20 



a puncture of the medulla oblongata, the animal at first rolls, and 

 after some instants, instead of rolling, it turns. If, when it is 

 turning, a slight puncture is made anew, close to the first, then 

 the animal rolls. 



Before trying to explain turning, I will give an outline of 

 some of its species. 



1st. Turning and Rolling caused by tearing the facial nerve. 



My friend Dr. Martin-Magron and myself have discovered 

 that if the facial nerve of a' rabbit or a guinea-pig be exposed at 

 its exit from the stylo-mastoid foramen, and be then drawn away 

 from the cranium, so as to tear it asunder near its origin, the 

 animal begins in about five minutes to turn itself round and 

 round, the movement being from left to right when the nerve 

 has been thus torn on the left side, and from right to left when 

 it has been torn on the right side. This rotation is generally 

 preceded by convulsive movements of the eyes, of the jaws, and 

 of the head upon the trunk : and the body is then bent (as in 

 pleurosthotonos) towards the injured side, by the contraction of 

 all the longitudinal muscles of that side, the power of which is 

 such as to resist considerable force applied to extend them. The 

 movement at first takes place in a small circle ; but the circle 

 generally enlarges more and more, until at last, after twenty or 

 thirty minutes, the animal walks in a straight line. There is no 

 paralysis of any muscles, save the facial. The effect is not pro- 

 duced, unless the nerve be torn close to its origin. 



When the nerve on the other side also is torn, even after a 

 long interval, instead of the tendency to turn to one side, there 

 is, at first, a rolling of the body on its longitudinal axis, which 

 takes place towards the side last operated on. After this has 

 continued, however, for twenty minutes or more, the animal 

 recovers its feet, and begins to turn, as after the first operation, 

 but towards the other side. This movement soon ceases. 



Dr. Martin-Magron and myself think that the cause of these 

 phenomena does not exist in the facial nerve itself, but in the 

 part of the medulla oblongata from which this nerve has origi- 

 nated.* 



* See Gaz. Med. de Paris, 1849, t. 4, p. 879. 



