is guided into position by the edges working in metal grooves a little | The latter would need to be worked and framed in the shop and fixed under an inch wide. When the width of the opening to be closed entire. Polished hard wood architraves may be secretly fixed, i.e. renders it necessary to divide the shutters into more than one portion, without the heads of nails or screws showing on the face, by putting grooved movable pilasters are used, and when the shutters have to be screws into the grounds with their heads slightly projecting, and hanglowered these are fixed in position with bolts, the shutter working ing the moulding on them by means of keyhole slots formed in the back. on the grooved edges of the pilasters. Spring roller canvas blinds Doors may be made in a variety of ways. The simplest form, work on a similar principle. The wrought-iron blind arms are the common ledged door, consists of vertical boards with plain or capable, when the blind is extended, of being pushed up by means of matched joints nailed to horizontal battens which correspond to the a sliding arrangement, and fixed with a pin at a level high enough to rails in framed doors. For openings over 2 ft. 3 in. wide, the doors allow foot passengers to pass along the pavement under them. should be furnished with braces. Ledged and braced doors are Doors External doors are usually hung to solid frames placed in the reveals of the brick or stone wall. The frames are rebated for the door and ornamented by mouldings either stuck or planted on. The jambs or posts are tenoned, wedged and glued to the head, and the feet secured to the sill by stub tenons or dowels of iron. Solid window frames are of similar construction and are used chiefly for casements and sashes hung on centres as already described. Internal doors are hung to jamb linings (fig. 7). They are usually about 1 in. thick and rebated for the door. When the width of jamb allows it, panelling may be introduced as in the example shown. The linings are nailed or screwed to rough framed grounds I in, in thickness plugged or nailed to the wall or partition. Architraves are the borders or finishing mouldings fixed around a window or door opening, and screwed or nailed to wood grounds. They are variously moulded according to the fancy of the designer. The ordinary form of architrave is shown in the illustration of a cased window frame (fig 8), and a variation appears in the combined architrave and over door frieze and capping fitted around the six-panelled door (fig. 7). | similar, but have, in addition to the ledges at the back, oblique braces which prevent any tendency of the door to drop. The upper end of the brace is birdsmouthed into the under side of the rail near the lock edge of the door and crosses the door in an oblique direction to be birdsmouthed into the upper edge of the rail below, near the hanging edge of the door. This is done between each pair of rails. Framed ledged and braced doors are a further development of this form of door. The framing consists of lock and hanging styles, top, middle and bottom rails, with oblique braces between the rails. These members are tenoned together and the door sheathed with boarding. The top rail and styles are the full thickness of the door, the braces and middle and bottom rails being less by the thickness of the sheathing boards, which are tongued into the top rail and styles and carried down over the other members to the bottom of the door. The three forms of door described above are used mainly for temporary purposes, and stables, farm buildings and outhouses of all descriptions. They are usually hung by wrought-iron cross garnet or strap hinges fixed with screws or through bolts and nuts. JOINERY The doors in dwelling-houses and other buildings of a like character are commonly framed and panelled in one of the many ways possible. The framing consists of styles, rails and muntins or mountings, and these members are grooved to receive and hold the panels, which are inserted previously to the door being glued and wedged up. The common forms are doors in four or six rectangular panels, and although they may be made with any form and number of panels, the principles of construction remain the same. The example shown in fig. 7 is of a six-panel door, with bolection moulded raised panels on one side, and moulded and flat panels on the other (fig. 11). Square & flat Bead flush Moulded & raised A clear idea of the method of jointing the Bolection moulded & fiat The tongues of raised panels should be of various members may be obtained from fig. 12. parallel thickness, the bevels being stopped at the moulding. The projecting ends or horns of the styles are cut off after the door has been FIG. 11.