152 



MAMMALIAN ANATOMY 



that it does not reach the surface of the sternum, and hence may be 

 easily overlooked. 



I have one specimen (No. 7 in the table) in which the number of 

 steriiebra3 is reduced to seven, apparently by the total absence of the 

 normal seventh, the sixth and eighth retaining their usual relative 

 proportions. 



THE THORAX. 



The Thorax (Fig. 103) occupies the cephalic part of the trunk, 

 and encloses, supports, and protects the heart and great blood-vessels, 

 the lungs, and to some extent also the abdominal viscera. To its sides 

 at the cephalic end are attached the thoracic limbs, and the rest of 



Hyoid. 



Clavicle. 

 Sternum. 



Metacarpus. 



Metatarsus. 

 Phalanges. 



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



its outer surface gives origin and insertion to important muscles of the 

 trunk and limbs. 



The bony thorax is a conical, cage-like structure, composed 

 principally of the twenty-six ribs and their costal cartilages, held 

 together at their dorsal ends by the thirteen thoracic vertebrae and at 

 their ventral ends by the eight sternebrse. 



The thorax is entirely filled by the viscera ; its walls are every- 

 where completely closed by muscles and membranes, and its cephalic 

 and caudal ends are shut off from the neck and abdomen, except to 

 give entrance and exit to the alimentary and respiratory passages and 

 to the blood-vessels and nerves ; but the thorax which has been stripped 

 of all its soft parts presents a very different appearance. It has a 



