OF THE NERVUS OCTAVUS. 169 



In this way, in pigeons, one N. octavus influences upon the 

 octavo-motor systems of both sides, though that influence is still 

 prevailing upon the homolateral system. Consequently there must 

 result a difference in their physiological behaviour after the loss of 

 one labyrinth , if compared to rabbits. 



From this anatomical view however a part of the motor distur- 

 bances, in pigeons different from rabbits may be understood. 



In rabbits the loss of one labyrinth immediately after the opera- 

 tions causes grave disturbances, forced attitudes of head, neck and 

 eyes to a maximal extensity and consequently rollings. Maximal 

 after the operation, those disorders undergo correction until a certain 

 amelioration is reached, nothing more. A part of the forced attitudes 

 remains permamently. 



In pigeons, the loss of one labyrinth, has no immediate effect. 

 If it is sought for , atony may be found to prevail on the operated 

 side, but the non-operated side being damaged by the operative 

 shock to a rather important degree, is not yet capable of main- 

 taining a forced attitude. If correction occurs , it first is observed 

 at the less damaged side ; and therefore at the third day , the 

 forced attitudes begin. 



The influence of the intact N. octavus upon the octavo-motor 

 systems of both sides, though homolaterally prevailing, is important 

 enough to maintain automatically the usual position and to prevent 

 forced attitudes, sustained as it is by unaltered kinaesthetic and 

 opticomotor impulses, as long as the animal is quite at ease. It 

 does so , nonobstant the loss of one labyrinth. 



But as soon as periferical stimuli (kinaesthetic, or optico-motor, 

 or octavo-motor of the sound side) or central stimuli (volition, emotion) 

 act, suddenly the different amount of innervation at the two sides 

 becomes evident and suddenly the forced position of the head, not 

 at all differing of that seen in rabbits, appears. 



In this way during the first days after the removal of one cochlea 

 a pigeon bears itself as if it were incompletely atonic on both 

 sides, though atony at the operated side prevails. Afterwards it 

 behaves at intervals, as if one side were atonic, but only in cases 

 when the different amount of innervation of the two sides is brought 

 forward by augmentation of stimulation. 



In pigeons, each N. octavus, sends a not very important number 

 of rootfibres towards all eye nuclei on both sides. They therefore 

 never show such a peculiar forced attitude of each eye as rabbits 

 do after the loss of one labyrinth. 



That pigeons with their long neck, having lost one labyrinth, do 



