FUNCTIONS OF THE CEPHALIC NERVES. 169 



supplied by anatomical research, would lead to the conclusion, that the two 

 first divisions are nerves of sensation only, and that the third division combines 

 sensory and motor endowments. Such an inference is fully borne out by 

 experiment. When the whole trunk is divided within the cranium (which 

 Magendie, by frequent practice, has been able to accomplish), evident signs of 

 acute pain are given. After the incision has been made through the skin, the 

 animal remains quiet until the nerve is touched ; and when it is pressed or 

 divided, doleful cries are uttered, which continue for some time, showing the 

 painful effect of the irritated state of the cut extremity. The common sensi- 

 bility of all the parts supplied by this nerve is entirely destroyed on the affected 

 side. The jaw does not hang loosely, because it is partly kept up by the mus- 

 cles 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 ani- 

 mal carries it in a curious vacillating manner, as if it were a foreign body. 



226. 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 ; since there is good reason to believe that 

 the long root of the ciliary ganglion, and the long ciliary nerves, possess motor 

 powers ; but these appear to be derived from the Sympathetic nerve. When 

 the whole nerve, or its anterior branch, is divided in the rabbit, the pupil is 

 exceedingly contracted, and remains immovable ; but in dogs and pigeons it 

 is dilated. The pupil of the other eye is scarcely affected ; or, if its dimen- 

 sions be changed, it soon returns to its natural state. The eyeball speedily 

 becomes inflamed, however; and the inflammation usually runs on to suppura- 

 tion and complete disorganization. The commencement of these changes may 

 be commonly noticed within twenty-four hours after the operation ; and they 

 appear to be due to the want of the protective secretion, 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 con- 

 nections with other nerves, through the spleno-palatine ganglion and its anasto- 

 mosing 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 com- 

 pletely of a sensory character. The latter is probably the nature of the Lin- 

 gual branch; and there seems good reason to believe, as will presently be 

 shown, 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 of the Fifth 

 pair, are solely those concerned in the masticatory movements. 



227. The Portio Dura of the Seventh pair, or Facial nerve, has been sup- 

 posed, since the first researches of Sir C. Bell, to be a nerve of motion only; 

 but some recent physiologists have maintained that it both possesses sensory 

 endowments and arises by a double root. The latter assertion is quite falla- 

 cious ; and the most carefully conducted experiments do not bear out the for- 

 mer. By exposing the roots of the Seventh pair within the cranium, Valentin 

 ascertained that it possesses no sensory endowments at its origin ; since, when 

 these were touched, the animals gave no signs of pain, though violent mus- 

 cular movements were excited in the face. Subsequently to its first entrance 

 into the canal by which it emerges, however, it anastomoses with other nerves ; 



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