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THE NERVOUS SYSTEM OF THE DOG 



also flattened laterally. Both contain a narrow cavity which communicates with 

 the lateral ventricle. The pyriform lobe is large and rounded. 



The cranial nerves present the following special features which are worthy of 

 notice : 



The ophthalmic nerve gives off lacrimal, frontal, long ciliary, ethmoidal, and 

 infratrochlear branches. The lacrimal nerve arises from the ophthalmic at its 

 origin;^ its recurrent branch emerges at the orbital ligament and concurs with the 

 zygomatic and frontal nerves in the formation of the anterior auricular plexus. 

 The frontal nerve emerges from the orbit in front of the upper end of the orbital 

 ligament, ramifies in the upper lid and the adjacent skin of the forehead, and sends 

 branches backward to the anterior auricular plexus. The long ciliary nerve ac- 

 companies the optic nerve and divides into several branches which pierce the pos- 

 terior part of the sclera. The ethmoidal nerve gives off internal nasal branches and 

 ends in the muzzle. The infratrochlear nerve runs forward between the internal 



Fig. 546. — Nerves of Face of Dog. Parotid Gland is Removed. 

 a, Facial nerve; h, pcsterior auricular nerve; c, internal auricular nerve; d, digastric nerve; e, inferior 

 buccal nerve; /, cervical branch of facial; g, auriculo-palpebral; /;, superior buccal nerve; /, temporal branch; 

 k, k' , k", zygomatic branch; /, auriculo-teraporal; m, malar branch of /; n, buccinator nerve; o, mylo-hyoid 

 branch; p, subcutaneus mala>; q, lacrimal nerve; r, frontal nerve; s, infratrochlear nerve; t, infraorbital nerve; 

 /, parama.stoid process; 2, diga-stricus muscle; 3, ba.se of concha; 4, masseter; 6, zygomaticus; 6, scutularis; 

 7, zygomatic arch; S, maxilla. (EUenberger-Baum, Anat. d. Hundes.) 



straight and the superior oblique muscles of the eye and ramifies on the face in 

 the vicinity of the inner canthus. 



The maxillary nerve, after giving off the zygomatic, divides into infraorbital 

 and sphenopalatine Ijranches. The zygomatic nerve emerges through an opening 

 in the upper part of the orbital ligament and ramifies in the lower lid and on the 

 adjacent surface of the face. The infraorbital nerves, two in number, divide within 

 the infraorl)ital canal and after their emergence upon the face, thus forming seven 

 or eight external nasal and superior labial branches. The sphenopalatine nerve 

 gives off lesser and greater palatine and posterior nasal nerves. 



Tlu> mandibular nerve i)asses out through the foramen ovale. The superficial 

 temporal nerve divides into auricular, temporal, and malar branches; the last- 

 nanu^l (.-rosses the masseter and ramifies with the buccal nerves. The mylo-hyoid 

 nerve is given off from the mandibular nerve almost immediately after the latter 

 emerges from the cranium; it innervates the mylo-hyoideus and digastricus and 

 gives off a branch which turns around the lower jaw, joins the inferior buccal nerve, 



1 The origin of the lacrimal nerve is such that Ellenberger-Baum and Martin describe it 

 as a branch of the maxillary nerve. 



