THE NERVOUS SYSTEM. 143 



of the face and other tegumentary parts which also accompany the paral- 

 ysis; and that these changes, which may appear unimportant when they 

 affect external parts, are sufficient to destroy that refinement of structure 

 by which the organs of the special senses are adapted to their functions. 



That complete paralysis of the fifth nerve may be unaccompanied, at 

 least for a considerable period, by injury to the organs of special sense, 

 with the exception of that portion of the tongue which is supplied by its 

 gustatory branch, is well illustrated by a valuable case recorded by 

 Althaus. 



According to Magendie and Longet, destruction of the eye ensues 

 more quickly after division of the trunk of the fifth beyond the Gas- 

 serian ganglion, or after division of the ophthalmic branch, than after 

 division of the roots of the fifth between the brain and the ganglion. 

 Hence it would appear as if the influence on nutrition were conveyed 

 in part through the filaments of the sympathetic, which joins the 

 branches of the fifth nerve at and beyond the Gasserian ganglion. 



The existence of ganglia of the sympathetic in connection with all 

 the principal divisions of the fifth nerve where it gives off those branches 

 which supply the organs of special sense for example, the connection of 

 the ophthalmic ganglion with the ophthalmic nerve at the origin of the 

 ciliary nerves; of the spheno-palatine ganglion with the superior maxil- 

 lary division, where it gives its branches to the nose and the palate; of 

 the otic ganglion with the inferior maxillary near the giving off of fila- 

 ments to the internal ear; and of the sub-maxillary ganglion with the 

 lingual branch of the fifth all these connections suggest that a peculiar 

 and probably conjoint influence of the sympathetic and fifth nerves is 

 exercised in the nutrition of the organs of the special senses; and the 

 results of experiment and disease confirm this, by showing that the 

 nutrition of the organs may be impaired in consequence of impairment of 

 the power of either of the nerves. 



In relation to Sight. A possible but doubtful connection between the 

 fifth nerve and the sense of sight, has been thought to be shown in cases 

 in which blows or other injuries implicating the frontal nerve as it passes 

 over the brow, are followed by total blindness in the corresponding eye. 

 In some cases the blindness occurs at once, probably from concussion of 

 the retina; but in others it is very slowly progressive, as if from defective 

 nutrition of the retina, and may be accompanied with inflammatory dis- 

 organization, like that previously referred to (p. 141, Vol. II.). The con- 

 nection of the fifth nerve with the result must, however, be considered 

 very doubtful. 



SIXTH NERVE. 



Functions. The sixth nerve, N,ervus abducens or ocularis externus, 

 is also, like the fourth, exclusively motor, and supplies only the rectus 

 externus muscle. 



The rectus externus is convulsed, and the eye is turned outward, when 



