COSTO- TRANS VERSE. 



199 



eleventh, and twelfth ribs, the interarticular ligament does not exist; consequently, 

 there is but one synovial membrane. 



Actions. The movements permitted in these articulations are limited to eleva- 

 tion, depression, and slightly forwards and backwards. This movement varies, 

 however, very much in its extent in different ribs. The first rib is almost entirely 

 immovable, excepting in deep inspiration. The movement of the second rib is 

 also not very extensive. In the other ribs, their mobility increases successively 

 to the last two, which are very movable. The ribs are generally more movable 

 in the female than in the male. 



2. ARTICULATION BETWEEN THE NECK AND TUBERCLE OF THE RIBS WITH 

 THE TRANSVERSE PROCESSES. 



The ligaments connecting these parts, are : 



Anterior Costo-transverse. 



Middle Costo-transverse (Interosseous). 



Posterior Costo-transverse. 



Capsular. 



The Anterior Costo-transverse Ligament (fig. 125) is a broad and strong band 

 of fibres, attached, below, to the sharp crest on the upper border of the neck of 

 each rib, and passing obliquely upwards and outwards, to the lower border of the 



Fig. 125. Costo-transverse Articulation. Seen from above. 



CAPSULAR MEMBRA S 



transverse process immediately above. It is broader below than above, broader 

 and thinner between the lower ribs than between the upper, and more distinct in 

 front than behind. This ligament is in relation, in front, with the intercostal 

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

 completes an aperture formed between it and the articular processes, through 

 -yhich pass the posterior branches of the intercostal vessels and nerves. Its ex- 

 it border is continuous with a thin aponeurosis, which covers the External 

 itercostal muscle. 



T\\Q first and last ribs have no anterior costo-transverse ligament. 

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

 trong, fibres, which pass between the rough surface on the posterior part of the 



