RIBS. 



19 



on the lateral surface is an elevated area, the tubercle, marked 

 by the smooth tubercular facet (c) for articulation with the 

 transverse process of a vertebra. 

 The constricted portion between the 

 head and tubercle is known as the 

 neck (collum) (d). The angle is 

 marked by a projecting process (e) 

 (angular process) on its lateral bor- 

 der, for attachment of a ligament. 



The ribs increase in length to 

 the ninth (the ninth and tenth arc 

 of the same length) and then de- 

 crease to the last. They decrease 

 in breadth behind the fifth. The 

 first is nearly in a dorsoventral 

 plane, while the others have their 

 dorsal ends inclined slightly craniad. 



The tubercles become less promi- 

 nent as we pass caudad and are absent 

 on the last two or three ribs, which 



do not articulate with the transverse 



Fig. 15. — Fifth Rib of Left 

 piocess. Side, Cranial View. 



The first nine ribs (true ribs or «, head; d, tubercle; c, tuber- 



costae verae)are attached separately wtth\tg?ii/proSs'; /, ""c^^^^^^^ 

 to the sternum by their costal carti- ^''^g^- 



lages. The last four (false ribs or costze spuria^) are not 

 attached separately to the sternum. The costal cartilages of 

 the tenth, eleventh, and twelfth are united to one another at 

 their sternal ends. They may be united also to the ninth 

 costal cartilage or to the sternum by a common cartilage of 

 insertion, or they may be quite free from the sternum. The 

 thirteenth costal cartilages are free (floating ribs). 



Ligaments of the Ribs.— The articular surfaces between 

 the head of the rib and the centra, and between the tubercle 

 and the transverse process of the vertebra, have each an 

 articular capsule. There are also a number of small liga- 

 mentous bands from the tuberosity and the neck of the rib to 

 the transverse process of the vertebra. 



