[p] Valsalva hath given us a more accurate Description of the Tuba Eustachiana, or Passage to the Palate, than any other Author, to whom I therefore refer, De Aur. Human. c. 2. §. 16, &c.
The chief Use hereof, he thinks, is to give way to the inner Air, upon every Motion of the Membrana Tympani, the Malleus, Incus and Stapes. This Passage, if it be shut up, Deafness ensues: Of which he gives two Instances: One a Gentleman, who lost his Hearing by a Polypus in the Nose reaching to the Uvula; the other a Yeoman, labouring with an Ulcer above the left Side of the Uvula; which when he stopt with a Tent dipped in Medicine, he lost his Hearing in the left Ear, and recovered it, as soon as the Tent was out. Ibid. c. 5. §. 10.
[q] Os [petrosum] ex quo interiores [Labyrinthi] cavitatum parietes conflati sunt, album, durissimum, necnon maximè compactum. Id autem à Naturâ ita comparatum esse videtur, ut materia ætherea Sonorum objectorum impressionibus onusta, dum prædictis impingitur Parietibus, nihil aut saltem ferè nihil motûs sui amittat, atque adeò illum qualem ab Objectis sonoris accepit, talem communicet spiritui animali contento intra expansiones rami mollioris Nervorum auris. Dr. Raym. Vieussens of Montpellier, in Phil. Trans. Nᵒ. 258.
[r] The Tympanum of the Ear, or as Valsalva and the Moderns, the Membrana Tympani was taken notice of as early as Hippocrates’s Time. In Birds, it is strained towards the outward Parts; in other Animals towards the Brain, or inner Parts. Monsieur Dionis saith, It is not equally fastened to the whole Circumference of the bony Circle, in which it is inchased; for on the upper Side it hath a free disengaged Part, by which some can give vent to the Smoak in their Mouth. Demonstr. 8. That there is some Passage I doubt not, but I question whether Monsieur Dionis ever saw the disengaged Part he mentions. I have my self carefully searched divers Subjects, and do not remember to have seen any such Passage; and I perceive it escaped the diligent Schelhammer’s Eye. Valsalva also by injecting in through the Tuba Eustachiana, could not force any Liquor into the Meatus Auditorius; but yet he imagines he found the Passage out in another Place of the Drum, in some morbid, and one sound Head. Valsalv. de Aur. Hum. c. 2. §. 8. Mr. Cowper also affirms there is a Passage by the upper Part of the Membrane. Anat. Ap. Fig. 8.
[] Dr. Vieussens, before-named, discovered a Membrane, tenuissimæ raræque admodùm texturæ intra cavitatem Tympani; as he describes it. Whose use he saith is, 1. Occludens Labyrinthi januam impedit nè naturalis purissimus ac subtilissimus Aer intra cavitates——communicationem——habeat cum aere crasso. 2. Labyrinthi basin calefacit, &c. ubi supra. Probably this double Membrane may be such, or after the same Manner as it is in the Tympanum of Birds: Of which see my Observations in [Book VII. Chap. 2. Note (d).]
[t] The four little Bones being treated of by all that have concerned themselves about this Sense of Hearing, since their Discovery, I shall take Notice of only two Things concerning them. 1. The Discovery of them is owing wholly to the Diligence and Sagacity of the latter Ages; of which Schelhammer gives this Account from Fallopius, Hæc Officula antiquis Anatomicis——ignota fuere; primusque qui in lucem produxit [Malleum & Incum] fuit Jac. Carpensis; primus quoque procul omni dubio Anatomicæ artis, quam Vesalius posteà perfecit, restaurator. Tertium [Stapedem] invenit ac promulgavit primus Joh. Phil. ab Ingrassia, Siculus, Philosophus ac Medicus doctissimus. Quartum, Thomâ Bartholin. teste, viro longè celeberrimo, Fran. Sylvio debetur Schel. ubi supr. c. 3. §. 9. 2. Their Difference in Animals: In Man, and Quadrupeds, they are four, curiously inarticulated with one another; with an external and internal Muscle to draw, or work them, in extending, or relaxing the Drum; but in Fowls the Case is very different: His unum Ossiculum solùm largita est Natura, quod Collumellam fortè appellaveris: teres enim est & subtilissimum, basi innitens latiori, rotundæ. Huic adnexa est cartilago valde mobilis, quæ in Tympanum videtur terminari. Id. Ib. §. 8. In the Ears of all the Fowl that I could examine, I never found any more than one Bone, and a Cartilage, making a Joynt with it, that was easily moveable. The Cartilage had generally an Epiphyse, or two, one on each Side.——The Bone was very hard and small, having at the end of it a broad Plate, of the same Substance, very thin, upon which it rested, as on its Basis. Dr. Al. Moulen in Phil. Trans. Nᵒ. 100.
These are the most material Things I find observed by others, concerning the Ears of Fowls, and some of them hardly, I believe, observed before. To which I shall subjoyn some other Things I have my self discovered, that I presume escaped the Eyes of those most curious and inquisitive Anatomists. Of which the last cited [Book VII. Chap. 2. Note (d).]
