PATHETICUS. 135 



Physiological Anatomy. The apparent origin of the 

 patheticus is from the superior peduncles of the cerebellum ; 

 but it may be easily traced to the valve of Yieussens. Ac- 

 cording to Yulpian, the deep roots, which are covered by 

 an extremely thin layer of nerve-substance, can be traced, 

 passing from without inward, to the following parts : One 

 filament is lost in the substance of the peduncles; other 

 filaments pass from before backward into the valve' of Yi- 

 eussens and are lost, and a few pass into the frenulum ; a 

 few filaments pass backward and are lost in the corpora 

 quadrigemina ; but the greatest number pass to the median 

 line and decussate with corresponding filaments from the 

 opposite side. Yulpian states that this decussation is quite 

 as distinct as that of the anterior pyramids of the medulla 

 oblongata, and that he has been able to follow fibres across 

 the median line on either side. 1 The decussation of the 

 fibres of origin of the fourth nerves has the same physio- 

 logical significance as the decussation of the roots of the 

 third. 



From this origin, the patheticus passes into the orbit by 

 the sphcnoidal fissure, and is distributed to the superior 

 oblique muscle of the eyeball. In the cavernous sinus, it 

 receives branches of communication from the ophthalmic 

 branch of the fifth, but these are not closely united with the 

 nerve. A small branch passes into the tentorium, and one 

 joins the lachrymal nerve, these, however, being exclusively 

 sensitive and coming from the ophthalmic branch of the 

 fifth. 2 It also receives a few filaments from the sympathetic. 



Properties and Functions of the Patheticus. Direct ob- 

 servations upon the patheticus in living animals have shown 

 that it is motor, and its galvanization excites contraction of 

 the superior oblique muscle only. These facts have been 



1 VULPIAX, Essai sur Torigine de plusieurs paires des nerfs craniens, 

 Paris, 1853, p. 15. 



2 SAPPEY, Traite d'ancdomie descriptive, Paris, 1852, tome ii., p. 209. 



