LIGAMENTS OF THE UPPER EXTREMITY. 149 



sacrum with the coccyx posteriorly, extending as far as the apex of the 

 latter bone. 



Between the two bones is a thin disc of soft fibrous cartilage. In 

 females there is frequently a small synovial membrane. This 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 disc of interosseous 

 cartilage : they exist only in the young subject ; 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 sym- 

 physis. 



The posterior pubic ligament consists of a few irregular fibres uniting 

 the pubic bones posteriorly. 



The superior pubic ligament is a thick band of fibres connecting the 

 angles of the pubic bones superiorly, and filling the inequalities upon 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 Jibro- cartilage unites the two surfaces of the pubic 

 bones, in the same manner as the intervertebral substance connects the 

 bodies of the vertebrae. 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. A synovial membrane is sometimes found in the poste- 

 rior 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 or membrane is not a ligament of articulation, 

 but simply a tendino-fibrous membrane stretched across the obturator 

 foramen. It gives attachment by its surfaces, to the two obturator mus- 

 cles, 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 very materially the pressure on the 

 soft parts during the passage of the head of the fetus through the pelvis 

 in parturition. 



LIGAMENTS OF THE UPPER EXTREMITY. 



The Ligaments of the upper extremity may be arranged in the order ot 

 the articulations between the different bones ; they are, the 



1. Sterno-clavicular articulation. 8. Articulation between the carpa,. 



2. Scapulo-clavicular articulation. bones. 



3. Ligaments of the scapula. 9. Carpo-metacarpal articulation 



4. Shoulder joint. 10. Metacarpo-phalangeal articuln- 



5. Elbow joint. tion. 



o. Radio-ulnar articulation. 11. Articulation of the phalanges. 



7. Wrist joint. 



1. Sterno-clavicular Articulation. The sterno- clavicular is an arth>o 

 dial articulation ; its ligaments are. 

 13* 



