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CHAP VII.
_Of the Myology, or Anatomy of the Muscles of the Head._
_How many Muscles are there appointed to move the Head, and which be they?_
The Head is mov"d by the means of fourteen Muscles, seven on each side; of these, two serve to depress it, eight to lift it up, and four to turn it round about.
The two Depressors are call"d _Sternoclinomastoidei_; they take their Rise in the _Sternum_, at the Clavicles, and proceed obliquely to join the _Apophysis Mastoides_.
Of the four Elevators on each side the first is the _Splenius_, which begins at the five _Vertebrae_ of the Back and the three lower ones of the Neck, and ascending obliquely, cleaves to the hinder part of the Head. The second, named _Complexus_ or _Trigeminus_, having its beginning as the _Splenius_, sticks in like manner to the hinder part of the Head, and they form together a figure resembling that of S. _Andrew_"s Cross. The third is the _Rectus Major_, which proceeding from the second _Vertebra_ of the Neck, shoots forward to join the hinder part of the Head. The fourth is the _Rectus Minor_, which begins at the first _Vertebra_ of the Neck, and ends likewise in the hinder part of the Head.
The two Muscles on each side, which move the Head circularly, are the _Obliquus Major_ and {22} _Minor_; the _greater Oblique_ taking its rise from the second _Vertebra_ of the Neck, goes to meet the first; but the _lesser Oblique_ hath its Origine in the hinder part of the Head, and proceeds to join the other obliquely in the first _Vertebra_.
_How many Muscles are there in the Lower-Jaw, and which be they?_
The Lower-Jaw hath twelve Muscles which cause it to move; that is to say, six on each side, whereof four serve to close and two to open it.
The first of the Openers is the _Latus_, which beginning at the top of the _Sternum_, Clavicle, and _Acromion_, cleaves on the outside to the bottom of the Lower-Jaw-Bone. The second of the Openers is the _Digastricus_, which takes its rise in a Fissure lying between the Occipital Bone and the _Apophysis Mastoides_, from whence it pa.s.seth to the bottom of the Chin on the inside.
The first of the Shutters is the _Crotaphites_ or Temporal Muscle, which hath its Origine at the bottom, and on the side of the _Os Coronale_, the _Os Parietale_, and the _Os Petrosum_, from whence it is extended till it cleaves to the _Apophysis Coronoides_ of the Lower-Jaw, after having pa.s.sed above the _Apophysis_ of the _Zygoma_: Its Fibres are spread from the Circ.u.mference to the Center, and it is covered again with the _Pericranium_, which renders its Wounds very dangerous; so that the least Incisions as can be, ought to be made therein.
The second is the _Pterygoideus_ or _Aliformis Externus_, whose rise is in the _Apophysis Pterygoides_, from whence it sets forward till it stick between the _Condylus_ and the Coronal of the Lower-Jaw.
The third is the _Ma.s.seter_, which hath two {23} Sources or Beginnings, and as many Insertions; the first Source thereof is at the Cheek-Knot or Ball of the Cheek, and the second at the lower part of the _Zygoma_. The first Insertion is at the outer Corner of the Jaw, and the second in the middle part, by that means forming the Figure of the Letter X.
The fourth is the _Pterygoideus_ or _Aliformis Internus_, which hath its beginning in the _Apophysis Pterygoides_, and is terminated in the inner Corner of the Jaw; so that Mastication or Chewing is perform"d by the means of these four Muscles.
_How many Muscles are there in the Face, and which be they?_
There are two for the Forehead, call"d _Frontal_, whose Origine is in the upper part of the Head, from whence they descend by streight Fibres, until they are fasten"d in the Skin of the Forehead near the Eye-Brows, where they are re-united: Their Action or Office is to draw the Skin of the Forehead upward, whereto they stick very close.
There are also two others call"d _Occipital_, which have their Beginning in the same place with the preceeding, but they descend backward, and cleave to the Skin of the hinder part of the Head, which they draw upward.
