347 



If we compare from the pliysiological standpoint the duration 

 and the deg'ree of tlie circus- and rolling-movements after lesions 

 of the periplieral organ (semi-circular canals), the vestibnlar}- nerve, 

 of its nuclei and of the ascending connections, we are struck by 

 the difference in the results. Vehement forced movements and, 

 peculiarly enough only rolling movements to the affected side, are 

 exclusively found after lesion of tlie vestibulary nerve. Especiall}' 

 so in the lower vertebrates as the rabbit and cavia. A lesion of the 

 nuclei is followed by less vigorous forced movements, mostly of 

 mixed type, rolling-movements combined with circus-movements. 

 According to the nuclei involved, all combinations may occur, 

 together with the corresponding conjugated deviation of the eyeballs. 



After a lesion of the ascending connections, it is due to the 

 anatomical arrangement, that circus-movements to one side and 

 rolling-movements to the other side combined, will prevail. Although 

 in a measure the degree and duration of the forced movements and 

 concomitant symptoms (falling aside, conjugated deviation), is depend- 

 ent on the quantity of the fibres degenerated, it appears, that the 

 compensation is arrived at the more early, the more central the 

 lesion is situated. 



In so far the extraordinary sensitiveness of the vestibulary trunk 

 cannot cause astonishment, as from clinical experience there is 

 sufficient reason to expect an uncommon irritability of that nerve 

 (Hidzig's vertigo by galvanisation of the head, the frequency of 

 dizziness in cases of tumour cerebri not ( nly of the posterior fossa 

 cerebri but also far distant). 



From my experiments T conclude, that the forced movements are 

 the result of an irritation, caused by the degeneration of the medul- 

 lary sheaths. If an haemorrhage occurs in the area of the P. L. B. 

 system, the forced movements show an uncommon vehement 

 character and last longer; but finally, after complete destruction of 

 the nerve fibres and after the process of compensation is set in 

 action, all traces of spontaneous forced movements disappeai' and can 

 only be elicited after certain measui-es (blindfolding, narcosis, 

 mutilation of the cerebral hemispheres). 



Although the 2 types of forced movements, which until now 

 (viz. locomotion in the horizontal plane and in the plane vertical 

 to the long axis of the animal) show many points of comparison, 

 they cannot be looked upon as quite similarly arranged mechanisms. 

 Not only is there disagreement in anatomical arrangement of the 

 ascending bundles, but we also failed to find a distinct centrifugal 

 bundle in the P. L. B. system, whose descending degeneration causes 



