48 OUTLINES OF EQUINE ANATOMY. 



reflected inwards and looks upwards ; inferiorly, a small 

 portion looks directly inwards and converges tow^ards, but 

 does not quite meet, its fellow. Thus we have formed an 

 irregular cotyloid cavity. 



The posterior expanded portion of the pedicle presents a 

 convex triangular facet, having its apex at the postero- 

 external angle of the lamina sharp and acute, its infero- 

 external angle rounded, its infero-internal angle continuous 

 with the smooth postero- superior part of the body. It 

 looks inwards and backwards, and comes into connection 

 with the anterior surface of the body and with the odontoid 

 process of the dentata. The laminae internally are concave 

 and rough ; exiernally convex, having a small ridge centrally 

 at the anterior part, a rounded and roughened promi- 

 nence for attachment of the superior spinous ligament and 

 rectus capitis posticus minor posteriorly. The anterior 

 margin is a sharp ridge, forming a concavity affording 

 attachment to the capsular and lateral ligaments of the 

 attoido-occipital joint, extending from the articular surface 

 for one condyle to that for the other. At the antero- 

 external angle the point of junction of the lamina and 

 pedicles is pierced by a foramen extending into the spinal 

 canal, continuous with one in the anterior part of the wing. 

 This gives passage to the suboccipital nerve, and to a 

 branch of artery going inwards to assist in forming the 

 basilar. The transverse process ala, or wing, extends from 

 above downwards and backwards, obliquely to the infero- 

 external angle of the posterior articular surface. It is a 

 thin plate of bone, extending downwards and outwards ; 

 since its surfaces are concave it is thinnest at its centre, and 

 here it is pierced by a foramen leading from a groove, through 

 which the vertebral artery passes from above downwards. 

 Its outer margin is convex, thick, and rough, and extends 

 obliquely downwards and outwards, posteriorly a little 

 behind the rest of the bone at its most convex part. It 

 affords attachment to several muscles of the neck, levator 

 humeri, splenius, trachelo-mastoideus, also to obliquus 

 capitis superior and obliquus capitis inferior. In the con- 

 cavity beneath the wing the union of the vertebral artery 

 with ramus anastomoticus takes place, and the resulting 

 branch passes through the anterior foramen, thus gaining 

 the superior surface, sending one branch into the spinal 

 canal, the other to the poll. The superior cervical ganglion 



