194: NERVOUS SYSTEM. 



been sustained by more recent experimenters ; and it is 

 probable that in some of the experiments of Magendie, other 

 nerves were divided as well as the fifth. This is a question 

 which will be touched upon again in connection with the 

 special senses ; suffice it to say at present that there is 110 

 evidence that branches of the fifth pair of nerves are en- 

 dowed with olfactory, auditory, or visual sensibility. This 

 statement is made without reserve by Miiller, 1 who adduces 

 cases of paralysis of the fifth in the human subject in proof 

 of its correctness. It is often the case that the special senses 

 are affected as an indirect and remote consequence of lesion 

 of the fifth, or rather of filaments of the sympathetic con- 

 nected with the fifth ; but division of this nerve alone does 

 not immediately affect any of the special senses. The loss 

 of taste is due always to division of the chorda tympani. 



As far as audition and olfaction are concerned, there are 

 no special effects immediately following section of the tri- 

 facial ; but there are interesting phenomena observed in 

 connection with the eye and the organs of taste. 



At the instant of division of the fifth, by the method just 

 described, the eyeball is protruded and the pupil becomes 

 strongly contracted. This occurs in rabbits, and the contrac- 

 tion of the pupil was observed in the first operations of Ma- 

 gendie. 2 The pupil, however, is usually restored to the nor- 

 mal condition in a few hours. Longet states that the pupil 

 is dilated by division of the fifth in dogs and cats. 3 After 

 division of the nerve, the lachrymal secretion becomes very 

 much less in quantity ; but this is not the cause of the sub- 

 sequent inflammation, for the eyes are not inflamed, as was 

 shown by Magendie, even after extirpation of both lachrymal 



sight in one eye was not extinct, the corresponding optic nerve being atrophied, 

 but by no means destroyed (La vue peui-elle etre conservee malgre la destruction 

 des nerfs optiques, tome viii., p. 27). 



1 MULLER, Physiologic du systeme nerveux, Paris, 1840, tome i., p. 303. 



8 Loc. tit. 



8 LONGET, Traite de physiologic, Paris, 1869, tome iii., p. 489, note. 



