Dissection of Sheep's Head. 209 



cord also displays the dorsal and ventral fissure by whicli it 

 is divided into two equal and symmetrical portions ; the ar- 

 rangement of grey matter in two crescentic masses, placed 

 one in each lateral half of the cord, with their convexities 

 towards each other, each crescent having a dorsal and a 

 ventral horn, of which the ventral is much the larger and 

 fuller ; and lastly in the centre, the central canal of the 

 spinal cord, which opens anteriorly into the Calamus Scripto- 

 rius of the fourth ventricle. The cord in its sheath rests 

 upon the basi-occipital, and is roofed over by the supra- 

 occipital bone ; the main bulk of the condyles being made up 

 of the ex-occipitals, though also containing a portion of basi- 

 occipital. 



In the middle line, on the crest of the supra- occipital bone, 

 will be found some yellow elastic substance, which is the 

 anterior extremity of the ligamentum nucha3. This ligament 

 extends from about the second dorsal spine posteriorly, and 

 supports the weight of the head and neck. Likewise on the 

 supra- occipital crest, but external to the ligamentum nuchas, 

 on either side will be seen a muscle cut short : this is the 

 origin of the Splenius muscle, which is situated along the side 

 of the neck, and is inserted into the transverse processes of 

 the posterior cervical vertebra), and the spinous processes of 

 the anterior dorsal vertebrae ; taken together, their action is 

 to elevate the Head ; singly, they flex the Head to one side. 



About half an inch ventrad of the external margin of each 

 occipital condyle, the firm point of a bone will be felt ; this 

 bone will be the par-occipital process, a development of 

 a process homologous with the jugular process in Man. 



From the root of the par- occipital (close to the condyle) an 

 imaginary line drawn forwards to the ventral margin of the 

 orbit will pass through the Ear cartilage, and along the 

 Zygomatic arch. 



Just anterior to the Ear is the situation of the condyle of 



E s 



