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produces turning, is sufficient to prove that it is a nervous centre. 



The degree of pain produced by an excitation of this nervous 

 centre appears to be as considerable as that caused by a similar 

 excitation of the trigeminal nerve. I will publish soon an ac- 

 count of the strange effects produced in different parts of the body 

 in consequence of an injury of that nervous centre. I will merely 

 say here that, after such an injury, there are muscles which 

 appear to be slightly paralyzed. Besides, there seems to be a 

 notable hyperaesthesia of the skin everywhere. 



Flourens has found that a section of the semi-circular canals 

 in birds and some mammals produces a peculiar disorder in the 

 movements of the head, and, in some .cases, turning. He says 

 that the auditive nerve must be considered as composed of two 

 nerves: one going to the semi- circular canals and possessing a 

 peculiar power on the movements of the body, and the other, 

 the vestibular or true auditory nerve. What I have found on 

 frogs is in opposition to these views. A section of the semi- 

 circular canals, in these amphibia, does not produce any effect 

 on the movements of the body, and the slightest excitation of 

 the true auditive nerve is sufficient to produce pain, hyperaesthe- 

 sia, turning, and other strange effects on many muscles of the 

 body. 



I have sometimes seen turning produced after the mere laying 

 bare of the kind of bladder, containing the terminal part of the 

 auditive nerve, in frogs. So slight may be the excitations on 

 that nerve sufficient to produce turning, that very likely turning 

 after the laying bare of that bladder was the result of some 

 slight mechanical injury of the nerve. The rapidity of turning 

 and the smallness of the circle then described are in proportion 

 to the degree of injury to the nerve. When the two auditive 

 nerves are injured, the animal turns on the side most injured. 

 Sometimes, instead of turning, the animals roll around the longi- 

 tudinal axis of their body; this takes place in very strong 

 animals after the terminal part of the nerve has been entirely 

 crushed. 



In frogs deprived of their cerebral lobes, the same effects are 

 produced after injuries of the auditive nerve, as in unmutilated 

 frogs. 



