Chap. 7. Of the Bones which serve the Sense of Hearing.
THere follow eight other Bones of the Head, which are least of all, on each side four, being the Bones subservient to the sense of Hearing, called from their shapes, Malleus the Mallet or Hammer, Incus the Anvil, Stapes the Stirrup, and the Orbicular bone: all which were unknown to the Ancients. The two first were found out by Jacobus Carpus, who was afterwards followed by Massa, Jacobus Sylvius, and Vesalius: and he being ad∣monished by Fallopius, at last made mention of the third, whose first finder out was Ingrassias; although Eustachius and Columbus do arrogate the Invention hereof unto themselves.
The fourth Auditory Bone, was found out and shewed to me by Franciscus Sylvius, being round and small, and by N. Fontanus likened to the Scale of a Pike: annexed by a small Ligament to the Stirrup side, where it is joyned to the Anvil; which you shall more easily find in the boyled Calves Heads, in which they are bigger than in the Heads of Men: howbeit in a Man it is visible enough. Pavius found in the Head of an Ox a year old, one like this, of a sesamoidean shape.
They are situate in the first Cavity or Concha.
They have a Substance hard and dense, hollow within, that they might be lighter, and might contain in them, Marrow for their nourishment, without any Periosteum about them: also that they might make the Ai•• drie••, and carry it along, like those Ropes which are fastened to doors to make them open and shut again of themselves. They are as perfect in new-born Children as in those that are grown up; though not so hard, but more moist, for which cause Infants are dull of Hearing.
The Connexion. The Hammer by its process sticks fast to the Membrane of the Drum, beyond the middle, like a tail turned back; the head whereof is articulated into the Cavity of of the Anvil, having a small Process, that the Tendon of the Musculus rotundus may be applied thereto; it hath also a longer Process, but smaller, first observed by Caecilius Folius, to which another Muscle is fastened, which belongs to the external Ear. It rests a∣thwart upon the bony circle, with which perhaps it grows together in persons that are of years, for commonly in Children it is only visible, in others it is easily broken be∣cause of its fineness, when the bones are taken out.
The Anvil resembling a grinding Tooth, lies under the Hammer, having beneath two processes; the one shorter resting upon the Os squamosum, the other longer, sustain∣ing the top of the Stirup or triangular bone, which rests upon the Cochlea, till it is sunk into the broad Basis of the Fenestra ovalis, or oval window, to which it is fastned by a loose Ligament, so that it may be lightly raised, but not moved upwards and downwards.
These three little bones, are joyned with a very fine Li∣gament, which is stretched over the whole Membrane, as the strings over the bottom of a Drum.
The Use of these little bones is not to make a sound, but that the species of sound being received, may pass to the lower parts, and that there may be a passage for the excrements of the Ears. For the Stirrup shutting the oval or upper window, is moved by the Anvil (whereupon the window is opened, that the species or representation of Sounds may pass into the Nerve, and the Anvil being smitten by the Hammer, and the Hammer by the Mem∣brane of the Drum, through the impulse of the external Air (which the Hammer hinders from being driven too far forwards) which while it is in doing, the membrane of the Drum is droven inwards▪ and becomes bunching out, whereby the inbred Air is affected, which wandring through the Cochlea causes, that the branches of the Au∣ditory