The complete works of John Hunter, F.R.S (Volume 2).

  • Hunter, John, 1728-1793.
Date:
1841
Catalogue details

Licence: Public Domain Mark

Credit: The complete works of John Hunter, F.R.S (Volume 2). Source: Wellcome Collection.

Provider: This material has been provided by the National Library of Medicine (U.S.), through the Medical Heritage Library. The original may be consulted at the National Library of Medicine (U.S.)

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    from the cavity to the eminence, and vice versd; so that while one condyle advances, the other moves backwards, turning the body of the jaw from side to side, and thus grinding between the teeth the morsel separated from the larger mass by the motion first described. In this case the centre of motion lies exactly in the middle between the two condyles. And it is to be observed, that in these slidings of the condyles forwards and backwards, the moveable cartilages do not accompany the condyles in the whole extent of their motion, but only so far as to adapt their surfaces to the different inequalities of the temporal bone: for as these cartilages are hollow on their lower surfaces where they receive the condyle, and on their opposite upper surfaces are convex where they lie in the cavity, but anteriorly, at the root of the eminence, are a little hollowed, if they accompanied the condyles through the whole extent of their motion, the eminences would be applied to the emi- nences, the cavities would not be filled up, and the whole articula- tion would be rendered very insecure. This account of the motion of the lower jaw and its cartilages clearly demonstrates the principal use of these cartilages, namely, the security of the articulation, the surfaces of the cartilage accom- modating themselves to the different inequalities, in the various and free motions of this joint. This cartilage is also very serviceable tor preventing the parts from being hurt by the friction; a circum- stance necessary to be guarded against where there is so much motion. Accordingly I find this cartilage in the different tribes of carnivorous animals, where there is no eminence and cavity, nor other apparatus for grinding, and where the motion is of the true ginglymus kind only. In the lower jaw, as in all the joints of the bod y, when the motion LVZnt ° ltSf ^ eX,tei!t' in any dkec«™> the muscles and igauients are strained and the person made uneasy. The state, therefore, into which every joint most naturally falls, especa ly extremes o7n !^T l^P fa the middle *ate ^wLn the are eouallv vp? °V V* ™e?M * the mUScles and ]igaments the 3 of ttT ■ nCS lt 1S that commoa»y and naturally the teeth of the two jaws are not in contact, nor are the condyles of the lower jaw so far back in the temporal cavities as they cango! Of the Muscles of the Lower Jaw ^rr^treS?; stks sstand ,,se °f the count of the muscles that are the cautesrf ,f ^o. orf'™ * ^ There are five pairs of muscles, each of them camht „f j various motions, according to the situation 7e?hTtP Producing they act singly or in conjunction^ olre 'T *JaW> whe,het them may be so situated as to be canahh. „f • 1 or more of same direction ; but every motion £prodncedTT* r JaW in lhe than one musde at a time. Thu T^aw* to CS^Sd