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lower fibres alone of the orbicularis contract, and the lower | the mouth and pharynx are continuous with each other, lid is elevated. The elevation of the upper lid, as in whilst in front the buccinator blends with the structures in opening the eye, is due to the levator palpebre superioris, the lips. It compresses the cheeks, and drives the air out which, arising within the orbit, is inserted into the upper of the cavity of the mouth as in playing a wind instrueyelid. Muscles are inserted into the framework of the ment; hence the name,“ trumpeter's muscle." nostrils so as to increase or diminish the size of their The aperture of communication between the mouth and orifices, and thus to promote or impede the passage of air pharynx is named the isthmus of the fauces. It is bounded into the nose. The size of the orifice is increased by below by the root of the tongue, on each side by the tonsils, two elevator muscles inserted into the ala, or side of the and above by the soft palate. The soft palate is a structure nostril ; and when violent exercise is being performed, or which hangs pendulous from the posterior edge of the hard respiration is from any cause impeded, the nostrils are bony palate. From its centre depends an elongated body, always widely dilated. One of these elevator muscles, the uvula, and from each of its sides two folds extend, one which also sends a slip down to the upper lip, and is con downwards and forwards to the tongue, the other downsequently called the common elevator, is the muscle by wards and backwards to the pharynx. These folds are the contraction of which a sneer is expressed. A partial called the anterior and posterior pillars of the fauces or closure of the nostril can be effected by small muscles palate. Between the anterior and posterior pillar, on each which depress and compress the alæ of the nose : in man side, the tonsil is seated. The soft palate and its pillars are these muscles are rudimentary as compared with the seal invested by the mucous lining of the mouth and pharynx, and other aquatic mammals, in which a powerful sphincter and contain small but important muscles. The muscles of muscle closes the nostrils in the act of diving. The lips the soft palate and uvula, termed the elevators and tensors, can be elevated or depressed so as to close or open the raise and make them tense during the process of deglutition. mouth; they can be protruded or retracted, or the corners The muscles of the posterior pillars, or palato-pharyngei, by of the mouth can be drawn to one side or the other, by their contraction, approximate the walls of the pharynx to the action of various muscles which are inserted into the soft palate and uvula, whilst the muscles of the anterior these movable folds of the integument. The orbicularis pillars, or palato-glossi, diminish the size of the fauces. oris is a sphincter muscle, the fibres of which lie both The pharynx is a tube with muscular walls, lined by a Muscles of in the upper and lower lips; by its contraction the mucous membrane, which communicates above and in front pharynx. mouth is closed and the lips pressed against the teeth, with the cavities of the nose, mouth, and larynx, whilst as when a firm resolution is intended to be expressed. below it is continuous with the esophagus or gullet. It The mouth is opened by the elevator muscles of the upper serves as the chamber or passage down which the food and the depressors of the lower lip; it is transversely elon- goes from the mouth to the cesophagus in the act of gated by the zygomatic and risorius muscles, which pass to swallowing, and through which the air is transmitted from its corners, and which are brought into action in the acts the nose or mouth to the larynx in the act of breathing. of smiling and laughing. But the muscles of the lips also It lies immediately behind the nose, mouth, and larynx, play an important

and in front of part in connection

the five upper with the rec ption

cervical verteof food into the

bræ. Its length mouth, and with

is from 41 to 5 the act of articula

inches; its widest tion.

part is opposite The cavity of

the back of the the mouth forms

mouth. The printhe commence

cipal muscles in ment of the ali

its walls are callmentary canal,

ed the constricand is lined by a

tors, and soft mucous mem

named, from brane. In it the

above downteeth and tongue

wards, superior, are situated, and

middle, and ininto it the secre

ferior. They are tion called saliva

arranged in is poured. It

pairs, and arise opens behind into

from the cartilthe pharynx. The

ages

of the side walls of the

larynx, from the mouth are called

hyoid bone,lower the cheeks, and

jaw, and internal into the formation

pterygoid pro

Fig. 21.--Interior of the pharynx, seen by opening its of each cheek a

cess of the sphe- posterior wall, a, a, Eustachian tube ; 0, 0, tensor; < flattened quadrila

noid; whilst the

levator palati; d, levator uvalæ; e, palato-pharyngeus; Fig. 20.-Profile of cheek and pharynx, a, buccinator;

s, palato-glossus; g, h, k, the three constrictors; 1, Xtonteral muscle, the

0, tensor; c, levator palati; 2, e, f, superior, middle; superior also buccinator, enters. and inferior constrictors; %; thyro-hyoid: h, hyo springs from the fibrous band to which the buccinator is This muscle is at pharyngeus; o, stylo-glossus ; 9, fibrous band which attached; their fasciculi curve backwards to the middle line tached above and gives origin to buccinator and superior constrictor; i, glosso-pharyngeal nerve; 2, superior laryngeal

of the posterior wall of the pharynx, to be inserted into a below to the upper artery; 3, superior laryngeal nerve; 4, its branch to tendinous band which extends longitudinally along this and lower jawcrico-thyroid; 5, inferior laryngeal nerve and artery.

