OF THE STERXUM 211 



above with the sui)cnor, and on the outer siile with the ])ostenor costo-transverse 

 hganients. The eleventh and twelfth ribs are unprovided with a ca])sule. 



The middle costo-transverse, or interosseous ligament (fig. 216), consists 

 of short libres passing between the Ixick of tlie neck of the rib and front of the 

 transverse process, with which the tubercle articulates. It extends from the 

 capsule of the central costo-vertebral joint to that of the costo-transverse. It is 

 best seen on horizontal section through the bones. In the eleventh and twelfth 

 ribs tliis ligament is rudimentary. 



The posterior costo-transverse ligament (iig. 216) is a short but tliiek, 

 strong, and bi-oad ligament, which extends outwards and upwards from the 

 extremity of the transverse process to the non-articular surface of the tubercle 

 of the corresponding rib. The eleventh and twelfth ribs have no posterior 

 ligament. 



The superior costo-transverse ligament (fig. 215) is a strong, broad band of 

 fil)res which ascends outwards from tlie crest on the upper border of the neck 

 of the rib, to the lower border of the transverse process above. A fcAV scattered 

 posterior fibres pass upwards and inwards from the neck to the transverse process. 

 It is best seen from the front. Its inner 1)order l)ounds the foramen through 

 Avhich the posterior branches of the intercostal vessels and nerves pass. To 

 the external border is attached the thm aponeurosis covering the external inter- 

 costals. Its anterior surface is in relation with the intercostal vessels and nerve; 

 the posterior with the lonjissimus dorsi. The first rib has no superior costo- 

 transverse ligament. 



The synovial membrane (fig. 216) is a single sac. 



The arterial and nerve supplies come from the posterior l)ranches of the inter- 

 costal arteries and nerves. 



The movements which take place at these j<jints are lindted to a gliding of the 

 tubercle of the rib upon the transverse process. The exact position of the facet on 

 the transverse process varies slightly from alcove downwards, being placed higln-r 

 on the processes of the lower vertebrae. The plane of movement in most of the 

 costo-transverse joints is inclined upwards and liackwards in inspiration, and 

 downwards and forwards in expiratiijn. The point round Avhieli these movements 

 occur is the head of the rib, so that the tubercle of the ril) glides upon the 

 transverse process in the circumference of a circle, the centre of which is at the 

 costo-central joint. 



•l. THE ARTICULATIONS AT THE FRONT OF THE THORAX 



These may be divided into four sets, viz. : — 



(a) The intersternal joints, or the union of the several parts of the sternum 

 with one another. 



(b) The costo-chondral joints, or tlie union of the ribs with their co.stal 

 cartilages. 



(c) The chondro-sternal articulations, or the junction of the costal cartilages 

 with the sternum. 



(d) The interchondral joints, or tlie union of five costal cartilages (sixth, 

 seventh, eightfi, ninth, and tenth) with one another. 



(a) The Intersternal Joints, or the Union of the Segments of the Sternum 



WITH ONE another 



The sternum being composed, in the adult, of three distinct jneces, — the manu- 

 brium, the gladiolus or body, and the xiphoid. — has two articulations, viz., the 

 Superior, Avhich unites the manubrium with the gladiolus, and tlie Inferior, which 

 unites the gladiolus with the xiphoid. 



