CLASS MAMMALIA. MAMMALS 



467 



2 small clavicles, and 2 knoblike coracoid 

 processes. The forelimb consists of the 

 humerus, radius, ulna, 7 carpal bones, 5 

 metacarpals, and the phalanges of the toes. 

 Each half of the pelvic girdle is called the 

 hipbone or innominate bone and is made up 

 of the ilium, ischium, and pubis fused to- 

 gether. The concavity in the innominate 

 bone in which the head of the femur articu- 

 lates is called the acetabulum. 



The hindlimb is made up of the femur, 

 tibia, fibula, 7 tarsals (ankle bones), 4 long 

 metatarsals and a rudiment of the first 

 (innermost), and the phalanges. The ankle 

 joint of the cat lies between the tibia and 

 fibula above, and the tarsal bones below. 

 One of the sesamoid bones of the hind- 



limb, which is situated on the front of the 

 distal end of the femur, is called the knee- 

 cap or patella. 



Muscular system 



Many of the muscles (Fig. 340) are more 

 or less the same as in the lower vertebrates, 

 but the mammals have a smaller amount of 

 muscle on the vertebrae and ribs, and more 

 highly developed muscles on the head, neck, 

 and limbs. A distinctive feature of mam- 

 malian musculature is the dome-shaped 

 partition or diaphragm, which separates the 

 coelom into an anterior thoracic cavity 

 containing the heart and lungs, and a pos- 

 terior abdominal cavity containing the ab- 



Promtor feres 



Ex\. carpi rod 



Ext. communis 



digitorum 



Ext. lateralis digiforum 



Ext. carpi ulnaris 



Flex, carpi 



ulnaris 



Figure 340. Superficial muscles of the domestic cat; some of the abdominal muscles are cut 

 to show others that lie beneath. 



