COSTO-STERNAL ARTICULATIONS, ETC.: POSTERIOR VIEW. 1 to 10. The ten superior ribs. 11. Clavicle. 12. Manubrium sterni. 13. Body of sternum. 14. Ensiform cartilage. 15, 15. Posterior costosternal ligaments. 16. Superior costosternal ligament. 17. Inferior costo-sternal ligament. Fig. 13 rests upon the middle of the posterior sternal ligament. 18, 18. Aponeurotic laminae of the exterior intercostal muscles. 19. Costo-clavicular or rhomboid ligament. 20. Posterior sterno-clavicular ligament.]

form cartilage, which latter they are intended to support. They are named the rosto-xyphoid ligaments.

[FIG. 128.

SECTION OF STERNUM, CLAVICLE, AND COSTAL CARTILAGES, showing the spongy character of the sternum; the sterno-clavicular articulation; and the articulations of the costal cartilages, with each other, with the sternum, and with the ribs. 1 to 10. The ten superior ribs. 1 to 4 shows the mode of union between the costal cartilages and the ribs. 11. Clavicle. 12. Manubrium sterni. 13. Body of sternum. 14. Ensiform cartilage. 15. Superior synovial membrane of sterno-clavicular joint. 16. Interarticular cartilage of same. 17. Inferior synovial membrane of same. 18, 18. Aponeurotic lamine of external intercostal muscles. 19. Costo-clavicular or rhomboid ligament. 20 to 21. Articulations of costal cartilages with each other, showing the synovial membranes. 22. A second articulation which sometimes occurs between the sixth and seventh cartilages. 23. Ligamentous fibres connecting the extremities of the ninth and tenth cartilages.]

The sixth, seventh, and eighth, and sometimes the fifth and the ninth costal cartilages, have articulations with each other, and a synovial membrane at cach articulation. They are connected by ligamentous fibres, (ligamenta corruscantia), which pass from one cartilage to the other, external and internal ligaments.

The ninth and tenth are connected at their extremity by ligamentous fibres, but have no synovial membrane.

Actions. The movements of the costo-sternal articulations are very trifling, being limited to a slight degree of sliding motion. The first rib is the least, the second the most movable.

[The costal cartilages are immovably united by their outer extremities to the anterior extremities of the ribs, which are excavated to receive them. The only bond of union between them, is periosteum.]

8. Articulation of the Sternum. The pieces of the sternum are connected by means of a thin plate of interosseous cartilage placed between each, and by an anterior and posterior ligament (membrana ossium sterni). The fibres of the anterior sternal ligament are longitudinal in direction, but so blended with the anterior costo-sternal ligaments and tendinous fibres of origin of the pectoral muscles, as scarcely to be distinguished as a distinct ligament. The posterior sternal ligament is a broad smooth plane of longitudinal fibres, placed on the posterior surface of the bone, and extending from the manubrium to the ensiform cartilage. These ligaments contribute very materially to the strength of the sternum and elasticity of the front of the chest; their continuation downwards on the ensiform cartilage constitutes the sterno-xyphoid ligaments.

9. Articulation of the Vertebral Column with the Pelvis. - The last lumbar vertebra is connected with the sacrum by the same ligaments as those with which the various vertebræ are connected to each other; viz., anterior and posterior common ligament, intervertebral substance, ligamenta subflava, capsular ligaments, interspinous and supraspinous ligament.

There are, however, two proper ligaments connecting the vertebral column with the pelvis; these are, the

The lumbo-sacral or sacro-vertebral ligament is a thick triangular fasciculus of ligamentous fibres, connected above with the transverse process of the last lumbar vertebra, and below with the posterior part of the upper border of the sacrum.

The lumbo-iliac or ilio-lumbar ligament passes from the apex of the transverse process of the last lumbar vertebra to that part of the crest of the ilium which surmounts the sacro-iliac articulation. It is triangular in form.

10. Articulations of the Pelvis. -The ligaments of the articulations of the pelvis are divisible into four groups: -1, those connecting the sacrum and ilium; 2, those passing between the sacrum and ischium; 3, between the sacrum and coccyx; and, 4, between the two pubic bones.

1st, Between the sacrum and ilium.

