In our time, exhibitions of a morbid religious enthusiasm, called forth, or promoted by music, are less common with Christians than with Mohammedans. In the sacred dance of the Dervishes, the music, which is soft and plaintive, represents the music of the spheres; while the Dervishes turning in a circle round their superior, who sits quietly in the centre, represent the planetary system in its relation to the sun. So far, the procedures of these fanatics are intelligible enough; but the words of their songs are so mystic that probably the Dervishes themselves are unable to attach a reasonable meaning to them. Still more extraordinary is the behaviour of the Aissaoua, a kind of Mohammedan fraternity in the Barbary States, who by means of music and dancing work themselves up to a state of ecstasy, in which they fancy themselves to be camels,--or, at any rate, in which they convey to others the impression that they are brutes rather than reasonable beings. As regards Christian sects, certain sacred evolutions of the Shakers, in the United States of North America, are not less extravagant than those of the Dervishes in Egypt or Turkey. Here too, music appears to have an injurious effect upon the people, inasmuch as it excites their morbid emotions. Turning now to our literature on the medical employment of music, we find a number of treatises, the most important of which shall be briefly noticed by their titles. Of such only as are not easily attainable, some account of their contents shall be added. 'Medica Musica: or, a Mechanical Essay on the effects of Singing, Musick, and Dancing, on Human Bodies; Revis'd and corrected. To which is annex'd a New Essay on the nature and cure of the Spleen and Vapours. By Richard Browne, Apothecary, in Oakham, in the County of Rutland; London, 1729.'--This is the second edition, enlarged. The first edition was published without the name of the author. 'Die Verbindung der Musik mit der Arzneygelahrtheit, von Ernst Anton Nicolai.' (The Association of Music with the Science of Medicine, by E. A. Nicolai; Halle, 1745.)--Nicolai was Professor of Medicine at the University of Jena, in Germany. 'Reflections on Antient and Modern Musick, with the application to the Cure of Diseases; to which is subjoined an essay to solve the question wherein consisted the difference of ancient musick from that of modern time;' London, 1749.--The author, Richard Brocklesby, was a physician in London.--A circumstantial account of the contents of this treatise is given in 'Historisch-Kritische Beytraege zur Aufnahme der Musik, von F. W. Marpurg;' Vol. II., Berlin, 1756; p. 16-37. 'Traite des Effets de la Musique sur le corps humain, traduit du Latin et augmente des notes, par Etienne Sainte-Marie;' Paris, 1803.--This is an annotated translation of a dissertation written in Latin by Joseph Ludovicus Roger, and published at Avignon in 1758.