HEAD AND NECK OF THE HORSE 131 



Though usually derived from the occipital, it may arise from the 

 external carotid, or from the posterior meningeal, or from the ter- 

 mination of the common carotid artery. 



(2) A. condyloidea. — The condyloid artery is also small. After 

 running obliquely across the surface of the diverticulum of the 

 Eustachian tube, it divides into branches, some of which are 

 muscular in distribution, while others enter the cranium by the 

 hypoglossal and jugular foramina and are expended in the dura 

 mater of the brain. 



(3) A. meningea i^osterior. — The posterior meningeal artery is 

 the largest collateral branch of the occipital. Following the posterior 

 border of the jugular process of the occipital bone underneath the 

 cranial oblique muscle, it reaches a transverse and sinuous groove 

 on the mastoid part of the temporal bone. The groove leads the 

 artery between the squamous and mastoid parts of the temporal 

 bone and so into the temporal meatus, by which it gains the 

 interior of the cranium where it supplies the dura mater. On its 

 way to the cranium, the meningeal artery contributes branches to 

 the cranial oblique muscle of the head and the joint between the 

 atlas and the skull. 



V. OCCIPITALIS. — The occipital vein begins by the union of radicles 

 equivalent to the descending and occipital rami of the artery, and 

 receives the inferior cerebral vein. It ends by joining the internal 

 maxillary vein. 



A. CAROTis INTERNUS. — One of the three terminal branches of the 

 common carotid artery, the internal carotid arises immediately behind 

 the point of origin of the occipital (the deep face of which it crosses), 

 ascends on the diverticulum of the auditory tube, and enters the 

 cranium by the carotid foramen. It is related to the vagus nerve 

 and the cranial cervical ganglion, and is crossed laterally by the glosso- 

 pharyngeal and hypoglossal nerves and the pharyngeal branch of the 

 vagus. 



M. LONGUS COLLI. — The whole extent of the cervical part of the 

 longus colli muscle is now exposed. The muscle should be revised 

 (see page 25), and its terminal insertion into the ventral tubercle 

 of the atlas noted. 



Dissection. — All the muscles must now be cleared away from the 

 cervical vertebrte, and the joints of the neck — including that between 

 the atlas and the occipital bone — must be examined. 



The cervical articulations.— The joints between the last six 



