830 PHYSIOLOGY. 



ganglion, its neuraxons are divided, one part going to the skin of 

 the face and the other, running toward the pons, also divides into 

 two parts, one going upward and the other downward. The gela- 

 tinous substance of Rolando on the posterior horn receives the fibers 

 running downward, which arborize around the cells. 



The descending part of the trigeminus, known as the ascending 

 root, extends down to the second cervical vertebra, continually giv- 

 ing off collaterals as it descends, which arborize around the gelatin- 

 ous substance of Rolando of the posterior horn, thus making the 

 lower trigeminal nucleus a long one. The descending branch also 



Fig. 376. Ophthalmic Division of the Fifth Nerve. 



1, Skin of the forehead turned down. 2, Optic nerve. 3, Third nerve. 4, 

 Fourth nerve. 5, Ophthalmic division of the fifth nerve. 6, Lacrymal branch. 

 7, Union of the fourth nerve with the lacrymal branch of the fifth. 8, Frontal. 

 9, Nasal. 10, Internal branch of nasal. 



has collaterals, which arborize around the motor nuclei of the hypo- 

 glossal, facial, and trifacial. The neuraxons of the sensory nuclei 

 in which the trigeminus ends decussate and go to the cortex in the 

 fillet. 



Cortical Connection. The sensory path ends in the inferior part 

 of the central region of the cortex, going up in the fillet and the 

 thalamus. The nucleus of the motor root lies in the pons, near the 

 sensory nucleus of the trigeminus and back of the nucleus of the 

 facial, of which it is probably a part. There is another nucleus, the 

 accessory nucleus of the motor nucleus, which is situated beneath 

 the aqueduct of Sylvius, and which sends descending fibers to tht 

 motor nucleus. 



