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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    brought to one side, either the masseter, temporal, or pterygoideus internus of the opposite side will not only raise the jaw but bring it to its middle state. It will be necessary in the description of each muscle to give its use in the different situations of the jaw, by which means, after they are all described, their compound actions will be better understood. I shall first describe those which raise the jaw ; then those which give it the lateral motion ; and lastly, those which depress it; proceeding in the order in which they present themselves in dissection. The most superficial is the masseter: it is situated upon the posterior and lower part of the face, between the cheek-bone and angle of the lower jaw, directly before the lower part of the ear. It is a thick, short, complex muscle, and a little flattened : it appears to have iwo distinct origins, an anterior and outer, and a posterior and inner; but that is owing only to its outer edge at its origin being slit, or double, and the fibres of these two edges having a different course, decussating each other a little. The anterior and outer portion of the muscle begins to rise from a small part of the lower edge of the malar process of the maxillary bone, adjoining to the os~mala3 ; and continues its origin all along the lower hori- zontal edge of this last bone to the angle where its zygomatic process turns up to join that of the temporal bone. The external layer oi fibres in this portion is tendinous at its beginning, while the internal is fleshy. The posterior and inner portion of this muscle begins to rise, partly tendinous and partlv fleshy, from the same lower edge of the os mate: not where the origin of the other portion terminates, but a little further forwards; and this origin is continued along the lower ed^e of the zygomatic process of the temporal bone, as far backwards as the eminence belonging to the articulation of the lower jaw. , . , . From this extent of its origin the muscle passes downwards to its insertion into the lower jaw. The anterior external portion is broader at its insertion than at its origin; for it occupies a trian- gular space of the lower jaw; which, above the angle and on the outside! is about an inch in breadth, but below about an inch and a half from the angle towards the chin. In consequence of this extent of insertion! the fibres of this portion divaricate very consi- derably They are mostly fleshy at their insertion, a few only bein- tendinous, particularly those that are inserted backwards. The'posterior and inner portion of the masseter is narrower at its insertion than at its origin : its posterior fibres running forwards as well as downwards, while its anterior run almost directly down- wards It occupies in its insertion the remaining part of the scabrous surface above the angle of the lower jaw, which lies hetween the anterior portion and the two upper processes, viz. the rondvle and coronoid. As the anterior fibres of this portion rise nn the inside of the posterior fibres of the other portion, and as its posterior fibres run forwards as well as downwards, and its ante-