282 SKELETON. 



considerable motion is admitted in these joints. The synovia 

 is in very small quantity, not abundant enough for satisfactory 

 examination, and its character is rather inferred than proved. 

 The first cartilage is continuous with the sternum, and not se- 

 parated from it by any joint, except in rare instances. The 

 second cartilage has its joint with the sternum, separated into 

 two, one above and the other below, by a ligamentous parti- 

 tion resembling that at the heads of the ribs. The lower arti- 

 culations become, successively, more moveable than the upper. 



Besides the attachments mentioned as connecting the carti- 

 lages of the true ribs to the sternum, there is one superadded 

 to the seventh cartilage, called the Costo-Xiphoid Ligament. 

 It arises from the inferior margin of the seventh cartilage, near 

 the sternum, and going obliquely downwards and inwards, is 

 inserted into the anterior face of the xiphoid cartilage, and has 

 its upper fibres running into the corresponding fibres of its fel- 

 low. It is, of course, placed behind the rectus abdominis mus- 

 cle, and fills up, in some measure, the angle between the se- 

 venth cartilage and the third bone of the sternum. 



At the surfaces where the sixth and seventh cartilages come 

 into contact by their edges, also the seventh and eighth, a sy- 

 novial membrane exists. A similar articulation is sometimes 

 found between the fifth and sixth, and the eighth and ninth car- 

 tilages, but not uniformly. These synovial membranes are co- 

 vered by strong fibres. 



It has been already stated that the anterior extremity of each 

 of the first three cartHages of the false ribs, is united by liga- 

 mentous fibres to the cartilage above. These ligaments are 

 strong and extensive, and give great solidity to the common 

 margin of the cartilages. The last two cartilages being much 

 smaller than the others, no ligaments pass from them; but they, 

 with their ribs, are held in their position by the intercostal and 

 abdominal muscles. 



The cartilages adhere very closely to their respective ribs, 

 which receive them into the oblong fossa?, at their anterior ex- 

 tremities. The periosteum of the rib is continuous with the 

 perichondrium of the cartilage, and the membrane, which is, 

 in fact, one and the same, adheres very closely to the margins 

 of the articulation; it is also re-enforced by some ligamentous 

 fibres beneath it. No motion whatever is admitted at this ar- 

 ticulation. 



