BRAIN 55 



V. N. trigeminus is next to the optic the thickest nerve, and of 

 a complex nature, being motory and sensory. It arises from the 

 sides of the mid- and hindbrain, forms the large Gasserian ganglion 

 in the wall of the cranium, and leaves the latter in the foi'm of three 

 branches. The iirst or ophthalmic branch comes directly out of the 

 ganglion through a foramen behind the optic (II), runs along the 

 dorsal corner of the orbital septum, and leaves the orbit at its 

 inner anterior corner in order to supply the palate, the bill, fore- 

 head, and the lacrymal gland. It is chiefly sensory, and con- 

 sequently strongest in birds with tactile bills, Hke Ducks and 

 Snipes. The second or upper maxillary branch runs along the 

 ventral edge of the orbital septum, and besides the palatine and 

 maxillary regions supplies the eyelids and Harder's gland. The 

 third or inferior maxillary branch is the strongest of the three ; it 

 leaves the cranium together with the second through a foramen 

 between the basi-alisphenoid and petrosal bones and innervates all 

 the masticatory muscles, the parotid gland, and the whole of the 

 under jaw. 



VI. N. alducens is a very thin nerve arising from the hindbrain 

 near the medio-ventral line, entering the orbit through a special 

 foramen latero-ventrally from the optic foramen, and supplying the 

 m. rectus externus and the two muscles of the nictitating membrane. 

 It is entirely motory. 



VII. N. facialis arises from the side of the hindbrain, possesses 

 a ganglion (g." geniculatum), passes through the petrosal bone into 

 the Fallopian canal, and sends the sympathetic sphenopalatine branch 

 to the second branch of the trigeminal nerve (V). The facial nerve 

 leaves the tympanic cavity behind the quadrate bone, supplies the 

 digastric muscle or depressor of the mandible, the little stapedius 

 muscle of the ear-bones, the mylo- and stylohyoid muscles of the 

 tongue, and further on connects itself with branches from the first 

 four cervical nerves and occasionally with branches from the glosso- 

 pharyngeal nerve (IX), ultimately supplying the skin on the front of 

 the neck. There are no branches, as in Mammals, to supply the 

 face, nor is there in Birds a chorda tympani, i.e. a branch of the 

 facial nerve joining the mandibular branch of the trigeminal nerve (V). 



VIII. N. acusticus arises dorsally from the facial nerve (VII), 

 of which it is the sensory portion. It is very short and thick, 

 possesses a little ganglion, and spreads out in the cochlea of the Ear 

 as the nerve of hearing. 



IX. N. glossopharyngeus takes its origin from the dorso-lateral 

 sides of the medulla oblongata, near the rhomboid fossa. It leaves 

 the cranium through the foramen jugulare, which lies between the 

 petrosal and the lateral occipital bones, and also serves as exit for 

 the vagus nerve (X) and the jugular vein. Here the ninth nerve 

 forms a big swelling, the ganglion jugulare, and is connected with the 



