52 ELEMENTS OF MAMMALIAN ANATOMY. 
12. Draw ventral aspect of sacrum and label all features. 
13. Give the two features distinguishing the caudal vertebrae from 
all others. 
14. Note the size and direction of the spinous process throughout 
the column. 
15. Describe the variation in number of the different groups of ver- 
tebre in other mammals. 
16. Draw lateral aspect of sternum and label all features. 
17. Describe the attachment of ribs to sternum. 
18. What features common to all the ribs? 
19. Name ribs having a tubercle. 
20. Draw first rib and label all features. 
21. Draw cranial aspect of ninth rib and label all features. 
22. How do you distinguish a false rib from a true rib? 
23. What features mark the caudal aspect of a rib? 
24. Make a drawing showing the articulation of a rib with the 
spinal column and label all parts. 
25. How do ribs vary as to number in mammals? 
THE THORACIC LIMB. 
The thoracic or fore-limb of the cat is composed of a 
scapula, clavicle, humerus, ulna, radius, seven carpals, five 
metacarpals, and fourteen phalanges (Fig. 21). The sca- 
pula and clavicle form the shoulder girdle. 
The scapula, commonly called the shoulder-blade (Fig. 
30), is not articulated with the bones of the trunk, but is 
held in position by the serratus magnus, levator anguli 
scapulz, and other less important muscles. It articulates 
with the head of the humerus by the glenoid cavity. It 
presents three well-marked borders: the cranial or anterior, 
the vertebral, and the axillary adjacent to the vertebre on 
the side near the axilla or armpit. The outer surface of this 
bone is divided by a strong spine into two nearly equal 
fossee, the cranial of which is the supraspinous, and the 
caudal one the infraspinous, fossa. From the lower part 
of the spine project the acromion and metacromion proc- 
esses. The subscapular fossa occupies the entire inner or 
medial surface. 
