THE STERNUM — BONES OF THE SKULL — CRANIUM 



139 



breeds, so that there is a fairly distinct angle, except toward the end of the series. 

 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 tuberosity fuses 

 with the head on the last five or six. The second to the fifth form diarthrodial 

 joints with their cartilages, which are wide and plate-like. 



THE STERNUM 



The sternum consists of six segments and resembles that of the ox in general 

 form. The first segment (Manubrium) is long, flattened laterally, 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 com- 

 pletely 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. 



Occipital 

 bone 



Parietal 

 bone Frontal 



bone Supraorbital 

 process 



Lacrimal 



foramina Lacrimal 

 bone 



A'asal 

 Maxilla bone 



I nfraorbital 

 foramen 



Preniaxilla 



X:C 



Fig. 109. — Skull of Pig, Lateral View without Mandible. 

 1, Occipital condyle; 2, paramastoid or styloid process; 5, bulla ossea; 4, external auditory meatus, 

 ■5, zygomatic process of temporal bone; 6, sphenoid bone; 7, orbital opening of supraorbital canal; S, malar 

 bone; 9, pterygoid bone; 10, pterygoid process of sphenoid; 11, pterygoid process of palate bone; Il-S, incisor 

 teeth; C, canine tooth; Pl-4, premolars; Ml-3, molars. 



BONES OF THE SKULL 



Cranium 

 The occipital bone has an extensive squamous part or supraoccipital, which 

 forms a very broad and prominent 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 downward, and is continuous with the temporal crest. Two diver- 

 gent ridges pass upward from the foramen magnum, and the surface between them 

 is concave and smooth. The greater part of the inner (or anterior) surface of the 

 supraoccipital is united with the parietal bones, but a lower concave area faces 