-Forms glued and wedged, as they prevent the ends of Panelling. of the styles being damaged by the wedging process. Where there is a great deal of traffic in both directions swing doors, either single or double, are used. To open them it is necessary simply to push, the inconvenience of turning a handle and shutting the door after passing through being avoided, as a spring causes the door to return to its original position without noise. glazed and should be of substantial conThey are usually Joints of struction. The door is hinged at the top on rails & style. shoe connected with the spring, which is placed a steel pivot; the bottom part fits into a metal in a box fixed below the floor. Top rail Frieze rail Lock rail Dottom rail For large entrances, notably for hotels and banks, a form of door working on the turnstile principle is frequently adopted. It is formed of four leaves fixed in the shape of a cross and working on top and bottom central ballbearing steel pivots, in a circular framing which forms a kind of vestibule. The leaves of the door are fitted with slips of india-rubber at their edges which, fitting close to the circular framing, prevent draughts. When an elegant appearance is desired, and it is at the same time necessary to keep the cost of production as low as possible, doors of pine or other soft wood are sometimes covered with a veneer or thin layer of hard wood, such as oak, mahogany or teak, giving the appearance of a solid door of the better material. Made in the ordinary way, however, the shrinkage or warping of the soft wood is very liable to cause the veneer to buckle and peel off. Veneered doors made on an improved method obviating this difficulty have been placed on the market by a Canadian company. The core is made up of strips of pine with the grain reversed, dried at a temperature of 200° F., and glued up under pressure. Both the core and the hard wood veneer are grooved over their surfaces, and a special damp-resistMuntin ing glue is applied; the two portions are then welded together under hydraulic pressure. By reason of their construction these doors possess the advantages of freedom from shrinking, warping and splitting, defects which are all too common in the ordinary veneered and solid hard wood doors. The best glue for internal woodwork is that FIG. 12.-Joints. made in Scotland. weather as it absorbs damp and thus hastens decay; in its place a should not be used in work exposed to the Ordinary animal glue compound termed beaumontique, composed of white lead, linseed oil and litharge, should be employed. Rail Joint of muntin & rall Church Work-Joinery work in connexion with the fitting up of church interiors must be regarded as a separate branch of the joiner's art. Pitchpine is often used, but the best work is executed in English oak; and when the screens, stalls and seating are well designed and made in this material, a distinction and dignity of effect are added to the interior of the church which cannot be obtained in any other medium. The work is often of the richest character, and frequently enriched with elaborate carving (fig. 13). Many beautiful specimens of early work are to be seen in the English Gothic cathedrals and churches; good work of a later date will be found in many churches and public buildings erected in more recent years. Fine examples of Old English joinery exist at Hampton Court Palace, the Temple Church in London, the Chapel of Henry VII. in Westminster Abbey, and Haddon Hall. Specimens of modern work are to be seen in Beverley Minster in Yorkshire, the Church of St Etheldreda in Ely Place, London, and the Wycliffe Hall Chapel at Oxford. Other examples both ancient and modern abound in the country. Carving is a trade apart from ordinary joinery, and requires a special ability and some artistic feeling for its successful execution. But even in this work machinery has found a place, and carved ornaments of all descriptions are rapidly wrought with its aid. being incomparably cheaper than those worked by manual labour, Small carved mouldings especially are evolved in this manner, and, panels also are made by machines and a result almost equal to work are used freely where a rich effect is desired. Elaborately carved done entirely by hand is obtained if, after machinery has done all in its power, the hand worker with his chisels and gouges puts the finishing touches to the work. Ironmongery. In regard to the finishing of a building, no detail fixing of suitable ironmongery, which includes the hinges, bolts, calls for greater consideration than the selection and accurate finishings required for the completion of a building. The task of the locks, door and window fittings, and the many varieties of metal performed by the joiner selection belongs to the employer or the architect; the fixing is FIG. 13. doors, and are so called from being fitted to the butt edge of the door. of a door and protect the painted work. Sash fasteners are fixed at the meeting rails of double hung sashes to prevent the window being opened from the outside and serve also to clip the two sashes tightly together