wall of the tube. bones, behind to a fibrous band, to which the upper The action of the muscles of the mouth, palate, and constrictor muscle is also connected, so that the walls of pharynx may now be considered in connection with the

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Process of process of deglutition or swallowing. When the food is rotated on the clavicle in the act of elevating the arm swallow received into the mouth, it is moistened by the secretion of above the head. The muscles which cause these moveing.

the salivary and other buccal glands, and is broken down ments are inserted into the bones of the shoulder girdle;
by the grinding action of the molar teeth. The buccinator the trapezius into the clavicle, acromion, and spine of the
muscles press it from between the gums and the cheek, scapula; the rhomboid, levator anguli scapulæ, and serratus
and, along with the movements of the tongue, aid in col- magnus into the vertebral border of the scapula; the
lecting into a bolus on the surface of that organ. Dur- pectoralis minor into the coracoid; and the subclavius into
ing the process of mastication the palato-glossi contract so the clavicle. Elevation of the entire shoulder, as in
as to close the fauces. When the bolus is sufficiently tritu- shrugging the shoulders, is due to the contraction of the
rated and moistened, the palato-glossi relax, the tip of the trapezius, levator scapulæ, and rhomboideus; depression
tongue is pressed against the roof of the mouth, and by a partly to the weight of the limb and partly to the action of
heave backward of that organ the bolus is pressed through the subclavius and pectoralis minor; movement forward to
the posterior orifice of the mouth into the pharynx, where the serratus and pectoralis; and backward to the trapezius
it is grasped by the superior constrictor muscles, and forced and rhomboid. In rotation of the scapula on the clavicle,
downwards by them and the other constrictor muscles into the inferior angle of the scapula is drawn forward by the
the csophagus, and thence into the stomach. As both serratus and lower fibres of trapezius, and backward by the
the nose and larynx open into the pharynx, the one imme- levator scapulæ, rhomboid, and lesser pectoral.
diately above, the other immediately below the orifice of The Shoulder Joint is a ball-and-socket joint, the ball Shoulder
the mouth, it is of great importance that none of the food being the head of the humerus, the socket the glenoid fossa joint.
should enter into these chambers, and obstruct the respira- of the scapula. A large capsular ligament, which is
tory passages. To guard against any accident of this kind, pierced by the long tendon of the biceps muscle, and lined
two valvular structures are provided, - viz., the soft palate by a synovial membrane, encloses the articular ends of
and the epiglottis,—which, whilst leaving the orifices into the two bones, and is so loose as to permit a range of
their respective chambers open during breathing, may movement greater than takes place in any other joint in
effectually close them when deglutition is being performed. the body. The muscles which cause these movements are
As the bolus is being projected through the fauces into the inserted into the humerus; the supra-spinatus, infra-
pharynx, the soft palate and uvula are elevated and made spinatus, and teres minor into the great tuberosity; the
tense, and at the same time the wall of the pharynx is sub-scapularis into the small tuberosity; the latissimus
brought in contact with it by the contraction of the palato- dorsi and teres major into the bottom of the bicipital
pharyngei; the part of the pharynx into which the nose opens groove; the pectoralis major into its anterior border; the
is thus temporarily shut off from that into which the mouth coraco-brachialis into the inner aspect, and the deltoid,
opens. If laughter, however, be excited at this time, the which forms the fleshy prominence of the shoulder, into
tension of the soft palate is destroyed, and part of the food the outer aspect of the shaft. Abduction and elevation or
may find its way upwards into the nose. The closure of extension of the arm outwards at the shoulder joint are
the larynx by the epiglottis is due partly to the depression due to the supra-spinatus and deltoid; adduction or de-
of that valve and partly to the elevation of the larynx. pression, to the coraco-brachialis, latissimus, and teres
The backward heave of the tongue relaxes the ligaments major, assisted by the weight of the limb; movement for-
which connect the front of the epiglottis to that organ, and wards and elevation, to the anterior fibres of the deltoid,
enables the small epiglottidean muscles to depress the pectoralis, and subscapularis; backward movement to the
valve. The elevation of the hyoid and larynx is due to the latissimus and teres; rotation outwards to the infra-spinatus
action of the mylo-hyoid, digastric, and genio-hyoid muscles, and teres minor; rotation inwards to the subscapularis,
which pass from the lower jaw to the hyoid, and of the pectoralis, latissimus, and teres. A combination of abduc-
thyro-hyoid, which pass from the hyoid to the thyroid tion, movement forwards, adduction, and movement back-
cartilage of the larynx; preliminary to their action, the wards, produces the movement of circumduction. Certain
lower jaw must be fixed, which is done by the closure of movements of the upper limb, however, take place not
the mouth prior to the act of swallowing. The aperture of only at the shoulder joint, but between the two bones of the
the larynx is thus brought into contact with the depressed shoulder girdle; for in elevating the arm, whilst the supra-
epiglottis, which is adapted more exactly to the opening spinatus and deltoid initiate the movement at the shoulder
by a change in its form due to the projection of a cushion-joint, the farther elevation, as in raising the arm above the
like pad from its posterior surface. By these ingenious head, takes place by the trapezius and serratus, which
arrangements the adaptation of a single chamber to the rotate the scapula and draw its inferior angle forward. The
very different functions of breathing and swallowing is free range of movement of the human shoulder is one of
effectually provided for.

