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JOINTS.

of which do not reach so far; are called the in a socket of the os innominatur: the false ribs.

great trochanter forms a conspicuous proThe sternam is a broad and flat bone, cess at the upper and outer part of the bone. placed in the front of the chest. It consists Below it has two condyles, which form part, of two pieces of bone, and of a cartilage of the knee. called the ensiform. T'he clavicles are arti The leg has two bones; the tibia and fibu. culated towards its upper parts, and the la. A large flat portion of the former, cocartilages of the ribs are joined to its sides. vered only by skin, is called the shin. The

The pelvis is formed by the two ossa in- foot is composed of the tarsus, metatarsus, nominata, or haunch bones, the sacrum, and and toes. The tarsus has seven bones:os coccygis. The former are very large and 1. Astragalus, composing the ankle, with flat bones, expanded into a broad surface the lower portion of the tibia and fibula. above for the support of the abdominal vis. 2. Os calcis. 3. Os naviculare.

4. Os cera, and the attachment of the abdominal cuboides. 3, 6, 7. Ossa cuneiformia. The muscles, and furnished with large tubero- metatarsal bones are five in mumber, and sities below, for the support of the body in the bones of each toe are three, except the the sitting position. Each os innominatum great toe, which has only two. is divided into the ilium, ischium, and pubes. It is firmly joined to the sacrum behind, and SYNDESMOLOGY, OR DOCTRINE OF THE to the opposite bone in front by the symphisis pubis. The conjoined portions form Construction of a joint. — The opposed an arch, called the arch of the pubes. The surfaces of bones, which form joints, are cavity of the pelvis is much larger in the covered by a thin crust of cartilage, most female than in the male, as it holds the exquisitely smooth and polished. Hence uterns and vagina in addition to what it con- they move on each other in whatever directains in the male, and as the fætus passes tion their structure admits, without any through it in parturition.

hindrance from friction. They are tied to: The bones of the upper extremity are gether by strong and unyielding corus, redistributed into those of the shoulder, arm, sembling tendons, and known by the name fore-arm, and hand.

of ligaments. These keep the surfaces of The shoulder contains two; the scapula the bones together, and restrict their moand clavicle. The former is situated at the tions to certain directions. In order still upper and outer part of the chest, and is further to promote the facility of motion, joined to the end of the clavicle.

and to obviate every possibility of friction, The humerus is a long and nearly cylin- the cartilaginous surfaces are smeared with drical bone, joined by a round head to the

an unctuons fluid, called synovia, which makes scapula above, and articulated with the ra- them perfectly slippery. This fluid is con. dius and ulna below.

fined to the surface of the joint by means of The fore-arm has two bones; the uloa, a thin and delicate membrane, called the which is joined by a hinge or ginglymus to capsular ligament, which envelopes the joint. the humerus; and the radius, which has a It is secreted from portions of a fatty subcavity playing upon a rounded head of stanee, called the synovial glands. The ligathat bone. The prominent extremity of the ments are usually situated on the outside of ulna, which forms the elbow, is called the the capsula; but in many instances they are olecranon. The hand is divided into the contained in the cavity of the joint, passing carpus, or wrist, the metacarpus, and the from the centre of one bone to another. fingers and thumb.

These are called interarticular ligaments. The carpus contains eight bones, disposed

Particular joints.--Joint of the lower jaw. in two phalanges, of which the first forms, This is formed between the condyle of the with the radius, the joint of the wrist, and jaw, and a hollow in the temporal bone. It the second is articulated to the metacarpus. contains a moveable cartilage, which ren

The bones of the first phalanx are the os ders the articulation more secure, when the naviculare, lunatum, cuneiforme, and orbicu- jaw is brought forwards on the bone under lare: those of the second, os trapezium, certain circumstances. trapezioides, capitatum, and unciforme.

