981 



orbit through the sphenoidal fissure (Fig. 738). It now becomes the highest 

 of all the nerves, lying at the inner extremity of the fissure internal to the frontal 

 nerve. In the orbit it passes inward, above the origin of the Levator palpe- 

 brae, and finally enters the orbital surface of the Superior oblique muscle. 



Branches of Communication. In the outer wall of the cavernous sinus it forms 

 communications with the cavernous plexus of the sympathetic* and with the 

 ophthalmic division of the trigeminal nerve. In the sphenoidal fissure it occa- 

 sionally gives off a h ranch to assist in the formation of the lacrimal nerve. 



Branches of Distrilution. It gives off a recurrent branch, which passes backward 

 ihe tentorium cerebelli, dividing into two or three filaments 

 N far back as the wall of the lateral sinus. 



Applied Anatomy. 



srior oblii; 



The trochlear nerve when paralyzed causes loss of function in the Su- 



ie patient is unable to turn his eye downward and outward. Should the 



he eye on the affected side is twisted inward, producing diplopia or 



igly, it is said that the first symptom of this disease which presents itself 



lown hill or in descending stairs, owing to the double vision produced 



t his steps while descending. 



:GSMINAL, OR TRIFACIAL NERVE (N. TRIGEMINUSJ 



(Figs. 732, 733). 



minal, or trifacial nerve is the largest cranial nerve. It resembles 

 v i ng two roots, motor and sensor; (2) in having a ganglion 

 " root. It is the great sensor nerve of the head and face and 

 >f the muscles of mastication; its upper two divisions are entirely 

 n is partly sensor and partly motor. It arises by two roots ; 

 is the smaller, and is the. motor root (Fig. 648); the dorsal, the 

 It emerges from the side of the pons near the upper border, 

 large sensor root. The small root consists of three or four 

 lot consists of numerous bundles of fibres, varying in number 

 idred. The two roots are separated from each other by a few 

 of the pons. The deep termination of the large or sensor 

 jng tract in the medulla oblongata, the lower sensor nucleus, 

 clow with the substantia gelatinosa Rolandi. The fibres 

 qfm the so-called ascending root of the fifth nerve ; they pass 

 pons and join with fibres from the upper sensor nucleus (Fig. 

 i to the outer side of the motor nucleus, from which the lower 

 takes origin. The deep origin of the small or motor root 

 lp a nucleus embedded in the ffray substance of the upper 

 fourth ventricle and partly from a collection of nerve cells 

 >f the aqueduct from which the fibres pass caudad under the 

 ^^Bucephalic or descending root of the fifth nerve (Fig. 648). 



the nerve pass forward below the tentorium as it bridges over 



r part of the superior border of the petrous portion of the 



32); they then run between the bone and the dura to the 



s portion of the temporal bone, where the fibres of the sensor 



rnter luto the formation of the large semilunar or Gasserian ganglion 



vvhile the motor root passes beneath the ganglion without 



with it, and joins outside the cranium with one of the trunks 



731 and 732). 



semilunar ganglion 1 (ganglion semilunare) (Figs. 731 and 

 n osteofibrous space, the cavum Meckelii (Fig. 719), near the 



mund Balthasar Hirsch (1765), was the first who recognized the ganglionic nature 

 -oot of the fifth nerve, and called it, in honor of his otherwise unknown teacher,. 

 ;lion Gasseri." Julius Casserius, whose name is given to the musculocutaneous 

 i>->r at Padua, 1545 to 1605. (See Hyrtl, Lehrbueh der Anatomie, p. 895 and p. 55.) 



