THE CRANIAL NERVES 285 



mediate loss of sensibility in the area of its distribution fol- 

 lows section, and even the cornea, which is normally ex- 

 quisitely sensitive, can be touched without exciting pain. 

 Both roots are usually cut at the same time, and besides a 

 loss of motion and general sensibility, section of this nerve 

 produces a decided effect upon the eye, the sense of taste, 

 deglutition and the nutrition of the parts to which the nerve 

 is distributed. The flow of tears is increased, the pupil be- 

 comes temporarily contracted and the ball protrudes. In a 

 few hours congestion is marked, and in a day or two the 

 cornea sloughs and the eye is destroyed. Section of the 

 fifth before its lingual branch is joined by the chorda tym- 

 pani from the facial causes a loss of general sensation, but 

 not of taste, in the anterior part of the tongue ; section of 

 the lingual branch after it has received the chorda is fol- 

 lowed by loss of general sensation and of taste. This 

 shows that the special^ sensibility distributed to the tongue 

 by the lingual branch of the fifth is furnished by the chorda 

 timpani. The fifth nerve sends filaments to give sensibility 

 to the velum palati. The reflex act of deglutition is due to 

 impressions carried from the velum and neighboring parts 

 to the centers ; when the fifth nerve is cut no such impres- 

 sions are conveyed and the reflex act cannot be excited. 



Regarding nutrition it is noticed that, besides the slough- 

 ing of the cornea, there is also, about the same time, the ap- 

 pearance of ulcers in the mouth and on the tongue, and ani- 

 mals thus experimented upon soon die. These lesions are 

 much less marked when the section is behind the semilunar 

 ganglion. Explanations of this difference are not altogether 

 satisfactory, but it is rational to suppose that section of sym- 

 pathetic fibers when the nerve is cut in front of Gasser's 

 ganglion is responsible for the disturbances of nutrition ; for 

 this is the system of nutrition, and changes following its sec- 

 tion in other parts of the body are not unlike those under, 

 discussion. Why, however, the changes should be inflam- 

 matory in character is not explained by this hypothesis, un- 



