86 THIRD REPORT 1833. 



was actually observed in the eye of the side, on which the fifth 

 nerve had been divided. 



Magendie has assigned another singular function to the fifth 

 pair, viz. to preside over the nutrition of the eye. Twenty-four 

 hours after section of this nerve, incipient opacity of the cornea 

 was observed, which gradually increased till the cornea became 

 as white as alabaster. There was also great vascularity of the 

 conjunctiva extending to the iris, with secretion of pus, and for- 

 mation of false membranes in the anterior chamber. About the 

 eighth day, the cornea began to detach itself from the sclerotica, 

 the centre ulcerated, and the humours of the eye finally escaped, 

 leaving only a small tubercle in the orbit. In this experiment, 

 the nerve had been divided in the temporal fossa, but when cut 

 immediately after leaving the pons Varolii, the morbid changes 

 were less marked, the movements of the globe of the eye were 

 preserved, the inflammation was limited to the superior part of 

 the eye, and the opacity occupied only a small segment of the 

 circumference of the cornea. After division of the nerve near 

 its origin in the medulla, no traces of disease were discoverable 

 in the eye till the seventh day, and these symptoms never be- 

 came very prominent. Several cases have been since recorded 

 of structural disease of this nerve in the human subject, with 

 the concomitant symptoms. That of Laine, described by Serres 

 in the 4th vol. of Magendie's Journal, furnishes strong support 

 to the views of Magendie *, 



A different explanation of this fact and of others which have 

 a tendency to refer secretion and nutrition to the control of 

 the nervous system has been proposed by Dr. Alison. Mucous 

 surfaces are protected from the contact of air and foreign bo- 

 dies by a copious secretion, which is evidently regulated in 

 amount by their sensibility, since it is increased by any unusual 

 iri'itation. This is especially true of the membrane of the eye. 

 Now section of the fifth pair is known to paralyse the sensibi- 

 lity of that organ, and the contact of air or other irritating body 

 upon the insensible membrane, instead of inducing an aug- 

 mented mucous discharge, will excite the inflammatory process 

 described by Magendie. The disorder of the digestive func- 

 tion f, which followed division of the par vagum in the experi- 

 ments of Dr. Wilson Philip, and the ulceration of the coats of 

 the bladder after injury of the lower part of the spinal marrow, 

 are attributed by Dr. Alison to the same cause. 



The class of nerves which comprehends the fifth pair and 



* See also a case of destruction of the olfactory nerves, lom. v. 

 •f Outlines of Phyniolngy, p. 71. 