The connection of the head to the verteThe metacarpus has five bones, and each bræ is effected by means of two prominences of the fingers three; the thumb only two. of the occiput, which are received into cor

In the lower extremity we have the fe- responding cavities of the atlas. By this mur, the largest of the cylindrical bones in joint the nodding motions of the head are the body. This has a round head, contained perforined. But the atlas itself turns hori

zontally round the tooth-like process of in the back, where strength more than the vertebra dentata, and as the head is flexure is wanted; greater in the loins, which closely connected to the atlas, it is carried it was necessary should be more supple than round at the same time. Therefore the la- the back; and greatest of all in the neck, teral or rotatory motions of the head are for the free motion of the head. Then, performed by a different joint from that secondly, in order to afford a passage for which performs the nodding motions. Nei- the descent of the medullary substance, each ther of these articulations admits of very ex of these bones is bored through in the mid-' tensive motion; but the deficiency is com dle in such a manner, as that, when put topensated by the mobility of the vertebra, gether, the hole in one bone falls into a line which enable us to carry the head freely in and corresponds with the holes in the two any direction we may wish. The head rests bones contiguous to it; by which means the nearly in equilibrio on the spinal column; perforated pieces, when joined, form an enyet, if left to itself, it would fall forwards, tire, close, uninterrupted channel. But, as as the joint is not precisely in the centre of a settled posture is inconsistent with its nse, the basis cranii. To counteract this ten a great difficulty still remained, which was dency there is a ligamentous substance ex to prevent the vertebræ from shifting npon tended from the spinous processes of the one another, so as to break the line of the cervical vertebræ to the occiput, and cal- canal as often as the body moves or twists, led the ligamentum nuchæ. In quadrupeds or the joints gaping externally whenever the this can be best seen, as the weight of the body is bent forwards, and the spine therehead is there supported to a much greater upon made to take the form of a bow. disadvantage. The muscles also contribute These dangers, which are mechanical, are to keep the head upright; and hence, when mechanically provided against. The vertea man drops asleep sitting, the relaxation of bræ, by means of their processes and prothe extensor muscles causes the head to nod jections, and of the articulations which some forwards,

of these form with one another at their exJoints of the spine. The spine, or back- tremities, are so locked in and confined, as hone, is a chain of joints of very wonderful to maintain in what are called the bodies or construction. Varions, difficult, and almost broad surfaces of the bones the relative poinconsistent offices were to be executed by sition nearly unaltered; and to throw the the same instrument. It was to be firm, change and the pressure produced by flexion yet flexible; firm, to support the erect po- almost entirely upon the intervening cartisition of the body; flexible, to allow of the lages, the spriuginess and yielding nature of bending of the trunk in all degrees of cur whose substance admits of all the motion vature. It was further also to become a which is necessary to be performed upon pipe or conduit for the safe conveyance of a them, without any chasm being produced most important part of the animal frame, by a separation of the parts. I say of all the spinal marrow; a substance, not only of the motion which is necessary; for, although the first necessity to action, if not to life, we bend our backs to every degree almost but of a nature so delicate and tender, so of inclination, the motion of each vertebra susceptible, and so impatient of injury, as is very small: sich is the advantage which that any unusual pressure upon it, or any we receive from the chain being composed considerable obstruction of its course, is of so many links. Had it been composed of followed by paralysis or death. It was also three or four bones only, in bending the to afford a fulcrum, stay, or basis for the in- body the spinal marrow must have been sertion of the muscles which are spread bruised at every angle. over the trunk of the body, in which trunk The substances which connect the bodies there are not, as in the limbs, cylindrical of the vertebræ to each other, called the inbones to which they can be fastened; and tervertebral cartilages, are thick, firm, and likewise, which is a similar use, to furnish a elastic. They are similar in shape, and support for the ends of the ribs to rest nearly so in size to the bones which they upon.

join. They are thicker before than behind, The breadth of the bases, tipon which the so that, when we stoop forwards, the comparts severally rest, and the closeness of the pressible cartilage, yielding to the force, jnnction, give to the chain its firmness and brings the surfaces of the adjoining vertebræ stability; the number of parts, and conse-, nearer to a state of parallelism than they quent frequency of joints, its flexibility; were before, instead of increasing the incliwhich flexibihty, we may also observe, va- nation of their planes, which must have oclies in different parts of the chain; is least casioned a fissure or opening between them :

and their elasticity restores the body to its hand and wrist, or what anatomists call the former state, when the compressing force pronation and supination, are performed by ceases.

