684 



OF THE FUNCTIONS OF THE NERVOUS SYSTEM. 



partly kept up by the muscles of the other side; but it falls in a slight degree; 

 and its movements are seen, when carefully observed, to be somewhat oblique. 

 If the trunk be divided on each side, the whole head is deprived of sensibility, 

 and the animal carries it in a curious vacillating manner, as if it were a 

 foreign body. If the anterior or Ophthalmic branch only be divided, all the 

 parts supplied by it are found to have lost their sensibility, but their motions 

 are unimpaired ; and all experiments and pathological observations concur in 

 attributing to it sensory endowments only. The only apparent exception is in 



the case of the naso-ciliary branch, 



Fig. 183. since there is good reason to be- 



lieve that the long root of the cili- 

 ary ganglion and the long ciliary 

 nerves possess motor powers ; but 

 these appear to be derived from 

 the Sympathetic or from the 3d 

 pair. When the whole nerve, or 

 its anterior branch, is divided in 

 the rabbit, the pupil is exceedingly 

 contracted, and remains immova- 

 ble ; but in dogs and pigeons it is 

 dilated. The pupil of the other 

 eye is scarcely affected ; or, if its 

 dimensions be changed, it soon re- 

 turns to its natural state. The 

 eyeball, however, speedily becomes 

 inflamed; and the inflammation 



Usually runs OU to Suppuration and 

 complete disorganization. The 



commencement of these changes 



r i i ,i 



^ ^ Commonly noticed Wlthm 



twenty-four hours after the Opera- 

 tion ; and they appear to be due 

 to the Want of the protective SCCre- 



tion, which (as will be explained 



when the direct influence of the nervous system upon the organic functions is 

 considered) is necessary to keep the mucous surface of the eye in its healthy 

 condition, and which is not formed when the sensibility of that surface is 

 destroyed. The Superior Maxillary branch, considered in itself, is equally 

 destitute of motor endowments with the ophthalmic ; but its connections with 

 other nerves, through the spheno-palatine ganglion and its anastomosing twigs, 

 may introduce a few motor fibres into it. The Inferior Maxillary branch is 

 the only one which possesses motor as well as sensory endowments from its 

 origin; but its different subdivisions possess these endowments in varying 

 proportions, some being almost exclusively motor, and others as completely of 

 a sensory character. The latter is probably the nature of the Lingual branch ; 

 and there seems good reason to believe, as will hereafter be shown ( 717), 

 that this ministers not only to the tactile sensibility of the tongue, but to the 

 sense of Taste. The muscles put in action by this division are solely those 

 concerned in the masticatory movements. The 5th pair is connected in differ- 

 ent parts of its course, with a number of small ganglia belonging to the Sym- 

 pathetic system. One of the most interesting of these ganglia is the Ophthal- 

 mic or Ciliary (Fig. 183), which is the centre whence the eyeball derives its 

 supply of nerves, sensory, motor, and sympathetic. This ganglion derives its 

 sensory fibres by its " long root" from the nasal branch of the Ophthalmic divi- 

 sion of the 5th pair; its motor fibres, by the "short root," from the 3d pair; 



A representation of some of the nerves of the orbit, espe- 

 cially to show the lenticular ganglion (Arnold). 1. Gan- 



giion of the fifth. 2. ophthalmic nerve. 3. Upper maxii- 



lary. 4. Lower maxillary. 5. Nasal hranch, giving the 

 iJg root to the lenticular ganglion. 6. Third nerve. %! 

 Inferior oblique branch of the third connected with the 

 ganglionbythesfcortrarf. 8. Optic nerve. 9. Sixth nerve, 

 10. Sympathetic on the carotid artery. 



