Melody may be termed a fusion of rhythm and sounds of different pitches, united in time, and assuming a regular and symmetrical form; melody, as others also have observed, constitutes the whole of music, since without it harmony itself is vague and indefinite. Notwithstanding the numerous elements which may be discerned in melody, and the labour implied in its analysis, it is the facile and spontaneous creation of man, at any rate in its simplest expression; uneducated people, ignorant of music, are able to invent very tolerable melodies, of which we have instances in popular and national songs, which are generated by the musical fancy of those unconscious of the laws of music. Melody has an independent existence, while harmony serves to accentuate its form, and conduces to its subsequent progress among peoples capable of developing it in all its power.[37] Music has a powerful influence upon all the senses. It has at all times been supposed to have a healing power, and in the Middle Ages it was believed to cure epilepsy, madness, convulsions, hysteria, and all forms of nervous affections; while in our own time it is usefully employed in cerebral diseases, since it has both a stimulating and soothing effect. Women, since they are generally more nervous and sensitive than men, are more especially affected by music. Animals as well as man are influenced by it, as it has been shown by exact and numerous experiments. Every one knows that many birds can be taught airs, which they sing with taste and lively satisfaction. The major key, with its regular proportions, its full and gradual sounds, arouses in man a sense of life and joy, while the minor key excites languor and invincible sadness, and animals are affected in the same way. It is evident that the formation of the scale, the essential foundation of music, varies with, the epoch, climate, habits, and physiological conditions of the different races which have successively adopted the diatonic, the major, and minor scales. The music of the Chinese differs from our own, and while it is equally elaborate, it does not quite please us, and the same may be said of the music of the Indians, of the ancient Egyptians, and others. Undoubtedly our scale is more convenient and conformable to art, setting aside the physiological conditions of race, since the notes separated by regular intervals form a more spiritual and independent, in short a more artistic system.