the radius revolving round the ulna, and carIn order still further to increase the rying the hand with it. In this case the strength of the compages, and to add a elbow joint is fixed; neither does the joint greater security against luxation, the verte- of the wrist move; but the radius moves bræ are articulated to each other by means freely round the ulna, and the hand is inof the processes before mentioned. And cluded in the motion. The pronation and these processes so lock in with and over- supination of the hand are well exemplified wrap one another as to secure the body of in the use of the broad-sword, and in cudthe vertebra, not only from accidentally gel-playing. slipping, but even from being pushed out of The carpal and metacarpal bones are its place by any violence short of that which united by joints and ligaments, but have no would break the bone. The roots of the obvious motion on each other. The phaspinous processes are also joined to each langes of the fingers are also articulated by other by very strong and highly elastic liga- ginglymi. mentous substances, which will tend power The bones of the pelvis are inseparably fully to restore the column after it has been connected by adhering cartilaginous surbent forwards.

faces and immense ligaments. Such is the The general result is, that not only the strength of this union, that it will yield to motions of the human body necessary for no force but one that would destroy and the ordinary offices of life are performed crush the whole fabric. with safety, but that it is an accident hardly Joints of the lower extremity.--In the hip, ever heard of, that even the gesticulations which supports the whole body, and which of a harlequin distort his spine.

is the centre of motion of the whole in The ribs are articulated by their posterior moving from place to place, we find an ap. extremities to the bodies and to the trans- paratus admitting of extensive motion, but verse processes of the vertebræ, and the at the same time most carefully guarded true ribs are also joined by means of their and strengthened. There is a very large cartilages to the sternum. Two great ad- rounded head of the thigh received into a vantages are derived from the ribs having deep cup of the os innominatum. Here it this cartilaginous portion. The effect of can revolve freely, and is prevented from blows, or of any accidental violence, is escaping by thick and strong rising edges, eluded by the flexibility which they thus that guard the brim of the cavity, From obtain ; and the elastic power of the carti- these edges there springs a very tough and lages restores the ribs to their former posi- stout orbicular ligament, which is firmly tion, after they have been raised by the in- stretched over the head of the bone, and tercostal muscles in breathing.

implanted into a contracted part called the Joints of the upper extremity.—The clavicle neck. In order to provide still further for is articulated to the sternum at one end, and the security of so important a joint as the to the scapula at the other.

hip, there is a short, strong ligament arising The shoulder is formed by a round, head from the head of the ball, and implanted in of the bumerus, which plays in a cup of the the bottom of the cup. This affords a very scapula ; and the ends of the bones are in- great obstacle to any force tending to disclosed by a thick and strong ligamentous place the bone; bat at the same time lies in membrane, called the orbicular ligament. the bottom of the cavity, so as not to interThere is here, therefore, every latitude of fere with any of the ordinary motions. motion allowed.

The knee-joint is formed by three bones : In the elbow, on the contrary, the joint is the head of the tibia, the condyles of the fea mere hinge: lateral motion is restrained mur, and the patella. It is a ginglymus, by strong ligaments placed at the sides of and its motions are accordingly restrained the joint, and the fore-arm can therefore be by two strong lateral ligaments, and it is moved only forwards and backwards. This secured still further by two immense ligajoint is formed between the nlna and the mentous ropes within the cavity of the bamerus.

joint, called the crucial ligaments. The wrist is formed by the junction of The ankle is a ginglymoid joint, formed the radius with the first phalanx of carpal by the tibia and fibula, together with the bones. Its motion is very little more than astragalus. This joint, which is an impor. that of a ginglymus. The rotation of the tant one, as bearing the weight of the whole

MYOLOGY.