Sacro-iliac anterior,
Sacro-iliac posterior.

2d, Between the sacrum and ischium.
Sacro-ischiatic anterior (short),
Sacro-ischiatic posterior (long).

3d, Between the sacrum and coccyx.
Sacro-coccygean anterior,
Sacro-coccygean posterior.

1. Between the Sacrum and Ilium. -The anterior sacro-iliac ligament consists of numerous short ligamentous bands and fibres, which pass from bone to bone on the anterior surface of the joint.

The posterior sacro-iliac or interosseous ligament (ileo-sacrale breve) is composed of numerous strong fasciculi of ligamentous fibres, which pass horizontally between the rough surfaces of the posterior half of the sacro-iliac articulation, and constitute the principal bond of connexion between the sacrum and ilium. One fasciculus of this ligament, longer and larger than the rest, is distinguished, from its direction, by the name of oblique sacro-iliac ligament (ileo-sacrale longum). It is attached, by one extremity, to the posterior superior spine of the ilium; and, by the other, to the third transverse tubercle on the posterior surface of the sacrum.

The surfaces of the two bones forming the sacro-iliac articulation are partly covered with cartilage, and partly rough and connected by the interosseous liga

FIG. 129.

JOINT.

1. Lower part of the anterior common ligament of the vertebræ, extending downwards over the front of the sacrum. 2. Lumbo-sacral ligament.

3. Lumbo-iliac ligament. 4. Anterior

sacro-iliac ligament. 5. Obturator mem

brane. 6. Poupart's ligament. 7. Gim

bernat's ligament. 8. Capsular ligament of the hip-joint. 9. Ilio-femoral or accessory ligament.

ment. The anterior or auricular half is coated with cartilage, which is thicker on the sacrum than on the ilium. The surface of the cartilage is uneven, and provided with a delicate synovial membrane, not demonstrable in the adult, but apparent in the young subject and in the female during pregnancy.

2. Between the Sacrum and Ischium.The anterior or lesser sucro-ischiatic ligament (sacro-ischiadicum minus) is thin, and triangular in form; it is attached by its apex to the spine of the ischium; and by its broad extremity to the side of the sacrum and coccyx, interlacing its fibres with the greater sacro-ischiatic ligament.

The anterior sacro-ischiatic ligament is in relation, in front, with the coccygeus muscle; behind, with the posterior ligament, with which its fibres are intermingled. By its upper border it forms part of the lower boundary of the great sacro-ischiatic foramen, and by the lower, part of the lesser sacroischiatic foramen.

The posterior or greater sacro-ischiatic ligament (sacro-ischiadicum majus), larger, thicker, and posterior to the preceding, is

narrower in the middle than at each extremity. It is attached, by the smaller end, to the inner margin of the tuberosity and ramus of the ischium; where it forms a falciform process, which protects the internal pudic artery, and is continuous with the obturator fascia. By its larger extremity it is inserted into the side of the coccyx, sacrum, and posterior inferior spine of the ilium.

The posterior sacro-ischiatic ligament is in relation, in front, with the anterior ligament; behind, with the gluteus maximus, to some fibres of which it gives origin. By its superior border it forms part of the boundary of the lesser ischi

atic foramen, and by its lower border, part of the boundary of the perineum. It is pierced by the coccygeal branch of the ischiatic artery. The two ligaments convert the sacro-ischiatic notches into foramina.

3. Between the Sacrum and Coccyx.-The anterior sacro-coccygean ligament is a thin fasciculus passing from the anterior surface of the sacrum to the front of the coccyx.

The posterior sacro-coccygean ligament is a thick ligamentous layer, which completes the lower part of the sacral canal, and connects the sacrum with the coccyx posteriorly, extending as far as the apex of the latter bone.

FIG. 130.

LIGAMENTS OF THE PELVIS AND HIP-JOINT; LATERAL VIEW. 1. Oblique sacro-iliac ligament. The other fasciculi of the posterior sacro-iliac ligament are not seen in this view of the pelvis. 2. Posterior sacro-ischiatic ligament. 3. Anterior sacro-ischiatic ligament. 4. Great sacro-ischiatic foramen. 5. Lesser sacro-ischiatic foramen. 6. Cotyloid ligament of the acetabulum. 7. Ligamentum teres. 8. Cut edge of the capsular ligament, showing its extent posteriorly, as compared with its anterior attachment. 9. Obturator membrane only partly seen.

