130 ARTICULATIONS OF THE TRUNK AND HEAD. 



The middle or interosseous costo-transverse ligament, or ligamentum colli 

 cost<x t consists of a series of very short parallel fibres, which unite the neck 



of the rib to the anterior 

 Fig. 119. surface of the contiguous 



Fig. 119. HORIZONTAL SECTION 

 OP A DORSAL VERTEBRA, WITH 

 THE ADJACENT PORTIONS OF TWO 

 RIBS. 



1, the rib ; 2, transverse pro- 

 cess ; 3, anterior costo-central liga- 

 ment ; 5, posterior costo-transverse 

 ligament ; 6, interosseous or middle 

 costo-transverse ligament. 



transverse process. These 

 fibres are seen on removing 

 by horizontal section a por- 

 tion of the rib and transverse process, and forcibly drawing the one from 

 the other. 



The anterior, superior, or long costo-transverse ligament 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 lowest ribs and the transverse processes. 



The COSTO-STERNAL AftTicuLATiONS, situated between the anterior angular 

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

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

 and supported by anterior, posterior, upper and lower ligaments. 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 inconsider- 

 able, and are placed above and below the joint. The synovial membranes are 

 interposed between the end of the cartilage of each true rib (excepting the 

 first) and the sternum, and may best be demonstrated by slicing off a little 

 of the anterior surface of the sternum and cartilage ; that of the seventh 

 is single ; the others are usually divided into an upper and lower cavity, be- 

 tween which interarticular fibres are attached to the end of the cartilage and to 

 the sternum. The cartilage of the first rib is 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 cartilage, is called the 

 costo-xiphoid ligament. 



Articulation of the cartilages one with another. The contiguous edges of 

 the cartilages of some of the ribs, viz. , from the sixth to the ninth, have 

 a part of their adjacent borders smoothed into articular surfaces, which are 

 lined by synovial membranes, and are held in connection by ligamentous 

 fibres. 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. 