body, is strengthened at its sides by two socket joint allows by its construction a robony processes, called the internal and ex- tatory or sweeping motion, tendons are ternal malleoli or ankles.

placed in such a position, and pull in such a The bones of the tarsus, metatarsus, and direction, as to produce the motion of which toes, are articulated like those of the band. the joint adinits. In the head and hand

there is a specific mechanism in the bones

for rotatory motion; and there is accordMuscles consist of bundles of red fibres; ingly in the oblique direction of the muscles but the colour is not essential, since it can belonging to them a specific provision for be removed by repeated washings and ma- putting this mechanism of the bones into acceration.

tion. The oblique muscles would have been The threads composing a muscle are en- inefficient without that particular articulaveloped by cellular substance, which con- tion, and that particular articulation would nects it to the surrounding parts. Each have been useless without the muscles. bundle consists of numerous fibres, so small As the muscles act only by contraction, it that our instruments of research cannot ar- is evident that the reciprocal energetic morive at the ultimate or original fibre: hence tion of the limbs, or their motion with force any perceivable fibre, however small, is in opposite directions, can only be produced formed by the juxta-position of numerous by the instrumentality of opposite or antafibrillæ ; and, as we employ magnifying in- gonist inuscles, of flexors and extensors anstruments of greater power, a fibre, which swering to each other. For instance, the before seemed simple, resolves itself into a biceps and brachialis internus, placed in the congeries of still more minute threads. We front of the arm, by their contraction bend pass over in silence the dreams of various the elbow, and with such degree of force as investigators who have busied themselves in the case requires, or the strength admits of. looking for the ultimate muscular fibre; The relaxation of these muscles after the efthese researches do not assist us in explain- fort would merely let the fore-arm drop ing the phenomena of muscular action. The down : for the back stroke therefore, and cohesion of the constituent particles of the that the arm may not only bend at the elmoving fibre is maintained by the vital bow, but also extend and straighten itself power: hence a dead muscle will be torn with force, other muscles, as the triceps and by a weight of a few ounces, which in the anconeus, placed on the hinder part of the living boviy would liave supported many arm, fetch back the fore-arın into a straight pounds. The muscular fibre receives a line with the humerus with no less force than copious supply of vessels and nerves.

that with which it was bent out of it. It Tendons are formed by an assemblage of is evident therefore that the animal funclongitudinal parallel fibres. They are ex tions require that particular disposition of tremely dense and tough, of a splendid the muscles, which we call antagonist muswhite colour, which is beautifully contrasted cles. with the florid red of a healthy muscie. The It often happens that the action of mus. muscular fibres terminate in these bodies, cles is wanted, where their situation would and they are connected to the bones. They be inconvenient. In which case, the body possess no apparent nerves, and very few of the muscle is placed in some commodions and small blood vessels.

position at a distance, and it communicates There is always an exact relation between with the point of action by slender tendons. the joint and the muscles that move it. If the muscles, which move the fingers, had Whatever motion the joint, by its mechani- been placed in the palm or back of the hand, cal construction, is capable of performing, they would have swelled that part to an that motion the annexed muscles by their awkward and clumsy thickness. The beauposition are capable of producing. For ex- ty, the proportions of the part wonld have ample, if there be, as at the knee and elbow, been destroyed. They are therefore disa hinge joint, capable of motion only in the posed in the arm, and even up to the elbow, same plane, the muscles and tendons are and act by long tendons strapped down at placed in directions parallel to the bone, so the wrist, and passing under the ligament as by their construction to produce that to the fingers, and to the joints of the finmotion and no other. If these joints were gers, which they are severally to move. In capable of a freer motion, there are no the same manner the muscles which move muscles to produce it. Whereas, at the the toes and many of the joints of the foot, shoulder and the hip, where the ball and are gracefully disposed in the calf of the

leg, instead of forming an unwieldy tume The foot is placed at a considerable angle faction in the foot itself.

