some electrical phenomenon connected with that state. Du Bois-Reymond constructed with his own hands a galvanometer of 24,000 coils, by far the most sensitive ever made up to that time, and by its means succeeded in disclosing an electrical phenomenon in the tetanized nerve, which, for certain reasons we cannot here explain, he styled the negative variation of the nerve-current. In point of fact, he transmuted into a deflection of the galvanometer that molecular change in the nerve which, had it reached the muscles, would have convulsed them, and which, had it reached the brain, would have caused pain. He also decided the long-vexed question whether the nervous fibres conduct only in one direction, or in both, by showing that the negative variation is equally well transmitted in a motor nerve in the centripetal, and in a sensitive nerve in the centrifugal direction.
Soon after the publication of his "Researches," Du Bois-Reymond, then thirty years old, was elected a member of the Royal Academy of Sciences of Berlin. As already stated, he has ever since pursued and extended his investigations; but it is impossible, in the compass of this brief notice, more fully to detail their results. Moreover, those of our readers who may feel interested in the subject will find a conscientious exposé of most of Du Bois-Reymond's papers in the book of one of our countrymen, of whose talents science has been robbed by a premature death—Mr. Charles E. Morgan, author of "Electro-Physiology and Therapeutics" (New York, William Wood & Co., 1868). These results will also be found in Prof. Rosenthal's German treatise on the "Physiology of Muscles and Nerves," contributed to the "International Scientific Series," and soon to be published in this country. Du Bois-Reymond's papers have also been collected in two volumes, under the title "Gesammelte Abhandlungen zur allgemeinen Muskel-und Nervenphysik" (Leipsic, Veit & Co., 1875-'77).
Several of Du Bois-Reymond's papers bear merely upon electricity, without reference to physiology. We will only mention his experimental and theoretical researches on the aperiodic state of the magnetic needle induced, under certain circumstances, by high dampening powers; these researches are of the greatest practical importance. Du Bois-Reymond also showed, contrary to what Berzelius and Liebig had stated, that the substance of muscles when at rest is neutral, or slightly alkaline, becoming acid only after death, when rigor mortis sets in, but that also in the act of contraction acid is evolved.
In 1858 John Müller died, and Du Bois-Reymond was appointed in his place Professor of Physiology in ordinary, and Director of the Physiological Laboratory at the University of Berlin. In this position he has exercised a considerable influence on the progress of physiological study in Germany. Many of the professors of physiology at the other German universities have been his pupils; and this influence has been increased by the friendship which has always connected him closely with his fellow-students Brucke, Helmholtz, and Ludwig—all of them physi-
