SYMPHYSIS PUBIS. 283 



front, by the tuber ischii ; above, by the spine and lesser ligament ; behind, 

 by the greater ligament. It transmits the tendon of the Obturator Internus 

 muscle, its nerve, and the pudic vessels and nerve. 



3. ARTICULATION OF THE SACRUM AND COCCYX. 



This articulation is an amphiarthrodial joint, formed between the oval sur- 

 face, on the summit of the sacrum, and the base of the coccyx. It is analogous 

 to the joints between the bodies of the vertebrae, and is connected by similar 

 ligaments. They are the 



Anterior Sacro-coccygeal. 



Posterior Sacro-coccygeal. 



Interarticular Fibro-cartilage. 



The Anterior Sacro-coccygeal Ligament consists of a few irregular fibres, which 

 descend from the anterior surface of the sacrum to the front of the coccyx, be- 

 coming blended with the periosteum. 



The Posterior Sacro-coccygeal Ligament is a flat band of ligamentous fibres, 

 of a pearly tint, which arises from the margin of the lower orifice of the sacral 

 canal, and descends to be inserted into the posterior surface of the coccyx. This 

 ligament completes the lower and back part of the sacral canal. Its superficial 

 fibres are much longer than the deep-seated ; the latter extend from the apex 

 of the sacrum to the upper cornua of the coccyx. This ligament is in relation 

 in front with the arachnoid membrane of the sacral canal, a portion of the 

 sacrum and almost the whole of the posterior surface of the coccyx ; behind, 

 with the Gluteus Maximus. 



An Interarticular Fibro-cartilage is interposed between the contiguous sur- 

 faces of the sacrum and coccyx ; it differs from that interposed between the 

 bodies of the vertebrae in being thinner, and its central part more firm in tex- 

 ture. It is somewhat thicker in front and behind than at the sides. Occasion- 

 ally a synovial membrane is found where the coccyx is freely movable, which 

 is more especially the case during pregnancy. 



The different segments of the coccyx are connected together by an extension 

 downwards of the anterior and posterior sacro-coccygeal ligaments, a thin an- 

 nular disk of fibro-cartilage being interposed between each of the bones. In 

 the adult male, all the pieces become ossified ; but in the female, this does not 

 commonly occur until a later period of life. The separate segments of the 

 coccyx are first united, and at a more advanced age the joint between the 

 sacrum and the coccyx is obliterated. 



Actions. The movements which take place between the sacrum and coccyx, 

 and between the different pieces of the latter bone, are slightly forwards and 

 backwards ; they are very limited. Their extent increases during pregnancy. 



4. ARTICULATION OF THE PUBES. (Fig. 196.) 



The articulation between the pubic bones is an amphiarthrodial joint, formed 

 by the junction of the two oval articular surfaces of the ossa pubis. The arti- 

 cular surface has been described above under the name of symphysis, and the 

 same name is given to the joint. The ligaments of this articulation are the 



Anterior Pubic. Posterior Pubic. 



Superior Pubic. Sub-Pubic. 



Interarticular Fibro-cartilage. 



The Anterior Pubic Ligament consists of several superimposed layers, which 

 pass across the front of the articulation. The superficial fibres pass obliquely 

 from one bone to the other, decussating and forming an interlacement with the 

 fibres of the aponeurosis of the External Oblique muscle. The deep fibres 

 pass transversely across the symphysis, and are blended with the interarticular 

 fibro-cartilage. 



