viii THE HIND-BRAIN 435 



cauterised side, but no rotation of its head towards the sound 

 side. 



Mechanical excitation of one-half of the cerebellum can also 

 evoke motor reactions predominating in the muscles of the 

 opposite side. Nothnagel observed in 1876 that puncture of the 

 vermis with a fine needle on one side of the median line, or of one 

 cerebellar hemisphere, produced pleurothotonus or curvature of 

 the vertebral column to the opposite side, with rotation of the 

 head in the same direction, i.e. opposite to that observed after 

 removal of one-half of the cerebellum. But reactions also occur 

 in the fore-limb and facial muscles of the excited side. Lewan- 

 dowsky and J. Munk confirmed these results ; they found that 

 fine needles must be used in order to evoke them, because with 

 coarser lesions the irritative symptoms are mingled with those of 

 the paralysis and produced quite different phenomena. 



Sergi repeatedly found that simple section of the lower and 

 internal portion of a cerebeilar hemisphere, including a part of 

 the peduncles, produces a tendency to rotate, or actual rotation, in 

 a direction opposite to that which we observed alter unilateral 

 cerebellar extirpation, and comparable with the effects of 

 cauterisation. 



Electrical stimulation of one-half of the cerebellum (Lewan- 

 dowsky, 1903) gave parallel results. Weak induced currents 

 produced restlessness and consecutive movements that suggested 

 that the animal was suffering from vertigo. Stronger currents 

 produced a forced position towards the side opposite that excited 

 (right pleurothotonus when left side is excited); movements of 

 facial muscles and horizontal nystagmus of the head ; falling of 

 the animal to the right if excited on the left, and rotation in the 

 opposite direction to that observed after unilateral extirpation. 

 Lewandowsky, of course, assumed that there was true irritative 

 rotation in his case, and that ours was due to paralytic rotation. 



On the other hand, Pagano (1902), working in Marcacci's 

 laboratory, found that merely injecting a few drops of 1 per cent 

 solution of curare into one cerebellar hemisphere in dogs produced 

 violent epileptiform reactions mainly of the muscles of the same 

 side, and especially various rotatory movements ten to fifteen 

 minutes after injection. 



Two general propositions can be positively stated, without 

 danger of contradiction, in regard to the rotation round the 

 longitudinal axis that is constantly seen after destruction of one- 

 half of the cerebellum : 



(a) Predominance of the functional activity of the cerebral 

 centres of one side is a necessary condition for forced rotations, 

 and the afferent disturbance (vertigo) due to the sudden upset of 

 functional equilibrium is its immediate cause. 



(&) The rotation phenomenon and the forced movements and 



