A systeme of anatomy, treating of the body of man, beasts, birds, fish, insects, and plants illustrated with many schemes, consisting of variety of elegant figures, drawn from the life, and engraven in seventy four folio copper-plates. And after every part of man's body hath been anatomically described, its diseases, cases, and cures are concisely exhibited. The first volume containing the parts of the lowest apartiments of the body of man and other animals, etc. / by Samuel Collins ...

CHAP. X. Of the Muscles of the lower Jaw.

THe strong and various Motions of the lower Jaw, * 1.1 upward, downward, outward, inward, are rarely accomplished by the diffe∣rent Contractions of Six pair of Muscles, among which the Temporal lead the Van: Upon the Dissection of this Muscle, it is most pleasant to treat the Eyes, * 1.2 with the various course of the Fibres, presenting an elegant Scheme, curiously drawn by Natures fine Pensil, from the acute Process of the lower Jaw to the Skull.

The lower Tendon climbing up into the body of the Muscle, is by little and little, as it were shaved into a thin Expansion, accompanied on each side with fleshy Particles, resembling in a manner the Feathers of Birds, beautifying their Quills. * 1.3

This pair of Temporal Muscles, invested with the Pericranium, for their greater security, do borrow their origen from the several Bones of the Fore∣head, Temples, and Synciput, from which they spring in a thin fleshy be∣ginning, adorned with a Semicircular Figure; and as they descend lower, they grow more Fleshy, and at last thinner again, as they make their near approach to the Os Jugale, which is raised in a segment of a Circle, both to secure, and give reception to the lower region of the Temporal Muscle, which creeping under it, is inserted with a short and strong Tendon, into the acute Process of the lower Jaw, and drawing it upward by a strong Contraction, closeth the Teeth of the upper with those of the lower Man∣dible; which may be acted with so great force, that the Mouth cannot be involuntarily opened, unless by the interposition of an Instrument, which we are constrained to make use of in giving Medicines to Distracted sullen Persons.

This pair of Muscles exert the strongest motion of all the Muscles of the lower Jaw, which is more remarkable in Bruits, then Men; as Lions, Wolves, Dogs, Hogs, and the like, which proceedeth from many large Nervous Fibres, springing from the Third and Fifth pair of Nerves: Where∣upon it is dangerous to make transverse Incisions, chiefly in the lower part of these Muscles, by reason of the great variety of Fibres, seated there; which being wounded Cross-ways, are frequently attended with dangerous and fatal Convulsions: Whereupon our great Master Hypocrates, asserteth the Laxation of the lower Mandible to be fatal, unless it be speedily re∣duced.

The second pair of Muscles appertaining to the lower Mandible, * 1.4 are sti∣led Digastrici, by reason of their double Belly; they take their rise behind and near the Processus Mammiformes, and first grow fleshy, and after dwin∣dle into a Tendinous body in the middle, and afterward are rendred fleshy again; so that they seem a double Muscle, conjoyned in the middle by the mediation of a small round Tendinous substance, and afterward growing fleshy again, are terminated inwardly into the fore and middle part of the Chin, and are Antagonists to the Temporal Muscles, which in their Con∣tractions do close the Teeth and Mouth, by drawing the lower Jaw

upward; but the Digastrici give a contrary motion to them, * 1.5 and by pulling them downward, do open the Teeth and Mouth.

The third pair of Muscles, which concern the lower Mandible, are the Quadrati, and are Muscular Expansions, or Membranes interlined with Mus∣cular substances, and deriving their origen from the upper parts of the Sternon, Clavicle, Scapula, and hinder part of the Neck are inserted with oblique Fibres into the Chin: These also being Antagonists to the Temporal Muscles, do assist the Digastrici: and in their Contractions, do depress the lower Mandible, thereby parting the upper Teeth and Lip from the nether, do open the Mouth.

These Muscles having a contexture of many carnous oblique Fibres, great Care ought to be taken, least they be wounded in a transverse Incision, whence may ensue Convulsions; to which some attribute the cause of a Spasmus Cynicus, * 1.6 because the Musculi Quadrati being chiefly inserted into the Chin, do also transmit some Fibres into the Lips, which being violently Contracted, may contribute somewhat to the distortion of the Mouth.

The fourth pair of Muscles of the lower Mandible, are called Masseteres, and having partly fleshy, and partly Nervous Originations, are derived from the lower and inward region of the Os Jugale, and from the upper Mandible, beginning in a kind of Angle near the Ear, and running along with a broad Origination, and descending, are implanted very broad and strongly into the lower Mandible. * 1.7

These Muscles being furnished with great variety of Fibres running dif∣ferent ways, do by several Contractions move the lower Mandible inward, outward, and forward.

The fifth pair of Muscles serving the lower Mandible, are the Pterigoeidei Interni, short and thick Muscles, arising from the inside of the Processus Pterigoeidei, do terminate with broad and strong Tendons, into the inferior and inside of the lower Mandibles, which they carry outward in their Con∣tractions.

The sixth pair of Muscles subservient to the lower Mandible, * 1.8 are the Pte∣rigoeidei Externi, consisting of double fleshy and Nervous Origens, and take their rise from the outward region of the Processus Pterigoeides, are inserted into the inside of the lower Mandible, and pull them inward in their Con∣tractions.

Notes

• * 1.1

  The lower Mandible hath various moti∣ons celebrated by six pair of Muscles.
• * 1.2

  The various progress of the Fibres of the Temporal Muscles is per∣formed in an elegant order.
• * 1.3

  The Tempo∣ral Muscles do take their ori∣gen from seve∣ral Bones of the Forehead, Temples, and Synciput, and are inserted into the acute process of the lower Mandi∣ble, and do raise it up∣ward.
• * 1.4

  The second pair of Mus∣cles, called Di∣gastrici, take their begin∣ning behind the Mammi∣forme Proces∣ses, and do ter∣minate into the fore and middle part of the Chin, and do pull the lower Jaw downward.
• * 1.5

  The third pair of Muscles ap∣pertaining to the lower Mandible are the Quadrati, and do take their rise from the top of the Sternon, Cla∣vicle, Scapu∣ia, and hinder part of the Neck, and are im∣planted with oblique Fibres into the Chin, and do draw the lower Jaw downward.
• * 1.6

  The fourth pair of Mus∣cles of the lower Mandi∣ble the Masse∣teres, do bor∣row their rise from the Os Jugale, and are inserted into the lower mandible.
• * 1.7

  The fifth pair are the Pteri∣goidei Interni which arise from the inside of Pro∣cessus Pterigoei∣dei, and do terminate in the lower mandible, which they carry out∣ward.
• * 1.8

  The sixth pair of muscles of the lower Mandible, the Pterigoeidei Externi, do arise out of the outward region of the Os Pterigoei∣dei, and are inserted into the inside of the lower Jaw and pull it in∣ward.