There are two Muscles to each Eye-Lid, one whereof is termed the _Attollens_ or _Elevator_ and the other the _Depressor_. The Elevator takes its rise in the bottom of the Orbit of the Eye, and is fastned by a large _Aponeurosis_ to the edge of the upper Eye-Lid. The Shutter or Depressor, call"d also the _Orbicular_, hath its Origine in the great _Canthus_, or Corner of the Eye, pa.s.seth over the {24} Eye-Lid upward, and is join"d to the lesser Corner of the same Eye, being extended along its whole Compa.s.s.
The Eyes have each six Muscles, _viz._ four _Recti_ and two _Obliqui_; the _Recti_ or streight Muscles are the _Elevator_, the _Depressor_, the _Adductor_, and the _Abductor_. The first of these call"d _Elevator_, or _Superbus_, draws the Eye upward, as it is pull"d downward by the _Depressor_ or _Humilis_; the _Adductor_ or _Bibitorius_ draws it toward the Nose, and the _Abductor_ or _Indignarorius_ toward the Shoulder: All these small Muscles have their Originals and Insertions in the bottom of the Orbit through which the Optick Nerve pa.s.seth, and are terminated in the Corneous Tunicle, by a very large _Tendon_.
The first of the Oblique ones is term"d the _Obliquus Major_, and the other _Obliquus Minor_, because they draw the Eye obliquely. These Muscles cause Children to squint when they do not act together. The _Obliquus Minor_ is fasten"d at the outward part of the Orbit near the great Corner, and draws the Eye obliquely toward the Nose: But the _Obliquus Major_ is fixt in the inner part of the Orbit, and ascends along the Bone to the upper part of the great Corner, where its Tendon pa.s.seth thro" a small Cartilage nam"d _Trochlea_, and is inserted in the little Corner with the lesser _Obliquus Minor_, to draw the Eye obliquely toward the lesser Corner.
The Ear, altho" not usually endu"d with any sensible Motion, nevertheless hath four Muscles, _viz._ one above, and three behind; the first being situated over the Temporal, and fasten"d to the Ear to draw it upward: The three others have {25} their beginning in the _Mammillary Apophysis_, and are terminated in the Root of the Ear, to draw it backward.
There are also three Muscles in the inner part of the Ear, whereof the external belonging to the _Malleus_ or Hammer lies under the exterior part of the Bony Pa.s.sage which reacheth from the Ear to the Palate of the Mouth, being fixt in a very oblique Sinuosity which is made immediately above the Bone that bears the Furrow, into which is let the Skin of the _Tympanum_ or Drum. The internal Muscle lies hid in a Bony Semi-Ca.n.a.l, in the _Os Petrosum_; one part of which Semi-Ca.n.a.l is without the Drum, and clos"d on the top with a Pa.s.sage that leads from the Ear into the Palate. But the other part within the Drum advanceth to the _Fenestra Ovalis_, and is inserted in the hinder part of the Handle of the _Malleus_. The Muscle of the _Stapes_ or Stirrup is also hid in a Bony Tube, almost at the bottom of the Drum, and fixt in the Head of the _Stapes_.
The Nose hath seven Muscles, that is to say, one common and six proper; the common const.i.tutes part of the orbicular Muscle of the Lips, and draws the Nose downward with the Lip. Of the six proper Muscles of the Nose, four serve to dilate it, being situated on the outside, and two to contract it, which are placed in the inside.
The two first Dilatators of a Pyramidal Figure, take their rise in the Suture of the Forehead, and are fasten"d by a large Filament to the _Alae_ of the Nose. The two other Dilatators resembling a Myrtle-Leaf have their Source in {26} the Bone of the Nose, and are inserted in the middle of the _Ala_.
The two Restrictors are Membranous, beginning in the internal part of the Bone of the Nose and adhering to the inner _Ala_ of the Nostril.