with the leg. It is manifest, therefore, that The great mechanical variety in the fignre flexible strings, passing along the interior of of the muscles may be thus stated. It ap- the angle, if left to themselves, would, when pears to be a fixed law, that the contrac- stretched, start from it. The obvious pretion of a muscle shall be towards its centre. ventive is to tie them down, and this is done Therefore the subject for mechanism on in fact. Across the instep, or rather just each occasion is, so to modify the figure, above it, the anatomist finds a strong ligaand adjust the position of the muscle, as to ment, under which the tendons pass to the produce the motion required, agreeably foot. The effect of the ligament, as a banwith this law. This can only be done by dage, can be made evident to the senses ; giving to different muscles a diversity of for if it be cut, the tendons start up. The configuration, suited to their several offices, simplicity, yet the clearness of this contriand to their situation with respect to the vance, its exact resemblance to established work, which they have to perform. On resources of art, place it among the most inwhich account we find them under a multi- dubitable manifestations of design, with plicity of forms and attitudes ; sometimes which we are acquainted. with double, sometimes with treble tendons, The number of the muscles of the lauman sometimes with none: sometimes one ten- body is so great, and the circumstances, don to several muscles, at other times one which demand attention in every muscle muscle to several tendons. The shape of are likewise so numerous, that a particular the organ is susceptible of an incalculable description of each would extend this arti. variety, whilst the original property of the cle beyond its prescribed limits. We shall muscle, the law and line of its contraction, therefore merely give a catalogue of the remains the same, and is simple. Herein muscles; which together with the refethe muscular system may be said to bear a rences to the annexed plates, will give the perfect resemblance to our works of art. reader a sufficiently clear notion of the subAn artist does not alter the native quality of ject. his materials, or their laws of action. He Muscles of the scalp.-1. Fronto-occipi. takes these as he finds them. His skill talis, or epicranius. and ingenmity are employed in turning them,

Muscles of the ear.–1. Attollens auricu. such as they are, to his account, by giving to

lam; 2. anterior auris ; 3, 4. retrahentes the parts of his machine a form and relation, auriculam; 5. major helicis; 6. minor heliin which these unalterable properties may cis; 7. tragicus; 8. antitragicus ; 9. transoperate to the production of the effects in versus auriculæ ; 10. laxator tympani major; tended.

11. laxator tympani minor; 12. tensor tymThe muscular system would affordus pani ; 13. stapedeus. numerous examples of what may be called Muscles of the eye.-1. Orbicularis palmechanical structure: i. e. of such contri- pebrarum; 2.'corrugator supercilii; 3. levavances employed to attain certain objects, tor palpebræ superioris ; 4. attollens óculi; as a human artist would adopt on similar 5. abductor oculi; 6. depressor oculi; 7. occasions. One of the muscles of the eye- adductor oculi, these are also called recti: ball presents us with a very perfect pulley; viz, rectus superior, externus, inferior, and by means of which the globe of the eye is internus; 8. obliquus superior oculi, or trochmoved in a direction exactly contrary to learis ; 9. obliquus inferior oculi. the original application of the force. This Muscles of the nose.-1. Compressor namuscle, which is called the trochlearis, arises rium ; 2. levator labii superioris et alæ nasi; from the very back part of the orbit; it has 3.nasalis labii superioris; 4.depressoralæ nasi. a long and slender tendon running through Muscles of the lips.-1. Levator labii sua pulley in the inner part of the front mar- perioris ; 2. zygomaticus major ; 3. zygogin of the orbit, and then going back to be maticus minor; 4. levator anguli oris ; 5. fixed in the hind portion of the eye-ball. depressor anguli oris ; 6. depressor labii inThus it draws the globe obliquely upwards ferioris ; 7. buccinator; 8. orbicularis oris ; and forwards, although the line of the con 9. anomalus maxillæ superioris; 10. levator traction of the muscle is directly backward. menti.

In the toes and fingers, the long tendon, Lower jaw.–1. Biventer maxillæ or di. which bends the first joint, passes through gastricus; 2. masseter ; 3. temporalis; 4. the short tendon, which bends the second pterygoideus externus ; 5. pterygoideru injoint.

ternus,

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