236 THE ARTICULATIONS 



The ligaments connecting these parts are the 



Anterior Costo-trans verse. 



Middle Costo-trans verse (Interosseous). 



Posterior Costo-transverse. 



Capsular. 



The Anterior Costo-transverse Ligament (superior or long) consists of two sets 

 of fibres : the one (anterior) is attached below to the sharp crest on the upper 

 border of the neck of each rib, and passes obliquely upward and outward to the 

 lower border of the transverse process immediately above; the other (posterior) is 

 attached below to the neck of the rib, and passes upward and inward to the base 

 of the transverse process and outer border of the lower articular process of the 

 vertebra above. This ligament is in relation, in front, with the intercostal vessels 

 and nerves ; behind, with the Longissimus dorsi. Its internal border is thickened 

 and free, and bounds an aperture through which pass the posterior branches of the 

 intercostal vessels and nerves. Its external border is continuous with a thin 

 aponeurosis which covers the External intercostal muscle. 



The first rib has no anterior costo-transverse ligament. 



The Middle Costo-transverse or Interosseous Ligament consists of short but 

 strong fibres which pass between the rough surface on the posterior part of the 

 neck of each rib and the anterior surface of the adjacent transverse process. In 



FIG. 161. Costo-transverse articulation. Seen from above. 



order fully to expose this ligament, a horizontal section should be made across the 

 transverse process and corresponding part of the rib ; or the rib may be forcibly 

 separated from the transverse process and its fibres put on the stretch. 



In the eleventh and twelfth ribs this ligament is quite rudimentary or 

 wanting. 



The Posterior Costo-transverse Ligament is a short but thick and strong fascic- 

 ulus which passes obliquely from the summit of the transverse process to the 

 rough non-articular portion of the tubercle of the rib. This ligament is shorter 

 and more oblique in the upper than in the lower ribs. Those corresponding to 

 the superior ribs ascend, while those of the inferior ribs descend slightly. 



In the eleventh and twelfth ribs this ligament is wanting. 



