OF THE NERYUS OCTAVUS. 41 



slight loss of ton us in all extremities. But the animal, as the opera- 

 tive shock is gone, is not always able to compensate totally the prepon- 

 derate disturbance of innervation at the operated side , and then 

 the turning of the neck and head begins. Only when all around is 

 quiet, the pigeon is able to master the turning of head and neck. 

 Still ever and anon it is recurring by fits. 



EWALD has even pointed out the memorable fact , that a pigeon , 

 presenting the phenomena of a turning of head and neck recur- 

 ring by fits, may lose again this involuntarily assumed position, 

 if the labyrinth is again sought for, and the trunk of the N. octa- 

 vus, whose terminal organ has once already been removed, is laid 

 bare and a new lesion produced in it. Tn so doing, the Octavus- 

 nuclei on both sides are damaged again by operative shock, and 

 the results are once more the same as those of an imperfect double- 

 sided operation. In all these cases however the turning of head 

 and neck by fits returns gradually again. 



For the rabbit things stand otherwise. Here we find in the 

 first place the strong deviation of the eyes , that does not exist in 

 pigeons, whose eyes are used for quite other purposes. Therefore 

 in pigeons the eyes have a great influence on the correction of the 

 deviation of the head. That also rabbits have not. So the turning 

 of the head and neck and its consequence the rolling round the 

 longitudinal axis, are the first symptoms of the rabbit. 



Gradually the grave one-sided disturbance of innervation in the 

 rabbit is corrected, but never to such a degree that the head may 

 be borne erect, though it were only for a moment. From the very 

 first the disturbance has too much prevailed on one side to allow 

 this. The rabbit likewise is showing fits, in which all phenomena 

 are aggravated , equivalent to the fits of turning of head and neck , 

 observed in the pigeon. 



But that , what in the pigeon is from the beginning a double- 

 sided disturbance of innervation, changing gradually to a partial 

 loss of innervation on each side, prevailing on that, where is operated, 

 becomes unperceivable when the animal is perfectly quiet. In the 

 rabbit, from the very first, a one-sided total loss of innervation exists, 

 and though slightly diminishing afterwards, an always perceivable 

 disturbance on one side remains. 



The pigeon therefore, whose labyrinth has been removed on 

 one side, is originally equivalent to an animal operated imperfectly 

 on both sides, in which gradually is prevailing the one-sided distur- 

 bance the turning of neck and head and the atony of the extre- 

 mities which is permanent. 