They should be of a pattern to resist the attack of a knife inserted between the rails. Sash lifts and pulls of brass or bronze are fitted to large sashes. Ornamental casement stays and fasteners in many different metals are made in numerous designs and styles. Fanlight openers for single lights, or geared for a number of sashes, may be designed to suit positions difficult of access. The following are the principal books of reference on this subject: J. Gwilt, Encyclopaedia of Architecture; Sutcliffe, Modern House Construction; Rivington, Notes on Building Construction (3 vols.); H. Adams, Building Construction; C. F. Mitchell, Building Construction; Robinson, Carpentry and Joinery; J. P. Allen, Practical Building Construction; J. Newlands, Carpenter and Joiner's Assistant; Bury, Ecclesiastical Woodwork; T. Tredgold and Young, Joinery; Peter Nicholson, Carpenter and Joiner's Assistant. (J. Br.) JOINT (through Fr. from Lat. junctum, jungere, to join), that which joins two parts together or the place where two parts are joined. (See JOINERY; JOINTS.) In law, the word is used adjectivally as a term applied to obligations, estates, &c., implying that the rights in question relate to the aggregate of the parties joined. Obligations to which several are parties may be several, i.e enforceable against each independently of the others, or joint, i.e. enforceable only against all of them taken together, or joint and several, i.e. enforceable against each or all at the option of the claimant (see GUARANTEE). So an interest or estate given to two or more persons for their joint lives continues only so long as all the lives are in existence. Joint-tenants are co-owners who take together at the same time, by the same title, and without any difference in the quality or extent of their respective interests; and when one of the jointtenants dies his share, instead of going to his own heirs, lapses to his co-tenants by survivorship. This estate is therefore to be carefully distinguished from tenancy in common, when the co-tenants have each a separate interest which on death passes to the heirs and not to the surviving tenants. When several take an estate together any words or facts implying severance will prevent the tenancy from being construed as joint. JOINTS, in anatomy. The study of joints, or articulations, is known as Arthrology (Gr. ap@pov), and naturally begins with the definition of a joint. Anatomically the term is used for any connexion between two or more adjacent parts of the skeleton, whether they be bone or cartilage. Joints may be immovable, like those of the skull, or movable, like the knee. Immovable joints, or synarthroses, are usually adaptations to growth rather than mobility, and are always between bones. When growth ceases the bones often unite, and the joint is then obliterated by a process known as synostosis, though whether the union of the bones is the cause or the effect of the stoppage of growth is obscure. Immovable joints never have a cavity between the two bones; there is simply a layer of the substance in which the bone has been laid down, and this remains unaltered. If the bone is being deposited in cartilage a layer of cartilage intervenes, and the joint is called synchondrosis (fig. 1), but if in membrane a thin layer of fibrous tissue persists, and the joint is then known as a suture (fig. 2). Good examples of synchondroses are the epiphysial lines which separate the epiphyses from the shafts of developing long bones, or the occipitosphenoid synchondrosis in the base of the skull. Examples of sutures are plentiful in the vault of the skull, and are given special names, such as sutura dentata, s. serrata, s. squamosa, according to the plan of their outline. There are two kinds of fibrous synarthroses, which differ from sutures in that they do not synostose. One of these is a schindylesis, in which a thin plate of one bone is received into a slot in another, as in the joint between the sphenoid and vomer. The other is a peg and socket joint, or gomphosis, found where the fangs of the teeth fit into the alveoli or tooth sockets in the jaws. Movable joints, or diarthroses, are divided into those in which there is much and little movement. When there is little movement the term half-joint or amphiarthrosis is used. The simplest kind of amphiarthrosis is that in which two bones are connected by bundles of fibrous tissue which pass at right angles from the one to the other; such a joint only differs from a suture in the fact that the intervening fibrous tissue is more plentiful and is organized into definite bundles, to which the name of interosseous ligaments is given, and also that it does not synostose when growth stops. A joint of this kind is called a syndesmosis, though probably the distinction is a very arbitrary one, and depends upon the amount of movement which is brought about by the muscles on the two bones. As an instance