The Lips have thirteen Muscles, _viz._ eight proper, and five common: Of the proper there are four for the Upper-Lip, and as many for the Lower: with two common for each, and the odd one.
The first of the proper of the Upper-Lip bears the Name of the _Incisivus_, its Origine being in the Jaw, in the place of the Incisive Teeth and its Insertion is in the Upper-Lip.
The second is the _Triangulis_, Antagonist to the former; its Rise is on the outside, at the bottom of the Lower-Jaw; and it is implanted in the Upper-Lip, near the Corner of the Mouth.
The third being the _Quadratus_, springs from the bottom of the Chin before, and cleaves to the edge of the Lower-Lip.
The fourth is the _Caninus_, Antagonist to the _Quadratus_, beginning in the Upper-Jaw-Bone and being terminated in the Lower-Lip near the Corner of the Mouth.
The first of the common is the _Zygomaticus_, the Origine whereof is in the _Zygoma_ and its Insertion in the Corner of the Mouth, to draw it toward the Ears; so that it is the Muscle which acts when we laugh.
The second of the common is the _Buccinator_ or Trumpeter, which is swell"d when one sounds a Trumpet. It hath its rise at the Root of the Molar Teeth of both the Jaws, and is extended quite round about the Lips. {27}
The odd Muscle, or the thirteenth in number, is the _Orbicular_, which makes a _Sphincter_ round about the Lips to close or shut them up.
The _Uvula_ or Palate of the Mouth hath four Muscles, whereof the two first are the _Peristaphylini Externi_, taking their rise from the Upper-Jaw, above the Left Molar Tooth, and being ty"d to the Palate by a thin _Tendon_.
The two others are the _Peristaphylini Interni_, which have their beginning in the _Apophysis Pterygoides_ on the inside, and likewise stick to the Palate.
The Tongue, altho" all over Musculous and Fibrous, yet doth not cease to have its peculiar Muscles, which are eight in Number.
The first of these is call"d _Genioglossus_, taking its rise in the lower part of the Chin, from whence it is extended till it cleave to the Root of the Tongue before, to cause it to go out of the Mouth.
The second is term"d _Styloglossus_, its Rise being in the _Apophysis Styloides_, from whence it pa.s.seth to the side above the Tongue, to lift it up.
The third bearing the Name of _Basiglossus_, commenceth in the _Basis_ or Root of the _Os Hyoides_, and thence insinuates it self into the Root of the Tongue, to draw it back to the bottom of the Mouth.
The fourth is the _Ceratoglossus_, deriving its Original from the Horn of the _Os Hyoides_, and cleaving to the side of the Tongue to draw it on one side: The Action of these Muscles of both sides together, causeth an Orbicular Motion in the Tongue. To these some add a fifth {28} Pair of Muscles, call"d _Myloglossus_, which serves to draw it obliquely upward.
_What is the Action of the _Os Hyoides_ in the Throat, and how many Muscles hath it?_
The use of the _Os Hyoides_ is to consolidate the Root of the Tongue; and it hath five Muscles on each side, which keep it as it were hung up.
The first of these, call"d the _Geniohyoideus_ hath its beginning in the Chin on the inside, and adheres to the top of the _Os Hyoides_, which it draws upward.
The second is the _Mylohyoideus_, whose Origine is in the inner side of the Jaw, from whence it cleaves side-ways to the Root of the _Os Hyoides_, which it draws upward, and to one side.
The third is the _Stylohyoideus_, which after it hath taken its rise in the _Apophysis Styloides_, is fasten"d to the Horn of the _Os Hyoides_, to draw it toward the side.
The fourth is the _Coracohyoideus_, which springing up from the _Apophysis Coracoides_ of the _Omoplata_, cleaves to the Root and side of the _Os Hyoides_, to draw it downward and to the side.
The fifth is the _Sternomohyoideus_, that hath its beginning in the Bone of the _Sternum_ on the inside and is inserted in the Root of the _Os Hyoides_, which it draws downward.
_How many Muscles hath the _Larynx_?_