strives for a still purer note than can be strained from human throats, and emulates the host of heaven with its unearthly "voice of angels." Within its breast all the passions of humanity seem to reign in turn. It moans with the dull ache of grief, and cries with the sudden thrill of pain; it sighs, it shouts, it laughs, it exults, it wails, it pleads, it trembles, it shudders, it threatens, it storms, it rages, it is soothed, it slumbers. Such is the organ, man's nearest approach to the creation of a true organism. But before the audacious conception of this instrument ever entered the imagination of man, before he had ever drawn a musical sound from pipe or string, the chambers where the royal harmonies of his grandest vocal mechanism were to find worthy reception were shaped in his own marvellous structure. The _organ_ of hearing was finished by its Divine Builder while yet the morning stars sang together, and the voices of the young creation joined in their first choral symphony. We have seen how the mechanism of the artificial organ takes on the likeness of life; we shall attempt to describe the living organ in common language by the aid of such images as our ordinary dwellings furnish us. The unscientific reader need not take notice of the words in parentheses. The annexed diagram may render it easier to follow the description. [Illustration] The structure which is to admit Sound as a visitor is protected and ornamented at its entrance by a light movable awning (the external ear). Beneath and within this opens a recess or passage, (_meatus auditorium externus_,) at the farther end of which is the parchment-like front-door, D (_membrana tympani_). Beyond this is the hall or entry, H, (cavity of the _tympanum_,) which has a ventilator, V, (Eustachian tube,) communicating with the outer air, and two windows, one oval, _o_, (_fenestra ovalis_,) one round, _r_, (_fenestra rotunda_,) both filled with parchment-like membrane, and looking upon the inner suite of apartments (labyrinth). This inner suite of apartments consists of an antechamber, A, (vestibule,) an arched chamber, B, (semicircular canals,) and a spiral chamber, S, (_cochlea_,) with a partition, P, dividing it across, except for a small opening at one end. The antechamber opens freely into the arched chamber, and into one side of the partitioned spiral chamber. The other side of this spiral chamber looks on the hall by the round window already mentioned; the oval window looking on the hall belongs to the antechamber. From the front-door to the oval window of the antechamber extends a chain, _c_, (_ossicula auditus_,) so connected that a knock on the first is transmitted instantly to the second. But as the round window of the spiral chamber looks into the hall, the knock at the front-door will also make itself heard at and through that window, being conveyed along the hall.