed himself to be swamped by the wave of materialism {250} so likely to seem irresistible to a scientist engaged in physiological researches. But, even Claude Bernard came back to the Church before the end, and, under the guidance of the great Dominican, Père Didon, reached the realization that the only peace in the midst of the mysterious problem of life and the question of a hereafter is to be found in a submissive faith of the doctrines of Christianity. Many years ago, when Virchow took it upon himself to say harsh words in public of Catholic scholarship, and to put forward the hampering influence of the Church on intellectual development as a reason for not allowing Catholics to have any weight in educational matters, the organ of the Catholics of Germany, _Germania_, reminded him that his own teacher, the great Johann Müller, the acknowledged father of modern German medicine, and the founder of the fecund scientific method to which so many discoveries in the biological and medical sciences are due, had been brought up and educated a Catholic, had lived all the years of his productive scholarship and fruitful investigation in her bosom, and had died as an acknowledged son of the great mother Church.