has been developed so far as to arouse in many the belief that psychology should be taught as but a branch of physiology. That Müller saw so clearly the interrelation of these two branches of knowledge is decidedly a point in his favor. His theories were upheld, moreover, by the many facts presented in his works, "Concerning the Comparative Physiology of the Sense of Sight in Man and the Lower Animals," "Regarding the Phantasmal Phenomena of Vision," also "Concerning the Life of the Soul"; and many other references in his "Handbook of Physiology."
Another, and perhaps the greatest, debt which the world of science to-day owes to Müller is for his establishment of physiology upon a comparative basis. This conception did not first arise in Müller, however, but was previously expressed by his teacher, Rudolphi, who had already emphasized the motto: Comparative anatomy is the surest support of physiology. Grasping the fuller significance of this thought, Müller worked throughout his life to uphold the view that physiology can be only comparative; and among the vast number of his physiological works, there are few in which this comparative principle is not more or less clearly expressed.
A further consideration of the nature of Müller's work shows to us the evident necessity of making one concession; and yet one which, under careful examination, may not, after all, detract from the fame which the world accords to him. This is the fact that in spite of his varied activities Müller was never able to make what we may call a scientific discovery of the first rank. We can find issuing from his hand no single observation which, as has often been the case with other so-called great natural scientists, carries down with it through the ages the name of the fortunate discoverer. With the names of Priestley and Lavoisier will ever be linked the discovery of oxygen. The mention of the name Harvey immediately brings to mind the thought of the circulation of the blood, as with the name of Newton we invariably associate the statements of the laws of gravity. But discoveries of equal or even lesser importance can never distinguish the name of Johannes Müller. Even his excellent work on reflex action and the function of the anterior and posterior spinal nerve roots—these do not belong to him alone, for Charles Bell some years before had already promulgated the theoretical law; yet it remained for Müller to prove this law, and by nice experimentation to establish its universal application as a fact. Schwann presented to the world of science that noteworthy discovery that the animal tissue, just as plant organization, is composed of elemental cells; but it remained for Müller to show the highest importance attaching to this discovery, and to lay down the law of the correspondence between embryonic and pathological development.