of this the inferior tibiofibular joint of mammals may be cited. In man this is an excellent example of a syndesmosis, and there is only a slight play between the two bones. In the mouse there is no movement, and the two bones form a synchondrosis between them which speedily becomes a synostosis, while in many Marsupials there is free mobility between the tibia and fibula, and a definite synovial cavity is established. The other variety of amphiarthrosis or halfjoint is the symphysis, which differs. from the syndesmosis in having both bony surfaces lined with cartilage and between the two cartilages a layer of fibro-cartilage, the centre of which often softens and forms a small synovial cavity. Examples of this are the symphysis pubis, the mesosternal joint, and the joints between the bodies of the vertebrae (fig. 3). of the joint cavity except where the articular cartilage is present, is the synovial membrane (fig. 4, dotted line); this is a layer of endothelial cells which secrete the synovial fluid to lubricate the interior of the joint by means of a small percentage of mucin, albumin and fatty matter which it contains. A compound diarthrodial joint is one in which the joint cavity is divided partly or wholly into two by a meniscus or inter-articular fibro-cartilage (fig. 5, Fc). The shape of the joint cavity varies greatly, and the different divisions of movable joints depend upon it. It is often assumed that the structure of a joint determines its movement, but there is something to be said for the view that the movements to which a joint is subject determine its shape. As an example of this it has been found of the two occipital condyles received into the cup-shaped that the mobility of the metacarpo-phalangeal joint of the thumb articular facets on the atlas and surrounded by capsular ligain a large number of working men is less than it is in a large number of women who use needles and thread, or in a large number of ments. The neural arches of the vertebrae articulate one with medical students who use pens and scalpels, and that the slightly another by the articular facets, each of which has a capsular movable thumb has quite a differently shaped articular surface from ligament. In addition to these the laminae are connected by the freely movable one (see J. Anat. and Phys. xxix. 446). R. Fick,the very elastic ligamenta subflava. The spinous processes are too, has demonstrated that the concavity or convexity of the joint surface depends on the position of the chief muscles which move the joint, and has enunciated the law that when the chief muscle or muscles are attached close to the articular end of the skeletal element that end becomes concave, while, when they are attached far off or are not attached at all, as in the case of the phalanges, the articular end is convex. His mechanical explanation is ingenious and to the present writer convincing (see Handbuch der Gelenke, by R. Fick, Jena, 1904). Bernays, however, pointed out that the articular ends were moulded before the muscular tissue was differentiated (Morph. Jahrb. iv. 403), but to this Fick replies by pointing out that muscular movements begin before the muscle fibres are formed, and may be seen in the chick as early as the second day of incubation. The freely movable joints (true diarthrosis) are classified as follows: (1) Gliding joints (Arthrodia), in which the articular surfaces are flat, as in the carpal and tarsal bones. (2) Hinge joints (Ginglymus), such as the elbow and interphalangeal joints. (3) Condyloid joints (Condylarthrosis), allowing flexion and extension as well as lateral movement, but no rotation. The metacarpophalangeal and wrist joints are examples of this. (4) Saddle-shaped joints (Articulus sellarís), allowing the same movements as the last with greater strength. The carpo-metacarpal joint of the chumb is an example. (5) Ball and socket joints (Enarthrosis), allowing free movement in any direction, as in the shoulder and hip, (6) Pivot-joint (Trochoides), allowing only rotation round a longitudinal axis, as in the radio-ulnar joints. Embryology. joined by interspinous ligaments, and their tips by a supraspinous ligament, which in the neck is continued from the spine of the seventh cervical vertebra to the external occipital crest and protuberance as the ligamentum nuchae, a thin, fibrous, median septum between the muscles of the back of the neck. The combined effect of all these joints and ligaments is to allow the spinal column to be bent in any direction or to be rotated, though only a small amount of movement occurs between any two vertebrae. The heads of the ribs articulate with the bodies of two contiguous thoracic vertebrae and the disk between. The ligaments which connect them are called costo-central, and are two in number. The anterior of these is the stellate ligament, which has three bands radiating from the head of the rib to the two vertebrae