Between the two bones is a thin disk of soft fibrous cartilage; and in females not unfrequently a synovial membrane. The articulation admits of a certain degree of movement backwards during parturition.

The ligaments connecting the different pieces of the coccyx consist of a few scattered anterior and posterior fibres, and a thin disk of interosseous cartilage; the latter exists only in the young subject, as in the adult the pieces become ossified.

4. Between the Ossa Pubis. The anterior pubic ligament is composed of ligamentous fibres, which pass obliquely across the union of the two bones from side to side, and form an interlacement in front of the symphysis.

The posterior pubic ligament consists of a few irregular bands of fibres uniting the pubic bones posteriorly.

The superior pubic ligament is a thick band of fibres connecting the angles of the ossa pubis superiorly, and filling the inequalities of the surface of the bones. The sub-pubic ligament is a thick arch of fibres connecting the two bones inferiorly, and forming the upper boundary of the pubic arch.

The interosseous fibro-cartilage unites the two surfaces of the pubic bones, in the same manner as the intervertebral substance connects the bodies of the vertebræ. It resembles the intervertebral substance also in being composed of oblique fibres disposed in concentric layers, which are more dense towards the

surface than near the centre. It is thick in front, and thin behind; and a synovial membrane is sometimes found in the posterior half of the articulation.

This articulation becomes movable towards the latter term of pregnancy, and admits of a slight degree of separation of its surfaces.

The obturator ligament (membrana obturatoria) is not a ligament of articulation, but simply a ligamentous membrane stretched across the obturator foramen. It gives attachment by its surfaces to the two obturator muscles, and leaves a space in the upper part of the foramen for the passage of the obturator vessels and nerve.

The numerous vacuities in the walls of the pelvis, and their closure by ligamentous structures, as in the case of the sacro-ischiatic fissures and obturator foramina, serve to diminish the pressure on the soft parts during the passage of the head of the foetus through the pelvis in parturition.

LIGAMENTS OF THE UPPER EXTREMITY.

The Ligaments of the upper extremity may be arranged in the order of the articulations of the different bones: they are,

1. Sterno-clavicular articulation.

2. Scapulo-clavicular articulation.
3. Ligaments of the scapula.
4. Shoulder joint.

5. Elbow joint.

6. Radio-ulnar articulation.

7. Wrist joint.

8. Articulation between the carpal bones.

9. Carpo-metacarpal articulation.

10. Metacarpo-phalangeal articulation.
11. Articulation of the phalanges.

1. Sterno-clavicular Articulation. - The sterno-clavicular is an arthrodial

articulation; its ligaments are,

Anterior sterno-clavicular,

Posterior sterno-clavicular,

Inter-clavicular,
Costo-clavicular (rhomboid).

Interarticular fibro-cartilage,
Two synovial membranes.

The anterior sterno-clavicular ligament is a broad ligamentous layer, extending

FIG. 131.

LIGAMENTS OF THE STERNO-CLAVICULAR AND COSTO-STERNAL ARTICULATIONS. 1. Anterior sterno-clavicular ligament. 2. Inter-clavicular ligament. 3. Costo-clavicular or rhomboid ligament; seen on both sides. 4. Interarticular fibro-cartilage, brought into view by the removal of the anterior and posterior ligaments. 5. Anterior costo-sternal ligaments of the first and second rib.

obliquely downwards and inwards, and covering the anterior aspect of the articulation. This ligament is in relation by its anterior surface with the integument and sternal origin of the sterno-mastoid muscle; and behind with the interarticular fibro-cartilage and synovial membranes.

The posterior sterno-clavicular ligament is a broad band covering the posterior surface of the articulation. It is in relation by its anterior surface with the interarticular fibro-cartilage and synovial membranes; and behind, with the sterno-hyoid and sterno-thyroid muscle.

The anterior and posterior ligament are continuous at the upper and lower part of the articulation, so as to form a capsule around the joint.

The inter-clavicular ligament is a cord-like band which crosses from the

extremity of one clavicle to that of the other, and is closely adherent to the