358 Analyses of Mr. C. Bell's Papers on the Nerves. 



of the eye, eye-lids, and forehead : hence it is allowable to at- 

 tribute the insensibility of the surfaces of the eye, as well as of 

 the skin around the eye, to the affection of the same nerve 

 near its root 



The author, moreover, has never been able to excite the 

 motion of the eye by irritating the ophthalmic branch of the 

 fifth after the division of its root, because no sensation was 

 conveyed to the sensorium ; and consequently, no mandate 

 transmitted from it for exciting the action of those muscles 

 whose office it is to move the eye on the presence of any fo- 

 reign body upon it. The young lady, in the case just described, 

 could see, and could move the eye and eye-lids ; the eye itself 

 was irritated by touch, as appeared from the rising inflamma- 

 tion; but by the insensibility of the ophthalmic nerve, a link was 

 lost in the relation necessary to join the action of the muscles 

 to the sensibility of the surface. 



Of the Nerves performing the involuntary Motions. 



Although nerves are found in great profusion to come out 

 upon the eye-lids and forehead ; yet they do not, as has been 

 supposed, direct the motions of these parts; this is effected by 

 means of a very small branch of the respiratory nerve of the 

 face, which comes out before the ear, and is designated the 

 portio dura of the seventh pair. The division of this branch 

 is followed by a loss of the motions of the eye-lids, and they 

 remain open ; hence the eye being unguarded and unwashed, 

 it becomes dry by evaporation, and inflames, and the cornea 

 becomes opaque. To be satisfied of the existence of certain 

 relations and of the connexions of remote parts in the animal 

 frame, it is only necessary to attend to the explanation of them 

 as given by the author himself. 



" During the state of excitement of the respiratory organs, 

 a very extensive consent of the muscular frame is necessary 

 to bind together and support the textures, that they may bear 

 the strain, either during violent efforts of the body, or in 

 coughing, sneezing, &c. We may take the act of sneezing, 

 as a familiar example of the manner in which the eye is 

 guarded during a sudden and violent act of expiration. 



" At the instant of this convulsive action of the respiratory 

 muscles, a violent impulse is communicated to the head along 

 the column of blood in the vessels of the head and neck. 

 Everybody is sensible of the eye flashing light, but the cause 

 is mistaken ; for it is supposed to be the impulse of blood 

 forced into the eye ; whereas it is the contraction of the eye- 

 lids to counteract the force of the impulse, and to guard the 

 delicate texture of the eye. If the eyelids be held open du- 

 ring 



