NEBVE OF MASTICATION. 143 



actively concerned in mastication, are animated by the mo- 

 tor root of the fifth. 



Properties and Functions of the Nerve of Mastimtion. 

 The anatomical distribution of the small root of the fifth 

 nerve points at once to its function. Charles Bell, whose 

 ideas of the nerves were derived almost entirely from their 

 anatomy, called it the nerve of mastication, in 1821, though 

 he does not state that any experiments were made with re- 

 gard to its function. 1 All anatomical and physiological 

 writers since that time have adopted this view. It would be 

 difficult, if not impossible, to galvanize the root in the cra- 

 nial cavity in a living animal ; but its galvanization, prob- 

 ably in an animal just killed, has been shown by Longet, 

 before 1 842, to determine very marked movements of the 

 lower jaw. 2 Longet states in his work on physiology that 

 no contractions of the muscles of mastication are produced 

 when the large root of the fifth alone is galvanized. The 

 experiments demonstrating this fact were made on horses 

 and dogs, operating upon the roots of the nerves after re- 

 moving the cerebral lobes. 3 Chauveau also found that gal- 

 vanization of the small root of the fifth produced contrac- 

 tion of the muscles which elevate the lower jaw sufficiently 

 sudden and violent to break sometimes, in old horses, little 

 fragments from the irregular surfaces of the teeth.* 



The above experiments are sufficient to show the physio- 

 logical properties of the small root, which is without doubt 

 solely a nerve of motion. 



1 BELL, On the Nerves; giving an Account of some Experiments on their 

 Structure and Functions, which lead to a New Arrangement of the System. 

 Philosophical Transaction^ London, 1821, Part i., p. 417. 



8 LONGET, Anatomic et physiologic du systeme ncrveux, Paris, 1842, tome iL, 

 p. 190. 



3 LOXGET, Traite de physiologic, Paris, 1869, tome iii., p. 562. 



4 CHAUVEAU, Recherches physiologiques sur Vorigine apparante et sur Foriffine 

 r'edle des nerfs moteurs craniens. Journal de la physiologic, Paris, 1862, tome 

 v., p. 276. 



110 



