518 A MANUAL OF VETERINARY PHYSIOLOGY 



thalamus of its own side. Further, it is connected with the 

 motor nuclei of the fifth, seventh, ninth, tenth, and twelfth 

 cranial nerves. The Gasserian ganglion behaves like a spinal 

 ganglion. From its axons the sensory fibres arise which pass 

 outwards to the structure of the face and head, and confer on 

 them ordinary, and, in the case of the lips, acute tactile sense. 

 Fibres passing from the Gasserian ganglion to the brain are linked 

 up, as shown above, with the optic thalamus, the central seat of 

 sensory impressions. The motor root arises from the pons on the 

 inside of the sensory root. From these two roots three branches 

 of nerve are formed — the ophthalmic, superior maxillary, and 

 inferior maxillary. The Ophthalmic branch is the smallest, and 

 is purely sensory. It supplies the lachrymal gland, upper eyelid, 

 membrana nictitans, temporal region, mucous membrane of 

 septum nasi, and superior turbinated bone, and provides the 

 sensory root of the ciliary ganglion. The Superior Maxillary 

 Branch is of great size, and purely sensory in function. It 

 supplies the septum of the nostril, hard palate, teeth, gums, soft 

 palate, upper lip, guttural pouch, parotid gland, external ear, 

 skin, and other structures of the face. The immense bundle 

 which issues from the infra-orbital canal of the horse is out of 

 all proportion to the extent of tissue to be supplied either with 

 ordinary sensation or with tactile sensibility. The Inferior 

 Maxillary Branch is a mixed nerve, its sensory fibres being 

 derived from the Gasserian ganglion, the motor fibres from the 

 the motor root of the main trunk. It is through the motor 

 fibres of this branch that mastication is carried on — in fact, it 

 has been termed the masticatory nerve. It supplies all the muscles 

 of mastication excepting the diagastricus. Its sensory fibres 

 are distributed to the lining membrane of the lips and mouth, 

 to the molar and incisor teeth in the lower jaw, and the 

 structures connected therewith, also to the anterior two-thirds 

 of the tongue, to the parotid gland and guttural pouch, to 

 the integument covering the lower half of the head, and to 

 the muscles of mastication. In addition to these extensive 

 functions, the lingual fibres not only supply sensation to the 

 tongue, but to the fungiform papillae, and so assist in the 

 sense of taste. 



If the fifth pair of nerves be divided, there is complete loss 

 of sensation to one half of the face, part of the ear, cornea, 

 conjunctiva, nasal mucous membrane, and anterior two-thirds 

 of the tongue. There is paralysis of the muscles of mastication, 

 the mouth and tongue become injured by the teeth, in consequence 

 of the loss of sensation ; the food collects on the paralysed side 

 of the mouth ; the cornea ulcerates, either in consequence of the 

 loss of trophic influence, or, as most physiologists think, from 



