Note u — BOOK IV.

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.

The Hearing of deaf Persons more easily by Means of loud Noises, is another Argument of the Use of the Straining or Relaxation of the Tympanum in Hearing. Thus Dr. Willis (ubi supra) Accepi olim à viro fide digno, se mulierem novisse, quæ licèt surda fuerit, quousque tamen intra conclave Tympanum pulsaretur, verba quævis clarè audiebat: quare Maritus ejus Tympanistam pro servo domestico conducebat, ut illius ope, colloquia interdum cum Uxore suâ haberet. Etiam de alio Surdastro mihi narratum est, qui prope Campanile degens, quoties unà plures Campanæ resonarent, vocem, quamvis facilè audire, & non aliàs, potuit.

Abscisso Musculo [Processus majoris Mallei] in recenti aure, relaxatur [Tympani Membrana]. Valsalv. de Aur. Hum. c. 2. §. 5.

Upon considering the great Difference in Authors Opinions, about the Use of the Parts, and Manner how Hearing is performed, as also what a curious Provision there is made in the Ear, by the four little Bones, the Muscles, Membrane, &c. I was minded (since I penned this Note) to make enquiry my self into this Part, and not to rely upon Authority. And after a diligent search of various Subjects, I find we may give as rational and easie an Account of Hearing, as of Seeing, or any other Sense; as I have shewn in my last cited Note (d) Book VII. Chap. 2. with relation to Birds. And as to Man and Beasts, the Case is the same, but the Apparatus more complex and magnificent. For whereas in Birds, the auditory Nerve is affected by the Impressions made on the Membrane, by only the Intermediacy of the Collumella; in Man, it is done by the Intervention of the four little Bones, with the Muscles acting upon them; his Hearing being to be adjusted to all kinds of Sounds, or Impressions made upon the Membrana Tympani. Which Impressions are imparted to the auditory Nerve, in this Manner, viz. First they act upon the Membrane and Malleus, the Malleus upon the Incus, and the Incus upon the Os Orbiculare and Stapes; and the Stapes upon the auditory Nerve: For the Base of the Stapes (the same as the Operculum in Birds) not only covers the Fenestra Ovalis, within which the auditory Nerve lieth, but hath a Part of the auditory Nerve spread upon it too. It is manifest that this is the true Process of Hearing; because, if the Membrane be mov’d, you may see all the Bones move at the same Time, and work the Base of the Stapes up and down in the Fenestra Ovalis, as I shewed in this Chapter, Note (d) concerning the Mole; and as it may be seen in other Ears carefully opened, if the Parts remain in situ.