142 



AETICULATIOXS OF THE TRUNK. 



fibres are seen on rcmovino; by horizontal section a portion of the rib 

 and transverse process, and forcibly drawing the one from the other. 



Fi£r. 12S. 



Fig. 128.— Horizontal Section 

 OP A Dorsal Vertebra, with 



THE adjacent I'ORTIOIfS OF TWO 



Ribs. | 



1, the rib ; 2, transverse i^ro- 

 cesi ; 3, anterior costo-central liga- 

 ment ; 5, iiosterior costo-trausverse 

 ligament ; 6, interosseous or middle 

 costo -transverse ligament. 



The superior costo- 

 transverse ligament, (Ul- 

 terior or Joiyi, consists of 

 fasciculi of fibres, passing 

 from the neck of the rib 

 obliquely upwards and outwards to the lower margin of the transverse 

 process next above it. It does not exist in the articulation of the first 

 rib. 



There are no synovial joints, but only posterior costo-transverse 

 ligaments, between the two lovrest ribs and the transverse processes. 



Tlie cosTO-STERNAL ARTICULATIONS, situated l:)etween the anterior 

 extremities of the cartilages of the sternal ribs, and the corresponding 

 fossa3 in the margins of the sternum, consist of small synovial capsules 

 covered and supported byjinterjor, posterior, upper aucLlower lignmcnff. 

 The anterior ligamentous fibres are thin, scattered, and radiated, passing 

 from the extremity of the cartilage to the anterior surface of the 

 sternum, where they interlace with those of the opposite side, and are 

 blended with the aponeurosis of the pectoralis major muscle ; the 

 posterior fibres are similarly disposed, but not so thick or numerous, 

 and connect the thoracic surfaces of the same parts ; the upper and 

 lower ligamentous fibres are inconsiderable, and are placed above and 

 below the joint. SijnoviaJ cavities are interpased between the end of 

 the cartilage of each true rib (excepting the first) and the sternum, that 

 of the seventh is single ; the others are usually divided into an upper 

 and lower cavity by interarticular fibres attached to the end of the 

 cartilage and to the sternum. The cartilage of the first rib is almost 

 always directly united to the sternum. 



A thin fasciculus of fibres connecting the cartilage of the seventh 

 rib, and sometimes likewise that of the sixth, with the xiphoid car- 

 tilage, is called the cosio-xiphoid ligament. 



Articulation of the cartilages one with another. — The cartilages 

 of some of the ribs, viz., from tlie sixth to the ninth, have a part of 

 their adjacent borders smoothed into articular surfaces, which are held 

 in connection l)y ligamentous fibres, lined by synovial membranes. Some 

 of the articular surfaces are occasionally found to be wanting. 



Connection of the ribs with their cartilages. — The external 

 extremities of the cartilages are fixed into the oval depressions on the 

 ends of the ribs, and the union receives support from the periosteum. 



Ligaments of the sternum. — The manubrium, ).)ody, and xiphoid 

 process of the sternum, so long as they are not united by bone, are 

 connected by ini:ervcning cartilage, and by anterior and posterior liga- 

 ments, which have chiefly a longitudinal direction. The whole sternum 



