22 ANATOMY OF THE HORSE. 



die lobes of the cerebrum, by which they are indented; they 

 also show the traces of the ramifications of the arteries sup- 

 plying the dura mater. 



Borders — Denticulated and squamous. The anterior is ser- 

 pentine and unites with the frontal bones ; the posterior lies 

 upon the occipital bone, and internally has two short bifid 

 crests growing from it, forming sides of the transverse grooves, 

 from which it extends down, on either side, to the wing of the 

 sphenoid bone ; the lateral borders are irregular, and are over- 

 laid by the temporal bone. 



Development. In the foal, indeed generally until the second 

 or third year, a longitudinal suture is demonstrable, dividing 

 this bone into two correspondent pieces. 



OCCIPITAL BONE. (OS OCCIPITIS.) 



Situation. Postero-superior and inferior parts of the cranium. 



Figure — Symmetrical ; irregular : presenting convexities and 

 projections outwardly ; concavities, and a large circular aper- 

 ture inwardly. 



Division — Into two surfaces, external and internal, and four 

 borders. 



The External Surface is divided by a transverse mark into two 

 portions, a super-occipital and a sub-occipital portion, which 

 were once two separate bones, and presents, 1st. along its 

 median line, and from above downwards, the occipital crest, 

 bounding the cranium posteriorly, and giving attachment to the 

 complexus ; below this, the occipital tuberosity, to which is 

 fixed the cervical ligament, with broad, rugged, posterior occipi- 

 tal depressions marked by the attachments of the recti capitis 

 postici ; still lower, the occipital hole, transversely oval, and 

 traversed by the spinal marrow and its membranes, the vertebral 

 artery, and accessory and sub-occipital nerves; below and in 

 front of this hole, the basilar process, articulating with the 

 sphenoid bone, whose under surface shews the basilar fissure, 

 triangular and widening in its course to the occipital hole, where 

 it terminates : to this process are attached the recti capitis an- 

 tici. 2clli/. On each side, the continuation of the crest, de- 

 scending to the root of the styloid process of the same bone, 

 into which is implanted the obliquus capitis superior ; below 

 this, continued from it, the styloid process, whose length is 

 regulated by that of the jaws, affording attachment to the ob- 

 liquus capitis anticus ; inwardly to this, bordering on the 

 occipital hole, the occipital condyles, extending backward for 

 articulation with the atlas, and roughened upon their inner sides 



