vii THE MEDULLA OBLONGATA 409 



VII. The cerebral nerve which presents the strongest analogy 

 to a spinal pair is certainly the Trigeminal or Trifacial, with its 

 sensory root connected with the semilunar or Gasserian ganglion, 

 and its single motor root which unites with one division of the 

 sensory root to form a mixed nerve. 



Both the larger sensory and the smaller motor root of the 

 trigeminus issue from the side of the pons, where the transverse 

 fibres of the latter pass into the middle cerebellar peduncle (Fig. 

 201). The motor fibres arise in a nucleus of large cells at the 

 level of the upper portion of the fourth ventricle ; they are joined 

 by a bundle of fibres known as the descending or mesencephalic 

 root, which springs from a long slender column of cells in the 

 central grey matter of the aqueduct of Sylvius (Fig. 209). The 

 fibres of the sensory root run in part direct to the upper nucleus, 

 which lies lateral and ventral to the motor nucleus. The greater 

 number turn spinalwards through the pons, into the bulb and cord, 

 to the level of the 4th cervical segment ; they terminate among 

 the cells of the substantia gelatinosa Eolandi (descending or bulbo- 

 spinal root of the 5th nerve). 



Distal to the Gasserian ganglion the trigeminus divides into 

 its three great branches : the ophthalmic, the superior maxillary, 

 and the inferior maxillary (Fig. 217). 



The ophthalmic division is the smallest of the three sensory 

 branches which arise from the unipolar cells of the semilunar 

 ganglion. It supplies branches to the dura mater and tentorium, 

 to the eyeball and lachrymal gland, to the mucous membrane of 

 the nose and the conjunctiva of the eyelids, to the skin of the tip 

 of the nose, upper eyelid, forehead, and of the anterior portion of 

 the scalp. The ciliary gland is connected with it. 



The superior maxillary nerve, with the sphenopalatine ganglion 

 (Meckel's ganglion) which is attached to it, sends branches to the 

 skin of the cheeks and anterior part of the temples, the lower 

 eyelid, the side of the nose and the upper lip ; also to the upper 

 teeth and mucous membrane of the nose, upper part of pharynx, 

 antrum of Highmore and posterior ethmoid sinuses, and the soft 

 palate ; finally to the tonsils, uvula, and glands of the buceal 

 cavity. 



The inferior maxillary or mandibular nerve, which is the 

 largest of the three branches of the trigeminal, is a mixed nerve 

 owing to its union with the motor root. Its sensory branches are 

 distributed to the side of the head and external ear, the external 

 ineatus, lower lip and lower part of the face. It also gives sensory 

 branches to the larger part of the tongue, to the mucous membrane 

 of the cheek, gums, and lower teeth, to the salivary glands, the 

 articulation of the jaw, the dura mater, the cranium, and the 

 mucous membrane lining the mastoid sinuses. The otic and sub- 

 maxillary ganglia are intimately connected with the mandibular 