and the intervening disk. The other one is the interarticular ligament, which connects the ridge, dividing the two articular cavities on the head of the rib, to the disk; it is absent in the first and three lowest ribs. The costo-transverse ligaments bind the ribs to the transverse processes of the thoracic vertebrae. The superior costo-transverse ligament binds the neck of the rib to the transverse process of the vertebra above; the middle or interosseous connects the back of the neck to the front of its own transverse process; while the posterior runs from the tip of the transverse process to the outer part of the tubercle of the rib. The inner and lower part Joints are developed in the mesenchyme, or that part of the of each tubercle forms a diarthrodial joint with the upper and mesoderm which is not concerned in the formation of the serous cavities. The synarthroses may be looked upon merely as a delay in development, because, as the embryonic tissue of the mesenchyme passes from a fibrous to a bony state, the fibrous tissue may remain along a certain line and so form a suture, or, when chondrification has preceded ossification, the cartilage may remain at a certain place and so form a synchondrosis. The diarthroses represent an arrest of development at an earlier stage, for a part of the original embryonic tissue remains as a plate of round cells, while the neighbouring two rods chondrify and ossify. This plate may become converted into fibro-cartilage, in which case an amphiarthrodial joint results, or it may become absorbed in the centre to form a joint cavity, or, if this absorption occurs in two places, two joint cavities with an intervening meniscus may result. Although, ontogenetically, there is little doubt that menisci arise in the way just mentioned, the teaching of comparative anatomy suggests that, phylogenetically, they originate as an ingrowth from the capsule pushing the synovial membrane in front of them. The subject will be returned to when the comparative anatomy of the individual joints is reviewed. In the human foetus the joint cavities are all formed by the tenth week of intra-uterine life. ANATOMY Joints of the Axial Skeleton. The bodies of the vertebrae except those of the sacrum and coccyx are separated, and at the same time connected, by the intervertebral disks. These are formed of alternating concentric rings of fibrous tissue and fibro-cartilage, with an elastic mass in the centre known as the nucleus pulposus. The bodies are also bound together by anterior and posterior common ligaments. The odontoid process of the axis fits into a pivot joint formed by the anterior arch of the atlas in front and the transverse ligament behind; it is attached to the basioccipital bone by two strong lateral check ligaments, and, in the mid line, by a feebler middle check ligament which is regarded morphologically as containing the remains of the notochord. This atlanto-axial joint is the one which allows the head to be shaken from side to side. Nodding the head occurs at the occipito-atlantal joint, which consists fore part of its own transverse process, except in the eleventh and twelfth ribs. At the junction of the ribs with their cartilages no diarthrodial joint is formed; the periosteum simply becomes perichondrium and binds the two structures together. Where another, diarthrodial joints with synovial cavities are estabthe cartilages, however, join the sternum, or where they join one lished. In the case of the second rib this is double, and in that of the first usually wanting. The mesosternal joint, between the of a symphysis. pre- and mesosternum. has already been given as an example Comparative Anatomy. For the convexity or concavity of the vertebral centra in different classes of vertebrates, see SKELETON: axial. The intervertebral disks first appear in the Crocodilia, the highest existing order of reptilia. In many Mammals the middle fasciculus of the stellate ligament is continued right across the ventral surface of the disk into the ligament of the opposite side, and is probably serially homologous with the ventral arch of the atlas. A similar ligament joins the heads of the ribs dorsal to the disk. To these bands the names of anterior (ventral) and posterior (dorsal) conjugal ligaments have been given, and they may be demonstrated in a seven months' human foetus (see B. Sutton, Ligaments, London, 1902). The ligamentum nuchae is a strong elastic band in the Ungulata which supports the weight of the head. In the Carnivora it only reaches as far forward as the spine of the axis. The JAW JOINT, or temporo-mandibular articulation, occurs between the sigmoid cavity of the temporal bone and the condyle of the jaw. Between the two there is an interarticular fibro-cartilage or meniscus, and the joint is surrounded by a capsule of which the outer part is the thickest. On first opening begins to glide forward on to the eminentia articularis (see SKULL) the mouth, the joint acts as a hinge, but very soon the condyle and takes the meniscus with it. This gliding movement between the meniscus and temporal bone may be separately brought about by protruding the lower teeth in front of the upper, or, on one side only, by moving the jaw across to the opposite side. Comparative Anatomy.