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) (¢). The angle is 
marked by a projecting process (¢) 
(angular process) on its lateral bor- 
der, for attachment of a ligament. 
The ribs increase in length to 
the ninth (the ninth and tenth are 
of the same length) and then de- 
crease to the last. They decrease iif | 
in breadth behind the fifth. The |i 
first is nearly in a dorsoventral Uli 
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 
process. Sipe, CRANIAL VIEW. 
The first nine ribs (true ribs or 4, head; 4, tubercle; «, tuber- 
cular facet; d, neck; e¢, angle, 
coste vere) are attached separately with angular process; f, carti- 
to the sternum by their costal carti- lage. 
lages. The last four (false ribs or coste spuriz) 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. 
