166 SKELETON OF THE PIG 
The backward slope of the posterior ribs is slight. The first rib is prismatic, has a 
large sternal end, and a very short cartilage. The width is greatest in the third 
to the sixth, and the length in the sixth and seventh usually. The tubercle fuses 
with the head on the last five or six. The second 
to the fifth form diarthrodial joints with their car- 
tilages, which are wide and plate-like. 
The fifteenth rib, when present, may be fully developed 
and its cartilage enter into the formation of the costal arch; 
but in most cases it is floating, and in some cases it is only 
about an inch (ca. 2-3 em.) in length. 
THE STERNUM 
The sternum consists of six segments and re- 
| sembles that of the ox in general form. The first 
= segment (Manubrium) is long, flattened laterally, 
4 . NE as 
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(J 
5 6 
Fic. 175.—E1curu Rip or Pic; Lat Fic. 176.—Frrst Rrs or Pic; Larerar View. 
ERAL VIEW. 1, Head; 2, neck; 3, tubercle; 4, anterior border; 5, vascular impression; 
1, Head; 2, neck; 3, tubercle; 4, ante- 6, sternal extremity. 
rior border; 5, sternal extremity. 
and bears a blunt-pointed cartilage on its anterior end; its posterior end forms a 
diarthrodial joint with the body. The latter is flattened, wide in its middle, narrow 
at either end. The widest segments are formed of two lateral parts, which are 
not completely fused in the adult. The last segment has a long, narrow part which 
bears the xiphoid cartilage. 
The thorax is long and is more barrel-shaped than in the horse or ox, since the 
ribs are more strongly curved and differ less in relative length. 
BONES OF THE SKULL 
CRANIUM 
The occipital bone has an extensive squamous part, which forms a very broad 
and prominent nuchal crest. The latter is concave, and is thick and rough above, 
where it forms the highest part of the skull; laterally it becomes thinner, turns 
