132 



MAMMALIAN ANATOMY 



CHAPTER III 



THE RIBS, THE STERNUM, AND THE THORAX 



FIG. 94. 



Vertebml Column. 



Hyoid. 



Clavicle. 

 Sternum. 



Metacarpus. 



Metatarsus. 

 Phalanges. 



THE SKELETON OF THE CAT. (LEFT SIDE ONLY.) 



THE RIBS. 



THE Ribs are slender, curved bars which form the greater part 

 of the chest-walls. They consist of thirteen pairs, each pair 

 composed of a right and a left rib. The thirteen pairs are arranged 

 parallel to one another, and with their long axes directed, in general, 

 from the dorsal to the ventral side of the body. Their dorsal ends 

 are attached to the vertebral column, and the ventral ends of most 

 of them join the sternum. A typical pair of ribs, therefore, forms 

 with a vertebral body and with a joint of the sternum a ventral 

 ring, sometimes called a haemal arch. The thirteen haemal arches 

 together form the conical cage known as the thorax or chest. 



The ribs are divided into two classes, namely, the true ribs and 

 the false ribs. 



The true ribs are the cephalic nine pairs, the ventral ends of 

 which directly join the sternum. 



The false ribs are the caudal four pairs, which do not directly 



