ELEMENTS OF MAMMALIAN ANATOMY. 



to the seventh inclusive are attached at the junctions of the 

 sternebrse. The eighth and ninth ribs are attached near 

 together on the caudal end of the seventh sternebra. 



RIBS. 



There are thirteen pairs of ribs in the cat. The nine 

 cranial are called true ribs because they articulate dorsally 

 with the spinal column and ventrally with the sternum. 

 The other four (Fig. 28) are false 

 ribs, three of which articulate ventrally 

 with other ribs, while the fourth has 

 no ventral articulation, and is there- 

 fore called a floating rib. Each rib 

 is composed of two parts, the vertebral 

 or bony portion and the sternal or car- 

 tilaginous portion. 



The following description of the 

 sixth will serve to give a correct idea 

 in general of the anatomy of a rib. Its 

 vertebral portion (Fig. 29) presents 

 four features: a head or capitulum, 

 which articulates with the bodies of 

 the fifth and sixth thoracic vertebrae ; a 

 tubercle, which articulates with the 

 transverse process of the sixth thoracic 

 vertebra; a neck, which is the con- 

 stricted portion between the capitulum 

 and tubercle; and the shaft, including 

 the portion of the rib between the 

 tubercle and its articulation with the sternal or cartilaginous 

 portion. The bend in the shaft beyond the tubercle is the 

 angle. The sternal portion of the rib, consisting of carti- 

 lage, is sometimes called the costal rib. In the sixth rib the 

 costal portion is about half as long as the vertebral portion. 



FIG. 29. CAUDAL AS- 

 PECT OF SIXTH RIB. 



ag, Angle; cr, pit for 

 articulation with 

 cartilaginous p o r - 

 tion; h, capitulum; 

 nk, neck ; sh, shaft ; 

 tb, tubercle with 

 facet for articula- 

 tion with transverse 

 process. 



