712 OF THE FUNCTIONS OF THE NERVOUS SYSTEM. 



torius and behind the corpora olivaria, according to Brown-Sequard's experi- 

 ments in common with Dr. Martin-Magron. 



Some of these two series of parts ordinarily produce turning, and others 

 rolling. But these two kinds of movements can be produced by the puncture 

 of a single part of the encephalon. Rolling is nothing but the exaggeration of 

 turning ; thus, after 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. 



1. Turning and Rolling caused by tearing the Facial Nerve. Dr. Martin- 

 Magron and Dr. Brown-Sequard 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 

 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 move- 

 ment 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 ro- 

 tation 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 pleurostho- 

 tonos) 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 produced, 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 the author 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 originates. 1 



2. Turning and Rolling produced by an Injury to the Medulla Oblongata. 

 M. Magendie 3 says : " Having raised up the cerebellum, I make a section per- 

 pendicularly to the surface of the fourth ventricle, and at three or four milli- 

 metres from the median line. If I cut on the right, the animal will turn on the 

 right side ; if I cut on the left, it will turn on the left side." 



If we suppose a plane cutting the medulla oblongata transversely at the dis- 

 tance of nearly two lines before the nib of the calamus scriptorius, the posterior 

 face of the medulla oblongata will be divided into two parts : one before that 

 plane which the author calls superior, and the other behind, or inferior. 



Now, every puncture on that superior part produces turning or rolling on the 

 side which has been punctured. The slightest puncture on the processus cere- 

 belli ad medullam oblongatam will produce a violent and very rapid rolling. 

 As long as the anim'al lives after the operation, it rolls or it turns every time it 

 tries to walk. 



When (as Dr. Martin-Magron and the author have discovered) a deep section 

 is made on the inferior part of the posterior face of the medulla oblongata, before 

 the nib of the calamus scriptorius, turning is produced on the side of the body 



1 [S 



2 L" 



See "Gaz. Med. de Paris," 1849, t. iv. p. 879.] 

 Precis Elem. de Physiol.," Paris, 1836, t. i. p. 414.] 



