SPINAL NERVES. FIFTH PAIR, OR TRIFACIAL. 



311 



anatomical research, would lead to the conclusion, that the first two divisions 

 are nerves of sensation only, and that the third division combines sensory and 

 motor endowments. Such an inference is fully borne out by experiment. 

 When the whole trunk is divided within the cranium by the penetration of a 

 sharp instrument (which Magendie, by frequent practice, has been able to ac- 

 complish), evident signs of acute pain are given. After the incision has been 

 made through the skin, the animal remains quiet until the nerve is touched ; 

 and when it is pressed or divided, doleful cries are uttered, which continue 

 for some time, showing the painful effect of the irritated state of the cut ex- 

 tremity. The common sensibility of all the parts supplied by this nerve is 

 entirely destroyed on the affected side. The jaw does not hang loosely, be- 

 cause it is partly kept up by the muscles of the other side ; but it falls in a 

 slight degree ; and its movements are seen, when carefully observed, to be 

 somewhat oblique. If the trunk be divided on each side, the whole head is 

 deprived of sensibility ; and the animal carries it in a curious vacillating man- 

 ner, as if it were a foreign body. 



Fig. 150. 



A diagram showing the Fifth pair of nerves with its branches. 1. The origin of the nerve by two roots. 

 2. The nerve escaping from the crus cerebelli. 3. The Gasserian ganglion. 4. Its ophthalmic division. 

 5. The frontal nerve, giving off the supra-trochlear branch, and escaping on the forehead through the 

 supra-orbital foramen. 0. The lachrymal nerve. 7. The nasal nerve, passing at 8 through the anterior 

 ethmoidal foramen, and giving off the infra-trochlear branch. 9. The communication of the nasal nerve 

 with the ciliary ganglion. 10. A small portion of the third nerve with which the ganglion is seen com- 

 municating; the ganglion gives off the ciliary branches from its anterior aspect. 11. The superior maxil- 

 lary nerve. 12. Its orbital branch. 13. The two branches communicating with Meckel's ganglion; the 

 three branches given off from the lower part of the ganglion are the posterior palatine nerves. 14, 14. 

 The superior dental nerves, posterior, middle, and anterior. 15. The infra-orbital branches distributed 

 upon the cheek. 16. The inferior maxillary nerve. 17. Its anterior or muscular trunk. IS. The pos- 

 terior trunk; the two divisions are separated by an arrow. 19. The gustatory nerve. 20 The corda 

 tympani joining it at an acute angle. 21. The submaxillary ganglion. 22. The inferior dental nerve. 

 23. Its mylo-hyoidean branch. 24. The auricular nerve, dividing behind the articulation of the lower 

 jaw, to reunite and form a single trunk. 25. Its branch of communication with the facial nerve. 26. Its 

 temporal branch. 



404. If the anterior or Ophthalmic branch only be divided, all the parts 

 supplied by it are found to have lost their sensibility, but their motions are 

 unimpaired ; and all experiments and pathological observations concur in at- 