[] Videtur quòd Tympanum Auditionis instrumentum præliminare, & quasi præparatorium fuerit, quad Soni impressionem, sive species sensibiles primo suscipiens, eas in debitâ proportione, & aptâ conformitate, versùs Sensorium, quod adhuc interiùs situm est, dirigat: simili officio fungitur respectu Auditûs, ac tunicæ Oculi Pupillam constituentes, respectu Visûs; utræque Membranæ Species sensibiles refringunt & quasi emolliunt, easque Sensorio non nisi proportionatas tradunt, cui nudo si adveniant, teneriorem ejus crasin facilè lædant, aut obruant. Reverà Tympanum non audit, sed meliori tutiorique Auditioni confert. Si hæc pars destruatur, Sensio adhuc aliquamdiu, rudi licèt modo, peragi possit; quippe experimento olim in Cane facto, &c.——Janitoris officio ut Tympanum rectè defungi possit, expansum ejus pro datâ occasione stringi, aut relaxari debet, veluti nimirùm Oculi Pupilla——Quapropter huic Auris Tympano, non secus ac bellico, machinæ sive tæniæ quædam apponuntur, quæ superficiem ejus modò tensiorem, modò laxiorem reddant: hoc enim efficiunt tria Ossicula, cum Musculo, &c. Willis’s de Anim. Brut. c. 14.
For this Opinion of Dr. Willis, Dr. Schelhammer is very severe upon him, deriding the Refractions he speaks of; and therefore seriously proves that they are the Humours, not Tunicks of the Eye, that refract the Rays of Light; and then jeeringly demandeth, Whether the sonorous Rays are refracted by passing through a different Medium? Whether the Convexity or Concavity of the Drum collects those Rays into a focal Point, or scatters them? &c. And then saith, Ob has rationes à clariss. Viri, ac de re Medicâ præclarè meriti, sententiâ non possumus non esse alieniores; in quo uti ingenium admiror, quoties medicamentorum vires, aut morborum causas explicat, sic ubi forum suum egressus, Philosophum agit, ac vel Partium usum, vel Chymicarum rerum naturam scrutetur, ejus haud semel non modò judicium desidero, verùm aliquando etiam fidem. This is so severe and unjust a Censure of our truly famous Countryman, (a Man of known Probity) that might deserve a better Answer; but I have only Time to say, that although Dr. Schelhammer hath out-done all that wrote before him, in his Book de Auditu, and shewed himself a Man of Learning and Industry; yet as our Countryman wrote more than he, (though perhaps not free from Errors too) so he hath manifested himself to have been as curious and sagacious an Anatomist, as great a Philosopher, and as learned and skilful a Physician, as any of his Censurers, and his Reputation for Veracity and Integrity, was no less than any of theirs too. But after all this terrible Clamour, Dr. Schelhammer prejudicately mistaketh Dr. Willis’s Meaning, to say no worse. For by utræque Membranæ refringunt, Dr. Willis plainly enough, I think, means no more than a Restriction of the Ingress of too many Rays; as his following explicatory Words manifest, viz. refringunt, & quasi emolliunt, easque Sensorio non nisi proportionatas tradunt. But indeed Dr. Schelhammer hath shewn himself a too rigid Censor, by making Dr. Willis say, the Ear-Drum hath such like Braces as the War-Drum, viz. Quod porrò de machinis seu tæniis Tympani bellici adducit, dicitque idem in Tympano auditorio conspici, id prorsus falsissimum est. I wonder Dr. Schelhammer did not also charge Dr. Willis with making it a Porter, since he saith in the same Paragraph, Janitoris officio, &c. But Dr. Willis’s Meaning is plain enough, that the little Bones and Muscles of the Ear-Drum do the same Office in straining and relaxing it, as the Braces of the War-Drum do in that. And considering how curious and solemn an Apparatus there is of Bones, Muscles, and Joynts, all adapted to a ready Motion; I am clearly of Dr. Willis’s Opinion, that one great Use of the Ear-Drum is for the proportioning Sounds, and that by its Extension and Retraction, it corresponds to all Sounds, loud or languid, as the Pupil of the Eye doth to several Degrees of Light: And that they are no other than secondary uses assigned by Dr. Schelhammer, as the principal or sole Uses of keeping out the external colder Air, Dust, and other Annoyances; but especially that, ob solius aerís interni potissimùm irrumpentis vim, hunc motum Tympani ac Mallei esse conditum, ut cedere primùm, deinde sibi restitui queat; as his Words are, P. ult. c. 6. §. 13.
It was no improbable thought of Rohault, nos attentos præbere, nil aliud est, nisi Tympanum, ubi ita opus est facto, contendere aut laxare, & operam dare ut illud in eâ positione intentum stet, in quâ tremulum aeris externi motum commodissimè excipere possit. Roh. Phys. p. 1. c. 26. §. 48.