Nervous System. 



543 



the spinal nerves. ( Fig. 267, P III.) They leave the cranium through the sphenoidal fis- 

 sures. (These consist of a hole in the skull on each side, opening from the hrain 

 through the sphenoidal bone into the upper back part of the orbit or eye cavity.) 



The fourth pair are the Pathetici, or Pathetic nerves. This nerve moves the eyeball 

 by its superior oblique muscle. It connects with the brain behind the corpora quadri- 

 gemina at the lateral parts of the valve of vieussens. It is both motor and sensory. It 

 leaves the cranial cavity through the sphenoidal fissure. 



FIG. 266. Front view of Medulla 

 Oblongnta, Ponx Varolii, &c., show- 

 ing nerve roots. (From Quain, with 

 additions.) 



On the right side, the convolutions 

 of the central lobe, or Island of 

 Keil, have been left ; on the left, the 

 cerebral lobes have all been re- 

 moved, exposing the Optic Thala- 

 mus. 



I. Olfactory nerve cut short. 

 II. Optic 



III. 3d pair Occulo Motor. 

 IV. 4th pair Pathetic. ( Muscles of 

 V. 5th Trigeminal. [eye.) 



d. Motor root of the 5th nerve. 

 a, b, c. -Divisions of 5th nerve. 

 VI. 6th nerve (Abducentes) (mus- 

 cle nerve of eye ). 

 VII. 7th nerve,Portio-Dura, Facial 



nerve. 



VIII. Auditory (Portio Mollis). 

 IX. Glosso Pharyngeal. 

 X. Par Vagum, or Pneumogastric. 

 XI, Spinal Accessory of 10th nerve. 

 XII. Hypoglossal, motor nerve of 



tongue. 



1. Globe of right eye, perfect. 

 2. Globe of left eye, sclerotic and 



choroid coats removed. 

 3. Pituitary body Hypophysis. 

 4. Optic Chiasm. [mns. 



6. Cut surface of left Optic Tbala- 

 6. Tuber cinereum and Infundibu- 

 7. Corpora Albicantia. [lum. 



8. Locus perforatus posticus. 

 9. External Corpus Geniculatum. 

 10. Internal ' r 

 11. Pens Varolii. 

 12. Olivary body. 

 13. Anterior pyramid. 

 14. Decussation of pyramids. 

 15. Lateral column of Spinal Cord. 

 16. Anterior column 

 17. Anterior median fissure of spinal cord. 20. Locus perforatus anticus. 

 18. The flocculus. 21. Island of Reil. 



19. Fissure of Sylvius. P. Placed on Cerebral Peduncles. 



The fifth pair are also called the Par Trigeminum (also Trifacial), from the fact that 

 they divide into three branches each. They are both motor and sensory. The first branch 

 is the Ophthalmic, which subdivides into three; viz., one, the lachrymal, to the lachrymal 

 gland and upper eyelid ; one to the forehead and upper eyelid ; and the third to the eye- 

 lids, nasal fossaa and nose. The second branch is the Superior Maxillary, which has four 

 subdivisions one to the orbit of the eye ; one to the last three molar teeth and gums ; one 

 to the front teeth and two lesser molars ; and the fourth to the upper lip, cheek and nose. 

 The third branch is the Inferior Maxillary, which has seven subdivisions, as follows: to 

 the temporal muscle ; to the masseter muscle, which moves the lower jaw ; to the inner 

 surface of the cheek; to the internal pterygoid muscle, which is also concerned in moving 

 the lower jaw; to the mucous membrane of the tongue; to the teeth of the lower jaw and 

 lower lip ; and to the forehead and ear shell. This nerve connects with the brain by two 

 roots, one motor and the other sensory, like the spinal nerves. The motor root connects 

 with the posterior edge of the olivary tract of the medulla oblongata, and the sensory root 

 runs back, or down between the olivary tract and restiform body to the sensory tract of 

 the medulla. (See fig. 266.) Before joining the motor part of the nerve, d, the sensory parts, 

 a, b, c, unite in a large nervous ganglion called the Gasserian ganglion. The part of this 

 nerve which is distributed to the tongue, is the nerve of taste. The ophthalmic branch of 

 this pair passes through the sphenoidal fissure. The superior maxillary branch leaves 

 skull through the foramen rotundum. 1 The inferior maxillary branch passes through 

 the foramen ovale. 2 



1 2 Holes in the sphenoid bone of the skull. 



