Not less an object of wonder is that curious piece of mechanism, the most perfect, within its limited range of powers, of all musical instruments, the _organ_ of the human voice. It is the highest triumph of our artificial contrivances to reach a tone like that of a singer, and among a hundred organ-stops none excites such admiration as the _vox humana_; a brief account of the vocal organ will not, therefore, be out of place. The principles of the action of the larynx are easily illustrated by reference to the simpler musical instruments. In a flute or flageolet the musical sound is produced by the vibration of a column of air contained in its interior. In a clarionet or a bassoon another source of sound is added in the form of a thin slip of wood contained in the mouth-piece, and called the _reed_, the vibrations of which give a superadded nasal thrill to the resonance of the column of air. The human organ of voice is like the clarionet and the bassoon. The windpipe is the tube containing the column of air. The larynx is the mouth-piece containing the reed. But the reed is double, consisting of two very thin membranous edges, which are made tense or relaxed, and have the interval between them through which the air rushes narrowed or widened by the instinctive, automatic action of a set of little muscles. The vibration of these membranous edges (_chordae vocales_) produces a musical sound, just as the vibration of the edge of a finger-bowl produces one when a wet finger is passed round it. The cavities of the nostrils, and their side-chambers, with their light, elastic sounding-boards of thin bone, are essential to the richness of the tone, as all singers find out when those passages are obstructed by a cold in the head. The human voice, perfect as it may be in tone, is yet always very deficient in compass, as is obvious from the fact that the bass voice, the barytone, the contralto, and the soprano have all different registers, and are all required to produce a complete vocal harmony. If we could make organ-pipes with movable, self-regulating lips, with self-shortening and self-lengthening tubes, so that each tube should command the two or three octaves of the human voice, a very limited number of them would be required. But as each tube has but a single note, we understand why we have those immense clusters of hollow columns. As we wish to produce different effects, sometimes using the pure flute-sounds, at other times preferring the nasal thrill of the reed-instruments, we see why some of the tubes have simple mouths and others are furnished with vibratory tongues. And, lastly, we can easily understand that the great interior spaces of the organ must of themselves furnish those resonant surfaces which we saw provided for, on a small scale, in the nasal passages,--the sounding-board of the human larynx. * * * * *