its most striking characters,

so that the arm can be moved JOINTS AND MUSCLES OF THE UPPER LIMB.

in every direction through The upper limb is jointed to the trunk at the sterno- space, and its efficiency as an clavicular articulation. This is a diarthrodial joint: the instrument of prehension is bones are retained together by investing ligaments; a thus greatly increased. The meniscus is interposed between the articular surfaces, so movement of abduction, or that the joint possesses two synovial membranes. A strong extension, which elevates the ligament, which checks too great upward movement, con arm in line with the axis of nects the clavicle and first rib. The two bones of the the scapula, is characteristishoulder girdle articulate with each other at the diarthrodial cally human, and a distinct Fig. 22.–Outline sketch of human haacromioclavicular joint; but, in addition, a strong ligament, articular area is provided on which checks too great displacement of the bones, passes the head of the humerus for plete extension lies to the right of the between the clavicle and coracoid. The movements of the this movement. upper limb on the trunk take place at the sterno-clavicular The Elbow Joint is the articulation between the humerus, Elbow. joint, and consist in the elevation, depression, and forward radius, and ulna : the great sigmoid cavity of the ulna iš and backward movement of the shoulder. The movements adapted to the trochlea of the humerus, and the cup of at the acromio-clavicular joint occur when the scapula is the radius to the capitellum. The joint is enclosed by a

merus.

The articular area for com

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capsular ligament lined by a synovial membrane, which is unciform are connected to the metacarpal bones of the
subdivided into anterior, posterior, internal, and ex- fingers by dorsal, palmar, and interosseous ligaments, and
ternal bands of fibres. Flexion and extension are the the metacarpal bones of the fingers have a like mode of
two movements of the joint, and the range of movement is union at their carpal ends; further, a transverse ligament
limited by the locking at the end of flexion of the coronoid extends between the distal ends of the metacarpal bones of
process into the coronoid fossa of the humerus, and at the the fingers, and checks too great lateral displacement. The
end of extension of the olecranon process into the olecranoid range of movement at any one of these carpal joints is very
fossa. The elbow joint is a hinge with screwed surfaces; slight, but the multiplicity of joints in this locality con-
the path described by the hand and fore-arm is a spiral, so tributes to the mobility of the wrist, and makes the junction
that during flexion they are thrown forwards and inwards. between the hand and fore-arm less rigid in its nature.
The muscles which cause the movements are inserted into The metacarpal bone of the thumb is not jointed to the
the bones of the fore-arm. The flexors are the brachialis index, and has a distinct saddle-shaped articulation with
anticus, inserted into the coronoid of the ulna ; the biceps, the trapezium, invested by a capsular ligament, so that its
which forms the fleshy mass on the front of the upper arm, range of movement is extensive.
into the tuberosity of the radius; the supinator longus into The Metacarpo-phalangeal and Inter-phalangeal Jointe Joints of
the styloid process of the radius. The only extensor is the are connected by lateral ligaments passing between the fingers.
triceps-anconeus, which forms the fleshy mass on the back bones, and by an arrangement of fibres on their dorsal and

