lO'Z OUTLINES OF EQUINE ANATOMY. 



In examining tlie synarthrodia! articulations of the skull 

 we notice several sutures, one of whicli divides the bone 

 into two parts longitudinally, only noticeable superiorly 

 and not extending to the posterior extremity ; this is the 

 saggittal suture between the nasal, frontal, and parietal 

 bones of the two sides of the head, forming the " plume " of 

 the arrow posteriorly between the parietal and triquatral 

 bones. Other sutures serve to mark the division of the 

 skull into four vertebral segments ; they are the 



Lambdoidal, between os occipitis and os parietale, so 

 called from its likeness to the Greek lambda (A), which is 

 caused by protrusion of the mastoid ridge of the petrous 

 temporal between these two bones. 



Coronal, between the frontal and parietal bones. 



Great transverse, between the frontal and nasal, malar, 

 lachrymal bones, extending into the orbit. All these 

 extend downwards on either side towards the base of the 

 skull. 



Atloido -occipital articulation 



is the union of the condyles of the occiput with the 

 anterior ai*ticulatory surfaces of the atlas. Each of these 

 condyles has a proper synovial membrane, and the two lie 

 together on their inner and inferior parts. Their outer 

 surfaces are strengthened by accessor}/ fih-es, which are con- 

 tinued superiorly, extending from the anterior margins of 

 the laminae of the Atlas to the superior part of foramen mag- 

 num of the occiput, forming the capsular ligament. Two flat, 

 white, fibrous bands extend from the styloid processes of the 

 occiput to the anterior margins of the laminae. This joint 

 is ginglymoid, admitting motion upwards and downwards. 



Atlo-axoid articulation 



is the union of the posterior part of the body of the atlas 

 and the posterior part of its superior surface with the 

 under surface of the odontoid jDrocess, and its antero-lateral 

 continuations on the dentata. These have one synovial 

 membrane attached to the outer circumferent margin of 

 both surfaces. Inferiorly along the central line this is 

 strengthened by a small band of yellow elastic tissue (a con- 

 tinuation of the inferior vertebral ligament). Laterally it 

 has accessory fibres, which are continued upivards, connecting 

 the anterior laminal margin of the axis with the posterior 



