THE NERVOUS SYSTEM OF THE OX 717 



interrupted at or near the level of tli(> ^fnu of the corpus callosum, in which case the genual fissure 

 continues it clownwani. 



10. The crucial fissure is faint and is (confined to the medial surface. It lies about one 

 centimeter in front of the transverse fissure and commonly joins the calloso-marginal fissure 

 below. 



11. Short and variable fissures occur in front of and behind the middle branch of the lateral 

 fissure (F. ectosylvia anterior, posterior). 



The olfactory bulb is mtich smaller than in the liorse. The external olfactory 

 tract is large, the inner one small and not distinct. 



The cranial nerves have in general the same superficial origin as in the horse. 

 The more important differences in other respects are as follows: 



The oculomotor nerve is larger than in the horse. It emerges with the fourth, 

 sixth, ophthalmic, and maxillary nerves through the large foramen, which is 

 equivalent to the foramen lacerum orl)itale and foramen rotimdum of the horse. 



The internal branch of the lacrimal nerve supplies twigs to the mucous mem- 

 brane of the frontal sinus; the large outer branch runs backward and supplies the 

 matrix of the horn. The frontal nerve emerges from the orbit l^elow the supraor- 

 bital process. The naso-ciliary nerve is large and sends filaments to the ocular 

 muscles. The ciliary ganglion is somewhat larger than in the horse and is connected 

 with the lower cUvision of the oculomotor nerve by several short filaments. In 

 consequence of the absence of the canine and upper incisor teeth the corresponding 

 branch of the infraorbital nerve is naturally wanting. The mandibular nerve 

 emerges through the foramen ovale. The superficial temporal nerve gives off a 

 large branch which joins the superior buccal division of the facial on the masseter, 

 about half-way between the zygomatic arch and the angle of the jaw. The otic 

 ganglion is larger than in the horse. According to Moussu the buccinator nerve 

 furnishes excito-secretory twigs to the parotid and inferior buccal glands. 



The facial nerve divides into its two terminal branches before reaching the 

 border of the jaw. The superior buccal nerve is the larger of the two; it crosses 

 the masseter much lower than in the horse. The relatively small inferior buccal 

 nerve runs beneath the parotid or in the gland substance parallel with the border 

 of the lower jaw, crosses under the insertion of the sterno-cephalicus, and runs for- 

 ward along the depressor labii inferioris. At the point where it crosses the facial 

 vein and parotid duct it gives off an anastomotic branch to the superior nerve. 

 The auriculo-palpebral nerve is large. 



The vagus bears — in addition to the relatively large jugular ganglion — a 

 ganglion nodosum at the point of origin of the superior laryngeal nerve. The 

 trunk is large. The pharyngeal branch is large and anastomoses with the superior 

 and external laryngeal nerves. The latter commonly arises directly from the trunk. 

 The superior oesophageal trunk communicates with the splanchnic nerve, contri- 

 butes twigs to the hepatic plexus, and ramifies chiefly on the right surface of the 

 rumen and the adjacent surface of the abomasum. The inferior oesophageal trunk 

 supplies branches to the hepatic plexus and to all the divisions of the stomach. 



The spinal accessory nerve presents two special features. Tlu^ part which 

 joins the jugular ganglion b(>ars a small ganglion. The ventral branch supplies 

 both parts of the sterno-cephalicus. 



The hsrpoglossal nerve is large. It is connected with the ventral division of 

 the first cervical nerve by a branch of considerable size, and detaches a long brancli 

 which runs backward along the carotid arter3\ 



The spinal nerves resemble those of the horse in origin and general arrange- 

 ment. The thoracic nerves number thirteen pairs. The more important differ- 

 ences in the limb-plexuses and their branches are as follows: 



The brachial plexus is formed by the ventral branches of the last three cervical 



