on the Structure, Distribution, and Functions of' the Nerves. 47 



the fifth nerve gives acute pain ; but its division causes no 

 change in the motion of the nostril, the cartilages continuing 

 to expand regularly in the act of respiration ; but the side of 

 the lip may be observed to hang low and to be dragged to the 

 other side ; and if the nerve of the opposite side be divided 

 also, the loss of motion of the lips in eating is very obvious. 

 The division of a branch of the fifth which goes to the fore- 

 head in a man, did not cause paralysis of the superciliary mus- 

 cles ; but an abscess and ulcer seated anterior to the ear of 

 another individual, affected the superior branch of the respi- 

 ratory nerve ; the eye-brow fell low, and did not follow the 

 other when the features were animated by discourse or emo- 

 tion. The infra-orbital branch of the fifth, on the left side, was 

 cut across, and the portio dura or respiratory nerve on the 

 right side of the same animal also; sensibility to pain re- 

 mained on this side, while that of the left was completely de- 

 stroyed. The difference of suffering moreover was most 

 marked at the time of their being divided ; the division of the 

 fifth was accompanied with signs of acute pain, that of the 

 seventh or respiratory with none at all. When carbonate of 

 ammonia was applied to the nostrils of the ass whose respi- 

 ratory nerve had been cut, the opposite side of the nose and 

 face was curled up with the peculiar expression of sneezing, 

 whilst the side on which the nerve was divided remained quite 

 relaxed, although the branches of the fifth pair and the sym- 

 pathetic were entire. The same experiment on a dog under 

 similar circumstances caused the action of sneezing on the 

 sound side only. 



From these facts and experiments it may be concluded, that 

 the nerves of the face are divisible, as to their functions, into 

 two distinct sets or classes ; and that it is the office of the portio 

 dura or respiratory class, to associate the actions of the mus- 

 cles of the face with those of the other organs of respiration ; 

 seeing that these muscles serve to actuate and expand the 

 passages to the lungs, and to controul the motions of the lips, 

 the nostrils, and velum palati, simultaneously with the respi- 

 ration of the lungs. It can also be proved that the throat, 

 neck, shoulders, and chest, have nerves similar to the portio 

 dura both in structure and in function, which serve to unite all 

 the extended apparatus of breathing and speaking. The ac- 

 tion of smiling seems also to be owing to the influence of this 

 nerve ; for although it has been presumed that this act is pe- 

 culiar to the human countenance, yet there is a great simi- 

 larity, if not identity of expression presented sometimes in the 

 face of the dog when he turns out the edge of his lips, leaps, 

 and twists his body and wags his tail as he is fawning on his 



master ; 