-The joint between the temporal and mandibular bones is only found in Mammals; in the lower vertebrates the jaw opens between the quadrate and articular bones. In the Carnivora it is a perfect hinge; in many Rodents only the anteroposterior gliding movement is present; while in the Ruminants the lateralizing movement is the chief one. Sometimes, as in the Ornithorhynchus, the meniscus is absent. Joints of the Upper Extremity. The sterno-clavicular articulation, between the presternum and clavicle, is a gliding joint, and allows slight upward and downward and forward and backward movements. The two bony surfaces are separated by a meniscus, the vertical movements taking place outside and the antero-posterior inside this. There is a well-marked capsule, of which the anterior part is strongest. The two clavicles are joined across the top of the presternum by an interclavicular ligament. The acromio-clavicular articulation is also a gliding joint, but allows a swinging or pendulum movement of the scapula on the clavicle. The upper part of the capsule is strongest, and from it hangs down a partial meniscus into the cavity. Comparative Anatomy.-Bland Sutton regards the inter-clavicular ligament as a vestige of the interclavicle of Reptiles and Monotremes. The menisci are only found in the Primates, but it must be borne in mind that many Mammals have no clavicle, or a very rudimentary By some the meniscus of the sterno-clavicular joint is regarded as the homologue of the lateral part of the interclavicle, but the fact that it only occurs in the Primates where movements in different planes are fairly free is suggestive of a physiological rather than a morphological origin for it." one. The SHOULDER JOINT is a good example of the ball and socket or enarthrodial variety. Its most striking characteristic is mobility at the expense of strength. The small size of the glenoid cavity in comparison with the head of the humerus, and the great laxity of the capsule, favour this, although the glenoid cavity is slightly deepened by a fibrous lip, called the glenoid ligament, round its margin. The presence of the coracoid and acromial processes of the scapula, with the coraco-acromial ligament between them, serves as an overhanging protection to the joint, while the biceps tendon runs over the head of the humerus, inside the capsule, though surrounded by a sheath of synovial membrane. Were it not for these two extra safeguards the shoulder would be even more liable to dislocation than it is. The upper part of the capsule, which is attached to the base of the coracoid process, is thickened, and known as the coracohumeral ligament, while inside the front of the capsule are three folds of synovial membrane, called gleno-humeral folds. Comparative Anatomy. In the lower Vertebrates the shoulder is adapted to support rather than prehension and is not so freely movable as in the Primates. The tendon of the biceps has evidently sunk through the capsule into the joint, and even when it is intracapsular there is usually a double fold connecting its sheath of synovial membrane with that lining the capsule. In Man this has been broken through, but remains of it persist in the superior glenohumeral fold. The middle gleno-humeral fold is the vestige of a strong ligament which steadies and limits the range of movement of the joint in many lower Mammals. The ELBOW JOINT is an excellent example of the ginglymus or hinge, though its transverse axis of movement is not quite at right angles to the central axis of the limb, but is lower internally than externally. This tends to bring the forearm towards the body when the elbow is bent. The elbow is a great contrast to the shoulder, as the trochlea and capitellum of the humerus are closely adapted to the sigmoid cavity of the ulna and head of the radius (see SKELETON: appendicular); consequently movement in one plane only is allowed, and the joint is a strong one. The capsule is divided into anterior, posterior, and two lateral ligaments, though these are all really continuous. The joint cavity communicates freely with that of the superior radio-ulnar articulation. The radio-ulnar joints are three: the upper one is an example of a pivot joint,. and in it the disk-shaped head of the radius rotates in a circle formed by the lesser sigmoid cavity of the ulna internally and the orbicular ligament in the other three quarters. The middle radio-ulnar articulation is simply an interosseous membrane, the fibres of which run downward and inward from the radius to the ulna. The inferior radio-ulnar joint is formed by the disk-shaped lower end of the ulna fitting into the slightly concave sigmoid cavity of the radius. Below, the cavity of this joint is shut off from that of the wrist by a triangular fibro-cartilage. The movements allowed at these three articulations are called pronation | and supination of the radius. The head of that bone twists, in the orbicular ligament,round its central vertical axis for about half a circle. Below, however, the whole lower end of the radius circles round the lower end of the ulna, the centre of rotation being close to the styloid process of the ulna. The radius, therefore, in its pronation, describes half a cone, the base of which is below, and the hand follows the radius. Comparative Anatomy.