of the upper arm, and is inserted into the olecranon. palmar surfaces.
Joints of The Radio-ulnar Joints are found between the two bones In studying the muscles which move the digits, it will
fore-arm. of the fore-arm. The head of the radius rolls in the lesser be advisable, on account of the freedom and importance of

sigmoid cavity of the ulna, and is retained in position by the movements of the thumb, to
a ring-like ligament which surrounds it; the shafts of the examine its muscles indepen-
two bones are connected together by the interosseous dently. These muscles either
membrane, their lower ends by a capsular ligament and a pass from the fore-arm to the
triangular fibro-cartilage or meniscus. The radius rotates thumb, or are grouped together
round an axis drawn through the centre of its head and at the outer part of the palm,
the styloid process of the ulna ; rotation of the fore-armand form the elevation known
and hand forward is called pronation,-rotation backwards, as the ball of the thumb; they
supination. The supinator and pronator muscles are all are inserted either into the
inserted into the radius : the supinators are the longus and metacarpal bone or the pha-
brevis and the biceps; the pronators are the teres and langes. The thumb is extended
quadratus. Where delicate manipulation is required the and abducted, i.e., drawn away
fore-arm is semi-flexed on the upper arm, for the cup- from the index, by three ex-
shaped head of the radius is then brought into contact tensor muscles descending from
with the capitellum of the humerus, and the rotatory the fore-arm, and inserted one
movements of the bone can be performed with greater | into each of its three bones,
precision.

and a small muscle, specially Wrist.

The Wrist or Radio-carpal Joint is formed above by the named abductor pollicis, in-
lower end of the radius and the triangular meniscus, below serted into the outer side of
by the upper articular surfaces of the scaphoid, semi-lunar, the first phalanx : its bones
and cuneiform bones. An investing ligament, lined by a are bent on each other by a
synovial membrane, and subdivided into anterior, posterior, long and short flexor muscle ;,
internal, and external bands of fibres, encloses the joint it is drawn back to the index
It is the oblong form of hinge-joint, and possesses two by an adductor muscle; and
axes, a long and a short; around the long axis movements the entire thumb is thrown Fto. 23.—Deep muscles of the palm of
occur which bend the hand forwards, or bring it in line across the surface of the palm the hand. 1, abductor pollicis cat

short; 2, opponens; 3 and 4, sub
with the fore-arm, or bend it backwards ; around the short by the opponens pollicis, divisions of flexor brevis; 6, ad-
axis the hand may be moved towards the radial or ulnar which is inserted into the ductor; 6, 6, tendon of long flexor

pollicis; 7, abductor of the little margins of the fore-arm. The flexors forward are the shaft of the metacarpal bone. tinger ; 8, short flexor; 9, opponens; palmaris longus, inserted into the palmar fascia; the flexor The four fingers can be

10, tendon of flexor carpi ulnaris;

11, tendon of long supinator; tt
carpi radialis into the metacarpal bone of the index; the either bent, or extended, or transverse metacarpal ligament
flexor carpi ulnaris into the pisiform bone; the extensors drawn asunder, i.e., abducted; or drawn together, i.e.,
and flexors backwards are the longer and shorter radial adducted. The ungual phalanges can be bent by the
extensors inserted into the metacarpal bones of the index
and middle fingers, and the ulnar extensor into the meta-
carpal bone of the little finger; the flexors and extensors
of the fingers have also a secondary action on the wrist
joint. The ulnar flexor and ulnar extensor of the wrist

d
draw the hand to the ulnar side, and the radial flexor and
extensor, together with the extensors of the thumb, draw

the hand towards the radial border of the fore-arm.
Joints of The Carpal and Carpo-metacarpal Joints are constructed
hand.

Fig. 24.—Tendons attached to a finger. a, the extensor tendon; 0, deep flexor,
thus :—The articular surfaces are retained in contact by

C, superficial flexor; d, a lumbrical muscle; e, an interosseous muscle;
certain ligaments passing between the dorsal surfaces of s, tendinous expansion from the lumbrical and interosseous muscles joining
adjacent bones, by others between their palmar surfaces,
and by interosseous ligaments between the semi-lunar and action of the deep flexor muscle, the four tendons of which
cuneiform, semi-lunar and scaphoid, os magnum and unci are inserted into them; the second phalanges by the super-
form, os magnum and trapezoid ; lateral ligaments also ficial flexor, also inserted by four tendons, one into each
attach the scaphoid to the trapezium, and the cuneiform to phalanx; these muscles descend from the front of the fore
the unciform. Similarly, the trapezoid, os magnum, and arm into the palm in front of the wrist, where they are

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the extensor tendon.

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