52 THE SKELETON OF THE HORSE 



and presents a deep central depression and two shallower lateral ones which adapt 

 it to the surface of the cerebellum. 



The parietal border (Margo parietalis) is united by suture with the parietal 

 and interparietal. The mastoid border (Margo mastoideus) joins the petro- 

 mastoid part of the temporal bone. The basilar part is connected by cartilage (in 

 the young subject) ^\dth the body of the sphenoid. The condyles articulate with 

 the atlas. 



Development. — The occipital bone ossifies in cartilage from four centers, and 

 consists at birth of four pieces as described above. The lateral parts unite with the 



Fig. 30. — Cranium of New-born Fo.^.L; Posterior View. 

 A, B, C, Squamous, lateral, and basilar parts sf occipital bone; X>, interparietal bone; S, parietal bone; F, squa- 

 mous temporal bone; G, petro-mastoid part of temporal bone; 1, external occipital protuberance; 2, 2, depressions in 

 which complexus tendons are attached; 3, sutural (preinterparietal?) bone; 4, supraorbital process; 5, zygomatic 

 proces.s of temporal bone; 6, postglenoid process: 7, posterior process of squamous temporal bone; 8, mastoid process; 

 9, paramastoid process; 10, occipital condyle; 11, arrow in foramen magnum. 



basilar part at three to four months, and with the squama in the second year, when 

 the bone is consolidated. 



The parieto-occipital suture and the spheno-occipital synchondrosis are ob- 

 literated about the fifth year usually. The occipito-mastoid suture partially ossifies 

 in old subjects. 



The Sphenoid Bone 



The sphenoid bone (Os sphenoidale) is situated in the base of the cranium, its 

 central part lying in front of the basilar part of the occipital. It consists of the 

 body, two pairs of wings, and two pterygoid processes. 



The body (Corpus) is situated medially; it is cylindrical, but flattened dorso- 

 ventrally, and wider in front than behind. Its ventral surface (Facies externa) is 

 convex in the transverse direction, and its anterior part is concealed to a large extent 

 by the vomer and pterygoid bones. The cerebral surface (Facies cerebralis) 

 presents the following features: (1) In front there is a raised, flattened part (Jugum 

 sphenoidale) which is partially subdivided by a median elevation into two slightly 

 concave lateral areas; this part has a posterior, thin, free margin (Limbus sphe- 