-In pronograde Mammals the forearm is usually permanently pronated, and the head of the radius, instead of being circular and at the side of the upper end of the ulna, is transversely oval and in front of that bone, occupying the same place that the coronoid process of the ulna does in Man. This type of elbow, which is adapted simply to support and progression, is best seen in the Ungulata; in them both lateral ligaments are attached to the head of the radius, and there is no orbicular ligament, since The olecranon process of the ulna forms merely a posterior guide or the shape of the head of the radius does not allow of any supination. guard to the joint, but transmits no weight. No better example of the maximum changes which the uses of support and prehension bring about can be found than in contrasting the elbow of the Sheep or other Ungulate with that of Man. Towards one or other of these types the elbows of all Mammals tend. It may be roughly stated that, when pronation and supination to the extent of a quarter of a circle are possible, an orbicular ligament appears. radius and triangular fibro-cartilage above, and the scaphoid, The WRIST JOINT, or radio-carpal articulation, lies between the semilunar, and cuneiform bones below. It is a condyloid joint allowing flexion and extension round one axis, and slight lateral is a well-marked capsule, divided into anterior, posterior, and lateral ligaments. The joint cavity is shut off from the inferior radio-ulnar joint above, and the intercarpal joints below. bones being connected by palmar, dorsal, and a few interosseous The intercarpal joints are gliding articulations, the various ligaments, but only those connecting the first row of bones are complete, and so isolate one joint cavity from another. That part of the intercarpal joints which lies between the first and second rows of carpal bones is called the transverse carpal joint, and at this a good deal of the movement which seems to take place at the wrist really occurs. movement (abduction and adduction) round the other. There The carpo-metacarpal articulations are, with the exception of that of the thumb, gliding joints, and continuous with the great intercarpal joint cavity. The carpo-metacarpal joint of the thumb is the best example of a saddle-shaped joint in Man. It allows forward and backward and lateral movement, and is very strong. The metacarpo-phalangeal joints are condyloid joints like the wrist, and are remarkable for the great thickness of the palmar ligaments of their capsules. In the four inner fingers these glenoid ligaments, as they are called, are joined together by the transverse metacarpal ligament. The interphalangeal articulations are simple hinges surrounded by a capsule, of which the dorsal part is very thin. Comparative Anatomy.-The wrist joint of the lower Mammals allows less lateral movement than does that of Mar, while the lower end of the ulna is better developed and is received into a cup-shaped At the same socket formed by the cuneiform and pisiform bones. time, unless there is pretty free pronation and supination, the triangular fibro-cartilage is only represented by an interosseous ligament, which may be continuous above with the interosseous membrane between the radius and ulna, and suggests the possibility that the Mammals the wrist is divided into two lateral parts, as it is in the fibro-cartilage is largely a derivative of this membrane. In most human foetus, but free pronation and supination seem to cause the disappearance of the septum. Joints of the Lower Extremity. The sacro-innominate articulation consists of the sacro-iliac' joint and the sacro-sciatic ligaments. The former is one of the amphiarthroses or half-joints by which the sacrum is bound to the ilium. The mechanism of the human sacrum is that of a suspension bridge slung between the two pillars or ilia by the very strong posterior sacro-iliac ligaments which represent the chains. The axis of the joint passes through the second sacral vertebra, but the sacrum is so nearly horizontal that the weight of the body, which is transmitted to the first sacral vertebra, tends to tilt that part down. This tendency is corrected by the |