108 OSTEOLOGY. 
be placed to one or other side of the internal occipital protuberance, more frequently 
the right; im some cases, however, 1t may occupy a central position. 
The superior angle, more or less sharp and pointed, is wedged in between the 
two parietal bones, its position corresponding to the site of the posterior fontanelle. 
The Jateral angle articulates on either side with the posterior extremity of the 
mastoid portion of the temporal bone. The superior borders, much serrated, articu- 
late with the parietal bones forming the lambdoid suture; and the lateral edges, 
extending from the external angles to the jugular process inferiorly, are connected 
with the inner sides of the mastoid portions of the temporals. 
The lateral or condylic parts of the occipital bone (partes laterales) are placed 
on either side of the foramen magnum; on their under surface they bear the 
condyles (condyli occipitales) by means of which the skull articulates with the 
atlas vertebra. Of elongated oval form, the condyles are so disposed that their 
anterior extremities, in line with the anterior margin of the foramen magnum, lie 
closer together than their posterior ends, which extend as far back as the middle of. 
the external borders of the foramen. Convex from before backwards, they are 
skewed so that their surfaces, which are nearly plane from side to side, are directed 
shehtly outwards. Each is supported on a boss of bone, pierced by the anterior 
condylic foramen (canalis hypoglossi), which opens obliquely from within outwards 
and forwards on the floor of a fossa called the anterior condylic fossa, situated just 
external to the fore part of the condyle. The foramen transmits the hypoglossal or 
XII. cranial nerve, together with a meningeal branch of the ascending pharyngeal 
artery and its companion veins. Behind the condyle is placed the posterior condylic 
fossa, in the floor of which the posterior condylic foramen fr equently opens. Through 
this a vein passes which joins the lateral sinus. The edge of the foramen magnum 
immediately behind the condyle is often grooved for the passage of the vertebral 
artery around it. Jutting out from the posterior half of the condyle is a stout bar 
of bone, serially homologous with the vertebral transverse process—this is the 
jugular process (processus jugularis); deeply notched in front, its anterior border 
is free and rounded, and forms the posterior boundary of the jugular foramen. 
Curving outwards from this margin, in line with the anterior condylic foramen, 
there is often a small pointed projection, the processus intra-jugulare, which serves 
to divide the jugular foramen into two compartments. Externally the jugular 
process articulates by means of a synchondrosis with the jugular surface of the 
petrous part of the temporal bone. Its posterior border is confluent with the lower 
and lateral portion of the occipital squama, and its under surface is rough and 
tubercular for the attachment of the rectus capitis lateralis muscle. The superior 
aspect of the lateral part displays on either side of the foramen magnum an elevated 
surface of oval form, the tuberculum jugulare ; this corresponds to the part of the 
bone which bridges over the canal for the hypoglossal nerve. Its upper surface in 
many instances displays an oblique groove running across it; in this are lodged the 
elosso- pharyngeal, vagus, and accessory nerves. The jugular process is deeply 
grooved above for the lower part of the lateral blood sinus, which here turns round 
the anterior free edge of the process into the jugular foramen. Joining this, close 
to its inner edge, is the opening of the posterior eondylic foramen when that canal 
exists. 
The basilar part of the occipital bone (pars basilaris) extends forwards and 
upwards from the foramen magnum. Its anterior extremity is usually sawn across, 
as after adult life it is necessary to sever it in this way from the sphenoid, the 
cartilage uniting the two bones having by that time become completely ossified. 
Broad and thin behind, it narrows and thickens anteriorly, where on section it 
displays a quadrilateral form. Projecting from its under surface some little 
distance in front of the foramen magnum is the pharyngeal tubercle (tuberculum 
pharyngeum) to which the fibrous raphe of the pharynx is attached; on either side 
of this the rectus capitis anticus major and minor muscles are inserted. The upper 
surface forms a broad and shallow groove which slopes upwards and forwards from 
the thin anterior margin of the foramen magnum; in this rests the medulla 
oblongata. On either side its lateral edges are faintly erooved for the inferior 
petrosal venous sinuses, below which the lateral aspect of the bone is rough for the 
