Such is the plan of the organ of hearing as an architect might describe it.  But the details of its special furnishing are so intricate and minute that no anatomist has proved equal to their entire and exhaustive delineation.  An Italian nobleman, the Marquis Corti, has hitherto proved most successful in describing the wonderful key-board found in the spiral chamber, the complex and symmetrical beauty of which is absolutely astonishing to those who study it by the aid of the microscope.  The figure annexed shows a small portion of this extraordinary structure.  It is from Koelliker’s well-known work on Microscopic Anatomy.

[Illustration]

Enough has been said to show that the ear is as carefully adjusted to respond to the blended impressions of sound as the eye to receive the mingled rays of light; and that as the telescope presupposes the lens and the retina, so the organ presupposes the resonant membranes, the labyrinthine chambers, and the delicately suspended or exquisitely spread-out nervous filaments of that other organ, whose builder is the Architect of the universe and the Master of all its harmonies.

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.