244 THE ARTICULATIONS. 



sciatic ligament. It transmits the tendon of the Obturator internus muscle, its 

 nerve, and the internal pudic vessels and nerve. 



3. ARTICULATION OF THE SACRUM AND COCCYX. 



This articulation is an amphiarthrodial joint, formed between the oval surface 

 at the apex 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. Lateral Sacro-coccygeal. 



Posterior Sacro-coccygeal. Interposed Fibro-cartilage. 



Interarticular. 



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, becom- 

 ing blended with the periosteum. 



The Posterior Sacro-coccygeal Ligament is a flat band 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 more deeply seated. This ligament is in relation, behind, with the 

 Gluteus maximus. 



The Lateral Sacro-coccygeal Ligaments connect the transverse processes of the 

 coccyx to the lower lateral angles of the sacrum. 



A Fibro-cartilage is interposed between the contiguous surfaces of the sacrum 

 and coccyx ; it differs from that interposed between the bodies of the vertebrae in 

 being thinner, and its central part firmer in texture. It is somewhat thicker in 

 front and behind than at the sides. Occasionally, a synovial membrane is found 

 when the coccyx is freely movable, which is more especially the case during 

 pregnancy. 



The Interarticular Ligaments are thin bands of ligamentous tissue which 

 connect the cornua of the two bones together. x 



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

 downward of the anterior and posterior sacro-coccygeal ligaments, a thin annular 

 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 coccyx is ob- 

 literated. 



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

 and between the different pieces of the latter bone, are forward and backward ; 

 they are very limited. Their extent increases during pregnancy. 



4. ARTICULATION OF THE OSSA PUBIS (SYMPHYSIS PUBIS) (Fig. 167). 



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 ligaments 

 of this articulation are the 



Anterior Pubic. Posterior Pubic. 



Superior Pubic. Subpubic. 



Interpubic Disk. 



