AETHROLOGY. 105 



placed are separated by tlie two layers of the membranif orm 

 portion of this ligament. The muscles mainly thus sei)a- 

 rated are the complexi majores. The superior margin of 

 this portion blends with the cordiform portion, which is a 

 rounded band of yellow elastic tissue, extending from the 

 superior extremity of the spine of the fifth dorsal ver- 

 tebra (where it is directly continuous with the superspinous 

 ligament) to the postero-inferior part of the crest of the 

 occiput and the line between its scabrous pits. To its 

 upper surface, which is flattened, is attached the fatty mane, 

 and on either side it affords more or less direct attach- 

 ment to panniculus carnosus, levator humeri, splenius, tra- 

 pezius, rhomboideus and complexus major. This elastic 

 ligament serves to support the head without muscular 

 exertion. 



COSTAL ARTICULATIONS. 



The upper extremity of the rib presents three synovial 

 surfaces for union with the spine. The tubercle articu- 

 lates with the transverse process of the vertebra behind, by one 

 facet which has a synovial membrane (strengthened to form 

 a capsular ligament) and tivo costo-transverse lateral 

 strengtheriincj bands, one externally, the other internally 

 placed. The head of the rib presents two facets separated 

 by a roughened groove. The facets unite by diarthrosis 

 with corresponding facets, one on the postero-superior and 

 lateral part of the body of the vertebra in front, the other 

 with the antero-superior and lateral part of the vertebra 

 behind. Each of these facets has a synovial membrane 

 strengthened to form a capsular ligament, and from the 

 groove between ligamentum teres runs to the intervertebral 

 disc. From the inner surface of the neck of the rib the 

 stellate ligament runs, and divides into three parts, one of 

 which runs to the body of the vertebra in front, another to 

 the body of the vertebra behind, the third to the inter- 

 vertebral disc of cartilage. 



The gomphotic union of the inferior extremity of the 

 rib with the sterno-costal cartilage is maintained by con- 

 tinuity of the costal periosteum with the investing peri- 

 chondrium of the cartilage. The inferior extremity of the 

 cartilage of elongatio7i has a diarthrodial union with the 

 sternal cartilage or bones in the case of all the true ribs ; 

 it presents a synovial membrane and tivo lateral ligaments, 



