616 FUNCTIONS OF THE CEREBRO -SPINAL NERVOUS SYSTEM. 



a very small proportion of their fibres being lost in the muscles ; whilst of the 

 brunches of the third division, a large number are distinctly Muscular. 

 Hence analogy, and the facts 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 by the penetration of a sharp instrument (which 

 Mageudie, by frequent practice, was 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 

 sensibility 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 muscles of the other side; but it falls in a slight degree; and its move- 

 ments 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, 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 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 immovable ; 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 returns to its natural state. The eye- 

 ball, however, speedily becomes inflamed ; and the inflammation usually runs 

 on to suppuration and complete disorganization. The commencement of these 

 changes may be commonly noticed within twenty-four hours after the opera- 

 tion ; and it is probable they may in part be attributed to the want of the pro- 

 tective secretion, which 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 ; since, as Snellin 1 has shown, if the eye be carefully pro- 

 tected from the action of external and injurious agencies, no ill effects are 

 observed. Pathological evidence, however, is not wanting to show that the 

 fifth exerts some influence over the nutritive processes in the parts it supplies, 

 which is probably transmitted through the vaso-motor nerves it contains. 2 - 

 The Knprrior Mn.riU<iry branch, considered in itself, is equally destitute of 

 motor endowments with the ophthalmic ; but its connection with other nerves, 

 through the spheuo palatine ganglion, or rather its anastomosing twigs,' may 

 introduce a few motor fibres into it. The Inferior Mn.riUnrtj 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 propor- 

 tions, 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 (^ 4!).'!), 

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



1 Ann. d'Orulist., ISC'), t. liii, p. 178. 



2 SIM. v..n (Jr.-ilr, Aivliiv I'. ()j)hth:il., 1s.")}-55, p. 306; Longct, Physiologic, 1861, 

 vol. ii, p. 480. 



8 Sim-'- tin' u;:iii^li<>n h;is I, ecu shown by Pivvo-t to be surely sensory. (Bnnvn- 

 Sequnrd's Archive >[< Phvsiol., 1808, pp. 7 and 207.) 



